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Hoffmann, R. A wiki for the life sciences where authorship matters. Nature Genetics (2008)

Cysteine string protein ( CSP) inhibition of N-type calcium channels is blocked by mutant huntingtin.

Cysteine string protein ( CSP), a 34-kDa molecular chaperone, is expressed on synaptic vesicles in neurons and on secretory vesicles in endocrine, neuroendocrine, and exocrine cells. CSP can be found in a complex with two other chaperones, the heat shock cognate protein Hsc70, and small glutamine-rich tetratricopeptide repeat domain protein (SGT). CSP function is vital in synaptic transmission; however, the precise nature of its role remains controversial. We have previously reported interactions of CSP with both heterotrimeric GTP-binding proteins (G proteins) and N-type calcium channels. These associations give rise to a tonic G protein inhibition of the channels. Here we have examined the effects of huntingtin fragments (exon 1) with (huntingtin(exon1/exp)) and without (huntingtin(exon1/nonexp)) expanded polyglutamine (polyQ) tracts on the CSP chaperone system. In vitro huntingtin(exon1/exp) sequestered CSP and blocked the association of CSP with G proteins. In contrast, huntingtin(exon1/nonexp) did not interact with CSP and did not alter the CSP/G protein association. Similarly, co-expression of huntingtin(exon1/exp) with CSP and N-type calcium channels eliminated CSP's tonic G protein inhibition of the channels, while coexpression of huntingtin(exon1/nonexp) did not alter the robust inhibition promoted by CSP. These results indicate that CSP's modulation of G protein inhibition of calcium channel activity is blocked in the presence of a huntingtin fragment with expanded polyglutamine tracts.[1]


  1. Cysteine string protein (CSP) inhibition of N-type calcium channels is blocked by mutant huntingtin. Miller, L.C., Swayne, L.A., Chen, L., Feng, Z.P., Wacker, J.L., Muchowski, P.J., Zamponi, G.W., Braun, J.E. J. Biol. Chem. (2003) [Pubmed]
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