Rab GTPase Protein Expression Changes in alpha-Synucleinopathy and Tauopathy Disorders

Nova Southeastern University, Davie, Florida, USA

Objective: Determine Rab GTPase expression changes in α-synucleinopathy and tauopathy disorders. Background: Alterations in Rab GTPase function are increasingly implicated in neurodegenerative diseases. In Lewy body disorders, Rab proteins interact with α-synuclein, supporting a potential role in Parkinson disease (PD). Expression of specific Rabs (e.g., Rab1, 8a) rescues α-synuclein associated trafficking deficits. Rab proteins have similarly been linked to Alzheimer disease (AD). However, little is known about the role of Rab GTPases in tau disorders and expression patterns in neurodegenerative disease. Design/Methods: We examined expression levels of several Rab GTPase proteins (Rab 3a, 5, 7, 8a, 10, 11a, and 35) in postmortem human brain regions from multiple tauopathy (AD, PSP, CBD), Lewy body (α-Synucleinopathy) disorders (PD, DLB, MSA), and matched controls. Frozen brain samples were homogenized in high salt buffer and analyzed by Western blot with specific Rab antibodies. Results: Rab3a expression was significantly increased in the striatum of DLB and MSA, but not PD. Rab8a levels were decreased in frontal and temporal cortex in atypical parkinsonian disorders (APD) compared to control. Rab11a was similarly decreased in frontal cortex in APD’s but increased in the striatum and white matter of PSP and CBD. Rab35 appeared unchanged in PD but was significantly decreased in the striatum in APD’s. Conclusions: These findings represent the first comprehensive analysis of Rab GTPase expression and demonstrate differential expression patterns for Rab proteins in disease-affected regions of tau and α-synuclein disorders. Grant: Supported by the Allen-Simmons Atypical Parkinsonism Fellowship. Work performed at the University of Florida by Dr. Parmar under the mentorship of Dr. McFarland.