Akt activation is necessary for growth factor-induced trafficking of functional K(Ca) channels in developing parasympathetic neurons

The protein kinase Akt is a crucial regulator of neuronal survival and apoptosis. Here we show that Akt activation is necessary for mobilization of large-conductance K(Ca) channels in ciliary ganglion (CG) neurons evoked by beta-neuregulin-1 (NRG1) and transforming growth factor-beta1 (TGFbeta1). Application of NRG1 to embryonic day 9 (E9) CG neurons increased Akt phosphorylation, as observed previously for TGF(beta)1. NRG1- and TGF(beta)1-evoked stimulation of K(Ca) is blocked by inhibitors of PI3K by overexpression of a dominant-negative form of Akt, by overexpression of CTMP, an endogenous negative regulator of Akt, and by application of the Akt inhibitor 1L-6-hydroxymethyl-chiro-inositol 2-(R)-2-O-methyl-3-O-octadecylcarbonate (HIMO). Conversely, overexpression of a constitutively-active form of Akt was sufficient by itself to increase mobilization of functional K(Ca) channels. NRG1 and TGF(beta)1 evoked an Akt-dependent increase in cell-surface SLO alpha-subunits. These procedures have no effect on voltage-activated Ca2+ currents. Thus Akt plays an essential role in the developmental regulation of excitability in CG neurons.