Association of the G protein alpha(q)alpha(11)-subunit with cytoskeleton in adrenal glomerulosa cells: Role in receptor-effector coupling

In 3-day primary cultures of rat glomerulosa cells, a 30-min preincubation with either 10 mu M colchicine (a microtubule-disrupting agent) or 10 mu M cytochalasin B (a microfilament-disrupting agent) decreased angiotensin II (Ang II)-induced Inositol phosphate accumulation by 50%. Moreover, both drugs decreased inositol phosphate production induced by fluoroaluminate (a nonspecific activator of all G proteins), indicating that both microtubules and microfilaments are essential for phospholipase C activation. Analysis of microfilament-and microtubule-enriched fractions and immunoprecipitation of actin and tubulin revealed that the alpha(q)/alpha(11)-subunit of the G(q/11) protein was associated with both structures. Ang II stimulation induced a rapid translocation of alpha(q)/alpha(11), microfilaments, and microtubules to the membrane and induced a time-dependent increase in the level of alpha(q)/alpha(11) associated with both microfilaments and microtubules. Moreover, double immunofluorescence staining clearly showed a colocalization of the alpha(q)/alpha(11)-subunit of the G(q/11) coupling protein and microfilament distribution. These associations and plasma membrane redistribution under Ang II stimulation indicate that microfilaments and microtubules are both involved in phospholipase C activation and inositol phosphate production. Moreover, our results indicate that the alpha(q)/alpha(11) protein is closely associated with cytoskeletal elements and is found both at the plasma membrane level as well as on intracellular stress fibers.