POLYPEPTIDE HORMONE BIOSYNTHESIS--AMPHIBIAN MODELS

低分子多肽激素的生物合成是依赖的 在翻译后处理事件的复杂序列上。这个 调节这些事件的处理酶在不同的 内质网/高尔基体/分泌颗粒网络的亚室。理解 这些过程的表达、调控和细胞内路径 细胞器中的酶是建立清晰认识的核心 关于分泌细胞的细胞生物学。非哺乳动物内分泌的研究进展 组织揭示了一系列的策略，这些策略已经进化成调解 多肽激素的生物合成。将使用两栖动物模型系统 分析前阿片黑素皮质素(POMC)生物合成的两个方面 通常与多肽生物合成途径相关的途径： 细胞内加工事件的分离，以及发育 对加工酶的调节。 中华大蟾蜍(Bufo Marinus)提供了一种独特的模式系统来研究N- POMC产物的乙酰化，α-MSH和β-内啡肽。在……里面 对于哺乳动物，这些反应是在分泌颗粒中平行进行的。 在无尾两栖动物的中间脑垂体部，这些反应是 在时间和空间上都是分开的。一系列的研究涉及 脉冲/追赶范例、免疫电子显微镜、亚细胞分离 动力学分析将试图解释这种两栖动物是如何 成功地分离了这些POMC最终产物的N-乙酰化。 这些项目将提供对路由和 调节囊泡内的加工酶。 虎纹伊蚊和新生肌瘤幼虫垂体前叶的研究 Micianum Ambystoma将研究 ACTH的蛋白水解性切割。ACTH加工中的发展转变 在两栖类中观察到的似乎是四足动物的共同特征 促肾上腺皮质激素个体发育。两栖类脑下垂体的研究提供了便利 研究ACTH翻译后机制的模型，并绕过许多 胎鼠垂体腺模型系统的局限性。ACTH- 幼虫促肾上腺皮质激素产生的相关切割产物将 以及这些产物对类固醇合成的影响。 幼虫肾上腺细胞将被测定。

The biosynthesis of low molecular weight polypeptide hormones is dependent upon a complex sequence of posttranslational processing events. The processing enzymes that mediate these events are found within distinct subcompartments of the ER/golgi/secretory granule network. Understanding the expression, regulation and intracellular routing of these processing enzymes within organelles is central to establishing a clear understanding of the cell biology of secretory cells. Studies on non-mammalian endocrine tissues reveal the array of strategies that have evolved to mediate the biosynthesis of polypeptide hormones. Amphibian model systems will be used to analyzed two aspects of the Proopiomelanocortin (POMC) biosynthetic pathway that are relevant to polypeptide biosynthetic pathways in general: the segregation of processing events within cells, and the developmental regulation of processing enzymes. The toad, Bufo marinus, provides a unique model system to study the N- acetylation of the POMC products, alpha-MSH and beta-endorphin. In mammals, these reactions are performed in parallel in secretory granules. In the intermediate pituitary of anuran amphibians, these reactions are separated both temporally and spatially. A series of studies involving pulse/chase paradigms, immunoelectron microscopy, subcellular fractionation and kinetics analyses will attempt to explain how this amphibian has succeeded in segregating the N-acetylation of these POMC end products. These projects will provide insights into the strategies for routing and regulating processing enzymes within vesicles. Studies on the anterior pituitary of larval Ambystoma tigrinum and neotenic Ambystoma mexicanum will investigate developmental changes in the proteolytic cleavage of ACTH. The developmental shift in ACTH processing observed in amphibian appears to be a common feature of tetrapod corticotrope ontogeny. The amphibian pituitary studies provide convenient models for studying ACTH posttranslational mechanisms, and circumvent many of the limitations of the fetal rat pituitary model system. The ACTH- related cleavage products generated by larval corticotropes will be characterized, and the effects of these products on steroid synthesis by larval adrenal cells will be determined.