| First Author | Shirafuji T | Year | 2018 |
| Journal | J Neurosci | Volume | 38 |
| Issue | 2 | Pages | 278-290 |
| PubMed ID | 29167402 | Mgi Jnum | J:258472 |
| Mgi Id | MGI:6111271 | Doi | 10.1523/JNEUROSCI.1649-17.2017 |
| Citation | Shirafuji T, et al. (2018) The Role of Cysteine String Protein alpha Phosphorylation at Serine 10 and 34 by Protein Kinase Cgamma for Presynaptic Maintenance. J Neurosci 38(2):278-290 |
| abstractText | Protein kinase Cgamma (PKCgamma) knock-out (KO) animals exhibit symptoms of Parkinson''s disease (PD), including dopaminergic neuronal loss in the substantia nigra. However, the PKCgamma substrates responsible for the survival of dopaminergic neurons in vivo have not yet been elucidated. Previously, we found 10 potent substrates in the striatum of PKCgamma-KO mice. Here, we focused on cysteine string protein alpha (CSPalpha), a protein from the heat shock protein (HSP) 40 cochaperone families localized on synaptic vesicles. We found that in cultured cells, PKCgamma phosphorylates CSPalpha at serine (Ser) 10 and Ser34. Additionally, apoptosis was found to have been enhanced by the overexpression of a phosphorylation-null mutant of CSPalpha, CSPalpha(S10A/S34A). Compared with wild-type (WT) CSPalpha, the CSPalpha(S10A/S34A) mutant had a weaker interaction with HSP70. However, in sharp contrast, a phosphomimetic CSPalpha(S10D/S34D) mutant, compared with WT CSPalpha, had a stronger interaction with HSP70. In addition, total levels of synaptosomal-associated protein (SNAP) 25, a main downstream target of the HSC70/HSP70 chaperone complex, were found to have decreased by the CSPalpha(S10A/S34A) mutant through increased ubiquitination of SNAP25 in PC12 cells. In the striatum of 2-year-old male PKCgamma-KO mice, decreased phosphorylation levels of CSPalpha and decreased SNAP25 protein levels were observed. These findings indicate the phosphorylation of CSPalpha by PKCgamma may protect the presynaptic terminal from neurodegeneration. The PKCgamma-CSPalpha-HSC70/HSP70-SNAP25 axis, because of its role in protecting the presynaptic terminal, may provide a new therapeutic target for the treatment of PD.SIGNIFICANCE STATEMENT Cysteine string protein alpha (CSPalpha) is a protein belonging to the heat shock protein (HSP) 40 cochaperone families localized on synaptic vesicles, which maintain the presynaptic terminal. However, the function of CSPalpha phosphorylation by protein kinase C (PKC) for neuronal cell survival remains unclear. The experiments presented here demonstrate that PKCgamma phosphorylates CSPalpha at serine (Ser) 10 and Ser34. CSPalpha phosphorylation at Ser10 and Ser34 by PKCgamma protects the presynaptic terminal by promoting HSP70 chaperone activity. This report suggests that CSPalpha phosphorylation, because of its role in modulating HSP70 chaperone activity, may be a target for the treatment of neurodegeneration. |
