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Huntingtin Protein (huntingtin + protein)
Selected AbstractsBimEL as a possible molecular link between proteasome dysfunction and cell death induced by mutant huntingtinEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 11 2010Rebecca Leon Abstract Huntington's disease (HD) is a devastating neurodegenerative disorder caused by an expanded polyglutamine repeat within the N-terminus of the huntingtin protein. It is characterized by a selective loss of medium spiny neurons in the striatum. It has been suggested that impaired proteasome function and endoplasmic reticulum (ER) stress play important roles in mutant huntingtin (mHtt)-induced cell death. However, the molecular link involved is poorly understood. In the present study, we identified the essential role of the extra long form of Bim (Bcl-2 interacting mediator of cell death), BimEL, in mHtt-induced cell death. BimEL protein expression level was significantly increased in cell lines expressing the N-terminus of mHtt and in a mouse model of HD. Although quantitative RT-PCR analysis indicated that BimEL mRNA was increased in cells expressing mHtt, we provided evidence showing that, at the post-translational level, phosphorylation of BimEL played a more important role in regulating BimEL expression. Up-regulation of BimEL facilitated the translocation of Bax to the mitochondrial membrane, which further led to cytochrome c release and cell death. On the other hand, knocking down BimEL expression prevented mHtt-induced cell death. Taken together, these findings suggest that BimEL is a key element in regulating mHtt-induced cell death. A model depicting the role of BimEL in linking mHtt-induced ER stress and proteasome dysfunction to cell death is proposed. [source] Cognitive disorders and neurogenesis deficits in Huntington's disease mice are rescued by fluoxetineEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 8 2005Helen E. Grote Abstract Huntington's disease (HD) is a neurodegenerative disorder caused by an expanded CAG trinucleotide repeat encoding an extended polyglutamine tract in the huntingtin protein. Affected individuals display progressive motor, cognitive and psychiatric symptoms (including depression), leading to terminal decline. Given that transgenic HD mice have decreased hippocampal cell proliferation and that a deficit in neurogenesis has been postulated as an underlying cause of depression, we hypothesized that decreased hippocampal neurogenesis contributes to depressive symptoms and cognitive decline in HD. Fluoxetine, a serotonin-reuptake inhibitor commonly prescribed for the treatment of depression, is known to increase neurogenesis in the dentate gyrus of wild-type mouse hippocampus. Here we show that hippocampal-dependent cognitive and depressive-like behavioural symptoms occur in HD mice, and that the administration of fluoxetine produces a marked improvement in these deficits. Furthermore, fluoxetine was found to rescue deficits of neurogenesis and volume loss in the dentate gyrus of HD mice. [source] Increased glucose metabolism and ATP level in brain tissue of Huntington's disease transgenic miceFEBS JOURNAL, Issue 19 2008Judit Oláh Huntington's disease (HD) is a progressive neurodegenerative disorder characterized by multifarious dysfunctional alterations including mitochondrial impairment. In the present study, the formation of inclusions caused by the mutation of huntingtin protein and its relationship with changes in energy metabolism and with pathological alterations were investigated both in transgenic and 3-nitropropionic acid-treated mouse models for HD. The HD and normal mice were characterized clinically; the affected brain regions were identified by immunohistochemistry and used for biochemical analysis of the ATP-producing systems in the cytosolic and the mitochondrial compartments. In both HD models, the activities of some glycolytic enzymes were somewhat higher. By contrast, the activity of glyceraldehyde-3-phosphate dehydrogenase was much lower in the affected region of the brain compared to that of the control. Paradoxically, at the system level, glucose conversion into lactate was enhanced in cytosolic extracts from the HD brain tissue, and the level of ATP was higher in the tissue itself. The paradox could be resolved by taking all the observed changes in glycolytic enzymes into account, ensuing an experiment-based detailed mathematical model of the glycolytic pathway. The mathematical modelling using the experimentally determined kinetic parameters of the individual enzymes and the well-established rate equations predicted the measured flux and concentrations in the case of the control. The same mathematical model with the experimentally determined altered Vmax values of the enzymes did account for an increase of glycolytic flux in the HD sample, although the extent of the increase was not predicted quantitatively. This suggested a somewhat altered regulation of this major metabolic pathway in HD tissue. We then used the mathematical model to develop a hypothesis for a new regulatory interaction that might account for the observed changes; in HD, glyceraldehyde-3-phosphate dehydrogenase may be in closer proximity (perhaps because of the binding of glyceraldehyde-3-phosphate dehydrogenase to huntingtin) with aldolase and engage in channelling for glyceraldehyde-3-phosphate. By contrast to most of the speculation in the literature, our results suggest that the neuronal damage in HD tissue may be associated with increased energy metabolism at the tissue level leading to modified levels of various intermediary metabolites with pathological consequences. [source] Protein misfolding inside cells: The case of huntingtin and Huntington's diseaseIUBMB LIFE, Issue 11 2008Danny M. Hatters Abstract Huntington's disease is one of the several neurodegenerative diseases caused by dominant mutations that expand the number of glutamine codons within an existing poly-glutamine (polyQ) repeat sequence of a gene. An expanded polyQ sequence in the huntingtin gene is known to cause the huntingtin protein to aggregate and form intracellular inclusions as disease progresses. However, the role that polyQ-induced aggregation plays in disease is yet to be fully determined. This review focuses on key questions remaining for how the expanded polyQ sequences affect the aggregation properties of the huntingtin protein and the corresponding effects on cellular machinery. The scope includes the technical challenges that remain for rigorously assessing the effects of aggregation on the cellular machinery. © 2008 IUBMB IUBMB Life, 60(11): 724,728, 2008 [source] Inclusion formation in Huntington's disease R6/2 mouse muscle culturesJOURNAL OF NEUROCHEMISTRY, Issue 1 2003M. Orth Abstract Huntington's disease (HD) is an autosomal dominant disorder caused by an expansion in the number of glutamine repeats in the N-terminal region of the huntingtin protein. Nuclear and cytoplasmic aggregates of the N-terminal portion of huntingtin have been found in the brains of HD patients and the brains and non-neuronal tissues of the R6/2 HD transgenic mouse. We have cultured myoblasts and myotubes from transgenic R6/2 mice and littermate controls to investigate the formation of these inclusions in post mitotic cells. Huntingtin immunoreactivity was intense in differentiating, desmin positive myoblasts and myotubes from both control and R6/2 mice suggesting that it may play a role in myotube differentiation. Following differentiation huntingtin and ubiquitin positive aggregates were observed in R6/2 but not control cultures. After 3 weeks in differentiation medium cytoplasmic huntingtin and ubiquitin immunoreactive aggregates were observed in non-myotube cells, while nuclear huntingtin aggregates were seen in a proportion of myotubes after 6 weeks. Growth in the absence of serum resulted in a marked increase in the number of R6/2 myotubes containing nuclear inclusions after 6 weeks demonstrating that environmental factors influenced huntingtin aggregate formation in these cells. Consequently, cultured myotubes from R6/2 mice may be a useful post mitotic cell culture model to study both the biochemical consequences of huntingtin aggregates and the factors that may influence aggregate formation. [source] Development of a Method for the High-Throughput Quantification of Cellular ProteinsCHEMBIOCHEM, Issue 10 2009Paolo Paganetti Dr. Abstract Hunting for huntingtin: We describe a screening assay based on the inducible expression of the mutant huntingtin protein in cells and on its highly sensitive homogenous determination. Rapid, reproducible, and robust protein determination was achieved through the use of two donor,acceptor-labeled antibodies and time-resolved FRET. The assay was developed and validated for ultra-throughput screening of low-molecular-weight compounds modulating the expression of the mutant protein. The quantification of cellular proteins is essential for the study of many different biological processes. This study describes an assay for the detection of the intracellular mutant huntingtin, the causative agent of Huntington's disease, with a method that may be generally applicable to other cellular proteins. A small recombinant protein tag that is recognized by a pair of readily available, high-affinity monoclonal antibodies was designed. This tag was then added to an inducible fragment of the mutant huntingtin protein by genetic engineering. We show that it is possible to use time-resolved FRET to detect low intracellular levels of huntingtin by a simple lysis and detection procedure. This assay was then adapted into a homogeneous, miniaturized format suitable for screening in 1536-well plates. The use of time-resolved FRET also permits the assay to be multiplexed with a standard readout of cell toxicity, thus allowing the identification of conditions causing reduction of protein levels simply due to cytotoxicity. The screening results demonstrated that the assay is able to identify compounds that modulate the levels of huntingtin both positively and negatively and that represent valuable starting points for drug discovery programs. [source] The neuropathogenic contributions of lysosomal dysfunctionJOURNAL OF NEUROCHEMISTRY, Issue 3 2002Ben A. Bahr Abstract Multiple lines of evidence implicate lysosomes in a variety of pathogenic events that produce neurodegeneration. Genetic mutations that cause specific enzyme deficiencies account for more than 40 lysosomal storage disorders. These mostly pre-adult diseases are associated with abnormal brain development and mental retardation. Such disorders are characterized by intracellular deposition and protein aggregation, events also found in age-related neurodegenerative diseases including (i) Alzheimer's disease and related tauopathies (ii) Lewy body disorders and synucleinopathies such as Parkinson's disease, and (iii) Huntington's disease and other polyglutamine expansion disorders. Of particular interest for this review is evidence that alterations to the lysosomal system contribute to protein deposits associated with different types of age-related neurodegeneration. Lysosomes are in fact highly susceptible to free radical oxidative stress in the aging brain, leading to the gradual loss of their processing capacity over the lifespan of an individual. Several studies point to this lysosomal disturbance as being involved in amyloidogenic processing, formation of paired helical filaments, and the aggregation of ,-synuclein and mutant huntingtin proteins. Most notably, experimentally induced lysosomal dysfunction, both in vitro and in vivo, recapitulates important pathological features of age-related diseases including the link between protein deposition and synaptic loss. [source] | |||||||||||||