Boittin François-Xavier, Dipp Michelle, Kinnear Nicholas P, Galione Antony, Evans A Mark
Division of Biomedical Sciences, School of Biology, Bute Building, University of St Andrews, St Andrews, Fife, KY16 9TS, United Kingdom.
J Biol Chem. 2003 Mar 14;278(11):9602-8. doi: 10.1074/jbc.M204891200. Epub 2002 Dec 16.
In artery smooth muscle, adenylyl cyclase-coupled receptors such as beta-adrenoceptors evoke Ca(2+) signals, which open Ca(2+)-activated potassium (BK(Ca)) channels in the plasma membrane. Thus, blood pressure may be lowered, in part, through vasodilation due to membrane hyperpolarization. The Ca(2+) signal is evoked via ryanodine receptors (RyRs) in sarcoplasmic reticulum proximal to the plasma membrane. We show here that cyclic adenosine diphosphate-ribose (cADPR), by activating RyRs, mediates, in part, hyperpolarization and vasodilation by beta-adrenoceptors. Thus, intracellular dialysis of cADPR increased the cytoplasmic Ca(2+) concentration proximal to the plasma membrane in isolated arterial smooth muscle cells and induced a concomitant membrane hyperpolarization. Smooth muscle hyperpolarization mediated by cADPR, by beta-adrenoceptors, and by cAMP, respectively, was abolished by chelating intracellular Ca(2+) and by blocking RyRs, cADPR, and BK(Ca) channels with ryanodine, 8-amino-cADPR, and iberiotoxin, respectively. The cAMP-dependent protein kinase A antagonist N-(2-[p-bromocinnamylamino]ethyl)-5-isoquinolinesulfonamide hydrochloride (H89) blocked hyperpolarization by isoprenaline and cAMP, respectively, but not hyperpolarization by cADPR. Thus, cADPR acts as a downstream element in this signaling cascade. Importantly, antagonists of cADPR and BK(Ca) channels, respectively, inhibited beta-adrenoreceptor-induced artery dilation. We conclude, therefore, that relaxation of arterial smooth muscle by adenylyl cyclase-coupled receptors results, in part, from a cAMP-dependent and protein kinase A-dependent increase in cADPR synthesis, and subsequent activation of sarcoplasmic reticulum Ca(2+) release via RyRs, which leads to activation of BK(Ca) channels and membrane hyperpolarization.
在动脉平滑肌中，诸如β - 肾上腺素能受体等与腺苷酸环化酶偶联的受体可引发Ca(2+)信号，该信号会打开质膜上的Ca(2+)激活钾通道（BK(Ca)）。因此，血压可能会部分地通过膜超极化引起的血管舒张而降低。Ca(2+)信号是通过质膜附近肌浆网中的兰尼碱受体（RyRs）引发的。我们在此表明，环二磷酸腺苷核糖（cADPR）通过激活RyRs，部分介导了β - 肾上腺素能受体引起的超极化和血管舒张。因此，在分离的动脉平滑肌细胞中，对cADPR进行细胞内透析可增加质膜附近的细胞质Ca(2+)浓度，并诱导伴随的膜超极化。分别由cADPR、β - 肾上腺素能受体和cAMP介导的平滑肌超极化，通过螯合细胞内Ca(2+)以及分别用兰尼碱、8 - 氨基 - cADPR和iberiotoxin阻断RyRs、cADPR和BK(Ca)通道而被消除。cAMP依赖性蛋白激酶A拮抗剂N - (2 - [对 - 溴肉桂氨基]乙基)-5 - 异喹啉磺酰胺盐酸盐（H89）分别阻断了异丙肾上腺素和cAMP引起的超极化，但未阻断cADPR引起的超极化。因此，cADPR在该信号级联反应中作为下游元件起作用。重要的是，cADPR和BK(Ca)通道的拮抗剂分别抑制了β - 肾上腺素能受体诱导的动脉舒张。因此，我们得出结论，腺苷酸环化酶偶联受体引起的动脉平滑肌舒张部分源于cADPR合成的cAMP依赖性和蛋白激酶A依赖性增加，以及随后通过RyRs激活肌浆网Ca(2+)释放，这导致BK(Ca)通道激活和膜超极化。
