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 preincuba tion with either 10 mu M colchicine (a microtubule-disrupting agent) o r 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), indic ating that both microtubules and microfilaments are essential for phos pholipase C activation. Analysis of microfilament-and microtubule-enri ched fractions and immunoprecipitation of actin and tubulin revealed t hat the alpha(q)/alpha(11)-subunit of the G(q/11) protein was associat ed with both structures. Ang II stimulation induced a rapid translocat ion of alpha(q)/alpha(11), microfilaments, and microtubules to the mem brane and induced a time-dependent increase in the level of alpha(q)/a lpha(11) associated with both microfilaments and microtubules. Moreove r, 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 red istribution under Ang II stimulation indicate that microfilaments and microtubules are both involved in phospholipase C activation and inosi tol phosphate production. Moreover, our results indicate that the alph a(q)/alpha(11) protein is closely associated with cytoskeletal element s and is found both at the plasma membrane level as well as on intrace llular stress fibers.