Differential mRNA expression and subcellular locations of PI3-kinase isoforms in sympathetic and sensory neurons

Phosphatidylinositol 3-kinase (PI3-kinase) enzymes are key signalling molecules in the PC12 and neuronal cell survival pathway and are also involved in the regulation of retrograde axonal transport of nerve growth factor (NGF), with sympathetic neurons more sensitive to the effects of wortmannin/LY294002 than sensory neurons (Bartlett et al. [1997]; Brain Res. 761:257-262; Reynolds et al. [1998] Brain Res. 798:6774). In this article, we characterized the mRNA expression of PI3-kinase isoforms in mouse sympathetic superior cervical ganglia (SCG) and sensory trigeminal ganglia (TGG) and examined the subcellular locations of immunoreactivity of the PI3-kinase isoforms in mouse cultured SCG and dorsal root ganglion (DRG) neurons. Both the SCG and the TGG express mRNA for the p110α, β, γ, δ, and vps34p PI3- kinase isoforms, but the TGG and not the SCG express mRNA for the p170 PI3- kinase isoform. In cultured SCG and DRG neurons, p110α, β, and immunoreactivity is in the SCG and DRG growth cones, and predominantly in puncta throughout the growth cone varicosity. However, in the cell bodies immunoreactivity varied, p110α is localized predominantly at the plasma membrane, while p110β and γ is localized in the perinuclear region of the cells. In addition, unlike other cell types, wortmannin has little effect on actin filament polymerization in either mouse cultured SCG or DRG neurons.