Mutant PKC gamma in Spinocerebellar Ataxia Type 14 Disrupts Synapse Elimination and Long-Term Depression in Purkinje Cells In Vivo
JourNeuroscience_31_14324.pdf 1.96 MB
Shuvaev, Anton N.
Cerebellar Purkinje cells (PCs) express a large amount of the gamma isoform of protein kinase C (PKC gamma) and a modest level of PKC alpha. The PKC gamma is involved in the pruning of climbing fiber (CF) synapses from developing PCs, and PKC alpha plays a critical role in long-term depression (LTD) at parallel fiber (PF)-PC synapses. Moreover, the PKC signaling in PCs negatively modulates the nonselective transient receptor potential cation channel type 3 (TRPC3), the opening of which elicits slow EPSCs at PF-PC synapses. Autosomal dominant spinocerebellar ataxia type 14 (SCA14) is caused by mutations in PKC gamma. To clarify the pathology of this disorder, mutant (S119P) PKC gamma tagged with GFP was lentivirally expressed in developing and mature mouse PCs in vivo, and the effects were assessed 3 weeks after the injection. Mutant PKC gamma-GFP aggregated in PCs without signs of degeneration. Electrophysiology results showed impaired pruning of CF synapses from developing PCs, failure of LTD expression, and increases in slow EPSC amplitude. We also found that mutant PKC gamma colocalized with wild-type PKC gamma, which suggests that mutant PKC gamma acts in a dominant-negative manner on wild-type PKC gamma. In contrast, PKC alpha did not colocalize with mutant PKC gamma. The membrane residence time of PKC alpha after depolarization-induced translocation, however, was significantly decreased when it was present with the mutant PKC gamma construct. These results suggest that mutant PKC gamma in PCs of SCA14 patients could differentially impair the membrane translocation kinetics of wild-type gamma and alpha PKCs, which would disrupt synapse pruning, synaptic plasticity, and synaptic transmission.
The Journal of Neuroscience
Society for Neuroscience
(c) 2011 the authors