Protein-tyrosine-phosphatase-mediated epidermal growth factor (EGF) receptor transinactivation and EGF receptor-independent stimulation of mitogen-activated protein kinase by bradykinin in A431 cells

Abstract

Transactivation of the epidermal growth factor (EGF) receptor (EGFR) has been proposed to represent an essential link between G-protein-coupled receptors and the mitogen-activated protein kinase (MAPK) pathway in various cell types. In the present work we report, in contrast, that in A431 cells bradykinin transinactivates the EGFR and stimulates MAPK activity independently of EGFR tyrosine phosphorylation. Both effects of bradykinin are mediated by a pertussis-toxin-insensitive G-protein. Three lines of evidence suggest the activation of a protein tyrosine phosphatase (PTP) by bradykinin: (i) treatment of A431 cells with bradykinin decreases both basal and EGF-induced EGFR tyrosine phosphorylation, (ii) this effect of bradykinin can be blocked by two different PTP inhibitors, and (iii) bradykinin significantly increased the PTP activity in total A431 cell lysates when measured in vitro. The transmembrane receptor PTP σ was identified as a putative mediator of bradykinin-induced downregulation of EGFR autophosphorylation. Activation of MAPK in response to bradykinin was insensitive towards AG 1478, a specific inhibitor of EGFR tyrosine kinase, but was blocked by wortmannin or bisindolylmaleimide, inhibitors of phosphatidylinositol 3-kinase (PI3-K) and protein kinase C (PKC) respectively. These results also suggest that the bradykinin-induced activation of MAPK is independent of EGFR and indicate a pathway involving PI3-K and PKC. In addition, bradykinin evokes a rapid and transient increase in Src kinase activity. Although Src does not participate in bradykinin-induced stimulation of PTP activity, inhibition of Src by 4-amino-5-(4-methylphenyl)-7-(t-butyl)pyrazolo(3,4-d)pyrimidine leads to an increase in MAPK activation by bradykinin. Our results suggest that in A431 cells the Gq/11-protein-coupled bradykinin B2 receptor may stimulate PTP activity and thereby transinactivate the EGFR, and may simultaneously activate MAPK by an alternative signalling pathway which can bypass EGFR.

Kinin B2 Receptor-Coupled Signal Transduction in Human Cultured Keratinocytes

“…Our results indicate that MAPK phosphorylation induced by LBK is only partially regulated by EGFR phosphorylation, confirming previous studies showing that in addition to the ligand itself, EGFR transactivation also depends on the cell type involved. A similar observation has been reported for A431 cells where BK independently activates MAPK via a pathway that is sensitive towards inhibitors of phosphoinositide 3 kinase and PKC, but not to AG1478, corroborating that EGFR transactivation is not necessarily a prerequisite for G protein-coupled receptors-induced activation of MAPK (Graness et al, 2000).…”

Mechanisms regulating the expression, self‐maintenance, and signaling‐function of the bradykinin B2 and B1 receptors

“…Cross regulation of BKB1R and BKB2R has been suggested based on the observation that activation of BKB2R also activates NF‐κB, which can then prime the expression of BKB1R (Schanstra et al, 1998; Phagoo et al, 1999; Xie et al, 2000). Additional pathways following BK activation include production of IL‐6 and IL‐8 in lung fibroblasts (Hayashi et al, 2000), generation of reactive oxygen species in vascular smooth muscle cells (Greene et al, 2000) and transinactivation of EGF receptor in A431 cells (Graness et al, 2000). BK also induces the synthesis of a number of vasoactive, inflammatory agents such as platelet activating factor, endothelium derived hyperpolarizing factor, nitric oxide, and leukotrienes (Regoli and Barabé, 1980; Vane and Botting, 1987; Cahill et al, 1988; Ahluwalia and Perretti, 1999).…”

Bradykinin inhibits high glucose- and growth factor-induced collagen synthesis in mesangial cells through the B2-kinin receptor

“…In addition, a stimulating effect of B2R activation on collagen I mRNA expression was only demonstrated in quiescent MC but not in EGF-or TGF-␤-stimulated MC (47). Studies have reported an effect of BK on EGFR activation, including transactivation of EGFR in quiescent fibroblast (12) and renal tubular cells (30) and transinactivation of EGFR in nonquiescent epithelial carcinoma (22) and mesangial cells (23). This suggests that BK could exert either a stimulating effect on quiescent cells or an inhibiting effect on nonquiescent cells.…”