Seebeck J, Kruse M L, Schmidt-Choudhury A, Schmidtmayer J, Schmidt W E
Department of Pharmacology, Christian-Albrechts University of Kiel, Germany.
Eur J Pharmacol. 1998 Jul 10;352(2-3):343-50. doi: 10.1016/s0014-2999(98)00372-0.
Pituitary adenylate cyclase activating polypeptide (PACAP) is a high-affinity ligand for at least two types of G-protein coupled receptors, the PACAP type 1 and type 2 receptor. In this study it is demonstrated that the C-terminal PACAP-fragment PACAP(6-27) stimulates serotonin release from rat peritoneal mast cells with higher potency (EC50: 0.2 vs. 2.0 microM) than the PACAP receptor ligand PACAP(1-27). PACAP-induced degranulation of rat peritoneal mast cells was abolished by pertussis toxin and by benzalkonium chloride (IC50: 9.1 microg/ml) indicating the involvement of heterotrimeric G-proteins of the Gi-type. The PACAP effect was also reduced by inhibitors of the phosphatidylinositol specific phospholipase C ((U73122), IC50: 4 microM; (ET-18-O-CH3), IC50: 18 microM), by D609, a specific inhibitor of the phosphatidylcholine specific phospholipase C (IC50: 41 microM), by the protein kinase C-inhibitor staurosporine (IC50: 0.6 microM) and by the lipoxygenase inhibitor nordihydroguaiaretic acid (NGDA) but not by indomethacin. It is concluded that PACAP peptides stimulate secretion in rat peritoneal mast cells in a PACAP receptor-independent manner, probably via direct activation of heterotrimeric G-proteins of the Gi-type; these G-proteins may lead to a sequential activation of different signaling cascades (see above), which may converge at the level of one or more staurosporine-sensitive protein kinase.
垂体腺苷酸环化酶激活多肽（PACAP）是至少两种G蛋白偶联受体即PACAP 1型和2型受体的高亲和力配体。本研究表明，C末端PACAP片段PACAP(6 - 27)刺激大鼠腹膜肥大细胞释放血清素的效力（EC50：0.2对2.0微摩尔）高于PACAP受体配体PACAP(1 - 27)。百日咳毒素和苯扎氯铵（IC50：9.1微克/毫升）可消除PACAP诱导的大鼠腹膜肥大细胞脱颗粒，表明涉及Gi型异源三聚体G蛋白。磷脂酰肌醇特异性磷脂酶C抑制剂（U73122，IC50：4微摩尔；ET - 18 - O - CH3，IC50：18微摩尔）、磷脂酰胆碱特异性磷脂酶C的特异性抑制剂D609（IC50：41微摩尔）、蛋白激酶C抑制剂星形孢菌素（IC50：0.6微摩尔）和脂氧合酶抑制剂去甲二氢愈创木酸（NGDA）可降低PACAP的作用，但吲哚美辛无此作用。得出的结论是，PACAP肽可能通过直接激活Gi型异源三聚体G蛋白，以一种不依赖PACAP受体的方式刺激大鼠腹膜肥大细胞分泌；这些G蛋白可能导致不同信号级联反应的顺序激活（见上文），这些反应可能在一种或多种对星形孢菌素敏感的蛋白激酶水平上汇聚。
