Association of the G Proteinα_q/α₁₁-Subunit with Cytoskeleton in Adrenal Glomerulosa Cells: Role in Receptor-Effector Coupling¹

Abstract

In 3-day primary cultures of rat glomerulosa cells, a 30-min pre-incubation with either 10 microM colchicine (a microtubule-disrupting agent) or 10 microM 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)/alpha11-subunit of the G(q/11) protein was associated with both structures. Ang II stimulation induced a rapid translocation of alpha(q)/alpha11, microfilaments, and microtubules to the membrane and induced a time-dependent increase in the level of alpha(q)/alpha11 associated with both microfilaments and microtubules. Moreover, double immunofluorescence staining clearly showed a colocalization of the alpha(q)/alpha11-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)/alpha11 protein is closely associated with cytoskeletal elements and is found both at the plasma membrane level as well as on intracellular stress fibers.

Differential Involvement of Cytoskeleton and Rho-Guanosine 5′-Triphosphatases in Growth-Promoting Effects of Angiotensin II in Rat Adrenal Glomerulosa Cells

“…In the present study, preincubation with cytochalasin B, which disrupts F-actin organization (11,15), decreased the sustained activation of p42/p44 mapk , inhibited p38 MAPK activation, and decreased both basal proliferation and protein synthesis induced by Ang II. Thus, the effect of Ang II on actin filaments may account for its ability to inhibit proliferation and alternatively favor cell protein synthesis.…”

“…On the other hand, we and others have also shown that the cytoskeleton modulates the action of Ang II in the adrenal gland. Indeed, cytochalasin and colchicine (which respectively depolymerize microfilaments and microtubules) decrease Ang II-induced inositol phosphates production and aldosterone secretion (14,15). In recent years, an increasing number of studies have shown cytoskeletal involvement in signal transduction and the activation of MAPK pathways [p42/p44 mapk , c-Jun N-terminal kinase (JNK), and p38 MAPK] (16 -18) (for review see Ref.…”

Nitric oxide decreases the production of inositol phosphates stimulated by angiotensin II and thyrotropin-releasing hormone in anterior pituitary cells

“…It is well established that AT 1A , AT 1B , TRH-R1 and TRH-R2, AngII and TRH receptor subtypes, respectively, trigger PLC activation via the mediation of heterotrimeric Gq/G 11 subfamily members of G-proteins (24,35). G-proteins participate in signal transduction and stimulus-secretion coupling in cells capable of exocytotic secretion, including anterior pituitary cells (12, 22 -24).…”

Connection between Integrins and Cell Activation in Rat Adrenal Glomerulosa Cells: A Role for Arg-Gly-Asp Peptide in the Activation of the p42/p44mapkPathway and Intracellular Calcium

“…At these sites, integrins mediate links between extracellular components and the cytoskeleton and can regulate the generation of specific second messengers, some of which are shared with Ang II (7,8). Indeed, both induce cytoskeletal organization (13) and activate the MAPK cascade, p42/p44 mapk (14). This cascade is involved in proliferation, one important property of glomerulosa cells, evidenced by the observation that the highest expression of p42/p44 mapk in the cortex is found in zona glomerulosa (15).…”