All ETDs from UAB

Advisory Committee Chair

Elizabeth Sztul

Advisory Committee Members

James Collawn

Kevin Kirk

Anne Burton Theibert

Bradley K Yoder

Document Type

Dissertation

Date of Award

2011

Degree Name by School

Doctor of Philosophy (PhD) Heersink School of Medicine

Abstract

This dissertation documents my findings in two unrelated projects. Project 1: Expansion of CAG repeats encoding glutamine in huntingtin and ataxin 3 causes the neurodegenerative diseases Huntington's disease (HD) and spinocerebellar ataxia 3 (SCA3), respectively. Both poly-glutamine (polyQ) expanded proteins misfold and ag-gregate within the cell. Preventing aggregation of polyQ proteins through molecular or pharmacological approaches provide therapeutic advantage in animal models of HD and SCA3. I hypothesized that the UL97 kinase encoded by the human cytomegalovirus (HCMV) may be able to prevent the aggregation of polyQ proteins. Initially, I showed that the UL97 kinase prevents the deposition of aggregates of two non-polyQ proteins: the Golgi protein GCP-170 (GFP170*); and the nuclear Werner Syndrome protein (WRN). Subsequently, I uncovered that UL97 prevents the deposition of aggregates of both polyQ huntingtin and ataxin 3. UL97 dispersed nuclear PML bodies and decreased p53-mediated transcription. These results identify UL97 as a novel tool to probe the cellular mechanisms that contribute to the formation of aggregates in polyQ disorders. Project 2: A major challenge in the field is to understand the mechanisms involved in the trafficking of transmembrane proteins to cilia. I hypothesized that a network of proteins functions within the secretory and the endosomal pathways to regulate the delivery of signaling proteins to cilia. To identify pathways and components of cellular machinery involved in ciliary trafficking, I tracked the transport of a ciliary cargo somatostain recep-tor 3 (SSTR3). I showed that SSTR3 localizes to cilia of inner medullary collecting duct cells (IMCDs). SSTR3 is also found in the early and recycling endosomes identified by labe-ling with the endosomal markers Rab5, Rab21, Rab4, and Rab11. Using time-lapse imag-ing, I observed the delivery of SSTR3 from endosomal compartments to the base of cilia. SSTR3 segregates within Rab21- and Rab4-containing subdomains of early endosomes and expression of dominant inactive mutants of Rab21, Rab4, and Rab11 severely im-pairs SSTR3 trafficking. My findings defined a novel role for Rab21 and Rab4 in ciliary trafficking. My work will pave the way towards better understanding of the mechanisms that regulate cilia traffic.

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