Date of Award

2017

Document Type

Dissertation/Thesis

Submission Date

October 2026

Thesis/Dissertation Advisor [Chair]

Subramaniam, Srinivasa

Abstract

The Rhes protein in the striatum of the brain coordinates motor defects related to Huntington’s disease (HD) and Parkinson’s disease (PD). The Rhes protein interacts with mutant Huntingtin protein to increase its solubility, resulting in cellular death (Subramaniam, Sixt, Barrow, & Snyder, 2009). In PD, Rhes promotes abnormal movements induced by continuous use of L-DOPA, the PD drug (Subramaniam et al., 2012). Thus, small molecule drugs that interact with Rhes are potential therapeutics for HD and PD and movement disorders that affect the striatum. Despite these emerging disease relevant roles, fundamental knowledge about Rhes stability, which is important for designing effective therapeutics, is unknown. In my previous research, I showed that Rhes has a half-life beyond 32 hours (Shahani et al., 2016). However, the mechanism of Rhes stability remains unknown. Here, using a series of cell culture and biochemical experiments, I have investigated the mechanisms of Rhes protein degradation. My data suggests that Rhes stability varies in a cell-type dependent manner. In Human Embryonic Kidney cells (HEK293) treated with cycloheximide (a protein synthesis inhibiter), Rhes will degrade rapidly. However, Rhes does not degrade in striatal-neuron derived cells (STHdhQ7/Q7) when treated with cycloheximide. Based on these findings, I tested the role of Rhes mRNA, autophagy, and proteasome pathways in Rhes protein stability. My results strongly suggest that the proteasome pathway degrades Rhes in HEK293 cells, while such mechanisms appear to be absent in STHdhQ7/Q7, opening a new area of investigation into discovering a novel ubiquitin E3 ligase, a potential therapeutic target for degrading Rhes.

Comments

Includes bibliography.

Extent

27 p.

Identifier

FA00012618

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