PKC‐ζ is required for angiotensin II‐induced activation of ERK and synthesis of C‐FOS in MCF‐7 cells

Abstract

We examined the signalling pathways responsible for the Ang II induction of growth in MCF-7 human breast cancer cells. Ang II in MCF-7 cells induced: (a) the translocation from the cytosol to membrane and nucleus of atypical protein kinase C-zeta (PKC-zeta) but not of PKC-alpha, -delta, - epsilon and -eta; (b) the expression of c-fos mRNA and protein; (c) the phosphorylation of the extracellular signal-regulated protein kinases 1 and 2 (ERK1/2). All these effects were due to the activation of the Ang II type I receptor (AT1) since they were blocked by the AT1 antagonist losartan. The Ang II-stimulated ERK1/2 phosphorylation was blocked by (a) high doses of staurosporine, inhibitor of PKC-zeta, and by a synthetic myristoylated peptide with sequences based on the endogenous PKC-zeta pseudosubstrate region (zeta-PS); (b) PD098059, a mitogen-activated protein kinase kinase inhibitor (MAPKK/MEK); and, moreover, (c) the inhibitors of phosphoinositide 3-kinases (PI3K), LY294002 and wortmannin, thus indicating that PI3K may act upstream of ERK1/2. The Ang II-evoked c-fos induction was blocked only by high doses of staurosporine and by zeta-PS whilst PD098059, LY294002 and wortmannin were ineffective, thus indicating that c-fos induction is not due to ERK1/2 activity. When the epidermal growth factor-receptor (EGFR) tyrosine kinase activity was inhibited by the use of its inhibitor AG1478, Ang II was still able to induce ERK1/2 phosphorylation and c-fos expression, therefore proving that the transactivation of EGFR was not required for these Ang II effects in MCF-7 cells. The previously reported proliferation of MCF-7 cells induced by Ang II was blocked by PD098059 and by wortmannin in a dose-dependent manner, thereby indicating that in MCF-7 cells the PI3K and ERK pathways mediate the mitogenic signalling of AT1. Our results suggest that in MCF-7 cells Ang II activates multiple signalling pathways involving PKC-zeta, PI3K and MAPK; of these pathways only PKC-zeta appears responsible for the induction of c-fos.

Protein kinase C (PKC)-δ/-ε mediate the PKC/Akt-dependent phosphorylation of extracellular signal-regulated kinases 1 and 2 in MCF-7 cells stimulated by bradykinin

“…4A); all the other isoforms expressed by the MCF-7 cells and reported previously (Muscella et al 2003) did not show any cytosol-to-membrane translocation (Fig. 4A).…”

“…In PC-12 cells, EGFR transactivation (Zwick et al 1997) as well as activation of a Pyk2/Src pathway (Dikic et al 1996) are involved in BK-mediated MAPK activation. Translocation of PKC isozymes to the membrane are mitogenic signals for the cells (Lafon et al 1995, Greco et al 2003, 2004 and can result in the phosphorylation of ERK1/2. In A431 cells, B 2 induces MAPK activation through a pathway involving both PI3K and PKC, and resulting in the inhibition of EGFR activity (Graness et al 1998).…”

“…The PLC activity triggers the translocation from cytosol to membrane and thus the activation of PKC isozymes, either conventional (PKC-, -), or novel (PKC-, -´, -and -), and such activation may be a mitogenic signal for breast cells (Lafon et al 1995, Greco et al 2003, 2004, 2005.…”

Gαq Acts as an Adaptor Protein in Protein Kinase Cζ (PKCζ)-mediated ERK5 Activation by G Protein-coupled Receptors (GPCR)

“…Consistent with the notion that PKC is a novel G␣ q effector, agonists acting through G q -coupled GPCR such as angiotensin II, phenylephrine, platelet-activating-factor, or thromboxane A2 have been shown to promote PKC translocation and activation in several cell types (24 -26, 32, 33), and PKC has been suggested to participate in GPCR-mediated control of cell proliferation (25)(26)(27), eosinophil degranulation (32), or smooth muscle cell adhesion, spreading, and hypertrophy (25). Several authors have suggested a role for PKC in ERK1/2 activation by GPCR (34,35), although another recent report indicates that inhibition of PKC in adult cardiomyocytes has no effect in ERK1/2 activation by G q -coupled GPCR (36).…”

The role of angiotensin II in the regulation of breast cancer cell adhesion and invasion

“…AII is known to stimulate breast cell proliferation (Greco et al 2002, Muscella et al 2003, but it may have other activities. One possibility is that it may be involved in breast disease progression as suggested by preliminary studies, in which it was demonstrated that treatment of breast cancer cells with AII reduced breast cancer cell invasion through a simple matrix composed of collagen type IV.…”