Papers by Stuart Maudsley
Scientific Reports, Oct 1, 2020
is an intrinsically disordered protein that can self-aggregate and plays a major role in Parkinso... more is an intrinsically disordered protein that can self-aggregate and plays a major role in Parkinson's disease (PD). Elevated levels of certain metal ions are found in protein aggregates in neurons of people suffering from PD, and environmental exposure has also been linked with neurodegeneration. Importantly, cellular interactions with metal ions, particularly Ca 2+ , have recently been reported as key for α-synuclein's physiological function at the pre-synapse. Here we study effects of metal ion interaction with α-synuclein at the molecular level, observing changes in the conformational behaviour of monomers, with a possible link to aggregation pathways and toxicity. Using native nano-electrospray ionisation ion mobility-mass spectrometry (nESI-IM-MS), we characterize the heterogeneous interactions of alkali, alkaline earth, transition and other metal ions and their global structural effects on α-synuclein. Different binding stoichiometries found upon titration with metal ions correlate with their specific binding affinity and capacity. Subtle conformational effects seen for singly charged metals differ profoundly from binding of multiply charged ions, often leading to overall compaction of the protein depending on the preferred binding sites. This study illustrates specific effects of metal coordination, and the associated electrostatic charge patterns, on the complex structural space of the intrinsically disordered protein α-synuclein. The intrinsically disordered protein (IDP) α-synuclein (α-syn) lacks a defined, unique structure in its native state and can adopt many different conformations 1. While α-syn is predominantly present in pre-synaptic terminals in the brain, smaller amounts are found throughout the body, e.g. in blood, in the enteric nervous system in the gut, and in heart and muscle tissue 2-6. Therefore, in vivo, the protein needs to adapt to different physiological environments where it experiences various biophysical conditions, such as pH, salt and metal ion concentrations 7-9. These external factors can be a trigger for structural transitions and therefore potentially reshape the conformational space of α-syn 10-13. The protein α-syn can self-associate into oligomers, condensates, protofibrils and eventually mature fibrils which occur in various structural forms 14. Aggregates of α-syn are important components of Lewy bodies, the most common pathological characteristic of Parkinson's disease (PD), found in dopaminergic neurons 15. Brain regions affected by neurodegenerative diseases such as PD or Alzheimer's disease (AD) are found to contain significantly higher concentrations of metal ions such as zinc, iron and copper 16-20. Divalent metal ions are known to play an important role in various biological processes such as transcription regulation, signal modulation and enzyme activation 21-23. Physiologically relevant metals such as Ca 2+ , which controls neurotransmitter release, are now proposed as important modulators of α-syn monomer conformations 8,24,25. While the exact physiological function of α-syn is still under debate, it is believed that it interacts with negatively charged lipids at the pre-synapse and plays a role in vesicle trafficking 8. Metal ions can play an important role in this process, for example the charge distribution of the negatively charged C-terminal region can be profoundly affected by Ca 2+ binding that can modulate subsequent protein-membrane interactions 8. It is well known that variations of the α-syn sequence, e.g. mutations and posttranslational modifications (PTMs), affect its structure and fibrillation behaviour 10,26,27. A key factor that influences the conformational space of IDPs is the effect of charge 28-31. The 140 amino acid long sequence of α-syn contains three separate regions (Supplementary Fig. S1). The first is the N-terminal region, amino acid (aa) 1-60, which has an overall positive charge and adopts an α-helical structure when interacting with, especially negatively charged, biological membranes. The central hydrophobic non-amyloid-β component (NAC) region (aa 61-95) is the part involved in the formation of β-sheets when protein aggregation occurs and fibrils are formed. The C-terminal region (aa 96-140) contains many negatively charged residues and is an important binding region for various metal
Nephrology Dialysis Transplantation, May 1, 2018
INTRODUCTION AND AIMS: Recent studies suggest hypoproteic diet (LPD) supplemented with ketoanalog... more INTRODUCTION AND AIMS: Recent studies suggest hypoproteic diet (LPD) supplemented with ketoanalogues of essential aminoacids (sLPD) to reduce proteinuria. This unicentric prospective interventional trial aimed to assess the effects of sLPD on nephrotic-range proteinuria in patients with Diabetic Kidney Disease (DKD). METHODS: Adult diabetic patients (452) with stable CKD stage 4þ, proteinuria>3g/g creatininuria and SGA A were enrolled in a run-in phase (3 mo), with LPD (0.6g/kg dry ideal bw). Those who proved adherent (92, 64% males, median age 55.7 yrs, 65% on insulin) received sLPD (KetosterilV R , 1 tablet/10kg) for 12mo. Monitoring and treatment followed the Best Practice Guidelines. The primary endpoint was proteinuria during intervention as compared to pre-enrolment. Level of kidney function, blood pressure, blood glucose control and metabolic disturbances of CKD were secondary efficacy variables. Nutrition, inflammation (SGA, BMI, serum albumin, CRP) and compliance were safety parameters. RESULTS: Proteinuria (g/g creatininuria) decreased from 5.2 (5.0-5.2) before enrolment to 1.6 (1.4-1.7), a reduction of 3.5 (-3.8 to-3.4). The rate of decline in eGFR (mL/min-mo) decreased from-0.5 (-0.6 to-0.5) to-0.11 (-0.14 to-0.09) during sLPD. BMI decreased, with no change in glucose control or SGA. Serum albumin (g/dL) significantly increased [4.1 (4.1-4.2) versus 3.9 (3.9-4.0)], while CRP (mg/L) decreased [9 (8-9) versus 14 (13-14)]. CONCLUSIONS: In patients with DKD and severe proteinuria, sLPD was associated with a 69 (63; 82)% reduction in proteinuria. Although ameliorated, BP control, the decline in renal function, BMI and inflammation appeared unrelated to proteinuria, suggesting the role of plurifactorial approach.
American Journal of Physiology-Heart and Circulatory Physiology, 2017
The neuregulin-1 (NRG-1)/receptor tyrosine-protein kinase erbB (ErbB) system is an endothelium-co... more The neuregulin-1 (NRG-1)/receptor tyrosine-protein kinase erbB (ErbB) system is an endothelium-controlled paracrine system modulating cardiac performance and adaptation. Recent studies have indicated that NRG-1 has antifibrotic effects in the left ventricle, which were explained by direct actions on cardiac fibroblasts. However, the NRG-1/ErbB system also regulates the function of macrophages. In this study, we hypothesized that the antifibrotic effect of NRG-1 in the heart is at least partially mediated through inhibitory effects on macrophages. We also hypothesized that the antifibrotic effect of NRG-1 may be active in other organs, such as the skin and lung. First, in a mouse model of angiotensin II (ANG II)-induced myocardial hypertrophy and fibrosis, NRG-1 treatment (20 µg·kg−1·day−1 ip) significantly attenuated myocardial hypertrophy and fibrosis and improved passive ventricular stiffness (4 wk). Interestingly, 1 wk after exposure to ANG II, NRG-1 already attenuated myocardial...
International Journal of Molecular Sciences
Arterial media calcification refers to the pathological deposition of calcium phosphate crystals ... more Arterial media calcification refers to the pathological deposition of calcium phosphate crystals in the arterial wall. This pathology is a common and life-threatening complication in chronic kidney disease, diabetes and osteoporosis patients. Recently, we reported that the use of a TNAP inhibitor, SBI-425, attenuated arterial media calcification in a warfarin rat model. Employing a high-dimensionality unbiased proteomic approach, we also investigated the molecular signaling events associated with blocking arterial calcification through SBI-425 dosing. The remedial actions of SBI-425 were strongly associated with (i) a significant downregulation of inflammatory (acute phase response signaling) and steroid/glucose nuclear receptor signaling (LXR/RXR signaling) pathways and (ii) an upregulation of mitochondrial metabolic pathways (TCA cycle II and Fatty Acid β-oxidation I). Interestingly, we previously demonstrated that uremic toxin-induced arterial calcification contributes to the act...
Journal of Neurochemistry, Jul 1, 2008
In many sensory systems, stimulus sensitivity is dynamically modulated through mechanisms of peri... more In many sensory systems, stimulus sensitivity is dynamically modulated through mechanisms of peripheral adaptation, efferent input, or hormonal action. In this way, responses to sensory stimuli can be optimized in the context of both the environment and the physiological state of the animal. Although the gustatory system critically influences food preference, food intake and metabolic homeostasis, the mechanisms for modulating taste sensitivity are poorly understood. In this study, we report that glucagon-like peptide-1 (GLP-1) signaling in taste buds modulates taste sensitivity in behaving mice. We find that GLP-1 is produced in two distinct subsets of mammalian taste cells, while the GLP-1 receptor is expressed on adjacent intragemmal afferent nerve fibers. GLP-1 receptor knockout mice show dramatically reduced taste responses to sweeteners in behavioral assays, indicating that GLP-1 signaling normally acts to maintain or enhance sweet taste sensitivity. A modest increase in citric acid taste sensitivity in these knockout mice suggests GLP-1 signaling may modulate sour taste, as well. Together, these findings suggest a novel paracrine mechanism for the regulation of taste function.
The FASEB Journal, May 1, 2022
Vitamins and hormones, 2017
Age-related neurodegenerative diseases, such as Alzheimer&#39... more Age-related neurodegenerative diseases, such as Alzheimer's disease, will represent one of the largest future burdens on worldwide healthcare systems due to the increasing proportion of elderly in our society. As deficiencies in neurotrophins are implicated in the pathogenesis of many age-related neurodegenerative disorders, it is reasonable to consider that global neurotrophin resistance may also become a major healthcare threat. Central nervous system networks are effectively maintained through aging by neuroprotective and neuroplasticity signaling mechanisms which are predominantly controlled by neurotrophin receptor signaling. Neurotrophin receptors are single pass receptor tyrosine kinases that form dimeric structures upon ligand binding to initiate cellular signaling events that control many protective and plasticity-related pathways. Declining functionality of the neurotrophin ligand-receptor system is considered one of the hallmarks of neuropathological aging. Therefore, it is imperative to develop effective therapeutic strategies to contend with this significant issue. While the therapeutic applications of cognate ligands for neurotrophin receptors are limited, the development of nonpeptidergic, small-molecule ligands can overcome these limitations, and productively regulate this important receptor system with beneficial effects. Using our advanced knowledge of the high-dimensionality complexity of receptor systems, the future generation of precision medicines targeting these systems will be an attainable goal.
Kidney International, May 1, 2022
Current treatment strategies for chronic kidney disease (CKD) mainly focus on controlling risk fa... more Current treatment strategies for chronic kidney disease (CKD) mainly focus on controlling risk factors. Metformin, a first-line drug for type-2 diabetes, exerts beneficial pleiotropic actions beyond its prescribed use and incipient data has revealed protective effects against the development of kidney impairment. This study evaluated the therapeutic efficacy of metformin and canagliflozin, a sodium-glucose cotransporter-2 (SGLT2) inhibitor recently approved by the United States Food and Drug Administration to treat diabetic nephropathy, in slowing the progression of established non-diabetic CKD. Rats with adenine-induced CKD were assigned to different treatment groups to receive either 200 mg/kg metformin, four or five weeks after the start of the adenine diet (established mild-moderate CKD), or 25 mg/kg canagliflozin four weeks after the start of the diet, by daily oral gavage administered during four weeks. Each treatment group was compared to a vehicle group. Chronic adenine dosing resulted in severe CKD in vehicle-treated rats as indicated by a marked rise in serum creatinine levels, a marked decrease in creatinine clearance, and a disturbed mineral metabolism. Metformin, but not canagliflozin, halted functional kidney decline. Additionally, kidneys of metformin-treated animals showed less interstitial area and inflammation as compared to the vehicle group. Proteomic analyses revealed that metformin's kidney-protective effect was associated with the activation of the Hippo signaling pathway, a highly conserved multiprotein kinase cascade that controls tissue development, organ size, cell proliferation, and apoptosis. Thus, metformin demonstrated therapeutic efficacy by halting the progression of established CKD in a rat model.
Neurobiology of Aging, Feb 1, 2019
A large proportion of the population suffers from endocrine disruption, e.g. menopausal women, wh... more A large proportion of the population suffers from endocrine disruption, e.g. menopausal women, which might result in accelerated aging and a higher risk for developing cognitive disorders. Therefore, it is crucial to fully understand the impact of such disruptions on the brain to identify potential therapeutic strategies. Here, we show using resting state functional MRI that ovariectomy and consequent hypothalamus-pituitary-gonadal (HPG) disruption results in the selective dysconnectivity of two discrete brain regions in mice. This effect coincided with cognitive deficits and an underlying pathological molecular phenotype involving an imbalance of neurodevelopmental/neurodegenerative signaling. Furthermore, this quantitative mass spectrometry proteomics-based analysis of molecular signaling patterns further identified a strong involvement of altered dopaminergic functionality (e.g. DAT and predicted upstream regulators DRD3, NR4A2), reproductive signaling (e.g Srd5a2), rotatin expression (rttn), cellular aging (e.g. Rxfp3, Git2), myelination and axogenesis (e.g. Nefl, Mag). With this, we have provided an improved understanding of the impact of HPG dysfunction and highlighted the potential of using a highly translational MRI technique for monitoring these effects on the brain.
Neurology, Dec 17, 2019
Objective To assess the clinical, radiologic, myopathologic, and proteomic findings in a patient ... more Objective To assess the clinical, radiologic, myopathologic, and proteomic findings in a patient manifesting a multisystem proteinopathy due to a homozygous valosin-containing protein gene (VCP) mutation previously reported to be pathogenic in the heterozygous state. Methods We studied a 36-year-old male index patient and his father, both presenting with progressive limb-girdle weakness. Muscle involvement was assessed by MRI and muscle biopsies. We performed whole-exome sequencing and Sanger sequencing for segregation analysis of the identified p.Arg159His VCP mutation. To dissect biological disease signatures, we applied state-of-the-art quantitative proteomics on muscle tissue of the index case, his father, 3 additional patients with VCP-related myopathy, and 3 control individuals. Results The index patient, homozygous for the known p.Arg159His mutation in VCP, manifested a typical VCP-related myopathy phenotype, although with a markedly high creatine kinase value and a relatively early disease onset, and Paget disease of bone. The father exhibited a myopathy phenotype and discrete parkinsonism, and multiple deceased family members on the maternal side of the pedigree displayed a dementia, parkinsonism, or myopathy phenotype. Bioinformatic analysis of quantitative proteomic data revealed the degenerative nature of the disease, with evidence suggesting selective failure of muscle regeneration and stress granule dyshomeostasis. Conclusion We report a patient showing a multisystem proteinopathy due to a homozygous VCP mutation. The patient manifests a severe phenotype, yet fundamental disease characteristics are preserved. Proteomic findings provide further insights into VCP-related pathomechanisms.
Toxins, Jul 21, 2019
Sclerostin is a well-known inhibitor of bone formation that acts on Wnt/β-catenin signaling. This... more Sclerostin is a well-known inhibitor of bone formation that acts on Wnt/β-catenin signaling. This manuscript considers the possible role of sclerostin in vascular calcification, a process that shares many similarities with physiological bone formation. Rats were exposed to a warfarin-containing diet to induce vascular calcification. Vascular smooth muscle cell transdifferentiation, vascular calcification grade, and bone histomorphometry were examined. The presence and/or production of sclerostin was investigated in serum, aorta, and bone. Calcified human aortas were investigated to substantiate clinical relevance. Warfarin-exposed rats developed vascular calcifications in a time-dependent manner which went along with a progressive increase in serum sclerostin levels. Both osteogenic and adipogenic pathways were upregulated in calcifying vascular smooth muscle cells, as well as sclerostin mRNA and protein levels. Evidence for the local vascular action of sclerostin was found both in human and rat calcified aortas. Warfarin exposure led to a mildly decreased bone and mineralized areas. Osseous sclerostin production and bone turnover did not change significantly. This study showed local production of sclerostin in calcified vessels, which may indicate a negative feedback mechanism to prevent further calcification. Furthermore, increased levels of serum sclerostin, probably originating from excessive local production in calcified vessels, may contribute to the linkage between vascular pathology and impaired bone mineralization.
Nephrology Dialysis Transplantation, 2020
Background and Aims CINAC patients present a newly discovered constellation of proximal tubular l... more Background and Aims CINAC patients present a newly discovered constellation of proximal tubular lysosomal lesions which is also observed in patients experiencing calcineurin inhibitor (CNI) nephrotoxicity, suggesting that CINAC is a toxin-induced nephropathy involving calcineurin inhibition. An alternate hypothesis advocates chronic heat stress/dehydration as the major etiological factor for CINAC. Here, we evaluated in rats to what extent heat stress/dehydration versus CNI exposure reflects proximal tubular CINAC histopathology. Method Wistar rats were divided in 3 groups. Group 1 (n=6) was given water ad libitum (control group). Group 2 (n=8) was water deprived for 10 hours per 24h, 5 days/week and were placed in an incubator (37°C) for 30 min/hr of water deprivation. Group 3 (n=8) underwent daily oral gavage with cyclosporine (50mg/kg body weight). Animals were weighed daily and urine was collected at day 3, 17 and 28. After 28 days, rats were sacrificed. Kidneys were collected f...
Molecular Pharmacology, Jul 1, 2015
The fact that over 30% of current pharmaceuticals target heptahelical G protein-coupled receptors... more The fact that over 30% of current pharmaceuticals target heptahelical G protein-coupled receptors (GPCRs) attests to their tractability as drug targets. Although GPCR drug development has traditionally focused on conventional agonists and antagonists, the growing appreciation that GPCRs mediate physiologically relevant effects via both G protein and non-G protein effectors has prompted the search for ligands that can "bias" downstream signaling in favor of one or the other process. Biased ligands are novel entities with distinct signaling profiles dictated by ligand structure, and the potential prospect of biased ligands as better drugs has been pleonastically proclaimed. Indeed, preclinical proof-of-concept studies have demonstrated that both G protein and arrestin pathwayselective ligands can promote beneficial effects in vivo while simultaneously antagonizing deleterious ones. But along with opportunity comes added complexity and new challenges for drug discovery. If ligands can be biased, then ligand classification becomes assay dependent, and more nuanced screening approaches are needed to capture ligand efficacy across several dimensions of signaling. Moreover, because the signaling repertoire of biased ligands differs from that of the native agonist, unpredicted responses may arise in vivo as these unbalanced signals propagate. For any given GPCR target, establishing a framework relating in vitro efficacy to in vivo biologic response is crucial to biased drug discovery. This review discusses approaches to describing ligand efficacy in vitro, translating ligand bias into biologic response, and developing a systemslevel understanding of biased agonism in vivo, with the overall goal of overcoming current barriers to developing biased GPCR therapeutics.
International Journal of Molecular Sciences, May 9, 2023
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
Free Radical Biology and Medicine, Nov 1, 2007
Science, Jan 29, 1999
The Ras-dependent activation of mitogen-activated protein (MAP) kinase pathways by many receptors... more The Ras-dependent activation of mitogen-activated protein (MAP) kinase pathways by many receptors coupled to heterotrimeric guanine nucleotide binding proteins (G proteins) requires the activation of Src family tyrosine kinases. Stimulation of β 2 adrenergic receptors resulted in the assembly of a protein complex containing activated c-Src and the receptor. Src recruitment was mediated by β-arrestin, which functions as an adapter protein, binding both c-Src and the agonist-occupied receptor. β-Arrestin 1 mutants, impaired either in c-Src binding or in the ability to target receptors to clathrin-coated pits, acted as dominant negative inhibitors of β 2 adrenergic receptor–mediated activation of the MAP kinases Erk1 and Erk2. These data suggest that β-arrestin binding, which terminates receptor–G protein coupling, also initiates a second wave of signal transduction in which the “desensitized” receptor functions as a critical structural component of a mitogenic signaling complex.
The FASEB Journal, Apr 1, 2018
Pharmacology & Therapeutics, Jul 1, 2021
Brain, Sep 17, 2015
19 on behalf of the autosomal recessive working group of the EuroEPINOMICS RES Consortium § § See... more 19 on behalf of the autosomal recessive working group of the EuroEPINOMICS RES Consortium § § See Appendix 1. The epileptic encephalopathies are a clinically and aetiologically heterogeneous subgroup of epilepsy syndromes. Most epileptic encephalopathies have a genetic cause and patients are often found to carry a heterozygous de novo mutation in one of the genes associated with the disease entity. Occasionally recessive mutations are identified: a recent publication described a distinct neonatal epileptic encephalopathy (MIM 615905) caused by autosomal recessive mutations in the SLC13A5 gene. Here, we report eight additional patients belonging to four different families with autosomal recessive mutations in SLC13A5. SLC13A5 encodes a high affinity sodium-dependent citrate transporter, which is expressed in the brain. Neurons are considered incapable of de novo synthesis of tricarboxylic acid cycle intermediates; therefore they rely on the uptake of intermediates, such as citrate, to maintain their energy status and neurotransmitter production. The effect of all seven identified mutations (two premature stops and five amino acid substitutions) was studied in vitro, using immunocytochemistry, selective western blot and mass spectrometry. We hereby demonstrate that cells expressing mutant sodium-dependent citrate transporter have a complete loss of citrate uptake due to various cellular loss-of-function mechanisms. In addition, we provide independent proof of the involvement of autosomal recessive SLC13A5 mutations in the development of neonatal epileptic encephalopathies, and highlight teeth hypoplasia as a possible indicator for SLC13A5 screening. All three patients who tried the ketogenic diet responded well to this treatment, and future studies will allow us to ascertain whether this is a recurrent feature in this severe disorder.
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Papers by Stuart Maudsley