G protein-coupled receptors desensitize and down-regulate epidermal growth factor receptors in renal mesangial cells

Different types of plasma membrane receptors engage in various forms of cross-talk. We used cultures of rat renal mesangial cells to study the regulation of EGF receptors (EGFRs) by various endogenous G protein-coupled receptors (GPCRs). GPCRs (5-hydroxytryptamine(2A) lysophosphatidic acid, angiotensin AT(1), bradykinin B-2) were shown to transactivate EGFRs through a protein kinase C-dependent pathway. This transactivation resulted in the initiation of multiple cellular signals (phosphorylation of the EGFRs and ERK and activation of cAMP-responsive element-binding protein (CREB), NF-kappaB, and E2F), as well as subsequent rapid down-regulation of cell-surface EGFRs and internalization and desensitization of the EGFRs without change in the total cellular complement of EGFRs. Internalization of the EGFRs and the down-regulation of cell-surface receptors in mesangial cells were blocked by pharmacological inhibitors of clathrin-mediated endocytosis and in HEK293 cells by transfection of cDNA constructs that encode dominant negative beta -arrestin-1 or dynamin. Whereas all of the effects of GPCRs on EGFRs were dependent to a great extent on protein kinase C, those initiated by EGF were not. These studies demonstrate that GPCRs can induce multiple signals through protein kinase C-dependent transactivation of EGFRs. Moreover, GPCRs induce profound desensitization of EGFRs by a process associated with the loss of cell-surface EGFRs through clathrin-mediated endocytosis.