Dynactin is a necessary cofactor for dynein-mediated transport of intracellular cargos. The p150Glued subunit of dynactin interacts directly with the dynein motor and also independently binds microtubules and microtubule plus-end binding proteins, including EB1, via interactions mediated by an N-terminal cytoskeleton- associated protein glycine-rich (CAP-Gly) domain. It has been proposed that the direct binding of dynactin to the microtubule enhances the processivity of dynein during transport;however, studies in non-neuronal cells show that the CAP-Gly domain is not necessary for normal dynein-mediated transport and localization of organelles. Thus the function of the CAP-Gly domain of p150Glued remains unclear. Interestingly, point mutations within the CAP-Gly domain cause two distinct, dominantly inherited neurodegenerative diseases, Perry syndrome and distal hereditary motor neuropathy 7B (HMN7B). Perry syndrome results in Parkinsonism, hypoventilation, weight loss and depression, while HMN7B is a motor neuropathy, effecting neurons in the ventral spinal cord and hypoglossal nucleus. These genetic data clearly demonstrate that the CAP-Gly domain is vital for neuronal survival. However, the mechanism by which a loss of CAP-Gly function causes neurodegeneration remains unclear. This proposal seeks to determine the normal function of the CAP-Gly domain of p150Glued in neurons and investigate why mutations in the CAP-Gly domain cause two distinct neurodegenerative diseases. I hypothesize that the CAP-Gly domain of p150Glued is necessary in neurons for the efficient initiation of transport and that the Perry syndrome and HMN7B mutations differentially disrupt dynactin function accounting for the cell-type specific degeneration of these two diseases. I will test this hypothesis using biochemical methods and live-cell imaging in primary neurons.
Dynactin is necessary in all cells, but the function of the CAP-Gly domain of p150Glued in neurons remains unclear. Studying this function is pertinent to human disease because different point mutations within the domain cause two distinct inherited neurodegenerative diseases. Understanding the role of the CAP-Gly domain and how the disease-causing mutations perturb this function may yield insight into the pathological mechanisms by which these mutations cause neurodegeneration as well as shed light onto the neuronal specificity of these disparate diseases.
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