Heterotrimeric G-proteins associate with microtubules during differentiation in PC12 pheochromocytoma cells

Tubulin modifies G-protein signaling and heterotrimeric G-proteins regulate microtubule assembly. Here we report an interplay among G-protein-coupled receptor and receptor tyrosine kinase (such as nerve growth factor-NGF) signaling systems in PC12 pheochromocytoma cells that resulted in a translocation of G_αs, G_αi1, and G_αo from cell bodies to cellular processes where they appear to localize with tubulin-containing structures. This relocation appeared to depend on the integrity of microtubules, as it was blocked and reversed by nocodazole. Latrunculin, which promotes actin filament depolymerization, had no effect. Both deconvolution microscopy and immunoprecipitation showed a significant increase of G_α association with microtubules that was coincident with the extension of "neurites." There were distinctions among the G_α subtypes, with G_αs showing the most profound NGF-induced colocalization with tubulin. Translocation of G_α was blocked by agents that inhibit the MAP kinases required for neuronal differentiation, suggesting that G-protein relocation is triggered by the intracellular signals for differentiation. Consistent with this, G_α in Neuro-2A cells, which spontaneously differentiate, showed a similar translocation coincident with differentiation. Thus, diverse signals that promote neuronal differentiation and changes in cell morphology may use specific G-proteins to evoke cytoskeletal rearrangement.