Deranged Calcium Signaling and Neurodegeneration in Spinocerebellar Ataxia Type 3

Spinocerebellar ataxia type 3 (SCA3), also known as Machado-Joseph disease (MJD), is an autosomal-dominant neurodegenerative disorder caused by a polyglutamine expansion in ataxin-3 (ATX3; MJD1) protein. In biochemical experiments, we demonstrate that mutant ATX3(exp) specifically associated with the type 1 inositol 1,4,5-trisphosphate receptor (InsP(3)R1), an intracellular calcium (Ca2+) release channel. In electrophysiological and Ca2+ imaging experiments, we show that InsP3R1 was sensitized to activation by InsP(3) in the presence of mutant ATX3(exp). We found that feeding SCA3-YAC-84Q transgenic mice with dantrolene, a clinically relevant stabilizer of intracellular Ca2+ signaling, improved their motor performance and prevented neuronal cell loss in pontine nuclei and substantia nigra regions. Our results indicate that deranged Ca2+ signaling may play an important role in SCA3 pathology and that Ca2+ signaling stabilizers such as dantrolene may be considered as potential therapeutic drugs for treatment of SCA3 patients.