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Function and regulation of endothelin type A receptor-operated transient receptor potential canonical channels

Takahiro Horinouchi1, Koji Terada, Tsunaki Higa

  • 1Department of Cellular Pharmacology, Hokkaido University Graduate School of Medicine, Hokkaido 060-8638, Japan.

Journal of Pharmacological Sciences
|December 2, 2011
PubMed

Insights

Transient Receptor Potential Canonical (TRPC) channels TRPC3, TRPC5, TRPC6, and TRPC7 mediate receptor-operated calcium entry (ROCE) upon endothelin type A receptor (ETAR) activation. The calmodulin/inositol 1,4,5-trisphosphate receptor binding domain is crucial for this ETAR-activated ROCE.

Area of Science:

  • Molecular Biology
  • Cell Physiology
  • Ion Channel Function

Background:

  • Endothelin type A receptor (ETAR) activation triggers calcium (Ca2+) influx.
  • Transient Receptor Potential Canonical (TRPC) channels are implicated in cellular Ca2+ signaling.
  • The role of specific TRPC isoforms and regulatory domains in ETAR-mediated Ca2+ entry remains to be fully elucidated.

Purpose of the Study:

  • Identify TRPC channels mediating receptor-operated Ca2+ entry (ROCE) downstream of ETAR activation.
  • Clarify the role of the calmodulin/inositol 1,4,5-trisphosphate receptor binding (CIRB) domain in TRPC channel regulation by ETAR.
  • Investigate the involvement of Gq protein, phospholipase C (PLC), and calmodulin (CaM) in this signaling pathway.

Main Methods:

  • Co-expression of ETAR with seven TRPC isoforms in HEK293 cells.
  • Stimulation of ETAR and measurement of ROCE using selective inhibitors.
  • Utilized TRPC3 and TRPC6 CIRB domain deletion mutants.
  • Assessed channel localization to the plasma membrane.

Main Results:

  • ETAR stimulation induced ROCE via TRPC3, TRPC5, TRPC6, and TRPC7.
  • TRPC3 and TRPC6-mediated ROCE were inhibited by Gq protein, PLC, and CaM inhibitors.
  • Deletion of the CIRB domain in TRPC3 and TRPC6 abolished ETAR-mediated ROCE.
  • CIRB domain deletion or CaM inhibition did not affect channel plasma membrane targeting.

Conclusions:

  • TRPC3, TRPC5, TRPC6, and TRPC7 function as ETAR-operated Ca2+ channels.
  • Gq protein, PLC, and CaM are essential for TRPC3 and TRPC6-mediated ROCE.
  • The CIRB domain is indispensable for ETAR-mediated activation of TRPC3 and TRPC6.
  • Impaired ROCE results from disrupted CaM binding, not altered channel localization.

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