Thiele E A, Eipper B A
Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205.
Endocrinology. 1990 Feb;126(2):809-17. doi: 10.1210/endo-126-2-809.
The mouse corticotrope tumor cell line AtT-20/D16v was used to investigate the effects of chronic treatment with various secretagogues on individual components of the secretory pathway. Secretagogues acting in part through receptors linked to guanine nucleotide-binding regulatory proteins [CRF and somatostatin (SS)] and agents by-passing membrane receptors (phorbol myristate acetate and dexamethasone) were examined. Effects on the secretory product were evaluated by measuring levels of pro-ACTH/endorphin mRNA and hormone secretion. Effects on posttranslational processing enzymes were evaluated by measuring levels of the mRNAs encoding carboxypeptidase-E and peptidyl-glycine-alpha-amidating monooxygenase (PAM); cellular levels of PAM activity were also measured. The mRNAs encoding the G-proteins in AtT-20 cells were identified, and secretagogue effects on the G-protein signal transduction system were evaluated by measuring levels of the mRNAs encoding (alpha s, alpha)i2, and beta 2. No single parameter adequately characterizes the regulatory state of the complex secretory apparatus. Although levels of pro-ACTH/endorphin (PAE) mRNA accurately reflected hormone secretion after chronic CRF or dexamethasone treatment, chronic SS treatment elevated PAE mRNA levels in the face of reduced hormone secretion. Levels of PAM mRNA generally changed in parallel with levels of PAE mRNA; in contrast, levels of carboxypeptidase-E mRNA were unaffected by any of the secretagogues tested. Secretagogues acting through distinct G-proteins (CRF and SS) as well as dexamethasone brought about a coordinate increase in the level of the mRNAs encoding the three G-protein subunits examined. Treatment with phorbol myristate acetate caused a slight decrease in the levels of the G-protein subunit mRNAs.
小鼠促肾上腺皮质激素分泌瘤细胞系AtT-20/D16v被用于研究各种促分泌素长期处理对分泌途径各个组分的影响。研究了部分通过与鸟嘌呤核苷酸结合调节蛋白相关的受体起作用的促分泌素[促肾上腺皮质激素释放因子（CRF）和生长抑素（SS）]以及绕过膜受体的试剂（佛波酯和地塞米松）。通过测量前促肾上腺皮质激素/内啡肽mRNA水平和激素分泌来评估对分泌产物的影响。通过测量编码羧肽酶E和肽基甘氨酸α-酰胺化单加氧酶（PAM）的mRNA水平来评估对翻译后加工酶的影响；还测量了细胞中PAM的活性水平。鉴定了AtT-20细胞中编码G蛋白的mRNA，并通过测量编码（αs、α）i2和β2的mRNA水平来评估促分泌素对G蛋白信号转导系统的影响。没有单一参数能够充分表征复杂分泌装置的调节状态。虽然在长期CRF或地塞米松处理后，前促肾上腺皮质激素/内啡肽（PAE）mRNA水平准确反映了激素分泌，但在激素分泌减少的情况下，长期SS处理会提高PAE mRNA水平。PAM mRNA水平通常与PAE mRNA水平平行变化；相反，羧肽酶E mRNA水平不受任何测试促分泌素的影响。通过不同G蛋白（CRF和SS）起作用的促分泌素以及地塞米松导致所检测的三种G蛋白亚基编码mRNA水平协同增加。用佛波酯处理会使G蛋白亚基mRNA水平略有下降。
