Cloning and pharmacological characterization of mouse TRPV1.
The Transient Receptor Potential cation channel V1 (TRPV1) is expressed in peripheral nociceptive neurons and is subject to polymodal activation via various agents including capsaicin, noxious heat, low extracellular pH, and direct phosphorylation by protein kinase C (PKC). We have cloned and heterologously expressed mouse TRPV1 (mTRPV1) and characterized its function utilizing FLIPR-based calcium imaging to measure functional responses to various small molecule agonists, low pH and direct phosphorylation via PKC. The various TRPV1 agonists activated mTRPV1 with a rank order of agonist potency of (resiniferatoxin (RTX) = arvanil > capsaicin = olvanil > OLDA > PPAHV) (EC50 values of 0.15+/-0.04 nM, 0.27+/-0.07 nM, 9.1+/-1.2 nM, 3.7+/-0.3 nM, 258+/-105 nM, and 667+/-151 nM, respectively). Additionally, mTRPV1 was activated by either low pH or with addition of the PKC activator phorbol 12-myristate 13-acetate (PMA). The TRPV1 antagonists iodinated-resiniferatoxin (I-RTX) or BCTC were both able to block capsaicin, pH and PKC-induced responses of mTRPV1 (IC50 (I-RTX) = 0.35+/-0.12 nM, 1.9+/-0.7 nM, and 0.80+/-0.68 nM, IC50 (BCTC) = 1.3+/-0.36 nM, 0.59+/-0.16 nM, and 0.37+/-0.15 nM, respectively). However, the antagonist capsazepine was only able to inhibit a capsaicin-evoked response of mTRPV1 with an IC50 of 1426+/-316 nM. Comparable results were achieved with rat TRPV1, while capsazepine blocked all modes of human TRPV1 activation. Thus, the mTRPV1 cation channel has a molecular pharmacological profile more akin to rat TRPV1 than either human or guinea pig TRPV1 and the molecular pharmacology suggests that capsazepine may be an ineffective TRPV1 antagonist for in vivo models of inflammatory pain in the mouse.
Correll
Craig C
CC
Department of Neurobiology, Schering-Plough Research Institute, 2015 Galloping Hill Road, K15-1-1600 Kenilworth, NJ 07033, USA. craig.correll@spcorp.com
Phelps
P Tara
PT
Anthes
John C
JC
Umland
Shelby
S
Greenfeder
Scott
S
D000595:Amino Acid Sequence; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002211:Capsaicin / Q000819:agonists / Q000494:pharmacology; D002460:Cell Line; D003001:Cloning, Molecular; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D004224:Diterpenes / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects; D006168:Guinea Pigs; D006801:Humans; D006863:Hydrogen-Ion Concentration; D020128:Inhibitory Concentration 50; D042541:Intracellular Space / Q000187:drug effects / Q000378:metabolism; D007473:Ion Channels / Q000235:genetics* / Q000502:physiology; D051379:Mice; D010703:Phorbol Esters / Q000494:pharmacology; D010766:Phosphorylation / Q000187:drug effects; D012333:RNA, Messenger / Q000096:biosynthesis; D011817:Rabbits; D051381:Rats; D011955:Receptors, Drug / Q000819:agonists / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology*; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods; D050916:TRPV Cation Channels; D014162:Transfection / Q000379:methods
D004224:Diterpenes; D007473:Ion Channels; D010703:Phorbol Esters; D012333:RNA, Messenger; D011955:Receptors, Drug; D050916:TRPV Cation Channels; C493921:TRPV1 protein, mouse; C468130:iodoresiniferatoxin; C008874:phorbol-12,13-diacetate; C024353:resiniferatoxin; D017868:Cyclic AMP-Dependent Protein Kinases; D002211:Capsaicin; D002118:Calcium