Na+ entry via TRPC6 causes Ca2+ entry via NCX reversal in ATP stimulated smooth muscle cells

Biochem Biophys Res Commun. 2007 Jan 5;352(1):130-4. doi: 10.1016/j.bbrc.2006.10.160. Epub 2006 Nov 7.

Abstract

Reversal of the Na+/Ca2+ -exchanger (NCX) has been shown to mediate Ca2+ influx during activation of G-protein linked receptors. Functional coupling between the reverse-mode NCX and the canonical transient receptor potential channels (TRPCs) has been proposed to mediate Ca2+ influx in HEK-293 cells overexpressing TRPC3. In this communication we present evidence for similar functional coupling of NCX to endogenously expressed TRPC6 in rat aorta smooth muscle cells. Selective inhibition of reverse-mode NCX with KB-R7943 and of non-selective cation-channels with SKF-96365 abolished Ca2+ influx in response to agonist stimulation (ATP). Expression of a dominant negative TRPC6 mutant also reduced the Ca2+ influx in proportion to its transfection efficiency. Calyculin A, which is known to disrupt the junctions of the plasma membrane and sarco/endoplasmic reticulum, increased global Na+ elevations and reduced stimulated Ca2+ influx. Together our data provide evidence that localized Na+ elevations are generated by TRPC6 and drive reversal of NCX to mediate Ca2+ influx.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenosine Triphosphate / pharmacology*
  • Animals
  • Calcium / metabolism*
  • Cells, Cultured
  • Marine Toxins
  • Myocytes, Smooth Muscle / drug effects*
  • Myocytes, Smooth Muscle / metabolism*
  • Oxazoles / pharmacology
  • Rats
  • Sodium / metabolism*
  • Sodium-Calcium Exchanger / metabolism*
  • TRPC Cation Channels / genetics
  • TRPC Cation Channels / metabolism*

Substances

  • Marine Toxins
  • Oxazoles
  • Sodium-Calcium Exchanger
  • TRPC Cation Channels
  • Trpc6 protein, rat
  • calyculin A
  • Adenosine Triphosphate
  • Sodium
  • Calcium