cPKCγ-Modulated Sequential Reactivation of mTOR Inhibited Autophagic Flux in Neurons Exposed to Oxygen Glucose Deprivation/Reperfusion

Abstract

We have reported that conventional protein kinase C&gamma; (cPKC&gamma;)-modulated neuron-specific autophagy improved the neurological outcome of mice following ischemic stroke through the Akt-mechanistic target of rapamycin (mTOR) pathway. However, its detailed molecular mechanism remains unclear. In this study, primary cortical neurons from postnatal one-day-old C57BL/6J <i>cPKC&gamma;</i> wild-type (<i>cPKC&gamma;</i>^+/+) and knockout (<i>cPKC&gamma;</i>^{&minus;/&minus;}) mice suffering oxygen glucose deprivation/reperfusion (OGD/R) were used to simulate ischemia/reperfusion injury in vitro. A block of autophagic flux was observed in <i>cPKC&gamma;</i>^+/+ neurons under OGD/R exposure, characterized by accumulation of p62. Immunofluorescent results showed a decrease in colocalization between LC3 and Atg14 or Stx17 in cPKC&gamma;^+/+ neurons when compared with <i>cPKC&gamma;</i>^{&minus;/&minus;} neurons after OGD/R. However, the colocalization between LC3 and Lamp2 was barely decreased, indicating the presence of autolysosomes. The larger lysotracker-positive structures were also significantly increased. These results suggest that cPKC&gamma;-induced inhibition of autophagy occurred at the stages of autophagosome formation, Stx17 anchoring, and the degradation of autolysosomes in particular. In addition, cPKC&gamma;-modulated phosphorylation of mTOR at Ser 2481 was dependent on the site of Ser 2448, which may have blocked autophagic flux. cPKC&gamma;-modulated sequential reactivation of mTOR inhibited autophagic flux in neurons exposed to OGD/R, which may provide endogenous interventional strategies for stroke, especially ischemia/reperfusion injury.