May regulate epithelial calcium transport by inhibiting TRPV5 activity. Interacts with YWHAZ/14-3-3 protein zeta (By similarity). Interacts with TRPV5 and TRPV6. Apical domain of kidney distal tubular cells. According to PubMed:10978534, testis-specific. According to PubMed:16371431, broadly expressed. Expression starts at 19 dpc in brain. Down-regulated by vitamin D.