TRPM8 channel as a novel molecular target in androgen-regulated prostate cancer cells

// Swapna Asuthkar 1 , Kiran Kumar Velpula 1 , Pia A. Elustondo 2 , Lusine Demirkhanyan 1 and Eleonora Zakharian 1 1 University of Illinois College of Medicine, Department of Cancer Biology and Pharmacology, Peoria, IL, USA 2 Dalhousie University, Halifax, NS, Canada Correspondence to: Eleonora Zakharian, email: // Swapna Asuthkar, email: // Keywords : prostate cancer (PC), transient receptor potential melastatin 8(TRPM8) ion channel, testosterone, DHT (5α-dihydrotestosterone), androgen receptor (AR) Received : March 18, 2015 Accepted : April 07, 2015 Published : April 29, 2015 Abstract The cold and menthol receptor TRPM8 is highly expressed in prostate and prostate cancer (PC). Recently, we identified that TRPM8 is as an ionotropic testosterone receptor. The TRPM8 mRNA is expressed in early prostate tumors with high androgen levels, while anti-androgen therapy greatly reduces its expression. Here, from the chromatin-immunoprecipitation (ChIP) analysis, we found that an androgen response element (ARE) mediates androgen regulation of trpm8 . Furthermore, using immunofluorescence, calcium-imaging and planar lipid bilayers, we identified that TRPM8 channel is functionally regulated by androgens in the prostate. Although TRPM8 mRNA is expressed at high levels, we found that the TRPM8 protein undergoes ubiquitination and degradation in PC cells. The mass-spectrometry analysis of TRPM8, immunoprecipitated from LNCaP cells identified ubiquitin-like modifier-activating enzyme 1 (UBA1). PYR-41, a potent inhibitor of initial enzyme in the ubiquitination cascade, UBA1, increased TRPM8 activity on the plasma membrane (PM) of LNCaP cells. Furthermore, PYR-41-mediated PM TRPM8 activity was accompanied by enhanced activation of p53 and Caspase-9. Interestingly, we found that the trpm8 promoter possesses putative binding sites for p53 and that the overexpression of p53 increased the TRPM8 mRNA levels. In addition to the genomic regulation of TRPM8 by AR and p53, our findings indicate that the testosterone-induced PM TRPM8 activity elicits Ca 2+ uptake, subsequently causing apoptotic cell death. These findings support the strategy of rescuing PM TRPM8 expression as a new therapeutic application through the regulation of PC cell growth and proliferation.