Molecular cloning of TRPC3a, an N-terminally extended, store-operated variant of the human C3 transient receptor potential channel

doi:10.1073/pnas.0409908102

Molecular cloning of TRPC3a, an N-terminally extended, store-operated variant of the human C3 transient receptor potential channel

Transmembrane Signaling Group, Laboratory of Signal Transduction, Division of Intramural Research, National Institute of Environmental Health Sciences, National Institutes of Health, Department of Health and Human Services, 111 T. W. Alexander Drive, Research Triangle Park, NC 27709

Contributed by Lutz Birnbaumer, December 31, 2004

Abstract

AK032317 is the GenBank accession no. of a full-length RIKEN mouse cDNA. It encodes a putative variant of the C3-type TRPC (transient receptor potential channel) that differs from the previously cloned murine TRPC3 cDNA in that it has a 5′ extension stemming from inclusion of an additional exon (exon 0). The extended cDNA adds 62 aa to the sequence of the murine TRPC3. Here, we report the cloning of a cDNA encoding the human homologue of this extended TRPC3 having a highly homologous 73-aa N-terminal extension, referred to as hTRPC3a. A query of the GenBank genomic database predicts the existence of a similar gene product also in rats. Transient expression of the longer TRPC3a in human embryonic kidney (HEK) cells showed that it mediates Ca²⁺ entry in response to stimulation of the Gq–phospholipase C β pathway, which is similar to that mediated by the shorter hTRPC3. However, after isolation of HEK cells expressing hTRPC3 in stable form, TRPC3a gave rise to Ca²⁺-entry channels that are not only activated by the Gq–phospholipase C β pathway (receptor-activated Ca entry) but also by thapsigargin triggered store depletion. In conjunction with findings from our and other laboratories that TRPC1, TRPC2, TRPC4, TRPC5, and TRPC7, can each mediate store-depletion-activated Ca²⁺ entry in mammalian cells, our findings with hTRC3a support our previous proposal that TRPCs form capacitative Ca-entry channels.

Footnotes

↵ * To whom correspondence should be addressed at: National Institute of Environmental Health Sciences, Building 101, Room A214, 111 T. W. Alexander Drive, Research Triangle Park, NC 27706. E-mail: birnbau1{at}niehs.nih.gov.
Author contributions: E.Y. and L.B. designed research; E.Y. and B.T.K. performed research; E.Y., B.T.K., and L.B. analyzed data; E.Y. and L.B. wrote the paper.
Abbreviations: HEK, human embryonic kidney; CCE, capacitative Ca²⁺ entry; IP3, inositol 1,4,5-trisphosphate; PLC, phospholipase C.
Data deposition: The sequence reported in this paper has been deposited in the GenBank database (accession no. AY865574, for the human TRPC3a clone).