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The focus of the lab is on the role of cell survival and differentiation signaling pathways in the
nervous system. The long-term goal of the laboratory is to understand the cellular and molecular basis of
neurological and psychiatric disorders. Experimental approaches used include molecular and chemical biology,
and functional proteomics. Systems used include cell culture and animal models of demyelination and other
neurological disorders involving proteotoxicity (Amyotrophic lateral Sclerosis (ALS), and Huntington's, and Alzheimer's disease).
Accumulation of misfolded proteins is a feature of aging and appears to be accelerated in many neurodegenerative disorders. Protein misfolding can result from defects in the chaperone system or may arise due to mutations or oxidative damage. Recent data indicates that the misfolded proteins play an active role in cellular toxicity. The broad objective of these studies is to understand the mechanisms by which misfolded proteins perturb cellular homeostasis including protein expression and turnover, and energy metabolism. Because a stretch of more than 37 glutamines is known to misfold, accumulate in cells and induce toxicity, we use expanded polyglutamine proteins as one of the systems to study the mechanisms of proteotoxicity.
We previously showed that caspase 8 activation plays a critical role in cell death following expression of the expanded polyglutamine repeats. Unlike in the Fas pathway, the active caspase 8 is triggered by its recruitment to the misfolded polyglutamine proteins. Moreover, oligomerization of the expanded repeats appears required for toxicity including metabolic inhibition and caspase activation as shown by FRET assays and use of the oligomer compound inhibitor, congo red. Therefore, our working hypothesis is that small oligomeric forms of misfolded proteins assuming an amyloid-like conformation acquire the ability to interact with multiple signaling proteins underlying multiple of downstream toxic events. To identify and characterize signaling pathways and mediators linking misfolded proteins to cellular toxicity we are using functional proteomics including 2D Differential In-gel electrophoresis (2D-DIGE), RNAi, and compounds identified by high-throughput screens against expanded polyglutamine induced ATP depletion.
Abnormal length of
triplet repeats in otherwise non-related genes have been shown to underlie several CNS disorders. A recent project in
the lab is focused on elucidating the role of triplet repeats in the regulation of the calcium activated potassium channel
subunit, SK3, a protein found mutated in a cohort of schizophrenia patients.
Using optic nerves from developing and
myelin mutant mice as model systems we and other investigators found that profound changes in the spatial organization,
stability, ultrastructure, and site specific phosphorylation of the axonal cytoskeleton are induced by myelinating glia. We
are interested in using molecular and chemical biology to identify the mediators and characterize the glia factors involved
in axonal maturation. In addition, because some of these changes occur at the peak of developmental programmed cell
death we are investigating the relationship between cell survival signals and neuronal differentiation.
Although the expression of two
kinases, cdk5 and erk2, known to phosphorylate cytoskeleton proteins, appears to be developmentally regulated, we and
other laboratories found that their activity and distribution appears to be regulated by myelin-mediated extrinsic
factors. Furthermore, increased levels of cytoskeleton bound cdk5 kinase have been detected in affected tissue
from Amyotrophic Lateral Sclerosis (ALS) patients and animal models and the cdk5 activator, p35 has been shown
to play a critical role in Alzheimer's disease. We are interested in understanding how the cytoskeleton contributes
to the modulation of signaling pathways during differentiation and in pathological conditions.
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