Adenosine-induced activation of ATP-sensitive K⁺channels in excised membrane patches is mediated by PKC

Abstract

. Adenosineinduced activation of ATP-sensitive K ϩ channels in excised membrane patches is mediated by PKC. Am. J. Physiol. 276 (Heart Circ. Physiol. 45): H488-H495, 1999.-Both protein kinase C (PKC) and adenosine receptor activation have been shown to enhance ATP-sensitive K ϩ (K ATP ) channels. The present studies were designed to determine whether PKC mediates adenosine effects on the K ATP channel. The dependence of K ATP channel activity (nP o ) on intracellular ATP concentration ([ATP] i ) was determined in excised rabbit ventricular membrane patches. External adenosine (100 µM in the pipette solution) significantly increased K ATP nP o at all [ATP] i between 5 and 50 µM by decreasing channel sensitivity to [ATP] i (dissociation constant increased from 7.4 Ϯ 0.8 to 22.2 Ϯ 3.1 µM, P Ͻ 0.001), an effect blocked by the adenosine receptor antagonist 8-phenyltheophylline (10 µM). When the highly selective PKC blocker bisindolylmaleimide (BIM) was included in the internal (bath) solution, the K ATP -stimulating action of adenosine was prevented. The addition of BIM to the superfusate rapidly inhibited K ATP channels activated by adenosine. Endogenous PKC activation by phorbol 12,13-didecanoate (PDD), but not administration of the inactive congener 4␣-PDD, enhanced K ATP activity. Internal guanosine 5Ј-O-(2-thiodiphosphate) prevented K ATP activation by adenosine, an effect which could be overridden by exposure to PDD. We conclude that PKC mediates adenosine activation of K ATP channels in excised membrane patches in a membranedelimited fashion. ischemic preconditioning; potassium channels; signal transduction; phorbol esters; protein kinase C

Compartmentalized autocrine signaling to cystic fibrosis transmembrane conductance regulator at the apical membrane of airway epithelial cells

“…A long-held dogma in the field of ion channel regulation is that signaling from GPCR to ion channels in cell free patches involves no readily diffusible second messenger (36)(37)(38). When such ''membrane-delimited'' signaling is coupled with a lack of change in whole cell second messenger levels, the results are often interpreted as direct modulation of ion channels by G proteins (39).…”

“…When such ''membrane-delimited'' signaling is coupled with a lack of change in whole cell second messenger levels, the results are often interpreted as direct modulation of ion channels by G proteins (39). This has been challenged by recent findings that membrane-delimited signaling may involve protein kinase Cmediated phosphorylation (38,40,41). However, there is no report showing receptor to ion channel effector regulation in excised membrane patches by an intact classic cAMP pathway, either in epithelia or any other tissues.…”

Electrophysiological Characterization of Cardiac Muscarinic Acetylcholine Receptors: Different Subtypes Mediate Different Potassium Currents

“…To date, no less than 15 distinct K + channel currents have been identified in primary tissues. In cardiac myocytes, the main K + currents include inward rectifier K + current (I K1 ) [1], transient outward K + current (I to ) [1][2], delayed rectifier K + currents (I Kr , the rapid component and I Ks , the slow component) (2)(3)(4)(5), ultrarapid delayed rectifier K + current (I Kur ) [2,[6][7], ATP-sensitive K + current (I KATP ) [8], and ACh-induced K + current (I KACh ) [9]. The were sensitive to pertussis ntoxin, whereas I KM3 was not.…”

Hypoxic preconditioning promotes the translocation of protein kinase C ε binding with caveolin-3 at cell membrane not mitochondrial in rat heart

“…9 Another important substrate for PKC activation could be ATP sensitive K C channels (K ATP ) since cardiac K ATP channels are mostly localized in caveolae and functionally regulated by adenosine receptors and PKC. [35][36][37][38] In summary, our data demonstrate that hypoxic preconditioning promotes selective translocation and caveolar targeting of PKCe, d and a but not PKCb1 and z. This finding provides new mechanistic insight into our understanding the role of caveolae in PKC-mediated cardioprotection.…”