Noradrenaline induces binding of Clathrin light chain A to α1-adrenoceptors in the human prostate

BACKGROUND Binding of clathrins or caveolin to G protein‐coupled receptors may induce post‐translational modifications of receptor function. Receptor regulation by clathrin requires cofactors ADP‐ribosylation factor 6 (ARF6) and adaptin, while dynamin is required for clathrin‐ and caveolin‐dependent mechanisms. OBJECTIVE To investigate the expression and α1‐adrenoceptor binding of clathrins, caveolin, and their cofactors in the human prostate. METHODS Prostate tissue was obtained from radical prostatectomy. Expression of clathrin heavy chain (HC), clathrin light chain A and B (LCA, LCB), caveolin‐1, ARF6, β‐adaptin, and dynamin‐2 was studied by RT‐PCR, Western blot, immunohistochemistry, and fluorescence staining. Interaction of α1A‐adrenoceptors with clathrins and caveolin‐1 was studied by coimmunoprecipitation. RESULTS mRNA and protein expression of clathrin HC, LCA, LCB, caveolin‐1, dynamin‐2, and β‐adaptin was detected in prostate tissues of each patient. Immunohistochemistry demonstrated the expression of clathrin HC, LCA, LCB, caveolin, dynamin, and β‐adaptin in stromal cells. Immunoreactivity for these proteins colocalized with α‐smooth muscle actin and α1A‐adrenoceptors in double fluorescence staining. Coimmunoprecipitation demonstrated that α1A‐adrenoceptors in prostate tissue interact with clathrin HC and LCB under resting conditions, but not with caveolin‐1. Stimulation of prostate tissues with noradrenaline (30 µM) in vitro induced binding of clathrin LCA to α1A‐adrenoceptors. CONCLUSIONS The prostatic α1‐adrenoceptor population is at least partially bound to clathrin HC and LCB. Upon receptor activation, prostate α1A‐adrenoceptors bind clathrin LCA. This points to a new concept of post‐translational α1‐adrenoceptor regulation in the prostate, which includes receptor interaction with accessory binding partners. Prostate 73: 715–723, 2013. © 2013 Wiley Periodicals, Inc.