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Toxicity and Endocytosis of Spinocerebellar Ataxia Type 6 Polyglutamine Domains: Role of Myosin IIB †
Author(s) -
MarquèzePouey Béatrice,
MartinMoutot Nicole,
SakkouNorton Marie,
Lévêque Christian,
Ji Yong,
Cornet Véronique,
Hsiao Wendy L.,
Seagar Michael
Publication year - 2008
Publication title -
traffic
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.677
H-Index - 130
eISSN - 1600-0854
pISSN - 1398-9219
DOI - 10.1111/j.1600-0854.2008.00743.x
Subject(s) - biology , spinocerebellar ataxia , myosin , endocytosis , microbiology and biotechnology , cytoplasm , biochemistry , cell , gene
Spinocerebellar ataxia type 6 (SCA6) is a dominantly inherited neurodegenerative disease caused by a small expansion of CAG repeats in the sequence coding for the cytoplasmic C‐terminal region of the Ca v 2.1 subunit of P/Q‐type calcium channels. We have tested the toxicity of mutated Ca v 2.1 C‐terminal domains expressed in the plasma membrane. In COS‐7 cells, CD4–green fluorescent protein fused to Ca v 2.1 C‐terminal domains containing expanded 24 polyglutamine (Q) tracts displayed increased toxicity and stronger expression at the cell surface relative to ‘normal’ 12 Q tracts, partially because of reduced endocytosis. Glutathione S‐transferase pull‐down and proteomic analysis indicated that Ca v 2.1 C‐termini interact with the heavy and light chains of cerebellar myosin IIB, a molecular motor protein. This interaction was confirmed by coimmunoprecipitation from rat cerebellum and COS‐7 cells and shown to be direct by binding of in vitro ‐translated 35 S‐myosin IIB heavy chain. In COS‐7 cells, incremented polyglutamine tract length increased the interaction with myosin IIB. Furthermore, the myosin II inhibitor blebbistatin reversed the effects of polyglutamine expansion on plasma membrane expression. Our findings suggest a key role of myosin IIB in promoting accumulation of mutant Ca v 2.1Ct at the plasma membrane and suggest that this gain of function might contribute to the pathogenesis of SCA6.