The goal of the present proposal is to study cross-talk between G protein-coupled receptors (GPCRs) and receptor tyrosine kinases (RTKs) that are present in physiological condition in renal mesangial cells. Specifically, we will study the involvement of metalloproteinases in this process. Further, we wish to study how extracellular matrix (ECM) receptors (called integrins) influence GPCR-RTK cross-talk in cultured mesangial cells.
The specific aims of this proposal are: 1. To investigate whether activation of mitogenic Gq-coupled receptors (such as angiotensin II AT1A, serotonin 5-HT2A and LPA-Edg receptors) induce transactivation of the epidermal growth factor receptor (EGFR) by exogenous growth factor(s) through metalloproteinases in renal mesangial cells. a) If yes, we will examine whether these processes involve the same EGF-like growth factor (namely heparin-bound EGF) or whether distinct EGF-like growth factors are employed by the various GPCRs. b) We will also determine whether these shed ligands are processed by the same metalloproteinase(s), or by different ones depending on which GPCR is activated. Our initial focus will be on the TACE/ADAM 17 metalloproteinase. 2. To study the involvement of integrins and effects of changes in the ECM on GPCR-RTK cross-talk in mesangial cells. a) Is Gq-coupled receptor activation of ERK dependent on integrin-mediated cell anchorage? b) Which integrins are involved in GPCR-RTK cross-talk? c) Does overexpression of a TACE enzyme lacking the disintegrin domain alter signaling? d) Is physical interaction of TACE with integrins necessary for the GPCR-RTK cross-talk to occur?
