Activation of TRPV4 channels (hVRL-2/mTrp12) by phorbol derivatives
Watanabe, H.; Davis, J.B.; Smart, D.; Jerman, J.C.; Smith, G.D.; Hayes, P.; Vriens, J.; Cairns, W.; Wissenbach, U.; Prenen, J.; Flockerzi, G.D.; Droogmans, G.; Benham, C.D.; Nilius, B.
Citation: Watanabe , H , Davis , J B , Smart , D , Jerman , J C , Smith , G D , Hayes , P , Vriens , J , Cairns , W , Wissenbach , U , Prenen , J , Flockerzi , G D , Droogmans , G , Benham , C D & Nilius , B 2002 , ' Activation of TRPV4 channels (hVRL-2/mTrp12) by phorbol derivatives ' Journal of Biological Chemistry , vol 277 , no. 16 , pp. 13569-13577 .
We have studied activation by phorbol derivatives of TRPV4 channels, the human VRL-2, and murine TRP12 channels, which are highly homologous to the human VR-OAC, and the human and murine OTRPC4 channel. 4α-Phorbol 12,13-didecanoate (4α-PDD) induced an increase in intracellular Ca2+ concentration, [Ca2+]i, in 1321N1 cells stably transfected with human VRL-2 (hVRL-2.1321N1) or HEK-293 cells transiently transfected with murine TRP12, but not in nontransfected or mock-transfected cells. Concomitantly with the increase in [Ca2+]i, 4α-PDD activated an outwardly rectifying cation channel with an Eisenman IV permeation sequence for monovalent cations that is Ca2+-permeable withP Ca/P Na = 5.8. Phorbol 12-myristate 13-acetate also induced an increase in [Ca2+]i but was ∼50 times less effective than 4α-PDD. EC50 for Ca2+ increase and current activation was nearly identical (pEC50 ∼ 6.7). Similar effects were observed in freshly isolated mouse aorta endothelial cells which express TRP12 endogenously. By using 4α-PDD as a tool to stimulate TRP12, we showed that activation of this channel is modulated by [Ca2+]i; an increase in [Ca2+]i inhibits the channel with an IC50 of 406 nm. Ruthenium Red at a concentration of 1 μm completely blocks inward currents at −80 mV but has a smaller effect on outward currents likely indicating a voltage dependent channel block. We concluded that the phorbol derivatives activate TRPV4 (VR-OAC, VRL-2, OTRPC4, TRP12) independently from protein kinase C, in a manner consistent with direct agonist gating of the channel.
The original article can be found at: http://www.jbc.org/ Copyright by The American Society for Biochemistry and Molecular Biology. DOI: 10.1074/jbc.M200062200 [Full text of this article is not available in the UHRA]