Wessels-Reiker M, Basiboina R, Howlett A C, Strong R
Department of Pharmacological and Physiological Science, St. Louis University School of Medicine, Missouri.
J Neurochem. 1993 Mar;60(3):1018-29. doi: 10.1111/j.1471-4159.1993.tb03250.x.
We investigated the receptor mechanisms by which vasoactive intestinal polypeptide (VIP) and related peptides exert their effects on tyrosine hydroxylase (TH) gene expression. VIP, secretin, and peptide histidine isoleucine (PHI) each produced increases in TH gene expression, as measured by increases in TH mRNA levels and TH activity. The concentrations at which the effects of these peptides were maximal differed for TH activity and TH mRNA. Moreover, maximal increases in TH activity were 130-140% of control, whereas maximal increases in TH mRNA were 250% of control. The concentration dependence of the increases in TH mRNA in response to the three peptides was analyzed by fitting the data to nonlinear regression models that assume either one or two components to the response. The data for secretin fit best to a model that assumes a single component to the increase in TH mRNA levels. The data derived for PHI and VIP fit best to models that assumed two components to the TH mRNA response. These data suggested that there may be more than one receptor or signal transduction mechanism involved in the response to the various peptides. We examined whether the peptides exerted their effects through common or multiple second messenger systems. The ability of maximally active concentrations of these peptides to stimulate increases in TH mRNA was not additive, indicating that the peptides work through a common receptor or signal transduction pathway. Each peptide stimulated increases in protein kinase A (PKA) activity. Secretin and VIP were ineffective in increasing TH mRNA levels in a PKA-deficient mutant PC12 cell line (A126-1B2). Moreover, the adenylate cyclase antagonist 2',5'-dideoxyadenosine prevented the increase in TH mRNA produced by each peptide. Thus, each peptide requires an intact cyclic AMP second messenger pathway to produce changes in TH gene expression, suggesting that the complex pattern of response to VIP and PHI revealed by concentration-response analysis was due to the actions of these peptides at multiple receptors. To evaluate this possibility, we examined the effect of several peptide receptor antagonists on the increase in TH gene expression elicited by VIP, PHI, and secretin. The secretin antagonist secretin (5-27) (20 microM) had no significant effect on VIP or PHI stimulation of TH gene expression, but reduced the effect of secretin. The VIP antagonist VIP (10-28) (20 microM) reduced the effect of VIP on increasing TH mRNA, but had no significant effect on the response of TH mRNA to secretin or PHI.(ABSTRACT TRUNCATED AT 400 WORDS)
我们研究了血管活性肠肽（VIP）及相关肽对酪氨酸羟化酶（TH）基因表达发挥作用的受体机制。通过检测TH mRNA水平和TH活性的增加，发现VIP、促胰液素和肽组氨酸异亮氨酸（PHI）均可使TH基因表达增加。这些肽发挥最大效应时的浓度，在TH活性和TH mRNA方面有所不同。此外，TH活性的最大增加幅度为对照的130% - 140%，而TH mRNA的最大增加幅度为对照的250%。通过将数据拟合到假设响应为一个或两个成分的非线性回归模型，分析了三种肽作用下TH mRNA增加的浓度依赖性。促胰液素的数据最适合假设TH mRNA水平增加为单一成分的模型。PHI和VIP的数据最适合假设TH mRNA响应为两个成分的模型。这些数据表明，对各种肽的响应可能涉及不止一种受体或信号转导机制。我们研究了这些肽是否通过共同或多个第二信使系统发挥作用。这些肽的最大活性浓度刺激TH mRNA增加的能力并非相加的，这表明这些肽通过共同的受体或信号转导途径起作用。每种肽都能刺激蛋白激酶A（PKA）活性增加。促胰液素和VIP在PKA缺陷的突变PC12细胞系（A126 - 1B2）中不能增加TH mRNA水平。此外，腺苷酸环化酶拮抗剂2'，5'-二脱氧腺苷可阻止每种肽引起的TH mRNA增加。因此，每种肽都需要完整的环磷酸腺苷第二信使途径来产生TH基因表达的变化，这表明浓度 - 反应分析所揭示的对VIP和PHI的复杂反应模式是由于这些肽作用于多个受体。为评估这种可能性，我们检测了几种肽受体拮抗剂对VIP、PHI和促胰液素引起的TH基因表达增加的影响。促胰液素拮抗剂促胰液素（5 - 27）（20 microM）对VIP或PHI刺激的TH基因表达无显著影响，但可降低促胰液素的作用。VIP拮抗剂VIP（10 - 28）（20 microM）可降低VIP增加TH mRNA的作用，但对TH mRNA对促胰液素或PHI的反应无显著影响。（摘要截断于400字）
