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Interaction of G q ‐ and G s ‐coupled Pathways in the Regulation of Ca 2+ Spiking and Activity of Kv7.5 Potassium Channels in A7r5 Vascular Smooth Muscle Cells
Author(s) -
Himes Christopher R,
Condon Bridget,
Rak Mariola,
Brueggemann Lyubov I,
Byron Kenneth L
Publication year - 2016
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.30.1_supplement.940.4
Subject(s) - vascular smooth muscle , depolarization , protein kinase c , chemistry , endocrinology , medicine , vasopressin , biophysics , agonist , receptor , membrane potential , signal transduction , biology , biochemistry , smooth muscle
The vasoconstrictor hormone arginine vasopressin (AVP), at picomolar concentrations, activates G q ‐coupled V a1 receptors and suppresses the activity of vascular Kv7.5 potassium (K + ) channels in a protein kinase C (PKC) ‐dependent manner. The PKC‐dependent inhibition of Kv7.5 K + current in vascular smooth muscle cells causes membrane depolarization and activation of L‐type voltage dependent Ca 2+ channels, leading to an increase in cytosolic Ca 2+ concentration, contraction of the vascular smooth muscle cells, and vasoconstriction. Conversely, we found that activity of vascular Kv7.5 channels is enhanced upon activation of β‐adrenergic G s ‐ coupled receptors, in a protein kinase A (PKA)‐ dependent manner. In the present study we investigated physiological consequences of the sequential activation of the PKC‐ and PKA‐dependent pathways. The amplitude of endogenous Kv7.5 currents in A7r5 vascular smooth muscle cells was measured using whole‐cell perforated‐patch voltage clamp, and the frequency of Ca 2+ spiking was measured using the Ca 2+ indicator fura‐2. We found that the Kv7.5 current amplitude was reduced by 100 pM AVP by 79 ± 5%, but addition of the β‐adrenergic agonist isoproterenol (1 μM) restored the amplitude to the original level. Applying the treatments in the opposite order, isoproterenol (1 μM) enhanced the Kv7.5 current by 6.1 ± 1.5 ‐fold and this much larger current was suppressed by 40% by addition of 100 pM AVP. In contrast, Ca 2+ spiking, induced by 50 pM AVP and dependent on activation of L‐type voltage dependent Ca 2+ channels, was not effected by treatment with 1 μM isoproterenol, added either before or after application of AVP. The discrepancy between the effectiveness of the isoproterenol to restore Kv7.5 current amplitude and its inability to reduce the frequency of AVP‐induced Ca 2+ spiking in A7r5 cells might be partially explained by an isoproterenol‐induced increase (54 ± 8%) in the amplitude of L‐type Ca 2+ currents. Support or Funding Information Loyola University Chicago