Papers by marcela colombres
Acta Neurologica Scandinavica, 2000
Previous studies have indicated that acetylcholinesterase (AChE) promotes amyloid-b-peptide (Ab) ... more Previous studies have indicated that acetylcholinesterase (AChE) promotes amyloid-b-peptide (Ab) ®bril formation and AChE-Ab complexes increase Ab-dependent neurotoxicity. Here we present evidence for the: i) identi®cation of the AChE motif that promotes amyloid formation, ii) in vivo effect of AChE on brain plaque formation, and iii) connection between AChE-Ab neurotoxicity and the Wnt signal transduction pathway. Computer modeling, stereotaxic infusions and cell biological techniques were used to study the above problems. Results indicated that a 3.4 kDa AChE peptide promotes Ab ®bril formation. AChE infusion into rat hippocampus determines the appearance of anti-Ab and thio¯avine-S positive plaques, and AChE-Ab toxicity on hippocampal cultures was blocked by lithium, an activator of the Wnt cascade. We suggest that AChE-Ab/Ab dependent neurotoxicity may result in loss of function of Wnt signaling components, and open the possibility that lithium may be considered as a candidate for therapeutic intervention in Alzheimer's disease pathology.
Nicotinic acetylcholine receptors (nAChRs) contribute significantly to hippocampal function. α7-... more Nicotinic acetylcholine receptors (nAChRs) contribute significantly to hippocampal function. α7-nAChRs are present in presynaptic sites in hippocampal neurons and may influence transmitter release, but the factors that determine their presynaptic localization are unknown. We report here that Wnt-7a, a ligand active in the canonical Wnt signaling pathway, induces dissociation of the adenomatous polyposis coli (APC) protein from the β-catenin cytoplasmic complex and the interaction of APC with α7-nAChRs in hippocampal neurons. Interestingly, Wnt-7a induces the relocalization of APC to membranes, clustering of APC in neurites, and coclustering of APC with different, presynaptic protein markers. Wnt-7a also increases the number and size of coclusters of α7-nAChRs and APC in presynaptic terminals. These short-term changes in α7-nAChRs occur in the few minutes after ligand exposure and involve translocation to the plasma membrane without affecting total receptor levels. Longer-term e...
mitochondrial dysfunction, energy imbalance, oxidative stress, and activation of pro-death signal... more mitochondrial dysfunction, energy imbalance, oxidative stress, and activation of pro-death signaling. Recent studies of human postmortem brains linked the molecular and pathological lesions in AD to major impairments in: 1) insulin and insulin-like growth factor (IGF) gene expression; 2) expression and function of the insulin and IGF receptors; 3) neuronal survival signaling; and 4) acetylcholine homeostasis, and showed each of these abnormalities increases with progression of AD. The coexistence of insulin/IGF deficiency and insulin/IGF resistance suggests that AD represents a brain-specific form of diabetes, i.e. Type 3 diabetes. We generated an experimental animal model in which intracerebral Streptozotocin (ic-STZ) was used to deplete brain and not pancreatic insulin/IGF, and produce neurodegeneration that is similar to human AD. The ic-STZ-injected rats did not have hyperglycemia, and pancreatic architecture and insulin immunoreactivity were similar to control, yet their brains were reduced in size and exhibited neurodegeneration with cell loss, gliosis, and increased immunoreactivity for p53, activated glycogen synthase kinase 3, phospho-tau, ubiquitin, and amyloid-. Real time quantitative RT-PCR studies demonstrated that the ic-STZ-treated brains had significantly reduced expression of genes corresponding to neurons, oligodendroglia, and choline acetyltransferase, and increased expression of genes encoding glial fibrillary acidic protein, microglia-specific proteins, acetylcholinesterase, tau, and amyloid precursor protein. These abnormalities were associated with reduced expression of genes encoding insulin, IGF-II, insulin receptor, IGF-I receptor, and insulin receptor substrate-1, and reduced ligand binding to the insulin and IGF-II receptors. Further studies showed that treatment with peroxisome-proliferator activated receptor agonists effectively prevented the ic-STZ-induced Type 3 diabetes and preserved learning and memory. These results demonstrate that many of the characteristic features of AD-type neurodegeneration can be produced experimentally by selectively impairing insulin/IGF functions together with increasing oxidative stress, and support our hypothesis that AD represents a neuro-endocrine disorder associated with brain-specific perturbations in insulin and IGF signaling mechanisms, i.e. Type 3 diabetes. The results also suggest that early treatment with insulin sensitizer agent may prevent or reduce the severity of AD.
Bmc Genomics, 2010
Background: The importance of in silico predictions for understanding cellular processes is now w... more Background: The importance of in silico predictions for understanding cellular processes is now widely accepted, and a variety of algorithms useful for studying different biological features have been designed. In particular, the prediction of cis regulatory modules in non-coding human genome regions represents a major challenge for understanding gene regulation in several diseases. Recently, studies of the Wnt signaling pathway revealed a connection with neurodegenerative diseases such as Alzheimer's. In this article, we construct a classification tool that uses the transcription factor binding site motifs composition of some gene promoters to identify new Wnt/β-catenin pathway target genes potentially involved in brain diseases. Results: In this study, we propose 89 new Wnt/β-catenin pathway target genes predicted in silico by using a method based on multiple Classification and Regression Tree (CART) analysis. We used as decision variables the presence of transcription factor binding site motifs in the upstream region of each gene. This prediction was validated by RT-qPCR in a sample of 9 genes. As expected, LEF1, a member of the T-cell factor/lymphoid enhancer-binding factor family (TCF/LEF1), was relevant for the classification algorithm and, remarkably, other factors related directly or indirectly to the inflammatory response and amyloidogenic processes also appeared to be relevant for the classification. Among the 89 new Wnt/β-catenin pathway targets, we found a group expressed in brain tissue that could be involved in diverse responses to neurodegenerative diseases, like Alzheimer's disease (AD). These genes represent new candidates to protect cells against amyloid β toxicity, in agreement with the proposed neuroprotective role of the Wnt signaling pathway. Conclusions: Our multiple CART strategy proved to be an effective tool to identify new Wnt/β-catenin pathway targets based on the study of their regulatory regions in the human genome. In particular, several of these genes represent a new group of transcriptional dependent targets of the canonical Wnt pathway. The functions of these genes indicate that they are involved in pathophysiology related to Alzheimer's disease or other brain disorders.
Genome-wide identification of new Wnt/β-catenin target genes in the human genome using CART method
Alzheimer's disease (AD) is the m... more Alzheimer's disease (AD) is the most prevalent neurodegenerative disease in the growing population of elderly people. Synaptic dysfunction is an early manifestation of AD. The cellular mechanism by which beta-amyloid peptide (Abeta) affects synapses remains unclear. Abeta oligomers target synapses in cultured rat hippocampal neurons suggesting that they play a key role in the regulation of synapses. The aim of this work is to study the effect of Abeta oligomers on the central synapses and the possible role of the Wnt signaling pathway in preventing the Abeta effects. We used rat hippocampal neurons, immunofluorescence and western blot procedures to detect synaptic proteins. Abeta oligomers induced a reduction of the postsynaptic density protein 95 (PSD-95) and the NMDA glutamate receptors. We found that Wnt-5a, a noncanonical Wnt ligand, prevents the decrease triggered by Abeta oligomers in the glutamate receptor and PSD-95. Altogether, our results suggest that Abeta oligomers decrease the synaptic responses by affecting the postsynaptic region at different levels. The Wnt signaling activation prevents synaptic damage induced by Abeta, which raises the possibility of a new therapeutic intervention for the treatment of synaptic changes observed in AD.
The soft-rot fungus Penicillium purpurogenum secretes to the culture medium a variety of enzymes ... more The soft-rot fungus Penicillium purpurogenum secretes to the culture medium a variety of enzymes related to xylan biodegradation, among them three acetyl xylan esterases (AXE I, II and III). AXE II has 207 amino acids; it belongs to family 5 of the carbohydrate esterases and its structure has been determined by X-ray crystallography at 0.9 Å resolution (PDB 1G66). The enzyme possesses the a/b hydrolase fold and the catalytic triad typical of serine esterases (Ser90, His187 and Asp175). AXE II can hydrolyze esters of a large variety of alcohols, but it is restricted to short chain fatty acids. An analysis of its threedimensional structure shows that a loop that covers the active site may be responsible for this strict specificity. Cutinase, an enzyme that hydrolyzes esters of long chain fatty acids and shows a structure similar to AXE II, lacks this loop. In order to generate an AXE II with this broader specificity, the preparation of a mutant lacking residues involving this loop (Gly104 to Ala114) was proposed. A set of molecular simulation experiments based on a comparative model of the mutant enzyme predicted a stable structure. Using site-directed mutagenesis, the loop's residues have been eliminated from the AXE II cDNA. The mutant protein has been expressed in Aspergillus nidulans A722 and Pichia pastoris, and it is active towards a range of fatty acid esters of up to at least 14 carbons. The availability of an esterase with broader specificity may have biotechnological applications for the synthesis of sugar esters.
Recent evidence supports a role of the Wnt pathway in neurodegenerative disorders such as Alzheim... more Recent evidence supports a role of the Wnt pathway in neurodegenerative disorders such as Alzheimer's disease (AD). A relationship between amyloid-b-peptide (Ab)-induced neurotoxicity and a decrease in the cytoplasmatic levels of b-catenin has been proposed. Also, the inhibition of glycogen synthase kinase (GSK-3b), a central modulator of the pathway, protects rat hippocampal neurons from Ab-induced damage. Interestingly, during the progression of AD, it has been described that active GSK-3b is found in neuronal cell bodies and neurites, co-localizing with preneurofibrillary tangles observed in disease brains. Since Ab oligomers are associated with the post-synaptic region and we have found that the non-canonical Wnt signaling modulates PSD-95 and glutamate receptors, we propose that the synaptic target for Ab oligomers in AD is the postsynaptic region and at the molecular level is the non-canonical Wnt signaling pathway. Altogether, our evidence suggests that a sustained loss of Wnt signaling function may be involved in the Ab-dependent neurodegeneration observed in AD brains and that the activation of this signaling pathway could be of therapeutic interest in AD.
Alzheimer's and Dementia, Jan 1, 2006
… kinase 3 (GSK-3) and its …, Jan 1, 2006
2 GLYCOGEN SYNTHASE KINASE 3b (GSK-3b) A KEY SIGNALING ENZYME: A DEVELOPMENTAL NEUROBIOLOGICAL PE... more 2 GLYCOGEN SYNTHASE KINASE 3b (GSK-3b) A KEY SIGNALING ENZYME: A DEVELOPMENTAL NEUROBIOLOGICAL PERSPECTIVE Nibaldo C. Inestrosa, Ginny Farías, and Marcela Colombres Centro de Regulación Celular y Patología Joaquín V. Luco(CRCP), MIFAB, Facultad de ...
… & Dementia: The …, Jan 1, 2006
Alzheimer's & Dementia: The Journal of the Alzheimer's Asso... more Alzheimer's & Dementia: The Journal of the Alzheimer's Association, Volume 2, Issue 3, Pages S476, July 2006, Authors:Marcela Colombres; Maite Bejide; Nibaldo Inestrosa. ...
… Kinase 3 (GSK‐3) and Its …, Jan 1, 2006
Glycogen Synthase Kinase 3β (GSK-3β) a Key Signaling Enzyme: A Developmental Neurobiological Pers... more Glycogen Synthase Kinase 3β (GSK-3β) a Key Signaling Enzyme: A Developmental Neurobiological Perspective-Glycogen Synthase Kinase 3 (GSK-3) and Its Inhibitors: Drug Discovery and Development-Inestrosa-Wiley Online Library
Background: The importance of in silico predictions for understanding cellular processes is now w... more Background: The importance of in silico predictions for understanding cellular processes is now widely accepted, and a variety of algorithms useful for studying different biological features have been designed. In particular, the prediction of cis regulatory modules in non-coding human genome regions represents a major challenge for understanding gene regulation in several diseases. Recently, studies of the Wnt signaling pathway revealed a connection with neurodegenerative diseases such as Alzheimer's. In this article, we construct a classification tool that uses the transcription factor binding site motifs composition of some gene promoters to identify new Wnt/β-catenin pathway target genes potentially involved in brain diseases.
Recent trends in the …, Jan 1, 2005
... Nicolet, Y., Lockridge, 0., Masson, P., Fontecilla-Camps, JC and Nachon, F.(2003) Crystal str... more ... Nicolet, Y., Lockridge, 0., Masson, P., Fontecilla-Camps, JC and Nachon, F.(2003) Crystal structure of human butyrylcholinesterase and of its ... Reyes, AE, Perez, DR, Alvarez, A., Garrido, J., Gentry, MK, Doctor, BP and Inestrosa, NC (1997) A monoclonal antibody against ...
BMC …, Jan 1, 2010
Background: The importance of in silico predictions for understanding cellular processes is now w... more Background: The importance of in silico predictions for understanding cellular processes is now widely accepted, and a variety of algorithms useful for studying different biological features have been designed. In particular, the prediction of cis regulatory modules in non-coding human genome regions represents a major challenge for understanding gene regulation in several diseases. Recently, studies of the Wnt signaling pathway revealed a connection with neurodegenerative diseases such as Alzheimer's. In this article, we construct a classification tool that uses the transcription factor binding site motifs composition of some gene promoters to identify new Wnt/β-catenin pathway target genes potentially involved in brain diseases.
Journal of computer- …, Jan 1, 2008
The soft-rot fungus Penicillium purpurogenum secretes to the culture medium a variety of enzymes ... more The soft-rot fungus Penicillium purpurogenum secretes to the culture medium a variety of enzymes related to xylan biodegradation, among them three acetyl xylan esterases (AXE I, II and III). AXE II has 207 amino acids; it belongs to family 5 of the carbohydrate esterases and its structure has been determined by X-ray crystallography at 0.9 Å resolution (PDB 1G66). The enzyme possesses the a/b hydrolase fold and the catalytic triad typical of serine esterases (Ser90, His187 and Asp175). AXE II can hydrolyze esters of a large variety of alcohols, but it is restricted to short chain fatty acids. An analysis of its threedimensional structure shows that a loop that covers the active site may be responsible for this strict specificity. Cutinase, an enzyme that hydrolyzes esters of long chain fatty acids and shows a structure similar to AXE II, lacks this loop. In order to generate an AXE II with this broader specificity, the preparation of a mutant lacking residues involving this loop (Gly104 to Ala114) was proposed. A set of molecular simulation experiments based on a comparative model of the mutant enzyme predicted a stable structure. Using site-directed mutagenesis, the loop's residues have been eliminated from the AXE II cDNA. The mutant protein has been expressed in Aspergillus nidulans A722 and Pichia pastoris, and it is active towards a range of fatty acid esters of up to at least 14 carbons. The availability of an esterase with broader specificity may have biotechnological applications for the synthesis of sugar esters.
Journal of cellular …, Jan 1, 2009
Journal of cellular …, Jan 1, 2008
Wnt factors are secreted ligands that affect different aspects of the nervous system behavior lik... more Wnt factors are secreted ligands that affect different aspects of the nervous system behavior like neurodevelopment, synaptogenesis and neurodegeneration. In different model systems, Wnt signaling has been demonstrated to be regulated by heparan sulfate proteoglycans (HSPGs). Whether HSPGs modulate Wnt signaling in the context of neuronal behavior is currently unknown. Here we demonstrate that activation of Wnt signaling with the endogenous ligand Wnt-7a results in an increased of neurite outgrowth in the neuroblastoma N2a cell line. Interestingly, heparin induces glycogen synthase kinase-3b (GSK-3b) inhibition, b-catenin stabilization and morphological differentiation in both N2a cells and in rat primary hippocampal neuronal cultures. We also show that heparin modulates Wnt-3a-induced stabilization of b-catenin. Several extracellular matrix and membrane-attached HSPGs were found to be expressed in both in vitro neuronal models. Changes in the expression of specific HSPGs were observed upon differentiation of N2a cells. Taken together, our findings suggest that HSPGs may modulate canonical Wnt signaling for neuronal morphogenesis.
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Papers by marcela colombres