Department of Medicine, University of California-San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0838, USA.
Cell Tissue Res. 2011 Jul;345(1):87-102. doi: 10.1007/s00441-011-1177-7. Epub 2011 May 20.
Pituitary adenylyl cyclase activating polypeptide (PACAP) and vasoactive intestinal polypeptide (VIP) augment the biosynthesis of tyrosine hydroxylase (TH). We tested whether secretin belonging to the glucagon/PACAP/VIP superfamily would increase transcription of the tyrosine hydroxylase (Th) gene and modulate catecholamine secretion. Secretin activated transcription of the endogenous Th gene and its transfected promoter (EC(50) ∼4.6 nM) in pheochromocytoma (PC12) cells. This was abolished by pre-treatment with a secretin receptor (SCTR) antagonist and by inhibition of protein kinase A (PKA), mitogen-activated protein kinase, or CREB (cAMP response element-binding protein). In agreement, secretin increased PKA activity and induced phosphorylation of CREB and binding to Th CRE, suggesting secretin signaling to transcription via a PKA-CREB pathway. Secretin stimulated catecholamine secretion (EC(50) ∼3.5 μM) from PC12 cells, but this was inhibited by pre-treatment with VIP-preferring receptor (VPAC1)/PACAP-preferring receptor (PAC1) antagonists. Secretin-evoked secretion occurred without extracellular Ca(2+) and was abolished by intracellular Ca(2+) chelation. Secretin augmented phospholipase C (PLC) activity and increased inositol-1,4,5-triphosphate (IP(3)) levels in PC12 cells; PLC-β inhibition blocked secretin-induced catecholamine secretion, indicating the participation of intracellular Ca(2+) from a phospholipase pathway in secretion. Like PACAP, secretin evoked long-lasting catecholamine secretion, even after only a transient exposure. Thus, transcription is triggered by nanomolar concentrations of the peptide through SCTR, with signaling along the cAMP-PKA and extracellular-signal-regulated kinase 1/2 pathways and through CREB. By contrast, secretion is triggered only by micromolar concentrations of peptide through PAC1/VPAC receptors and by utilizing a PLC/intracellular Ca(2+) pathway.
垂体腺苷酸环化酶激活肽（PACAP）和血管活性肠肽（VIP）可增加酪氨酸羟化酶（TH）的生物合成。我们测试了属于胰高血糖素/PACAP/VIP 超家族的肠促胰液素是否会增加酪氨酸羟化酶（Th）基因的转录并调节儿茶酚胺的分泌。肠促胰液素在嗜铬细胞瘤（PC12）细胞中激活内源性 Th 基因及其转染启动子的转录（EC（50）∼4.6 nM）。这一作用可被肠促胰液素受体（SCTR）拮抗剂预处理和蛋白激酶 A（PKA）、丝裂原激活蛋白激酶或 CREB（cAMP 反应元件结合蛋白）抑制所阻断。一致地，肠促胰液素增加了 PKA 活性，并诱导 CREB 的磷酸化和与 Th CRE 的结合，提示肠促胰液素通过 PKA-CREB 途径信号转导至转录。肠促胰液素刺激 PC12 细胞儿茶酚胺的分泌（EC（50）∼3.5 μM），但这一作用可被 VIP 优先受体（VPAC1）/PACAP 优先受体（PAC1）拮抗剂预处理所抑制。肠促胰液素诱导的分泌发生在没有细胞外 Ca（2+）的情况下，且被细胞内 Ca（2+）螯合所阻断。肠促胰液素增加了 PC12 细胞中的磷脂酶 C（PLC）活性和肌醇-1,4,5-三磷酸（IP（3））水平；PLC-β 抑制阻断了肠促胰液素诱导的儿茶酚胺分泌，表明在分泌过程中存在来自磷脂酶途径的细胞内 Ca（2+）。与 PACAP 一样，肠促胰液素甚至在短暂暴露后也能引起持久的儿茶酚胺分泌。因此，通过 SCTR，肽以纳摩尔浓度触发转录，通过 cAMP-PKA 和细胞外信号调节激酶 1/2 途径以及 CREB 进行信号转导。相比之下，仅通过 PAC1/VPAC 受体以微摩尔浓度的肽触发分泌，并通过利用 PLC/细胞内 Ca（2+）途径进行分泌。
