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Contribution of Kv7.5 potassium channels inhibition and TRPC6 non‐selective channels activation in AVP induced calcium oscillations in A7r5 smooth muscle cells
Author(s) -
Mani Bharath Kumar,
Brueggemann Lioubov I.,
Cribbs Leanne L.,
Byron Kenneth L.
Publication year - 2008
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.22.1_supplement.912.33
Subject(s) - trpc6 , vascular smooth muscle , gene knockdown , potassium channel , chemistry , medicine , endocrinology , calcium , biophysics , microbiology and biotechnology , biology , biochemistry , transient receptor potential channel , receptor , smooth muscle , apoptosis
Activation of TRPC6 non‐selective cation channels and inhibition of KCNQ5 voltage‐gated K + channels have both been implicated in Ca 2+ signaling in response to [Arg 8 ]‐vasopressin (AVP) in vascular smooth muscle cells. In A7r5 cells, AVP (25 pM) induces repetitive Ca 2+ ‐dependent action potential firing and Ca 2+ spiking. The contributions of KCNQ5 channels and TRPC6 channels to AVP‐stimulated Ca 2+ spiking were examined using fura‐2 fluorescence measurements in A7r5 cells. KCNQ5 or TRPC6 expression levels were suppressed by short hairpin RNA constructs. KCNQ5 knockdown was sufficient to induce spontaneous Ca 2+ spiking, but the frequency was less than that induced by 25 pM AVP (2.5 ± 0.6 spikes/min (n=3) and 5.1 ± 0.4 spikes/min (n=10), respectively). AVP‐activated non‐selective cation currents (I CAT ) were significantly reduced by knockdown of TRPC6 channel expression or removal of external Na+. Both of these treatments also significantly delayed the onset of Ca 2+ spiking induced by 25 pM AVP (a 2.9 ± 1.0 min delay with TRPC6 knockdown (n=6) and an 11.3 ± 2.8 min delay in Na + ‐free medium (n=4)). Spike frequency was also significantly reduced by the latter treatment (by 3.3 ± 0.7 spikes/min, n=4). These results suggest that although suppression of KCNQ5 currents alone is sufficient to excite A7r5 vascular smooth muscle cells, AVP‐induced activation of TRPC6 non‐selective cation channels contributes to the stimulation of Ca 2+ spiking.