Abstract 1168: Novel Involvement Of Caveolin-1 In Adam 17-dependent EGF Receptor Transactivation Induced By Angiotensin II
We have demonstrated that a metalloprotease-dependent HB-EGF shedding is required for EGF receptor (EGFR) transactivation and subsequent hypertrophy of vascular smooth muscle sells (VSMCs) induced by angiotensin II (AngII). Recently, we have further identified the metalloprotease as ADAM17. However, the underlying molecular mechanism by which AngII activates ADAM17 remains unclear. Here, we hypothesized that AngII stimulates ADAM17 activity by a mechanism involving a membrane microdomain, caveolae. In cultured rat aortic VSMCs, we found a constitutive association between ADAM17 and caveolin 1 (Cav1) by immunoprecipitation and immunohistochemistry. Interestingly, AngII (100 nM) stimulation causes a rapid (within 2 min) dissociation of Cav1 from ADAM17. Moreover, non-detergent sucrose gradient fractionation revealed that ADAM17 localizes in the Cav1-rich lipid raft fraction of VSMCs, and AngII induces a fraction shift of ADAM 17 from low to high density membrane fractions. Thus, infection of adenovirus encoding Cav1 in VSMCs markedly inhibits AngII-induced EGFR transactivation. In addition, methyl-β-cyclodextrin, a cholesterol-sequestering reagent, stimulates HB-EGF shedding and subsequent EGFR transactivation in VSMCs. From these data, we conclude that raft/caveolae provides an indispensable environment for ADAM17-dependent EGFR transactivation utilized by AngII. Moreover, our data indicate that dissociation of Cav1 from ADAM17 is the mechanism by which AngII induces ADAM17 activation in VSMCs. This novel mechanism would provide important information to target cardiovascular diseases under the enhanced renin angiotensin system.