title: Adenosine A1receptor signaling inhibits BK channels through a PKCα-dependent mechanism in mouse aortic smooth muscle.
abstract: Adenosine receptors (AR; A1, A2A, A2B, and A3) contract and relax smooth muscle through different signaling mechanisms. Deciphering these complex responses remains difficult because relationships between AR subtypes and various end-effectors (e.g., enzymes and ion channels) remain to be identified. A1AR stimulation is associated with the production of 20-hydroxyeicosatetraenoic acid (20-HETE) and activation of protein kinase C (PKC). 20-HETE and PKC can inhibit large conductance Ca2+/voltage-sensitive K+(BK) channels that regulate smooth muscle contraction. We tested the hypothesis that activation of A1AR inhibits BK channels via a PKC-dependent mechanism. Patch clamp recordings and Western blots were performed using aortae of wild type (WT) and A1AR knockout (A1KO) mice. There were no differences in whole-cell K+current or α and β1 subunits expression between WT and A1KO. 20-HETE (100 nM) inhibited BK current similarly in WT and A1KO mice. NECA (5'-N-ethylcarboxamidoadenosine; 10 μM), a non-selective AR agonist, increased BK current in myocytes from both WT and A1KO mice, but the increase was greater in A1KO (52±15 vs. 17±3%; p<0.05). This suggests that A1AR signaling negatively regulates BK channel activity. Accordingly, CCPA (2-chloro-N(6)-cyclopentyladenosine; 100 nM), an A1AR-selective agonist, inhibited BK current in myocytes from WT but not A1KO mice (81±4 vs. 100±7% of control; p<0.05). Gö6976 (100 nM), a PKCα inhibitor, abolished the effect of CCPA to inhibit BK current (99±3% of control). These data lead us to conclude that, in aortic smooth muscle, A1AR inhibits BK channel activity and that this occurs via a mechanism involving PKCα.
authors: Department of Physiology & Pharmacology, West Virginia University School of Medicine ; Center for Cardiovascular and Respiratory Sciences, West Virginia University School of Medicine.
authors: Ss
authors: S
authors: Kunduri
authors: Gm
authors: G
authors: Dick
authors: Ma
authors: M
authors: Nayeem
authors: Sj
authors: S
authors: Mustafa
keywords: 2-chloro-N (6)-cyclopentyladenosine; 20-hydroxy-eicosatetraenoic acid; 5′-N-ethylcarboxamidoadenosine; Large conductance Ca2+/voltage-sensitive K+ channels; protein kinase C alpha
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