Endocrine Abstracts

PKCα has been implicated in different neuronal functions like, apoptosis, synaptic plasticity, and memory formation. PKCα has been linked to control insulin signalling in peripheral tissues as a feedback regulator. However, the exact mechanism how this kinase regulates insulin signalling in neuron is not yet understood completely. Therefore the objective of the present study was to understand the mechanism of action of PKCα on neuronal insulin signalling cascade. Recently we have shown in differentiated Neuro-2a (N2a) cells in vitro, that acute phorbol 12-myrisate 13-acetate (PMA), a well-known activator of PKC, (400 nM for 2.5 min) decreased Akt activity because of the activation of PKCα. In order to understand how the Akt activity was decreased, in our present study we have used differentiated N2a cells, treated them with or without chronic PMA (1 µM, 24 hours) (chronic PMA decreases endogenous PKC levels) or acute (400 nM for 2.5 min) PMA, with or without insulin (100 nM, 30 min). The inhibition in Akt activity was reversed and increased by 25% when neuronal cells were treated with chronic PMA, which decreased PKCα levels. This showed that PKCα inhibits insulin signalling pathway through Akt. To test PKCα contribution in insulin-resistance, N2a cells were differentiated in insulin-sensitive (MF) and insulin-resistance (MFI) condition, as reported earlier from our laboratory. Results have demonstrated that PKCα translocated 2.5 fold more in plasma membrane in MFI condition as compared to MF condition. However, when PKCα was inhibited using Go6983 (which blocked PKCα membrane translocation), Akt activity increased by 30% in the plasma membrane of neurons in MF (insulin- sensitive) condition. However, as the translocation of PKCα was more in plasma membrane in MFI (insulin resistant) condition, Akt activity was reduced in the plasma membrane in MFI condition. These data together demonstrated that PKCα negatively regulates insulin signalling in insulin-sensitive neurons and even worsen the signalling in insulin resistant N2a cells. Further studies are required to elucidate the role of PKCα in neuronal insulin signalling and insulin-resistance.