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- Title
- THE ENDOCYTIC PROTEIN NUMB REGULATES APP METABOLISM AND NOTCH SIGNALING: IMPLICATIONS FOR ALZHEIMER'S DISEASE.
- Creator
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Kyriazis, George, Chan, Sic, University of Central Florida
- Abstract / Description
-
Increased production of amyloid beta (A-beta) peptide, via altered proteolytic cleavage of amyloid protein precursor (APP), and abnormalities in neuronal calcium homeostasis play central roles in the pathogenesis of Alzheimer's disease (AD). Notch1, a membrane receptor that controls cell fate decisions during development of the nervous system, has been linked to AD because it is a substrate for the gamma-secretase protein complex in which mutations cause early-onset inherited AD. Numb is...
Show moreIncreased production of amyloid beta (A-beta) peptide, via altered proteolytic cleavage of amyloid protein precursor (APP), and abnormalities in neuronal calcium homeostasis play central roles in the pathogenesis of Alzheimer's disease (AD). Notch1, a membrane receptor that controls cell fate decisions during development of the nervous system, has been linked to AD because it is a substrate for the gamma-secretase protein complex in which mutations cause early-onset inherited AD. Numb is an evolutionarily conserved endocytic adapter involved in the internalization of transmembrane receptors. Mammals produce four Numb isoforms that differ in two functional domains, a phosphotyrosine-binding domain (PTB) and a proline-rich region (PRR). Recent studies showed that the PTB domain of Numb interacts with the cytoplasmic tails of APP and Notch but the functional relevance of these interactions with respect to AD pathogenesis is not clear. In the current studies, we proposed to investigate the biological consequences of the interaction of the Numb proteins with APP and Notch in neural cells stably overexpressing each of the four human Numb proteins. In the first part of our studies, we found that expression of the Numb isoforms lacking the insert in the PTB (SPTB-Numb) caused the abnormal accumulation of cellular APP in the early endosomes, and increased the levels of C-terminal APP fragments and A-beta. By contrast, expression of the Numb isoforms with the insert in PTB (LPTB-Numb) leads to the depletion of cellular APP and coincides with significantly lower production of APP derivatives and A-beta. The contrasting effects of the Numb isoforms on APP metabolism were not attributed to differences in the expression of APP nor the activities of the various APP-processing secretases. In the second part of our studies, we found that expression of SPTB-Numb protein enhances neuronal vulnerability to serum deprivation-induced cell death by a mechanism involving the dysregulation of cellular calcium homeostasis. Neural cells expressing SPTB-Numb exhibited enhanced Notch activity, which markedly upregulated the expression of transient receptor potential canonical 6 (TRPC6) channels enhancing calcium entry in response to store depletion. We also found that serum deprivation increased TRPC6 expression, mediating the serum deprivation-induced death in neural cells. Interestingly, expression of LPTB-Numb protein suppressed serum deprivation-induced activation of Notch and the subsequent upregulation of TRPC6 and cell death. Finally, we showed that the Numb proteins differentially impact Notch activation by altering the endocytic trafficking and processing of Notch. Taken together, these studies demonstrate that aberrant expression of the Numb proteins may influence APP metabolism and Notch-mediated cellular responses to injury by altering their endocytic trafficking and processing.
Show less - Date Issued
- 2008
- Identifier
- CFE0002233, ucf:47917
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0002233
- Title
- ELECTROCONVULSIVE SHOCK AMELIORATES DISEASE PROCESSES AND EXTENDS SURVIVAL IN HUNTINGTON MUTANT MICE.
- Creator
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Baharani, Akanksha, Chan, Sic L., University of Central Florida
- Abstract / Description
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ABSTRACT Huntington's disease (HD) is a devastating autosomal dominantly inherited neurological disorder caused by an abnormal expansion of CAG trinucleotide repeats in the gene coding for the N-terminal region of the huntingtin (Htt) protein, which leads to the formation of a polyglutamine stretch. The greater the CAG repeats, the earlier the onset of the disease. The polyglutamine stretch destabilizes the Htt protein leading to misfolding, abnormal processing, aggregation, and inclusion...
Show moreABSTRACT Huntington's disease (HD) is a devastating autosomal dominantly inherited neurological disorder caused by an abnormal expansion of CAG trinucleotide repeats in the gene coding for the N-terminal region of the huntingtin (Htt) protein, which leads to the formation of a polyglutamine stretch. The greater the CAG repeats, the earlier the onset of the disease. The polyglutamine stretch destabilizes the Htt protein leading to misfolding, abnormal processing, aggregation, and inclusion formation. Mutant Htt protein is believed to damage and kill neurons in the striatum by a mechanism involving increased oxidative and metabolic stress, and impaired adaptive cellular stress responses. A large number of abnormalities have been reported in HD, including transcription deficits, energy impairment, excitotoxicity, and lack of trophic support. Reduced trophic support contributes importantly to striatal degeneration in human HD. Specifically, brain-derived neurotrophic factor (BDNF) expression is reduced in patients with HD. BDNF is also decreased in brain tissue from mice transgenic for mutant Htt. BDNF levels influences the onset and the severity of motor dysfunction in HD mice. In addition to BDNF, levels of the molecular chaperones heat shock proteins (Hsp40 and 70) decrease progressively in HD brain. Hsp70 is a highly stress-inducible member of a chaperone family of proteins that functions to prevent misfolding and aggregation of newly synthesized mutant proteins and stress-denatured proteins. Hsps appear to play a critical role in HD since expression of active heat shock factor HSF1, a transcription factor responsible for the induction of Hsps, markedly reduces polyglutamine aggregate formation in both cell and mouse models. Many efforts have been made to develop preventive treatments for HD because of the strong genetic link and a freely available genetic test to identify individuals at risk. At present, only symptomatic therapy is available and effective therapeutic approaches to slow the disease process have yet to be developed. Previous studies have shown that electroconvulsive shock (ECS) induces the production of growth factors including BDNF and the molecular chaperones HSP40 and HSP70. Because ECS can stimulate the production of neuroprotective proteins, we determined whether ECS treatment could slow the progressive nature of the disease process and provide a therapeutic benefit in a mouse model of HD. ECS or sham treatment was administered to male N171-82Q Htt mutant mice. End points measured included motor function, striatal and cortical pathology, and levels of neurotrophic factors, protein chaperones, and proteins involved in synaptic plasticity. ECS treatment delayed the onset of motor symptoms, reduced body weight loss and extended the survival of HD mice. Striatal neurodegeneration was attenuated and levels of neurotrophic factors, protein chaperones and mitochondria-stabilizing protein were elevated in striatal cells of ECS-treated compared to sham-treated HD mice. Our findings suggest that ECS can increase the resistance of neurons to mutant huntingtin resulting in improved functional outcome and extended survival. The potential of ECS as a treatment for HD patients merits further consideration.
Show less - Date Issued
- 2010
- Identifier
- CFE0003486, ucf:48981
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0003486
- Title
- "ACETAZOLAMIDE-INDUCED DECREASE OF APICAL FLUID FLOW IN CHOROID PLEXUS IS INDEPENDENT OF THE CONCOMITANT CHANGES IN AQUAPORIN-1 EXPRESSION".
- Creator
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Ameli, Pouya, Chan, Sic, University of Central Florida
- Abstract / Description
-
Acetazolamide (AZA), the only drug approved for treatment of hydrocephalus, is effective in only 25-30% of patients while its effect on fluid flow in the choroid plexus (CP) is unknown. The drug reversibly inhibits Aquaporin 4 (AQP4), the most highly expressed "water pore" in the brain, and it is postulated that it reduces cerebrospinal fluid (CSF) production by modulating AQP1 (mostly found in the apical membrane of the CP). In this study, we sought to elucidate the effect of AZA on AQP1 and...
Show moreAcetazolamide (AZA), the only drug approved for treatment of hydrocephalus, is effective in only 25-30% of patients while its effect on fluid flow in the choroid plexus (CP) is unknown. The drug reversibly inhibits Aquaporin 4 (AQP4), the most highly expressed "water pore" in the brain, and it is postulated that it reduces cerebrospinal fluid (CSF) production by modulating AQP1 (mostly found in the apical membrane of the CP). In this study, we sought to elucidate the effect of AZA on AQP1 and fluid flow in CP. Primary CP culture from p10 Sprague-Dawley rats and TRCSF-B cell line were grown on Transwell permeable supports, treated with 100uM AZA or 100uM Vinpocetine (previously shown to increase AQP1 levels), and tested by: a) Fluid assays using TRITC-labeled Dextran to assay direction and extent of fluid flow; b) Immunoblot, Immunocytochemistry (ICC), and RT-PCR for AQP1 expression. Immnoblots and ICC analyses showed that AQP1 protein levels decrease in a delayed manner (lowest at 12 hours) with AZA treatment. The reduction in AQP1 protein was transient and preceded by a reduction in mRNA levels (lowest at 6 hours). Transwell fluid assays indicate a shift in fluid flow at 2 hours, prior to the changes in AQP1 mRNA or protein. Alteration of fluid flow by AZA (in both primary culture and TR-CSFB) is similar to Vinpocetine's effect in primary culture. Together with drug-induced alterations in AQP1 levels, these data suggest independent mechanisms behind fluid flow and AQP1 expression.
Show less - Date Issued
- 2010
- Identifier
- CFE0003501, ucf:48935
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0003501
- Title
- Mechanisms of Alpha-Synuclein-Induced Neurodegenertaion in Parkinson's Disease and Stroke.
- Creator
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Belal, Cherine, Chan, Sic, Ebert, Steven, Self, William, Teter, Kenneth, University of Central Florida
- Abstract / Description
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Parkinson's disease (PD) is a debilitating neurodegenerative disorder affecting one million Americans. Despite its social and economic impact, the pathological cascades that lead to neuron dysfunction and degeneration in PD are poorly understood. Endoplasmic reticulum (ER) stress has been implicated as an initiator or contributing factor in neurodegenerative diseases including PD. The ER is an organelle central to protein folding and intracellular Ca2+ homeostasis. Perturbations of these...
Show moreParkinson's disease (PD) is a debilitating neurodegenerative disorder affecting one million Americans. Despite its social and economic impact, the pathological cascades that lead to neuron dysfunction and degeneration in PD are poorly understood. Endoplasmic reticulum (ER) stress has been implicated as an initiator or contributing factor in neurodegenerative diseases including PD. The ER is an organelle central to protein folding and intracellular Ca2+ homeostasis. Perturbations of these functions result in ER stress and upregulation of ER stress proteins, of which some have been implicated in counteracting ER stress-induced cell death. The mechanisms that lead to ER stress and how ER stress proteins contribute to the degenerative cascades remain unclear but their understanding is critical to devising effective therapies for PD. Both the accumulation of mutant a-synuclein (aSyn), which causes an inherited form of PD, and the inhibition of mitochondrial complex I function by PD-inducing neurotoxin lead to ER stress. The critical involvement of ER stress in experimental models of PD supports its potential relevance to PD pathogenesis and led us to test the hypothesis whether the homocysteine-inducible ER protein (Herp), an ubiquitin-like domain (UBD) containing ER-resident protein, can counteract mutant Alpha Syn- and neurotoxin- induced pathological cascades.
Show less - Date Issued
- 2011
- Identifier
- CFE0004470, ucf:49310
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0004470
