Alpha 7 nicotinic receptor coupling to heterotrimeric G proteins modulates RhoA activation, cytoskeletal motility, and structural growth

Nicotinic acetylcholine receptors (nAChRs) modulate the growth and structure of neurons throughout the nervous system. Ligand stimulation of the 7 nAChR has been shown to regulate the large heterotrimeric GTP-binding protein (G protein) signaling in various types of cells. Here, we demonstrate a role for 7 nAChR/G protein interaction in the activation of the small (monomeric) RhoA GTPase leading to cytoskeletal changes during neurite growth. Treatment of PC12 cells with the 7 nAChR agonist choline or PNU-282987 was associated with an increase in RhoA activity and an inhibition in neurite growth. Specifically, choline treatment was found to attenuate the velocity of microtubule growth at the growth cone and decrease the rate of actin polymerization throughout the cell. The effects of 7 nAChR activation were abolished by expression of a dominant negative 7 nAChR (7(345-348A)) deficient in G protein coupling. Proteomic analysis of immunoprecipitated 7 nAChR complexes from differentiating PC12 cells and synaptic fractions of the developing mouse hippocampus revealed the existence of Rho GTPase-regulating guanine nucleotide exchange factors within 7 nAChR interactomes. These findings underscore the role of 7 nAChR/G protein in cytoskeletal regulation during neurite growth.