Chik C L, Inukai T, Ogiwara T, Boyd H, Li B, Karpinski E, Ho A K
Department of Medicine, Faculty of Medicine, University of Alberta, Edmonton, Canada.
J Neurochem. 1996 Sep;67(3):1005-13. doi: 10.1046/j.1471-4159.1996.67031005.x.
In this study, the effects of three related peptides, pituitary adenylate cyclase-activating polypeptide 38 (PACAP38), PACAP27, and vasoactive intestinal peptide (VIP), on cyclic AMP (cAMP) accumulation and intracellular Ca2+ concentration ([Ca2+]i) were compared in N1E-115 cells. PACAP38 and PACAP27 stimulated cAMP accumulation up to 60-fold with EC50 values of 0.54 and 0.067 nM, respectively. The effect of VIP on cAMP accumulation was less potent. The binding of 125I-PACAP27 to intact cells was inhibited by PACAP38 and PACAP27 (IC50 values of 0.44 and 0.55 nM, respectively) but not by VIP. In fura-2-loaded cells, both PACAP38 and PACAP27 increased [Ca2+]i with EC50 values around 10 nM. The interactions of these three peptides with ionomycin, a Ca2+ ionophore, and 4 beta-phorbol 12-myristate 13-acetate (PMA), an activator of protein kinase C, were also determined. Ionomycin increased the cAMP accumulation caused by all three peptides. With low concentrations of PACAP38 or PACAP27, the effect of PMA was inhibitory, whereas at higher concentrations of PACAP (> 1 nM), the effect of PMA was stimulatory. Similar to other agents that elevate cAMP, PACAP38 was an effective stimulator of neurite outgrowth. These results show that (a) PACAP27 and PACAP38 stimulate cAMP accumulation and increase [Ca2+]i through the type I PACAP receptors in N1E-115 cells, (b) ionomycin enhances cAMP accumulation by all three peptides, and (c) activation of protein kinase C has a dose-dependent stimulatory or inhibitory effect on the PACAP38- or PACAP27-stimulated cAMP accumulation.
在本研究中，我们比较了三种相关肽，即垂体腺苷酸环化酶激活多肽38（PACAP38）、PACAP27和血管活性肠肽（VIP）对N1E - 115细胞中环磷酸腺苷（cAMP）积累和细胞内钙离子浓度（[Ca2+]i）的影响。PACAP38和PACAP27刺激cAMP积累可达60倍，其半数有效浓度（EC50）分别为0.54和0.067 nM。VIP对cAMP积累的作用较弱。125I - PACAP27与完整细胞的结合受到PACAP38和PACAP27的抑制（IC50值分别为0.44和0.55 nM），但不受VIP的抑制。在负载fura - 2的细胞中，PACAP38和PACAP27均使[Ca2+]i升高，EC50值约为10 nM。我们还确定了这三种肽与钙离子载体离子霉素以及蛋白激酶C激活剂4β - 佛波醇12 - 肉豆蔻酸酯13 - 乙酸酯（PMA）之间的相互作用。离子霉素增加了所有三种肽引起的cAMP积累。在低浓度的PACAP38或PACAP27时，PMA的作用是抑制性的，而在较高浓度的PACAP（>1 nM）时，PMA的作用是刺激性的。与其他升高cAMP的试剂类似，PACAP38是神经突生长的有效刺激剂。这些结果表明：（a）PACAP27和PACAP38通过N1E - 115细胞中的I型PACAP受体刺激cAMP积累并增加[Ca2+]i；（b）离子霉素增强了所有三种肽引起的cAMP积累；（c）蛋白激酶C的激活对PACAP38或PACAP27刺激的cAMP积累具有剂量依赖性的刺激或抑制作用。
