TRPV5 and TRPV6 constitute the Ca 2+ in¯ux pathway in a variety of epithelial cells. Here, we identi®ed S100A10 as the ®rst auxiliary protein of these epithelial Ca 2+ channels using yeast two-hybrid and GST pull-down assays. This S100 protein forms a heterotetrameric complex with annexin 2 and associates speci®cally with the conserved sequence VATTV located in the C-terminal tail of TRPV5 and TRPV6. Of these ®ve amino acids, the ®rst threonine plays a crucial role since the corresponding mutants (TRPV5 T599A and TRPV6 T600A) exhibited a diminished capacity to bind S100A10, were redistributed to a subplasma membrane area and did not display channel activity. Using GST pull-down and co-immunoprecipitation assays we demonstrated that annexin 2 is part of the TRPV5±S100A10 complex. Furthermore, the S100A10±annexin 2 pair colocalizes with the Ca 2+ channels in TRPV5-expressing renal tubules and TRPV6-expressing duodenal cells. Importantly, downregulation of annexin 2 using annexin 2-speci®c small interfering RNA inhibited TRPV5 and TRPV6-mediated currents in transfected HEK293 cells. In conclusion, the S100A10±annexin 2 complex plays a crucial role in routing of TRPV5 and TRPV6 to plasma membrane.

ORAI family channels have emerged as important players in malignant transformation, yet the way in which they reprogram cancer cells remains elusive. Here we show that the relative expression levels of ORAI proteins in prostate cancer are different from that in noncancerous tissue. By mimicking ORAI protein remodeling observed in primary tumors, we demonstrate in in vitro models that enhanced ORAI3 expression favors heteromerization with ORAI1 to form a novel channel. These channels support store-independent Ca(2+) entry, thereby promoting cell proliferation and a smaller number of functional homomeric ORAI1-based store-operated channels, which are important in supporting susceptibility to apoptosis. Thus, our findings highlight disrupted dynamic equilibrium of channel-forming proteins as an oncogenic mechanism.

Castration resistance in prostate cancer (PCa) constitutes an advanced, aggressive disease with poor prognosis, associated with uncontrolled cell proliferation, resistance to apoptosis, and enhanced invasive potential. The molecular mechanisms involved in the transition of PCa to castration resistance are obscure. Here, we report that the nonselective cationic channel transient receptor potential vanilloid 2 (TRPV2) is a distinctive feature of castration-resistant PCa. TRPV2 transcript levels were higher in patients with metastatic cancer (stage M1) compared with primary solid tumors (stages T2a and T2b). Previous studies of the TRPV2 channel indicated that it is primarily involved in cancer cell migration and not in cell growth. Introducing TRPV2 into androgen-dependent LNCaP cells enhanced cell migration along with expression of invasion markers matrix metalloproteinase (MMP) 9 and cathepsin B. Consistent with the likelihood that TRPV2 may affect cancer cell aggressiveness by influencing basal intracellular calcium levels, small interfering RNA-mediated silencing of TRPV2 reduced the growth and invasive properties of PC3 prostate tumors established in nude mice xenografts, and diminished expression of invasive enzymes MMP2, MMP9, and cathepsin B. Our findings establish a role for TRPV2 in PCa progression to the aggressive castration-resistant stage, prompting evaluation of TRPV2 as a potential prognostic marker and therapeutic target in the setting of advanced PCa. Cancer Res; 70(3); 1225-35. ©2010 AACR.