Rapid effects of 17β-estradiol on epithelial TRPV6 Ca2+ channel in human T84 colonic cells

SummaryThe control of calcium homeostasis is essential for cell survival and is of crucial importance for several physiological functions. The discovery of the epithelial calcium channel Transient Receptor Potential Vaniloid (TRPV6) in intestine has uncovered important Ca2+ absorptive pathways involved in the regulation of whole body Ca2+ homeostasis. The role of steroid hormone 17β-estradiol (E2), in [Ca2+]i regulation involving TRPV6 has been only limited at the protein expression levels in over-expressing heterologus systems. In the present study, using a combination of calcium-imaging, whole-cell patch-clamp techniques and siRNA technology to specifically knockdown TRPV6 protein expression, we were able to (i) show that TRPV6 is natively, rather than exogenously, expressed at mRNA and protein levels in human T84 colonic cells, (ii) characterize functional TRPV6 channels and (iii) demonstrate, for the first time, the rapid effects of E2 in [Ca2+]i regulation involving directly TRPV6 channels in T84 cells. Treatment with E2 rapidly (<5 min) enhanced [Ca2+]i and this increase was partially but significantly prevented when cells were pre-treated with ruthenium red and completely abolished in cells treated with siRNA specifically targeting TRPV6 protein expression. These results indicate that when cells are stimulated by E2, Ca2+ enters the cell through TRPV6 channels. TRPV6 channels in T84 cells contribute to the Ca2+ entry/signalling pathway that is sensitive to 17β-estradiol.