Association of cross-talk between α1D-adrenergic receptor (α1D -AR) and transient receptor potential vanilloid 1 (TRPV1) with the proliferation of PC3 prostate cancer cells

87 Background: Growing evidence supports the role of α1-ARs in the direct mitogenic effect of catecholamines on prostate cancer (PC) cell growth. The expression of α1D-AR on PC3 prostate cancer cells and the ability of noradrenalin (NA) to stimulate PC3 cell proliferation in a α1D-AR-dependent manner were reported (Quaglia et al., 2005). In addition, TRPV1 expression was also found in prostate cancers (Sanchez et al., 2006). Aim of this study was to investigate the relationship between α1D-AR and TRPV1 receptors and the involvement of TRPV1 in NA-induced proliferation in PC3 cells. Methods: By western blot analysis and confocal microscopy the expression α1D-AR and TRPV1 and localization in PC3 cells were evaluated. PC3 cells were incubated with NA alone or in combination with WS433 and capsazepine (CPZ), α1D-AR and TRPV1 antagonists. Proton release, calcium influx and cell proliferation were assessed in α1D-AR-, TRPV1- or α1D-AR/TRPV1 double-silenced PC3 cells by cytosensor and cytofluorymetric analyses. Finally, lysates from NA-treated PC3 cells alone or in combination with WS433 or CPZ were blotted with anti-phospho ERK, anti-ERK and anti-phospho-(Ser) PKC substrate Abs and Inositol-1,4,5-trisphosphate [3H] radioreceptor assay were performed. Results: α1D-AR and TRPV1 co-localize and are co-immunoprecipitated in PC3 cells. Treatment of PC3 cells with NA strongly stimulated proton release, calcium influx and cell proliferation that were reverted by α1D-AR WS433 and TRPV1 antagonist. NA-induced increase of survival and proliferation was totally abrogated in α1D-AR/TRPV1 silenced cells. In addition, NA stimulates ERK and PKC substrate phosphorylation that was inhibited by WS433 and CPZ. Finally, CPZ treatment inhibited NA-dependent PLC activation, while WS433 had no effect. Conclusions: A functional and structural cross-talk between α1D-AR and TRPV1 receptors control NA-induced proliferation of PC cells. These data strongly suggest the development of new pharmaceutical approaches based on bifunctional antibodies and molecules recognizing both α1D-AR and TRPV1 receptors.