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 (Ca(2+)) release channel. In electrophysiological and Ca(2+) imaging experiments, we show that InsP(3)R1 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 Ca(2+) signaling, improved their motor performance and prevented neuronal cell loss in pontine nuclei and substantia nigra regions. Our results indicate that deranged Ca(2+) signaling may play an important role in SCA3 pathology and that Ca(2+) signaling stabilizers such as dantrolene may be considered as potential therapeutic drugs for treatment of SCA3 patients.