Abstract 979: A Metalloprotease, ADAM17/TACE, Mediates EGF Receptor Transactivation and Vascular Smooth Muscle Cell Hypertrophy Induced by Angiotensin II
Angiotensin II (AngII) promotes growth and migration of vascular smooth muscles cells (VSMCs) via EGF receptor (EGFR) transactivation mediated through a metalloprotease-dependant heparin-binding EGF-like growth factor (HB-EGF) shedding. We have previously reported that elevation of intracellular Ca2+ and reactive oxygen species production are required for HB-EGF shedding and EGFR transactivation by AngII in COS7 cells expressing AngII type I receptor (AT1). However, the identity of the protease responsible for this process that likely mediates vascular remodeling induced by AngII remains unknown. Therefore, the aim of this study is to uncover the protease together with its role in mediating protein synthesis. To identify the metallopro-tease required for AngII-induced EGFR transactivation in VSMCs, VSMCs were infected with retrovirus encoding dominant negative (dn) mutants of ADAM10, ADAM17 or a control vector. EGFR transactivation as detected by its Tyr1068 phosphorylation induced by AngII (100 nM) but not by EGF (10 ng/ml) was inhibited in VSMCs infected with dnADAM17 retrovirus but not with dnADAM10 retrovirus. AngII enhanced protein synthesis and cell volume in VSMCs infected with control retrovirus, but not in VSMCs infected with dnADAM17 retrovirus. However, AngII similarly stimulated intracellular Ca2+ elevation and JAK2 Tyr1007/1008 phosphorylation in these VSMCs. In addition, dnADAM17 retrovirus infection inhibited HB-EGF shedding induced by AngII in A10 VSMCs co-transfected with plasmids encoding AT1 receptor and HB-EGF-ALP. Moreover, AngII rapidly (within 2min) stimulated tyrosine phosphorylation of HA-tagged ADAM17 retrovirally introduced in VSMCs. Taken together, we conclude that ADAM17 activated via the AT1 receptor is responsible for EGFR transactivation and subsequent hypertrophy in VSMCs. These findings demonstrate a previously missing molecular mechanism by which AngII promotes vascular remodeling and provide a novel therapeutic target for the treatment of cardiovascular disease.