Molecular cloning of an N-terminal splice variant of the capsaicin receptor. Loss of N-terminal domain suggests functional divergence among capsaicin receptor subtypes.
Recently a cDNA clone, vanilloid receptor subtype-1 (VR1), was isolated and found to encode an ion channel that is activated by both capsaicin, the pain producing compound in chili peppers, and by noxious thermal stimuli. Subsequently, two related cDNAs have been isolated, a stretch inactivating channel with mechanosensitive properties and a vanilloid receptor-like protein that is responsive to high temperatures (52-53 degrees C). Here, we report the isolation of a vanilloid receptor 5'-splice variant (VR.5'sv) which differs from VR1 by elimination of the majority of the intracellular N-terminal domain and ankyrin repeat elements. Both VR.5'sv and VR1 mRNA were shown to be expressed in tissues reportedly responsive to capsaicin including dorsal root ganglion, brain, and peripheral blood mononuclear cells. Functional expression of VR.5'sv in Xenopus oocytes and mammalian cells showed no sensitivity to capsaicin, the potent vanilloid resiniferatoxin, hydrogen ions (pH 6.2), or noxious thermal stimuli (50 degrees C). Since VR.5'sv is otherwise identical to VR1 throughout its transmembrane spanning domains and C-terminal region, these results support the hypothesis that the N-terminal intracellular domain is essential for the formation of functional receptors activated by vanilloid compounds and noxious thermal stimuli.
Schumacher
M A
MA
Department of Anesthesia, University of California, San Francisco, California 94143, USA. schumac@itsa.ucsf.edu
Moff
I
I
Sudanagunta
S P
SP
Levine
J D
JD
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D015139:Blotting, Southern; D003001:Cloning, Molecular; D018076:DNA, Complementary; D005727:Ganglia, Spinal / Q000378:metabolism; D008969:Molecular Sequence Data; D012326:RNA Splicing; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D051381:Rats; D011955:Receptors, Drug / Q000737:chemistry / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012689:Sequence Homology, Nucleic Acid; D014981:Xenopus
D018076:DNA, Complementary; D012333:RNA, Messenger; D011955:Receptors, Drug