Meurs H, Kauffman H F, Timmermans A, van Amsterdam F T, Koëter G H, de Vries K
Biochem Pharmacol. 1986 Dec 1;35(23):4217-22. doi: 10.1016/0006-2952(86)90698-2.
Tumour-promoting phorbol esters such as phorbol 12-myristate 13-acetate (PMA) have been reported to modulate beta-adrenergic receptor responses in various cell types, presumably by the activation of protein kinase C. In the present investigation we assessed the effect of PMA on the beta-adrenergic receptor-adenylate cyclase system of human mononuclear leukocytes (MNL). It was found that incubation of MNL with PMA resulted in a time- and concentration-dependent desensitization of isoproterenol-induced adenylate cyclase activity. However, the effect of PMA was not restricted to the beta-adrenergic receptor system, since basal adenylate cyclase activity and histamine-, prostaglandin E1-, 5'-guanylylimidodiphosphate (GppNHp)-, and NaF-stimulated values were also reduced. By contrast, no effect was found on the forskolin-induced adenylate cyclase activity. The inactive phorbol ester, 4 alpha-phorbol 12,13-didecanoate had no effect on adenylate cyclase at all, suggesting that the observed PMA effect was specifically mediated by activation of protein kinase C. The reduced beta-adrenergic response induced by PMA was not associated with a reduced beta-adrenergic receptor number, indicating uncoupling of this receptor from adenylate cyclase. Isoproterenol competition curves for 3H-dihydroalprenolol binding to membranes from untreated and PMA-treated cells demonstrated that the uncoupling was due to a reduced ability of the agonist to promote formation of the guanine nucleotide-sensitive high affinity state of the receptor. The results indicate that PMA may cause desensitization of catecholamine-responsive adenylate cyclase in MNL, and that the major locus of alteration is the guanine nucleotide regulatory protein.
据报道，肿瘤促进剂佛波酯，如佛波醇12 -肉豆蔻酸酯13 -乙酸酯（PMA），可能通过激活蛋白激酶C来调节多种细胞类型中的β-肾上腺素能受体反应。在本研究中，我们评估了PMA对人单核白细胞（MNL）的β-肾上腺素能受体 - 腺苷酸环化酶系统的影响。发现用PMA孵育MNL会导致异丙肾上腺素诱导的腺苷酸环化酶活性出现时间和浓度依赖性脱敏。然而，PMA的作用并不局限于β-肾上腺素能受体系统，因为基础腺苷酸环化酶活性以及组胺、前列腺素E1、5'-鸟苷酰亚胺二磷酸（GppNHp）和氟化钠刺激的值也降低了。相比之下，发现PMA对福斯可林诱导的腺苷酸环化酶活性没有影响。无活性的佛波酯4α-佛波醇12,13 -二十二烷酸酯对腺苷酸环化酶完全没有影响，这表明观察到的PMA效应是由蛋白激酶C的激活特异性介导的。PMA诱导的β-肾上腺素能反应降低与β-肾上腺素能受体数量减少无关，表明该受体与腺苷酸环化酶解偶联。未处理和PMA处理细胞的膜上3H -二氢阿普洛尔结合的异丙肾上腺素竞争曲线表明，解偶联是由于激动剂促进受体形成鸟嘌呤核苷酸敏感的高亲和力状态的能力降低。结果表明，PMA可能导致MNL中儿茶酚胺反应性腺苷酸环化酶脱敏，并且改变的主要位点是鸟嘌呤核苷酸调节蛋白。
