Electrophysiological study to explore the functional consequences of Ng expression on neuroblastoma cells (N2A)

Abstract

Neurogranin (Ng) is a neuron-specific protein kinase C (PKC) substrate, Here we stably transfected Ng in report using neuroblastoma N2A cell line to probe Ng functions. Our data showed that over-expression of Ng decreased Na+ currents density, mainly due to the reduce of the channel open probability and the increase in channel close time, after depolarization. We proposed the phosphorylation of Ng play a significant role in mediating Na+ channel functions through changing equilibriums between Ng-CaM and Na+ channel-CaM complexes. Calcium image experiments were also carried out to determine the functional consequence of Ng on cytosolic calcium level. Our data showed that the activation of PKC led to calcium release from IP3 sensitive calcium store only in the Ng expressed clone N2A cell. The increase of [Ca2+]i induced by PMA was extracellular calcium dependent, and the activation of store operate calcium (SOC) channels is necessary during PMA stimulation. U73122, an inhibitor of phospholipase C (PLC), could also significantly inhibit PMA induced [Ca2+]i increase. suggesting that the Ng phosphorylation may lead to the activation of IP3 sensitive calcium store.