cPKCγ-mediated down-regulation of UCHL1 alleviates ischaemic neuronal injuries by decreasing autophagy via ERK-mTOR pathway

Stroke is one of the leading causes of death in the world, but its underlying mechanisms remain unclear. Both conventional protein kinase C (cPKC)gamma and ubiquitin C-terminal hydrolase L1 (UCHL1) are neuron-specific proteins. In the models of 1-hr middle cerebral artery occlusion (MCAO)/24-hr reperfusion in mice and 1-hr oxygen-glucose deprivation (OGD)/24-hr reoxygenation in cortical neurons, we found that cPKC gamma gene knockout remarkably aggravated ischaemic injuries and simultaneously increased the levels of cleaved (Cl)-caspase-3 and LC3-I proteolysis product LC3-II, and the ratio of TUNEL-positive cells to total neurons. Moreover, cPKC gene knockout could increase UCHL1 protein expression via elevating its mRNA level regulated by the nuclear factor B inhibitor alpha (I kappa B-alpha)/nuclear factor kappa B (NF-kappa B) pathway in cortical neurons. Both inhibitor and shRNA of UCHL1 significantly reduced the ratio of LC3-II/total LC3, which contributed to neuronal survival after ischaemic stroke, but did not alter the level of Cl-caspase-3. In addition, UCHL1 shRNA reversed the effect of cPKC gamma on the phosphorylation levels of mTOR and ERK rather than that of AMPK and GSK-3 beta. In conclusion, our results suggest that cPKC gamma activation alleviates ischaemic injuries of mice and cortical neurons through inhibiting UCHL1 expression, which may negatively regulate autophagy through ERK-mTOR pathway.