Differential Pathways of Angiotensin II-Induced Extracellularly Regulated Kinase 1/2 Phosphorylation in Specific Cell Types: Role of Heparin-Binding Epidermal Growth Factor

Abstract

Stimulation of the angiotensin II (Ang II) type 1 receptor (AT1-R) causes phosphorylation of extracellularly regulated kinases 1 and 2 (ERK1/2) via epidermal growth factor receptor (EGF-R) transactivation-dependent or -independent pathways in Ang II target cells. Here we examined the mechanisms involved in agonist-induced EGF-R transactivation and subsequent ERK1/2 phosphorylation in clone 9 (C9) hepatocytes, which express endogenous AT1-R, and COS-7 and human embryonic kidney (HEK) 293 cells transfected with the AT1-R. Ang II-induced ERK1/2 activation was attenuated by inhibition of Src kinase and of matrix metalloproteinases (MMPs) in C9 and COS-7 cells, but not in HEK 293 cells. Agonist-mediated MMP activation in C9 cells led to shedding of heparin-binding EGF (HB-EGF) and stimulation of ERK1/2 phosphorylation. Blockade of HB-EGF action by neutralizing antibody or its selective inhibitor, CRM197, attenuated ERK1/2 activation by Ang II. Consistent with its agonist action, HB-EGF stimulation of these cells caused marked phosphorylation of the EGF-R and its adapter molecule, Shc, as well as ERK1/2 and its dependent protein, p90 ribosomal S6 kinase, in a manner similar to that elicited by Ang II or EGF. Although the Tyr319 residue of the AT1-R has been proposed to be an essential regulator of EGF-R transactivation, stimulation of wild-type and mutant (Y319F) AT1-R expressed in COS-7 cells caused EGF-R transactivation and subsequent ERK1/2 phosphorylation through release of HB-EGF in a Src-dependent manner. In contrast, the noninvolvement of MMPs in HEK 293 cells, which may reflect the absence of Src activation by Ang II, was associated with lack of transactivation of the EGF-R. These data demonstrate that the individual actions of Ang II on EGF-R transactivation in specific cell types are related to differential involvement of MMP-dependent HB-EGF release.

Neuregulin-1-Human Epidermal Receptor-2 Signaling Is a Central Regulator of Pulmonary Epithelial Permeability and Acute Lung Injury

“…HER1/ EGFR and HER2 can be activated by stimuli that do not interact directly with these receptors, a process that can occur through ligand-dependent or -independent means (12,38). For example, stimulation of the angiotensin II receptor induces shedding of the EGFR ligand heparin-binding EGF, leading to activation of EGFR in hepatocytes (39). In contrast, agonists of G proteincoupled receptors (such as lysophosphatidic acid) phosphorylate EGFR directly through Src kinase-dependent phosphorylation (40).…”

G Protein Coupling and Second Messenger Generation Are Indispensable for Metalloprotease-dependent, Heparin-binding Epidermal Growth Factor Shedding through Angiotensin II Type-1 Receptor

“…However, this mutant is able to stimulate HB-EGF shedding and EGFR transactivation in our study. The mutant also stimulated ERK in COS7 cells that was blocked by an EGFR kinase inhibitor or a metalloprotease inhibitor (66). The discrepancy may be due to the different nature of the cells utilized together with distinct experimental strategies (Seta and Sadoshima used cells expressing an exogenous EGFR gene) (37).…”

Angiotensin II induces phosphorylation of glucose-regulated protein-75 in WB rat liver cells

“…Previous reports have shown that cell types exhibiting Ang II signaling through EGF-R activation include VSMCs, cardiac myocytes and fibroblasts, COS 7 cells, C9 hepatic cells, glomerular mesengial cells, prostrate stromal cells, anterior pituitary cells, and breast cancer cells [23]. However, the EGF-R transactivation does not appear to be a universal process and has a minor or no role in HEK 293 cells [23] and pre-glomerular smooth muscle cells [24].…”

“…In rat aortic VSMCs, EGF-R transactivation was shown to be crucial for Ang II mediated p42/p44 MAP kinases [10,14,16]; however, in human embryonic kidney (HEK) cells transfected with AT 1 -R [23] and preglomular smooth muscle cells expressing endogenous AT 1 -R [24], MAP kinase activation by Ang II has been shown to occur independent of EGF-R transactivation. Since involvement of caveolin-1 in AT 1 -R signaling has not been well studied in non-vascular smooth muscle cell types, we initiated studies to determine if exposure of WB cells (a continuously passaged rat liver cell line), which expresses endogenous AT 1 -R, to Ang II, causes tyrosine phosphorylation of caveolin-1 and transactivation of EGF-R. WB cells are epithelial cells that were originally isolated from the liver of adult rats [25,26] and they have been used by numerous investigators to study Ang IIinduced signal transduction pathways [25][26][27][28][29][30][31][32][33][34].…”