GTP-BINDING PROTEINS AND SIGNAL TRANSDUCTION--STRUCTURE AND FUNCTION

GTP 结合蛋白和信号转导——结构和功能

• 批准号: 5202270
• 负责人: M RODBELL
• 金额: --
• 依托单位: NATIONAL INSTITUTE OF ENVIRONMENTAL HEALTH SCIENCES
• 依托单位国家: 美国
• 资助国家: 美国
• 起止时间: 至
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/5202270
• 关键词: G protein; adipocytes; adrenergic receptor; adrenocorticotropic hormone; biological signal transduction; calcium; cell differentiation; confocal scanning microscopy; cyclic AMP; endocytosis; hormone regulation /control mechanism; isoproterenol; muscarinic receptor; protein structure function; receptor coupling; second messengers; tissue /cell culture; transfection

Previous studies have shown that G-proteins are multimeric structures with many structural and functional similarities to cytoskeletal proteins such as actin and tubulin. Also found in cells are punctate forms of G- proteins associated with stress fibers in at least two cell types; similar findings have been reported by others. Further complexity is revealed by findings that G-proteins and the effector signalling enzyme, adenylyl cyclase, are sequestered and taken into vesicular or endocytic structures that are internalized and which fuse with other vesicular elements. In CHO cells, the newly internalized structures do not return to the cell membrane but appear to be sequestered within the cell. However, when muscarinic receptors (transfected into the cells) are exposed to agonists, the endocytic process is dramatically and rapidly altered in that the endocytic vesicles return to the surface membrane with renewed localization of the G-proteins. The muscarinic signal-ling process interferes with early fusion steps that culminate in quasi- irreversible internal sequestration. Similar studies with rat adipocytes demonstrate a similar phenomenen when exposed to isoproterenol or ACTH. These findings suggest that signalling may be carried out not only at the surface membrane but also by the internalized endocytic vesicle. New approaches to the study of the hormonally controlled endocytic processes are needed. To this end, 3T3-L1 cell lines adapted to differention to adipocytes will be employed along with specific antibodies to the components of the signal transduction elements. Since these cells have the essential elements seen with isolated rat adipocytes it is planned to follow, using various techniques such as confocal microscopy, the fate of the internalized G-proteins and the dynamics of the endocytic process under different hormonal conditions, including the actions of lipolytic hormones and insulin.

先前的研究表明G蛋白是多聚体结构 与细胞骨架蛋白有许多结构和功能上的相似性 如肌动蛋白和微管蛋白。 在细胞中也发现了点状G- 与至少两种细胞类型中的应力纤维相关的蛋白质; 其他人也报告了类似的调查结果。 更复杂的是 发现G蛋白和效应信号酶， 腺苷酸环化酶，被隔离并进入囊泡或内吞 这些结构被内化，并与其他囊泡融合， 元素 在CHO细胞中，新内化的结构不会返回 但似乎被隔离在细胞内。 然而，当毒蕈碱受体（转染到细胞中）被激活时， 暴露于激动剂，内吞过程是显着和迅速的， 内吞囊泡返回到表面膜 G蛋白重新定位。 毒蕈碱信号 过程干扰早期融合步骤，最终在准- 不可逆的内部隔离 大鼠脂肪细胞的类似研究 当暴露于异丙肾上腺素或促肾上腺皮质激素时，显示出类似的现象。 这些发现表明，信号可能不仅在 表面膜也被内化的内吞囊泡吸收。 新 细胞内吞过程的研究方法 是必要的。 为此，3 T3-L1细胞系适应分化为 脂肪细胞将与针对所述细胞的特异性抗体一起沿着使用。 信号转导元件的组成部分。 由于这些细胞具有 在离体大鼠脂肪细胞中观察到的基本元素， 为了跟踪，使用各种技术，如共聚焦显微镜， 和内吞过程的动力学 在不同的激素条件下，包括脂解作用， 激素和胰岛素。