Connection between Integrins and Cell Activation in Rat Adrenal Glomerulosa Cells: A Role for Arg-Gly-Asp Peptide in the Activation of the p42/p44^mapkPathway and Intracellular Calcium

Abstract

Integrins are responsible for adhesion and activation of several intracellular cascades. The present study was aimed at determining whether the interaction between fibronectin and integrins could generate pathways involved in physiological functions of rat adrenal glomerulosa cells. Immunofluorescence studies and adhesion assays showed that fibronectin was the best matrix in promoting the formation of focal adhesion. Binding of glomerulosa cells to fibronectin, but not to collagen I or poly-L-lysine, involved the integrin-binding sequence Arg-Gly-Asp (RGD). Activation of glomerulosa cells with Arg-Gly-Asp-Ser (RGDS) induced an increase in [Ca(2+)](i), whereas fibronectin triggered a release of Ca(2+) from InsP(3)-sensitive Ca(2+) stores. Aldosterone secretion induced by ACTH, angiotensin II, and RGDS and proliferation were improved on fibronectin, compared with poly-L-lysine. The RGDS peptide induced a transient increase in the activity of the p42/p44(mapk), independent of phosphatidylinositol-3 kinase and protein kinase C. Integrins alpha(5) and alpha(V) as well as their fibronectin receptor partners beta(1) and beta(3), were identified. These results suggest that in rat adrenal glomerulosa cells, binding of the alpha(5)beta(1), alpha(v)beta(1), or alpha(v)beta(3) integrins to fibronectin is involved in the generation of two important signaling events, increase in intracellular calcium, and activation of the p42/p44(mapk) cascade, leading to cell proliferation and aldosterone secretion.

A non–RGD-based integrin binding peptide (ATN-161) blocks breast cancer growth and metastasis in vivo

“…Constitutive MAPK activation is known to occur in tumor cells and high basal levels of activated MAPK have been described, specifically, in MDA-MB-231 (35) although adhesion of these cells could also up-regulate MAPK activation (36). However, the inhibition of MAPK by ATN-161 in MDA-MB-231 tumor cells in vitro was insufficient by itself to affect the proliferation or migration of these cells, and some studies have shown that the simultaneous inhibition of both FAK and MAPK signaling is required to attenuate integrin-mediated migration or proliferation (36). In addition to low copy numbers or an alternate receptor for ATN-161, this could also explain the lack of an effect on proliferation of MDA-MB-231 cells in vitro.…”

Integrin Ligands Mobilize Ca2+ from Ryanodine Receptor-gated Stores and Lysosome-related Acidic Organelles in Pulmonary Arterial Smooth Muscle Cells

“…Integrins physically bridge the ECM and cytoskeleton, and act as transducers of "outside-in" and "inside-out" signaling (1). Extracellular integrin ligation changes [Ca 2ϩ ] i in a variety of cell types, including platelets, neutrophils, monocytes, lymphocytes, fibroblasts, endothelial cells, osteoclasts, neurons, glomerulosa cells, epithelial and smooth muscle cells (2)(3)(4)(5). Integrin ligation also activates other intracellular signaling molecules, including H ϩ and a plethora of protein kinases such as the focal adhesion kinase, Rac, and extracellular signal regulated kinases (1,6).…”

Expression of extracellular matrix proteins and integrins in rat adrenal gland: importance for ACTH-associated functions

“…For example, in the bovine adrenal gland, laminin (LN) is mainly associated with migration (Pellerin et al 1997, Feige et al 1998. On the other hand, in rat adult glomerulosa cells, we have shown that adhesion of glomerulosa cells to fibronectin (FN) is able to promote an increase in intracellular calcium, activate p42/p44 mapk and stimulate proliferation and aldosterone secretion (Campbell et al 2003). The ECM proteins interact with cells through binding of integrin receptors localized on plasma cell membranes (Tamkun et al 1986).…”