Kostic Tatjana S, Tomić Melanija, Andric Silvana A, Stojilkovic Stanko S
Endocrinology and Reproduction Research Branch, NICHD, National Institutes of Health, Bethesda, Maryland 20892-4510, USA.
J Biol Chem. 2002 May 10;277(19):16412-8. doi: 10.1074/jbc.M112439200. Epub 2002 Feb 26.
It is well established that G protein-coupled receptors stimulate nitric oxide-sensitive soluble guanylyl cyclase by increasing intracellular Ca(2+) and activating Ca(2+)-dependent nitric-oxide synthases. In pituitary cells receptors that stimulated adenylyl cyclase, growth hormone-releasing hormone, corticotropin-releasing factor, and thyrotropin-releasing hormone also stimulated calcium signaling and increased cGMP levels, whereas receptors that inhibited adenylyl cyclase, endothelin-A, and dopamine-2 also inhibited spontaneous calcium transients and decreased cGMP levels. However, receptor-controlled up- and down-regulation of cyclic nucleotide accumulation was not blocked by abolition of Ca(2+) signaling, suggesting that cAMP production affects cGMP accumulation. Agonist-induced cGMP accumulation was observed in cells incubated in the presence of various phosphodiesterase and soluble guanylyl cyclase inhibitors, confirming that G(s)-coupled receptors stimulated de novo cGMP production. Furthermore, cholera toxin (an activator of G(s)), forskolin (an activator of adenylyl cyclase), and 8-Br-cAMP (a permeable cAMP analog) mimicked the stimulatory action of G(s)-coupled receptors on cGMP production. Basal, agonist-, cholera toxin-, and forskolin-stimulated cGMP production, but not cAMP production, was significantly reduced in cells treated with H89, a protein kinase A inhibitor. These results indicate that coupling seven plasma membrane-domain receptors to an adenylyl cyclase signaling pathway provides an additional calcium-independent and cAMP-dependent mechanism for modulating soluble guanylyl cyclase activity in pituitary cells.
众所周知,G蛋白偶联受体通过增加细胞内Ca(2+)并激活Ca(2+)依赖性一氧化氮合酶来刺激一氧化氮敏感的可溶性鸟苷酸环化酶。在垂体细胞中,刺激腺苷酸环化酶的受体、生长激素释放激素、促肾上腺皮质激素释放因子和促甲状腺激素释放激素也刺激钙信号传导并增加cGMP水平,而抑制腺苷酸环化酶的受体、内皮素-A和多巴胺-2也抑制自发钙瞬变并降低cGMP水平。然而,受体控制的环核苷酸积累的上调和下调并未因Ca(2+)信号传导的消除而被阻断,这表明cAMP的产生会影响cGMP的积累。在存在各种磷酸二酯酶和可溶性鸟苷酸环化酶抑制剂的情况下培养的细胞中观察到激动剂诱导的cGMP积累,证实G(s)偶联受体刺激了新的cGMP产生。此外,霍乱毒素(一种G(s)激活剂)、福斯高林(一种腺苷酸环化酶激活剂)和8-Br-cAMP(一种可渗透的cAMP类似物)模拟了G(s)偶联受体对cGMP产生的刺激作用。在用蛋白激酶A抑制剂H89处理的细胞中,基础、激动剂、霍乱毒素和福斯高林刺激的cGMP产生,但不是cAMP产生,显著降低。这些结果表明,将七个质膜结构域受体与腺苷酸环化酶信号通路偶联提供了一种额外的钙非依赖性和cAMP依赖性机制,用于调节垂体细胞中可溶性鸟苷酸环化酶的活性。