Store-operated Ca2+ current and TRPV6 channels in lymph node prostate cancer cells

The contribution of endogenous and recombinant transient receptor potential vanilloid type 6 ( TRPV6) channels to Ca2+ entry across the plasma membrane was studied in the human lymph node prostate cancer cell line ( LNCaP). LNCaP cells do express the TRPV6 gene, and Ca2+ entry currents in these cells were detected after active and passive Ca2+ store depletion by intracellular application of inositol 1,4,5- trisphosphate, Ca2+ chelators, and the sarcoplasmic/ endoplasmic reticulum Ca2+ -ATPase inhibitor thapsigargin. This store- operated Ca2+ current ( I-SOC) had biophysical properties similar to those of the Ca2+ release- activated Ca2+ current ( I-CRAC) in rat basophilic leukemia cells such as the activation mechanism, inward rectification, and Ca2+ selectivity. These properties are also shared by the Ca2+- sensing Ca2+ current ( I-TRPV6) recorded after heterologous expression of TRPV6 cDNA in human embryonic kidney and rat basophilic leukemia cells ( Bodding, M., Wissenbach, U., Flockerzi, V. ( 2002) J. Biol. Chem. 277, 36656 - 36664). TRPV6 cDNA transfection of LNCaP cells restored recombinant I-TRPV6, which can be distinguished from I-SOC by the mechanism of activation, the voltage dependence of monovalent currents in the absence of external divalent cations, and the changes in Ca2+ current densities due to different membrane potentials. In addition, I-SOC was not affected by antiandrogen or 1,25- dihydroxyvitamin D-3 treatment of LNCaP cells, which up- regulates TRPV6 gene expression, or by androgen treatment, which has the opposite effect. Therefore, native channels responsible for I-SOC are different from those for recombinant I-TRPV6 and do not appear to be affected if one of their assumed subunits, TRPV6, is up- or down- regulated, suggesting a rather rigid subunit composition in vivo.