Proteostasis is an integral component of healthy aging. In most metazoans, protein quality declin... more Proteostasis is an integral component of healthy aging. In most metazoans, protein quality declines during aging, resulting in accrual of damaged or self-aggregating cytotoxic proteins, linked to several age-associated diseases (e.g, Alzheimer’s Disease, Parkinson’s Disease) and pathology (e.g.,sarcopenia). The mouse-sized naked mole-rat [NMRs] lives ~5 times longer than expected based on body size, and despite detected high levels of oxidative damage even at a young age, maintain good health for most of their long lives. Like other long-lived animal models, both in vivo and in vitro studies reveal that NMRs are resistant to a broad spectrum of environmental stressors. Collectively these findings suggest that NMRs possess efficient mechanisms to maintain protein quality. Our research has previously shown that this is attributed in part to altered proteasome forms and subcellular location. However, changes in proteasome-related molecular chaperone activity that assists in the transport of damaged proteins ...
a b s t r a c t a r t i c l e i n f o The naked mole-rat (NMR) is the longest-lived rodent and po... more a b s t r a c t a r t i c l e i n f o The naked mole-rat (NMR) is the longest-lived rodent and possesses several exceptional traits: marked cancer resistance, negligible senescence, prolonged genomic integrity, pronounced proteostasis, and a sustained health span. The underlying molecular mechanisms that contribute to these extraordinary attributes are currently under investigation to gain insights that may conceivably promote and extend human health span and lifespan. The ubiquitin-proteasome and autophagy-lysosomal systems play a vital role in eliminating cellular detritus to maintain proteostasis and have been previously shown to be more robust in NMRs when compared with shorterlived rodents. Using a 2-D PAGE proteomics approach, differential expression and phosphorylation levels of proteins involved in proteostasis networks were evaluated in the brains of NMRs in an age-dependent manner. We identified 9 proteins with significantly altered levels and/or phosphorylation states tha...
As the molecular mechanisms of biological aging become better understood, there is growing intere... more As the molecular mechanisms of biological aging become better understood, there is growing interest in identifying interventions that target those mechanisms to promote extended health and longevity. The budding yeast Saccharomyces cerevisiae has served as a premier model organism for identifying genetic and molecular factors that modulate cellular aging and is a powerful system in which to evaluate candidate longevity interventions. Here we screened a collection of natural products and natural product mixtures for effects on the growth rate, mTOR-mediated growth inhibition, and replicative lifespan. No mTOR inhibitory activity was detected, but several of the treatments affected growth rate and lifespan. The strongest lifespan shortening effects were observed for green tea extract and berberine. The most robust lifespan extension was detected from an extract of Pterocarpus marsupium and another mixture containing Pterocarpus marsupium extract. These findings illustrate the utility of the yeast system for longevity intervention discovery and identify Pterocarpus marsupium extract as a potentially fruitful longevity intervention for testing in higher eukaryotes.
The maintenance of skeletal muscle mass depends on the overall balance between the rates of prote... more The maintenance of skeletal muscle mass depends on the overall balance between the rates of protein synthesis and degradation. Thus, age-related muscle atrophy and function, commonly known as sarcopenia, may result from decreased protein synthesis, increased proteolysis, or simultaneous changes in both processes governed by complex multifactorial mechanisms. Growing evidence implicates oxidative stress and reactive oxygen species (ROS) as an essential regulator of proteolysis. Our previous studies have shown that genetic deletion of CuZn superoxide dismutase (CuZnSOD, Sod1) in mice leads to elevated oxidative stress, muscle atrophy and weakness, and an acceleration in age-related phenotypes associated with sarcopenia. The goal of this study is to determine whether oxidative stress directly influences the acceleration of proteolysis in skeletal muscle of Sod1 −/− mice as a function of age. Compared to control, Sod1 −/− muscle showed a significant elevation in protein carbonyls and 3-nitrotyrosine levels, suggesting high oxidative and nitrosative protein modifications were present. In addition, age-dependent muscle atrophy in Sod1 −/− muscle
Karl A. Rodriguez’s laboratory at the University of Texas Health Science Center, San Antonio, Tex... more Karl A. Rodriguez’s laboratory at the University of Texas Health Science Center, San Antonio, Texas, is interested in the role of small heat shock proteins in the proteostasis network and aging using the model organism, Caenorhabditis elegans. Molecular chaperones facilitate protein folding and improve the degradation activity of the proteasome and autolysosome hence decreasing disease-associated aggregates. Previous work in rodents have shown an increase in expression levels of the small heat shock protein 25 (HSP-25) correlates with maximum lifespan potential. To further explore the role of HSP-25 in C. elegans, two HSP-25 knock-out strains were exposed to a one-hour heat stress, heat shock, and two non-heat stress conditions.
Accumulation of protein aggregates are a common pathology in many neurodegenerative disorders. Th... more Accumulation of protein aggregates are a common pathology in many neurodegenerative disorders. This accumulation may be due to a function decline in the protein homeostasis network known to occur during the aging process. Small heat shock proteins are a class of molecular chaperones that assist in protein folding and ameliorates the degradation activity of the proteasome and autolysosome thereby decreasing disease-associated aggregates. Prior work in rodents and C. elegans has shown expression levels of the small heat shock protein 25 (HSP25) correlates with maximum lifespan potential. Increased levels of HSP25 extends lifespan in a transgenic C. elegans model. This lifespan extension is dependent on skn-1 with evidence suggesting an enrichment in several skn-1-related pathways, such as lysosomal genes. Concomitantly, proteasome activity declines while autolysosome activity increases. This observation might suggest a switch from proteasome degradation to autophagy as the main driver...
Journal of the neurological sciences, Jan 15, 2016
Aging is associated with a decline in peripheral nerve function of both motor and sensory nerves.... more Aging is associated with a decline in peripheral nerve function of both motor and sensory nerves. The decline in function of peripheral sensorimotor nerves with aging has been linked to sarcopenia, the age-related decline in muscle mass and function that significantly compromises the quality of life in older humans. In this study, we report a significant increase in oxidized fatty acids and insoluble protein carbonyls in sciatic nerves of aged C57BL/6 male mice (28-30mo) that exhibit a profound decline in motor nerve function and degenerative changes in both axon and myelin structure, compared to young mice (6-8mo). Our data further suggests that this age-related loss of function of peripheral motor nerves is likely precipitated by changes in mechanisms that protect and/or repair oxidative damage. We predict that interventions that target these mechanisms may protect against age-related decline in peripheral sensorimotor nerve function and likely improve the debilitating outcome of ...
Proceedings of the National Academy of Sciences of the United States of America, Jan 4, 2015
Sympatric speciation (SS), i.e., speciation within a freely breeding population or in contiguous ... more Sympatric speciation (SS), i.e., speciation within a freely breeding population or in contiguous populations, was first proposed by Darwin [Darwin C (1859) On the Origins of Species by Means of Natural Selection] and is still controversial despite theoretical support [Gavrilets S (2004) Fitness Landscapes and the Origin of Species (MPB-41)] and mounting empirical evidence. Speciation of subterranean mammals generally, including the genus Spalax, was considered hitherto allopatric, whereby new species arise primarily through geographic isolation. Here we show in Spalax a case of genome-wide divergence analysis in mammals, demonstrating that SS in continuous populations, with gene flow, encompasses multiple widespread genomic adaptive complexes, associated with the sharply divergent ecologies. The two abutting soil populations of S. galili in northern Israel habituate the ancestral Senonian chalk population and abutting derivative Plio-Pleistocene basalt population. Population diverge...
The multisubunit, multifunctional protease called proteasome as a part of the essential proteasom... more The multisubunit, multifunctional protease called proteasome as a part of the essential proteasome-ubiquitin pathway constitutes an attractive target for anti-cancer drugs. A proteasome inhibitor bortezomib is successful in blood cancers treatment, however trials with breast cancers yield disappointingly inconsistent results, likely stemming from the cancers’ diversity. Since bortezomib preferentially induces an apoptosis in cancerous cells, it is likely that differences in the proteasome pathway between the control and cancerous cells, and also between distinct cancers, contribute to this effect. Here we compared components of proteasome assemblies and their peptidase activities in seven breast cancer and two control cell lines in an attempt to find a common proteasomal signature of breast cancer. Defining a common proteolytic denominator for breast cancer cells should facilitate a rational drug design based on proteasomal inhibition. For this purpose, we analyzed cytosolic, nuclear and microsomal extracts from human cultured breast cells: control (MCF10A, Hs 578 Bst) and derived from distinct types of breast cancer: luminal A MCF7 and T47D, triple negative basal A MDA-MB-468, and triple negative basal B MDA-MB-231, Hs 578 T and BT-549. We found a high content of total proteasome in a microsomal fraction with a relatively prominent contribution from immuno proteasomes in all cancer cell lines. These proteasomes are believed to be localized on the outside of endoplasmic reticulum membrane and presumably take part in the endoplasmic reticulum - associated degradation system. Markedly, the pattern of peptidase activities of proteasome and content of subunits of its exchangeable sub-assemblies were specific for each fraction and discriminated between cancerous and control cells. Statistical analysis identified two clusters formed by the cell lines in the microsomal and nuclear fractions and a distinct clustering of the cytosols. Furthermore, three groups of variables, which tend to always cluster together were identified: the 19S regulatory particle subunits, immunoproteasome subunits and peptidolytic activities. Variables that the best quantitatively discriminate between the cell lines at a given level of total proteasome were immunoproteasome subunits and 19S cap subunit Rpt5. Additionally, the housekeeping subunit beta5 in the cytosol, the PA28 activator gamma subunit in the microsomal fraction and chymotrypsin like activity in the nuclear fraction qualitatively were the best markers aiding classification of the cell lines. We speculate that the distinct properties of proteasomes in the microsomal and nuclear fractions may contribute to specific response of the cancer cell lines to the treatment with proteasomal inhibitors. The study shows that a comprehensive analysis of the proteasome system in the established breast cancer cell lines may help to guide diagnostics and therapy design. Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P4-05-11.
Naked mole-rats (NMRs) are the oldest-living rodent species. Living underground in a thermally st... more Naked mole-rats (NMRs) are the oldest-living rodent species. Living underground in a thermally stable ecological niche, NMRs have evolved certain exceptional traits, resulting in sustained health spans, negligible cognitive decline, and a pronounced resistance to age-related disease. Uncovering insights into mechanisms underlying these extraordinary traits involved in successful aging may conceivably provide crucial clues to extend the human life span and health span. One of the most fundamental processes inside the cell is the production of ATP, which is an essential fuel in driving all other energy-requiring cellular activities. Not surprisingly, a prominent hallmark in age-related diseases, such as neurodegeneration and cancer, is the impairment and dysregulation of metabolic pathways. Using a two-dimensional polyacrylamide gel electrophoresis proteomics approach, alterations in expression and phosphorylation levels of metabolic proteins in the brains of NMRs, aged 2-24 years, were evaluated in an age-dependent manner. We identified 13 proteins with altered levels and/or phosphorylation states that play key roles in various metabolic pathways including glycolysis, β-oxidation, the malate-aspartate shuttle, the Tricarboxylic Acid Cycle (TCA) cycle, the electron transport chain, NADPH production, as well as the production of glutamate. New insights into potential pathways involved in metabolic aspects of successful aging have been obtained by the identification of key proteins through which the NMR brain responds and adapts to the aging process and how the NMR brain adapted to resist age-related degeneration. This study examines the changes in the proteome and phosphoproteome in the brain of the naked mole-rat aged 2-24 years. We identified 13 proteins (labeled in red) with altered expression and/or phosphorylation levels that are conceivably associated with sustained metabolic functions in the oldest NMRs that may promote a sustained health span and life span.
The Oxidative Stress Theory of Aging has had tremendous impact in research involving aging and ag... more The Oxidative Stress Theory of Aging has had tremendous impact in research involving aging and age-associated diseases including those that affect the nervous system. With over half a century of accrued data showing both strong support for and against this theory, there is a need to critically evaluate the data acquired from common biomedical research models, and to also diversify the species used in studies involving this proximate theory. One approach is to follow Orgel's second axiom that "evolution is smarter than we are" and judiciously choose species that may have evolved to live with chronic or seasonal oxidative stressors. Vertebrates that have naturally evolved to live under extreme conditions (e.g., anoxia or hypoxia), as well as those that undergo daily or seasonal torpor encounter both decreased oxygen availability and subsequent reoxygenation, with concomitant increased oxidative stress. Due to its high metabolic activity, the brain may be particularly vulnerable to oxidative stress. Here, we focus on oxidative stress responses in the brains of certain mouse models as well as extremophilic vertebrates. Exploring the naturally evolved biological tools utilized to cope with seasonal or environmentally variable oxygen availability may yield key information pertinent for how to deal with oxidative stress and thereby mitigate its propagation of age-associated diseases.
Biochimica et Biophysica Acta (BBA) - Molecular Basis of Disease, 2014
The naked mole-rat maintains robust proteostasis and high levels of proteasome-mediated proteolys... more The naked mole-rat maintains robust proteostasis and high levels of proteasome-mediated proteolysis for most of its exceptional (~31 years) life span. Here, we report that the highly active proteasome from the naked mole-rat liver resists attenuation by a diverse suite of proteasome-specific small molecule inhibitors. Moreover, mouse, human, and yeast proteasomes exposed to the proteasome-depleted, naked mole-rat cytosolic fractions, recapitulate the observed inhibition resistance, and mammalian proteasomes also show increased activity. Gel filtration coupled with mass spectrometry and atomic force microscopy indicates that these traits are supported by a protein factor that resides in the cytosol. This factor interacts with the proteasome and modulates its activity. Although Heat shock protein 72 kDa (HSP72) and Heat shock protein 40 kDa (Homolog of bacterial DNAJ1) (HSP40(Hdj1)) are among the constituents of this factor, the observed phenomenon, such as increasing peptidase activity and protecting against inhibition cannot be reconciled with any known chaperone functions. This novel function may contribute to the exceptional protein homeostasis in the naked mole-rat and allow it to successfully defy aging.
Rapamycin, an allosteric inhibitor of the mTOR kinase, increases longevity in mice in a sex-speci... more Rapamycin, an allosteric inhibitor of the mTOR kinase, increases longevity in mice in a sex-specific manner. In contrast to the widely accepted theory that a loss of proteasome activity is detrimental to both life- and healthspan, biochemical studies in vitro reveal that rapamycin inhibits 20S proteasome peptidase activity. We tested if this unexpected finding is also evident after chronic rapamycin treatment in vivo by measuring peptidase activities for both the 26S and 20S proteasome in liver, fat, and brain tissues of old, male and female mice fed encapsulated chow containing 2.24 mg/kg (14 ppm) rapamycin for 6 months. Further we assessed if rapamycin altered expression of the chaperone proteins known to interact with the proteasome-mediated degradation system (PMDS), heat shock factor 1 (HSF1), and the levels of key mTOR pathway proteins. Rapamycin had little effect on liver proteasome activity in either gender, but increased proteasome activity in female brain lysates and lower...
The longest-lived rodent, the naked mole-rat (Bathyergidae; Heterocephalus glaber), maintains rob... more The longest-lived rodent, the naked mole-rat (Bathyergidae; Heterocephalus glaber), maintains robust health for at least 75% of its 32 year lifespan, suggesting that the decline in genomic integrity or protein homeostasis routinely observed during aging, is either attenuated or delayed in this extraordinarily long-lived species. The ubiquitin proteasome system (UPS) plays an integral role in protein homeostasis by degrading oxidatively-damaged and misfolded proteins. In this study, we examined proteasome activity in naked mole-rats and mice in whole liver lysates as well as three subcellular fractions to probe the mechanisms behind the apparently enhanced effectiveness of UPS. We found that when compared with mouse samples, naked mole-rats had significantly higher chymotrypsin-like (ChT-L) activity and a twofold increase in trypsin-like (T-L) in both whole lysates as well as cytosolic fractions. Native gel electrophoresis of the whole tissue lysates showed that the 20S proteasome was more active in the longer-lived species and that 26S proteasome was both more active and more populous. Western blot analyses revealed that both 19S subunits and immunoproteasome catalytic subunits are present in greater amounts in the naked mole-rat suggesting that the observed higher specific activity may be due to the greater proportion of immunoproteasomes in livers of healthy young adults. It thus appears that proteasomes in this species are primed for the efficient removal of stress-damaged proteins. Further characterization of the naked mole-rat proteasome and its regulation could lead to important insights on how the cells in these animals handle increased stress and protein damage to maintain a longer health in their tissues and ultimately a longer life.
The ubiquitin-proteasome pathway plays a crucial role in regulation of intracellular protein turn... more The ubiquitin-proteasome pathway plays a crucial role in regulation of intracellular protein turnover. Proteasome, the central protease of the pathway, encompasses multisubunit assemblies sharing a common catalytic core supplemented by regulatory modules and localizing to different subcellular compartments. To better comprehend age-related functions of the proteasome we surveyed content, composition and catalytic properties of the enzyme in cytosolic, microsomal and nuclear fractions. obtained from mouse livers subjected to organismal aging. We found that during aging subunit composition and subcellular distribution of proteasomes changed without substantial alterations in the total level of core complexes. We observed that the general decline in proteasomes functions was limited to nuclear and cytosolic compartments. Surprisingly, the observed changes in activity and specificity were linked to the amount of the activator module and distinct composition of the catalytic subunits. In contrast, activity, specificity and composition of the microsomal-associated proteasomes remained mostly unaffected by aging; however their relative contribution to the total activity was substantially elevated. Unexpectedly, the nuclear proteasomes were affected most profoundly by aging possibly triggering significant changes in cellular signaling and transcription. Collectively, the data indicate an age-related refocusing of proteasome from the compartment specific functions towards general protein maintenance.
Proteasome is a major protease of the ubiquitin-proteasome pathway involved in the regulation of ... more Proteasome is a major protease of the ubiquitin-proteasome pathway involved in the regulation of practically all intracellular biochemical processes. The enzyme core is created by a heteromultimer of complex architecture built with multiple subunits arranged into a tube-like structure. The multiple active sites of diverse peptidase specificity are hidden inside the tube. Access to the interior is guarded by a gate formed by the N-termini of specialized subunits and by the attachment of additional multisubunit protein complexes controlling the enzymatic capabilities of the core. Proteasome, due to its Byzantine molecular architecture and equally sophisticated enzymatic mechanism, is by itself a fascinating biophysical object. Recently, the position of the protease advanced from an academically remarkable protein processor to a providential anticancer drug target and futuristic nanomachine. Proteomics studies actively shape our current understanding of the protease and direct the future applications of the proteasome in medicine.
Reactive oxygen species (ROS), by-products of aerobic metabolism, cause oxidative damage to cells... more Reactive oxygen species (ROS), by-products of aerobic metabolism, cause oxidative damage to cells and tissue and not surprisingly many theories have arisen to link ROS-induced oxidative stress to aging and health. While studies clearly link ROS to a plethora of divergent diseases, their role in aging is still debatable. Genetic knock-down manipulations of antioxidants alter the levels of accrued oxidative damage, however, the resultant effect of increased oxidative stress on lifespan are equivocal. Similarly the impact of elevating antioxidant levels through transgenic manipulations yield inconsistent effects on longevity. Furthermore, comparative data from a wide range of endotherms with disparate longevity remain inconclusive. Many long-living species such as birds, bats and mole-rats exhibit high-levels of oxidative damage, evident already at young ages. Clearly, neither the amount of ROS per se nor the sensitivity in neutralizing ROS are as important as whether or not the accrued oxidative stress leads to oxidative-damage-linked ageassociated diseases. In this review we examine the literature on ROS, its relation to disease and the lessons gleaned from a comparative approach based upon species with widely divergent responses. We specifically focus on the longest lived rodent, the naked mole-rat, which maintains good health and provides novel insights into the paradox of maintaining both an extended healthspan and lifespan despite high oxidative stress from a young age.
Biochimica et Biophysica Acta (BBA) - Molecular Basis of Disease, 2015
The naked mole-rat (NMR) is the longest-lived rodent and possesses several exceptional traits: ma... more The naked mole-rat (NMR) is the longest-lived rodent and possesses several exceptional traits: marked cancer resistance, negligible senescence, prolonged genomic integrity, pronounced proteostasis, and a sustained health span. The underlying molecular mechanisms that contribute to these extraordinary attributes are currently under investigation to gain insights that may conceivably promote and extend human health span and lifespan. The ubiquitin-proteasome and autophagy-lysosomal systems play a vital role in eliminating cellular detritus to maintain proteostasis and have been previously shown to be more robust in NMRs when compared with shorterlived rodents. Using a 2-D PAGE proteomics approach, differential expression and phosphorylation levels of proteins involved in proteostasis networks were evaluated in the brains of NMRs in an age-dependent manner. We identified 9 proteins with significantly altered levels and/or phosphorylation states that have key roles involved in proteostasis networks. To further investigate the possible role that autophagy may play in maintaining cellular proteostasis, we examined aspects of the PI3K/Akt/mammalian target of rapamycin (mTOR) axis as well as levels of Beclin-1, LC3-I, and LC3-II in the brain of the NMR as a function of age. Together, these results show that NMRs maintain high levels of autophagy throughout the majority of their lifespan and may contribute to the extraordinary health span of these rodents. The potential of augmenting human health span via activating the proteostasis network will require further studies.
Proteostasis is an integral component of healthy aging. In most metazoans, protein quality declin... more Proteostasis is an integral component of healthy aging. In most metazoans, protein quality declines during aging, resulting in accrual of damaged or self-aggregating cytotoxic proteins, linked to several age-associated diseases (e.g, Alzheimer’s Disease, Parkinson’s Disease) and pathology (e.g.,sarcopenia). The mouse-sized naked mole-rat [NMRs] lives ~5 times longer than expected based on body size, and despite detected high levels of oxidative damage even at a young age, maintain good health for most of their long lives. Like other long-lived animal models, both in vivo and in vitro studies reveal that NMRs are resistant to a broad spectrum of environmental stressors. Collectively these findings suggest that NMRs possess efficient mechanisms to maintain protein quality. Our research has previously shown that this is attributed in part to altered proteasome forms and subcellular location. However, changes in proteasome-related molecular chaperone activity that assists in the transport of damaged proteins ...
a b s t r a c t a r t i c l e i n f o The naked mole-rat (NMR) is the longest-lived rodent and po... more a b s t r a c t a r t i c l e i n f o The naked mole-rat (NMR) is the longest-lived rodent and possesses several exceptional traits: marked cancer resistance, negligible senescence, prolonged genomic integrity, pronounced proteostasis, and a sustained health span. The underlying molecular mechanisms that contribute to these extraordinary attributes are currently under investigation to gain insights that may conceivably promote and extend human health span and lifespan. The ubiquitin-proteasome and autophagy-lysosomal systems play a vital role in eliminating cellular detritus to maintain proteostasis and have been previously shown to be more robust in NMRs when compared with shorterlived rodents. Using a 2-D PAGE proteomics approach, differential expression and phosphorylation levels of proteins involved in proteostasis networks were evaluated in the brains of NMRs in an age-dependent manner. We identified 9 proteins with significantly altered levels and/or phosphorylation states tha...
As the molecular mechanisms of biological aging become better understood, there is growing intere... more As the molecular mechanisms of biological aging become better understood, there is growing interest in identifying interventions that target those mechanisms to promote extended health and longevity. The budding yeast Saccharomyces cerevisiae has served as a premier model organism for identifying genetic and molecular factors that modulate cellular aging and is a powerful system in which to evaluate candidate longevity interventions. Here we screened a collection of natural products and natural product mixtures for effects on the growth rate, mTOR-mediated growth inhibition, and replicative lifespan. No mTOR inhibitory activity was detected, but several of the treatments affected growth rate and lifespan. The strongest lifespan shortening effects were observed for green tea extract and berberine. The most robust lifespan extension was detected from an extract of Pterocarpus marsupium and another mixture containing Pterocarpus marsupium extract. These findings illustrate the utility of the yeast system for longevity intervention discovery and identify Pterocarpus marsupium extract as a potentially fruitful longevity intervention for testing in higher eukaryotes.
The maintenance of skeletal muscle mass depends on the overall balance between the rates of prote... more The maintenance of skeletal muscle mass depends on the overall balance between the rates of protein synthesis and degradation. Thus, age-related muscle atrophy and function, commonly known as sarcopenia, may result from decreased protein synthesis, increased proteolysis, or simultaneous changes in both processes governed by complex multifactorial mechanisms. Growing evidence implicates oxidative stress and reactive oxygen species (ROS) as an essential regulator of proteolysis. Our previous studies have shown that genetic deletion of CuZn superoxide dismutase (CuZnSOD, Sod1) in mice leads to elevated oxidative stress, muscle atrophy and weakness, and an acceleration in age-related phenotypes associated with sarcopenia. The goal of this study is to determine whether oxidative stress directly influences the acceleration of proteolysis in skeletal muscle of Sod1 −/− mice as a function of age. Compared to control, Sod1 −/− muscle showed a significant elevation in protein carbonyls and 3-nitrotyrosine levels, suggesting high oxidative and nitrosative protein modifications were present. In addition, age-dependent muscle atrophy in Sod1 −/− muscle
Karl A. Rodriguez’s laboratory at the University of Texas Health Science Center, San Antonio, Tex... more Karl A. Rodriguez’s laboratory at the University of Texas Health Science Center, San Antonio, Texas, is interested in the role of small heat shock proteins in the proteostasis network and aging using the model organism, Caenorhabditis elegans. Molecular chaperones facilitate protein folding and improve the degradation activity of the proteasome and autolysosome hence decreasing disease-associated aggregates. Previous work in rodents have shown an increase in expression levels of the small heat shock protein 25 (HSP-25) correlates with maximum lifespan potential. To further explore the role of HSP-25 in C. elegans, two HSP-25 knock-out strains were exposed to a one-hour heat stress, heat shock, and two non-heat stress conditions.
Accumulation of protein aggregates are a common pathology in many neurodegenerative disorders. Th... more Accumulation of protein aggregates are a common pathology in many neurodegenerative disorders. This accumulation may be due to a function decline in the protein homeostasis network known to occur during the aging process. Small heat shock proteins are a class of molecular chaperones that assist in protein folding and ameliorates the degradation activity of the proteasome and autolysosome thereby decreasing disease-associated aggregates. Prior work in rodents and C. elegans has shown expression levels of the small heat shock protein 25 (HSP25) correlates with maximum lifespan potential. Increased levels of HSP25 extends lifespan in a transgenic C. elegans model. This lifespan extension is dependent on skn-1 with evidence suggesting an enrichment in several skn-1-related pathways, such as lysosomal genes. Concomitantly, proteasome activity declines while autolysosome activity increases. This observation might suggest a switch from proteasome degradation to autophagy as the main driver...
Journal of the neurological sciences, Jan 15, 2016
Aging is associated with a decline in peripheral nerve function of both motor and sensory nerves.... more Aging is associated with a decline in peripheral nerve function of both motor and sensory nerves. The decline in function of peripheral sensorimotor nerves with aging has been linked to sarcopenia, the age-related decline in muscle mass and function that significantly compromises the quality of life in older humans. In this study, we report a significant increase in oxidized fatty acids and insoluble protein carbonyls in sciatic nerves of aged C57BL/6 male mice (28-30mo) that exhibit a profound decline in motor nerve function and degenerative changes in both axon and myelin structure, compared to young mice (6-8mo). Our data further suggests that this age-related loss of function of peripheral motor nerves is likely precipitated by changes in mechanisms that protect and/or repair oxidative damage. We predict that interventions that target these mechanisms may protect against age-related decline in peripheral sensorimotor nerve function and likely improve the debilitating outcome of ...
Proceedings of the National Academy of Sciences of the United States of America, Jan 4, 2015
Sympatric speciation (SS), i.e., speciation within a freely breeding population or in contiguous ... more Sympatric speciation (SS), i.e., speciation within a freely breeding population or in contiguous populations, was first proposed by Darwin [Darwin C (1859) On the Origins of Species by Means of Natural Selection] and is still controversial despite theoretical support [Gavrilets S (2004) Fitness Landscapes and the Origin of Species (MPB-41)] and mounting empirical evidence. Speciation of subterranean mammals generally, including the genus Spalax, was considered hitherto allopatric, whereby new species arise primarily through geographic isolation. Here we show in Spalax a case of genome-wide divergence analysis in mammals, demonstrating that SS in continuous populations, with gene flow, encompasses multiple widespread genomic adaptive complexes, associated with the sharply divergent ecologies. The two abutting soil populations of S. galili in northern Israel habituate the ancestral Senonian chalk population and abutting derivative Plio-Pleistocene basalt population. Population diverge...
The multisubunit, multifunctional protease called proteasome as a part of the essential proteasom... more The multisubunit, multifunctional protease called proteasome as a part of the essential proteasome-ubiquitin pathway constitutes an attractive target for anti-cancer drugs. A proteasome inhibitor bortezomib is successful in blood cancers treatment, however trials with breast cancers yield disappointingly inconsistent results, likely stemming from the cancers’ diversity. Since bortezomib preferentially induces an apoptosis in cancerous cells, it is likely that differences in the proteasome pathway between the control and cancerous cells, and also between distinct cancers, contribute to this effect. Here we compared components of proteasome assemblies and their peptidase activities in seven breast cancer and two control cell lines in an attempt to find a common proteasomal signature of breast cancer. Defining a common proteolytic denominator for breast cancer cells should facilitate a rational drug design based on proteasomal inhibition. For this purpose, we analyzed cytosolic, nuclear and microsomal extracts from human cultured breast cells: control (MCF10A, Hs 578 Bst) and derived from distinct types of breast cancer: luminal A MCF7 and T47D, triple negative basal A MDA-MB-468, and triple negative basal B MDA-MB-231, Hs 578 T and BT-549. We found a high content of total proteasome in a microsomal fraction with a relatively prominent contribution from immuno proteasomes in all cancer cell lines. These proteasomes are believed to be localized on the outside of endoplasmic reticulum membrane and presumably take part in the endoplasmic reticulum - associated degradation system. Markedly, the pattern of peptidase activities of proteasome and content of subunits of its exchangeable sub-assemblies were specific for each fraction and discriminated between cancerous and control cells. Statistical analysis identified two clusters formed by the cell lines in the microsomal and nuclear fractions and a distinct clustering of the cytosols. Furthermore, three groups of variables, which tend to always cluster together were identified: the 19S regulatory particle subunits, immunoproteasome subunits and peptidolytic activities. Variables that the best quantitatively discriminate between the cell lines at a given level of total proteasome were immunoproteasome subunits and 19S cap subunit Rpt5. Additionally, the housekeeping subunit beta5 in the cytosol, the PA28 activator gamma subunit in the microsomal fraction and chymotrypsin like activity in the nuclear fraction qualitatively were the best markers aiding classification of the cell lines. We speculate that the distinct properties of proteasomes in the microsomal and nuclear fractions may contribute to specific response of the cancer cell lines to the treatment with proteasomal inhibitors. The study shows that a comprehensive analysis of the proteasome system in the established breast cancer cell lines may help to guide diagnostics and therapy design. Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P4-05-11.
Naked mole-rats (NMRs) are the oldest-living rodent species. Living underground in a thermally st... more Naked mole-rats (NMRs) are the oldest-living rodent species. Living underground in a thermally stable ecological niche, NMRs have evolved certain exceptional traits, resulting in sustained health spans, negligible cognitive decline, and a pronounced resistance to age-related disease. Uncovering insights into mechanisms underlying these extraordinary traits involved in successful aging may conceivably provide crucial clues to extend the human life span and health span. One of the most fundamental processes inside the cell is the production of ATP, which is an essential fuel in driving all other energy-requiring cellular activities. Not surprisingly, a prominent hallmark in age-related diseases, such as neurodegeneration and cancer, is the impairment and dysregulation of metabolic pathways. Using a two-dimensional polyacrylamide gel electrophoresis proteomics approach, alterations in expression and phosphorylation levels of metabolic proteins in the brains of NMRs, aged 2-24 years, were evaluated in an age-dependent manner. We identified 13 proteins with altered levels and/or phosphorylation states that play key roles in various metabolic pathways including glycolysis, β-oxidation, the malate-aspartate shuttle, the Tricarboxylic Acid Cycle (TCA) cycle, the electron transport chain, NADPH production, as well as the production of glutamate. New insights into potential pathways involved in metabolic aspects of successful aging have been obtained by the identification of key proteins through which the NMR brain responds and adapts to the aging process and how the NMR brain adapted to resist age-related degeneration. This study examines the changes in the proteome and phosphoproteome in the brain of the naked mole-rat aged 2-24 years. We identified 13 proteins (labeled in red) with altered expression and/or phosphorylation levels that are conceivably associated with sustained metabolic functions in the oldest NMRs that may promote a sustained health span and life span.
The Oxidative Stress Theory of Aging has had tremendous impact in research involving aging and ag... more The Oxidative Stress Theory of Aging has had tremendous impact in research involving aging and age-associated diseases including those that affect the nervous system. With over half a century of accrued data showing both strong support for and against this theory, there is a need to critically evaluate the data acquired from common biomedical research models, and to also diversify the species used in studies involving this proximate theory. One approach is to follow Orgel's second axiom that "evolution is smarter than we are" and judiciously choose species that may have evolved to live with chronic or seasonal oxidative stressors. Vertebrates that have naturally evolved to live under extreme conditions (e.g., anoxia or hypoxia), as well as those that undergo daily or seasonal torpor encounter both decreased oxygen availability and subsequent reoxygenation, with concomitant increased oxidative stress. Due to its high metabolic activity, the brain may be particularly vulnerable to oxidative stress. Here, we focus on oxidative stress responses in the brains of certain mouse models as well as extremophilic vertebrates. Exploring the naturally evolved biological tools utilized to cope with seasonal or environmentally variable oxygen availability may yield key information pertinent for how to deal with oxidative stress and thereby mitigate its propagation of age-associated diseases.
Biochimica et Biophysica Acta (BBA) - Molecular Basis of Disease, 2014
The naked mole-rat maintains robust proteostasis and high levels of proteasome-mediated proteolys... more The naked mole-rat maintains robust proteostasis and high levels of proteasome-mediated proteolysis for most of its exceptional (~31 years) life span. Here, we report that the highly active proteasome from the naked mole-rat liver resists attenuation by a diverse suite of proteasome-specific small molecule inhibitors. Moreover, mouse, human, and yeast proteasomes exposed to the proteasome-depleted, naked mole-rat cytosolic fractions, recapitulate the observed inhibition resistance, and mammalian proteasomes also show increased activity. Gel filtration coupled with mass spectrometry and atomic force microscopy indicates that these traits are supported by a protein factor that resides in the cytosol. This factor interacts with the proteasome and modulates its activity. Although Heat shock protein 72 kDa (HSP72) and Heat shock protein 40 kDa (Homolog of bacterial DNAJ1) (HSP40(Hdj1)) are among the constituents of this factor, the observed phenomenon, such as increasing peptidase activity and protecting against inhibition cannot be reconciled with any known chaperone functions. This novel function may contribute to the exceptional protein homeostasis in the naked mole-rat and allow it to successfully defy aging.
Rapamycin, an allosteric inhibitor of the mTOR kinase, increases longevity in mice in a sex-speci... more Rapamycin, an allosteric inhibitor of the mTOR kinase, increases longevity in mice in a sex-specific manner. In contrast to the widely accepted theory that a loss of proteasome activity is detrimental to both life- and healthspan, biochemical studies in vitro reveal that rapamycin inhibits 20S proteasome peptidase activity. We tested if this unexpected finding is also evident after chronic rapamycin treatment in vivo by measuring peptidase activities for both the 26S and 20S proteasome in liver, fat, and brain tissues of old, male and female mice fed encapsulated chow containing 2.24 mg/kg (14 ppm) rapamycin for 6 months. Further we assessed if rapamycin altered expression of the chaperone proteins known to interact with the proteasome-mediated degradation system (PMDS), heat shock factor 1 (HSF1), and the levels of key mTOR pathway proteins. Rapamycin had little effect on liver proteasome activity in either gender, but increased proteasome activity in female brain lysates and lower...
The longest-lived rodent, the naked mole-rat (Bathyergidae; Heterocephalus glaber), maintains rob... more The longest-lived rodent, the naked mole-rat (Bathyergidae; Heterocephalus glaber), maintains robust health for at least 75% of its 32 year lifespan, suggesting that the decline in genomic integrity or protein homeostasis routinely observed during aging, is either attenuated or delayed in this extraordinarily long-lived species. The ubiquitin proteasome system (UPS) plays an integral role in protein homeostasis by degrading oxidatively-damaged and misfolded proteins. In this study, we examined proteasome activity in naked mole-rats and mice in whole liver lysates as well as three subcellular fractions to probe the mechanisms behind the apparently enhanced effectiveness of UPS. We found that when compared with mouse samples, naked mole-rats had significantly higher chymotrypsin-like (ChT-L) activity and a twofold increase in trypsin-like (T-L) in both whole lysates as well as cytosolic fractions. Native gel electrophoresis of the whole tissue lysates showed that the 20S proteasome was more active in the longer-lived species and that 26S proteasome was both more active and more populous. Western blot analyses revealed that both 19S subunits and immunoproteasome catalytic subunits are present in greater amounts in the naked mole-rat suggesting that the observed higher specific activity may be due to the greater proportion of immunoproteasomes in livers of healthy young adults. It thus appears that proteasomes in this species are primed for the efficient removal of stress-damaged proteins. Further characterization of the naked mole-rat proteasome and its regulation could lead to important insights on how the cells in these animals handle increased stress and protein damage to maintain a longer health in their tissues and ultimately a longer life.
The ubiquitin-proteasome pathway plays a crucial role in regulation of intracellular protein turn... more The ubiquitin-proteasome pathway plays a crucial role in regulation of intracellular protein turnover. Proteasome, the central protease of the pathway, encompasses multisubunit assemblies sharing a common catalytic core supplemented by regulatory modules and localizing to different subcellular compartments. To better comprehend age-related functions of the proteasome we surveyed content, composition and catalytic properties of the enzyme in cytosolic, microsomal and nuclear fractions. obtained from mouse livers subjected to organismal aging. We found that during aging subunit composition and subcellular distribution of proteasomes changed without substantial alterations in the total level of core complexes. We observed that the general decline in proteasomes functions was limited to nuclear and cytosolic compartments. Surprisingly, the observed changes in activity and specificity were linked to the amount of the activator module and distinct composition of the catalytic subunits. In contrast, activity, specificity and composition of the microsomal-associated proteasomes remained mostly unaffected by aging; however their relative contribution to the total activity was substantially elevated. Unexpectedly, the nuclear proteasomes were affected most profoundly by aging possibly triggering significant changes in cellular signaling and transcription. Collectively, the data indicate an age-related refocusing of proteasome from the compartment specific functions towards general protein maintenance.
Proteasome is a major protease of the ubiquitin-proteasome pathway involved in the regulation of ... more Proteasome is a major protease of the ubiquitin-proteasome pathway involved in the regulation of practically all intracellular biochemical processes. The enzyme core is created by a heteromultimer of complex architecture built with multiple subunits arranged into a tube-like structure. The multiple active sites of diverse peptidase specificity are hidden inside the tube. Access to the interior is guarded by a gate formed by the N-termini of specialized subunits and by the attachment of additional multisubunit protein complexes controlling the enzymatic capabilities of the core. Proteasome, due to its Byzantine molecular architecture and equally sophisticated enzymatic mechanism, is by itself a fascinating biophysical object. Recently, the position of the protease advanced from an academically remarkable protein processor to a providential anticancer drug target and futuristic nanomachine. Proteomics studies actively shape our current understanding of the protease and direct the future applications of the proteasome in medicine.
Reactive oxygen species (ROS), by-products of aerobic metabolism, cause oxidative damage to cells... more Reactive oxygen species (ROS), by-products of aerobic metabolism, cause oxidative damage to cells and tissue and not surprisingly many theories have arisen to link ROS-induced oxidative stress to aging and health. While studies clearly link ROS to a plethora of divergent diseases, their role in aging is still debatable. Genetic knock-down manipulations of antioxidants alter the levels of accrued oxidative damage, however, the resultant effect of increased oxidative stress on lifespan are equivocal. Similarly the impact of elevating antioxidant levels through transgenic manipulations yield inconsistent effects on longevity. Furthermore, comparative data from a wide range of endotherms with disparate longevity remain inconclusive. Many long-living species such as birds, bats and mole-rats exhibit high-levels of oxidative damage, evident already at young ages. Clearly, neither the amount of ROS per se nor the sensitivity in neutralizing ROS are as important as whether or not the accrued oxidative stress leads to oxidative-damage-linked ageassociated diseases. In this review we examine the literature on ROS, its relation to disease and the lessons gleaned from a comparative approach based upon species with widely divergent responses. We specifically focus on the longest lived rodent, the naked mole-rat, which maintains good health and provides novel insights into the paradox of maintaining both an extended healthspan and lifespan despite high oxidative stress from a young age.
Biochimica et Biophysica Acta (BBA) - Molecular Basis of Disease, 2015
The naked mole-rat (NMR) is the longest-lived rodent and possesses several exceptional traits: ma... more The naked mole-rat (NMR) is the longest-lived rodent and possesses several exceptional traits: marked cancer resistance, negligible senescence, prolonged genomic integrity, pronounced proteostasis, and a sustained health span. The underlying molecular mechanisms that contribute to these extraordinary attributes are currently under investigation to gain insights that may conceivably promote and extend human health span and lifespan. The ubiquitin-proteasome and autophagy-lysosomal systems play a vital role in eliminating cellular detritus to maintain proteostasis and have been previously shown to be more robust in NMRs when compared with shorterlived rodents. Using a 2-D PAGE proteomics approach, differential expression and phosphorylation levels of proteins involved in proteostasis networks were evaluated in the brains of NMRs in an age-dependent manner. We identified 9 proteins with significantly altered levels and/or phosphorylation states that have key roles involved in proteostasis networks. To further investigate the possible role that autophagy may play in maintaining cellular proteostasis, we examined aspects of the PI3K/Akt/mammalian target of rapamycin (mTOR) axis as well as levels of Beclin-1, LC3-I, and LC3-II in the brain of the NMR as a function of age. Together, these results show that NMRs maintain high levels of autophagy throughout the majority of their lifespan and may contribute to the extraordinary health span of these rodents. The potential of augmenting human health span via activating the proteostasis network will require further studies.
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Papers by Karl Rodriguez