Mednieks M I, Popova I A, Grindeland R E
Department of Pediatrics, University of Chicago, Pritzker School of Medicine, IL 60637.
Aviat Space Environ Med. 1991 Oct;62(10):947-52.
A frequent cellular response to organismal stress is the increase in ligand binding by beta-adrenergic receptors. The extracellular signal is amplified by intracellular increases in cyclic AMP and the ensuing activation of cyclic AMP-dependent protein kinase (cAPK). The molecular mechanisms involve the binding of cyclic AMP to regulatory (R) subunits of cAPK, thus freeing the catalytic subunit for protein phosphorylation. This study was carried out to determine the cellular compartmentalization of the cyclic AMP-receptor proteins in heart ventricular tissue obtained from rats flown on the Cosmos 1887 mission. Photoaffinity labeling of soluble and particulate cell fractions with an [32P]-8-azido analog of cyclic AMP was followed by electrophoretic separation of the proteins and by autoradiographic identification of the labeled isoforms of cAPK R subunits. The results showed that RII in the particulate subcellular fraction was significantly decreased in heart cells from rats in the flight group when compared to controls. Protein banding patterns in both the cytoplasmic fraction and in a fraction enriched in chromatin-bound proteins showed some variability in tissues of individual animals, but exhibited no changes that could be directly attributed to flight conditions. No significant change was apparent in the distribution of RI or RII cyclic AMP binding in the soluble fractions. These findings indicate that the cardiac cell integrity or its protein content is not compromised under flight conditions. There is, however, what appears to be an adaptive molecular response which can be detected using microanalytical methods, indicating that a major hormone regulated mechanism may be affected during some phase of travel in space.
机体应激时常见的细胞反应是β-肾上腺素能受体的配体结合增加。细胞外信号通过细胞内环磷酸腺苷（cAMP）增加及随后的环磷酸腺苷依赖性蛋白激酶（cAPK）激活而放大。分子机制涉及cAMP与cAPK调节（R）亚基结合，从而使催化亚基游离出来进行蛋白质磷酸化。本研究旨在确定从执行“宇宙1887”任务的大鼠获取的心室组织中环磷酸腺苷受体蛋白的细胞区室化情况。用[32P]-8-叠氮基环磷酸腺苷类似物对可溶性和颗粒性细胞组分进行光亲和标记，随后对蛋白质进行电泳分离，并通过放射自显影鉴定cAPK R亚基的标记同工型。结果显示，与对照组相比，飞行组大鼠心脏细胞中颗粒性亚细胞组分中的RII显著减少。细胞质组分和富含染色质结合蛋白的组分中的蛋白质条带模式在个别动物的组织中显示出一些变异性，但未表现出可直接归因于飞行条件的变化。可溶性组分中RI或RII环磷酸腺苷结合的分布没有明显变化。这些发现表明，飞行条件下心脏细胞完整性或其蛋白质含量未受损害。然而，存在一种似乎是适应性分子反应，可通过微量分析方法检测到，这表明在太空旅行的某个阶段，一种主要的激素调节机制可能受到影响。
