Activation of Microtubule Dynamics Increases Neuronal Growth via the Nerve Growth Factor (NGF)- and Gαs-mediated Signaling Pathways

Signals that activate the G protein G(s) and promote neuronal differentiation evoke G(s) internalization in rat pheochromocytoma (PC12) cells. These agents also significantly increase G(s) association with microtubules, resulting in an increase in microtubule dynamics because of the activation of tubulin GTPase by G(s). To determine the function of G(s)/microtubule association in neuronal development, we used real-time trafficking of a GFP-G(s) fusion protein. GFP-G(s) concentrates at the distal end of the neurites in differentiated living PC12 cells as well as in cultured hippocampal neurons. G(s) translocates to specialized membrane compartments at tips of growing neurites. A dominant-negative G chimera that interferes with G(s) binding to tubulin and activation of tubulin GTPase attenuates neurite elongation and neurite number both in PC12 cells and primary hippocampal neurons. This effect is greatest on differentiation induced by activated G(s). Together, these data suggest that activated G(s) translocates from the plasma membrane and, through interaction with tubulin/microtubules in the cytosol, is important for neurite formation, development, and outgrowth. Characterization of neuronal G protein dynamics and their contribution to microtubule dynamics is important for understanding the molecular mechanisms by which G protein-coupled receptor signaling orchestrates neuronal growth and differentiation.