Cell swelling, heat, and chemical agonists use distinct pathways for the activation of the cation channel TRPV4.
TRPV4 is a Ca(2+)- and Mg(2+)-permeable cation channel within the vanilloid receptor subgroup of the transient receptor potential (TRP) family, and it has been implicated in Ca(2+)-dependent signal transduction in several tissues, including brain and vascular endothelium. TRPV4-activating stimuli include osmotic cell swelling, heat, phorbol ester compounds, and 5',6'-epoxyeicosatrienoic acid, a cytochrome p450 epoxygenase metabolite of arachidonic acid (AA). It is presently unknown how these distinct activators converge on opening of the channel. Here, we demonstrate that blockers of phospholipase A(2) (PLA(2)) and cytochrome p450 epoxygenase inhibit activation of TRPV4 by osmotic cell swelling but not by heat and 4alpha-phorbol 12,13-didecanoate. Mutating a tyrosine residue (Tyr-555) in the N-terminal part of the third transmembrane domain to an alanine strongly impairs activation of TRPV4 by 4alpha-phorbol 12,13-didecanoate and heat but has no effect on activation by cell swelling or AA. We conclude that TRPV4-activating stimuli promote channel opening by means of distinct pathways. Cell swelling activates TRPV4 by means of the PLA(2)-dependent formation of AA, and its subsequent metabolization to 5',6'-epoxyeicosatrienoic acid by means of a cytochrome p450 epoxygenase-dependent pathway. Phorbol esters and heat operate by means of a distinct, PLA(2)- and cytochrome p450 epoxygenase-independent pathway, which critically depends on an aromatic residue at the N terminus of the third transmembrane domain.
Vriens
J
J
Department of Physiology, Campus Gasthuisberg, Katholieke Universiteit Leuven, B-3000 Leuven, Belgium.
Watanabe
H
H
Janssens
A
A
Droogmans
G
G
Voets
T
T
Nilius
B
B
D000818:Animals; D027682:Cation Transport Proteins / Q000819:agonists / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002412:Cations / Q000378:metabolism; D002460:Cell Line; D000090762:Cytochrome P-450 CYP2J2; D065607:Cytochrome P-450 Enzyme Inhibitors; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006358:Hot Temperature; D006801:Humans; D007473:Ion Channels / Q000819:agonists / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D016297:Mutagenesis, Site-Directed; D009997:Osmotic Pressure; D010105:Oxygenases / Q000037:antagonists & inhibitors / Q000378:metabolism; D010703:Phorbol Esters / Q000494:pharmacology; D010741:Phospholipases A / Q000037:antagonists & inhibitors / Q000378:metabolism; D010766:Phosphorylation; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D050916:TRPV Cation Channels; D014443:Tyrosine / Q000737:chemistry
D027682:Cation Transport Proteins; D002412:Cations; D065607:Cytochrome P-450 Enzyme Inhibitors; D004791:Enzyme Inhibitors; D007473:Ion Channels; D010703:Phorbol Esters; D011994:Recombinant Proteins; D050916:TRPV Cation Channels; C416986:TRPV4 protein, human; C486576:Trpv4 protein, mouse; C008876:phorbol-12,13-didecanoate; D014443:Tyrosine; D003577:Cytochrome P-450 Enzyme System; D010105:Oxygenases; D000090762:Cytochrome P-450 CYP2J2; D010741:Phospholipases A