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

Abstract

The expression of main extracellular matrix (ECM) and their integrins were studied in the adult rat adrenal gland. Collagen I, IV (CI, CIV), laminin (LN) and fibronectin (FN) expression was observed surrounding each glomerulosa cell and as long fibrils between the cords of fasciculata cells. In the medulla, FN was present around chromaffin cells or bordering blood vessels. Integrin a2, a3 and a5 were present mainly in the cortex, while a1 was present in the medulla. In culture, all ECM favoured proliferation of both glomerulosa and fasciculata cells, while protein synthesis was lower on FN and LN in glomerulosa cells. CIV promoted ACTH-induced proliferation whereas FN favoured ACTH-induced protein synthesis in glomerulosa cells. Except for LN, ECM increased expression of 3b-hydroxysteroid dehydrogenase and enhanced basal aldosterone, although corticosterone secretion was only enhanced by CI and CIV. In fasciculata cells, the potency of ACTH-induced cAMP production was lower on ECM, compared with plastic. Moreover, ACTH, but not ECM, activated mitogenic-activated protein kinase p38 and stress-activated protein kinases. Glomerulosa and fasciculata cells grown on CI and CIV had a polygonal morphology, while cells grown on LN appeared as clusters of small rounded cells. On FN, the glomerulosa cells exhibited polygonal morphology while fasciculata cells appeared as clusters of small rounded cells. Together, these results indicate that ECM modulates basal and ACTH-induced cell functions, with FN, CI and CIV specifically favouring steroid secretion, as opposed to LN which inhibits secretion while promoting proliferation.

60 YEARS OF POMC: Adrenal and extra-adrenal functions of ACTH

“…The contribution of cell-matrix interactions to intracellular events leading to steroidogenesis is now well documented (Cheng & Hornsby 1992), in which fibronectin and collagens favor steroid synthesis and laminin favors cell proliferation (Otis et al 2007), chemotaxis, and haptotaxis (Feige et al 1998). Binding of ECM components to their receptors, integrins, favors tyrosine phosphorylation of several focal adhesion proteins that facilitate spreading of cells on their substratum, in particular on fibronectin and collagens.…”

Living-cell imaging of transgenic rat anterior pituitary cells in primary culture reveals novel characteristics of folliculo-stellate cells

“…They were then sorted by a MoFlo XDP (Beckman Coulter, Inc., Fullerton, CA, USA) and were incubated with RNase-free DNase I (1 U/tube; Promega Corp). As positive controls of integrin subunit gene expression, total RNA fractions were also prepared from the adrenal gland (Otis et al 2007) and whole fetus of S100b-GFP male rats. After inactivation of DNase I by heating for 10 min at 65 8C, cDNA was synthesized using a Superscript III reverse transcription kit with oligo-(dT) 20 primer (Invitrogen).…”

Mechanisms of adrenal gland growth: signal integration by extracellular signal regulated kinases1/2

“…In addition to its tropic effects angiotensin II dependent activation of ERK1/2 resulted in an activation of the hormonesensitive lipase (cholesterol ester hydrolase) in adrenal zona glomerulosa cells, which supports a role of ERK1/2 for steroidogenesis, as activation of this lipase initializes cholesterol mobilization to the outer mitochondrial membrane (Cherradi et al 2003). The function of angiotensin II as one important regulator of adrenal ERK1/2 activity is further substantiated by the existence of a number of co-effectors of angiotensin II dependent ERK1/2 phosphorylation like ACTH (Chabre et al 1995), integrins (Campbell et al 2003, Otis et al 2007b or BMP-6 (Suzuki et al 2004, Inagaki et al 2006. The effect of BMP-6 is thought to be exerted in an autocrine fashion via SMAD proteins, which are known modulators of ERK1/2 activity (Kano et al 2005).…”

“…ACTH as a key regulator of adrenal gland growth and function affects several intracellular signaling cascades which have been reviewed (Gallo-Payet & Payet 2003, Forti et al 2006, Otis et al 2007b) and which cannot be discussed here in a comprehensive manner. Concerning the effects of ACTH on ERK activation, positive (Le & Schimmer 2001, Ferreira et al 2004, McNeill et al 2005, weak (Lotfi et al 1997, Lepique et al 2000, negative ( Watanabe et al 1997), or no effects have been described (Cote et al 1998).…”

“…In this cortext it is important to mention that the effects of ACTH on ERK1/2 can also be indirect since it has been demonstrated that ACTH blocks angiotensin II or FGF2 dependent ERK1/2 activation (Chabre et al 1995). Interestingly, also integrins co-regulate ACTH effects (Otis et al 2007b). From these interactions a core regulatory system can be established consisting of ACTH as the principal regulator and angiotensin II.…”