Opposite regulation of KCNQ5 and TRPC6 channels contributes to vasopressin-stimulated calcium spiking responses in A7r5 vascular smooth muscle cells

Bharath K. Mani, Lioubov I. Brueggemann, Leanne L. Cribbs, Kenneth L. Byron

Research output: Contribution to journalArticle

30 Scopus citations

Abstract

Physiologically relevant concentrations of [Arg8]-vasopressin (AVP) induce repetitive action potential firing and Ca2+ spiking responses in the A7r5 rat aortic smooth muscle cell line. These responses may be triggered by suppression of KCNQ potassium currents and/or activation of non-selective cation currents. Here we examine the relative contributions of KCNQ5 channels and TRPC6 non-selective cation channels to AVP-stimulated Ca2+ spiking using patch clamp electrophysiology and fura-2 fluorescence measurements in A7r5 cells. KCNQ5 or TRPC6 channel expression levels were suppressed by short hairpin RNA constructs. KCNQ5 knockdown resulted in more positive resting membrane potentials and induced spontaneous action potential firing and Ca2+ spiking. However physiological concentrations of AVP induced additional depolarization and increased Ca2+ spike frequency in KCNQ5 knockdown cells. AVP activated a non-selective cation current that was reduced by TRPC shRNA treatment or removal of external Na+. Neither resting membrane potential nor the AVP-induced depolarization was altered by knockdown of TRPC6 channel expression. However, both TRPC6 shRNA and removal of external Na+ delayed the onset of Ca2+ spiking induced by 25 pM AVP. These results suggest that suppression of KCNQ5 currents alone is sufficient to excite A7r5 cells, but AVP-induced activation of TRPC6 contributes to the stimulation of Ca2+ spiking.

Original languageEnglish (US)
Pages (from-to)400-411
Number of pages12
JournalCell Calcium
Volume45
Issue number4
DOIs
StatePublished - Apr 2009

Keywords

  • Calcium spiking
  • KCNQ
  • Resting membrane potential
  • TRPC6
  • Vasopressin

ASJC Scopus subject areas

  • Physiology
  • Molecular Biology
  • Cell Biology

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