Modulation of TRPV4 gating by intra- and extracellular Ca2+.

Abstract We have studied the modulation of gating properties of the Ca 2+ -permeable, cation channel TRPV4 transiently expressed in HEK293 cells. The phorbol ester 4αPDD transiently activated a current through TRPV4 in the presence of extracellular Ca 2+ . Increasing the concentration of extracellular Ca 2+ ([Ca 2+ ] e ) reduced the current amplitude and accelerated its decay. This decay was dramatically delayed in the absence of [Ca 2+ ] e . It was also much slower in the presence of [Ca 2+ ] e in a mutant channel, obtained by a point mutation in the 6th transmembrane domain, F707A. Mutant channels, containing a single mutation in the C-terminus of TRPV4 (E797), were constitutively open. In conclusion, gating of the 4αPDD-activated TRPV4 channel depends on both extra- and intracellular Ca 2+ , and is modulated by mutations of single amino acid residues in the 6th transmembrane domain and the C-terminus of the TRPV4 protein.