【作者】 酒亚明；

【导师】 徐涛；

【作者基本信息】 华中科技大学 ， 生物物理学， 2010， 博士

【摘要】 细胞必须具有有效而精密的机制,确保在糙面内质网上合成的各种蛋白,在反面高尔基复合体上以出芽的方式通过不同的转运囊泡以不同的途径被分选、转运并发挥其生理功能。分泌囊泡(secretory granules, SGs)也叫做致密核心囊泡(dense core vesicles, DCVs)是装载并转运分泌蛋白的载体,其在胞内的转运过程不仅涉及蛋白本身(分泌蛋白和囊泡膜蛋白)的修饰、加工和装配,还涉及到多种囊泡特异组分的定向转运和复杂的调控过程。hid-1编码一个全新的蛋白,由Ailion和Thomas在筛选具有Hid (high temperature-induced dauer formation)表型的线虫种系过程中发现。HID-1蛋白高度保守,在果蝇、小鼠和人类中都只有唯一的同源物。此外,hid-1基因突变的线虫还具有多种表型,如轻微的行动不协调(Unc),对乙酰胆碱酯酶抑制剂的抗性(Ric),排便缺陷(Aex)等。本文主要利用线虫这个经典的动物模型对HID-1蛋白的作用机理和生理功能进行深入的研究。本文第一部分为研究背景介绍,简要概述了分泌囊泡的生成、加工成熟、转运、分选及分泌机制和学习记忆、信息整合的神经通路及分子机理。本文第二部分研究了hid-1蛋白参与学习记忆这个高级认知功能的调节过程,主要是信息整合和联系性学习记忆。我们发现除了参与调节NaCl-饥饿模式和温度-饥饿模式这两种联系性学习记忆模式外,hid-1基因还对两种感觉信号的整合及相应的抉择行为有重要调控作用,并且确定了其功能的发挥主要是通过调节神经元内负责神经多肽分泌的DCVs实现的。我们试图确定hid-1调节信息整合的信号通路,但遗憾的是,我们只能排除hid-1不是通过hen-1途径和胰岛素受体信号途径来调节学习记忆过程,下一步我们需要研究hid-1基因的作用靶点和信号通路,进而深入透析其分子机制。第三部分通过电生理技术、荧光成像技术以及生物化学技术研究了HID-1作为一个高度保守的蛋白,是DCVs成熟、转运和再循环的必需调节因子。HID-1主要定位在高尔基复合体上,它的缺失会导致DCVs的可溶性内容物减少,但以高度聚集形式存在于致密核心内的神经多肽却不受影响,此外还会引起特异膜蛋白的增加。我们推测HID-1主要通过影响DCVs特异组分从早期内涵体到高尔基体的逆向转运,从而影响囊泡的成熟和再循环过程,但它并不参与突触囊泡(synaptic vesicles, SVs)的分泌。这些发现对于理解分泌囊泡成熟、转运及再循环回高尔基体的具体作用机理有所帮助。本文第四部分研究了由黑寡妇蜘蛛分泌的神经毒素α-LTX及其突变体α-LTXN4C通过不同机制促进胰腺β细胞[Ca2+]i升高。我们发现α-LTX引起[Ca2+]i的升高依赖于细胞外液中的Ca2+,并且这种升高可以被La3+特异阻断。而α-LTXN4C引起的[Ca2+]i上升则依赖于二价阳离子的存在。更多还原

【Abstract】 Peptide hormones and neuropeptides are packaged and stored in specialized intracellular organelles called secretory granules (SGs, also known as dense core vesicles, DCVs). DCV is the specialized organelle that facilitates long-term intracellular storage of secretory proteins at high concentration. While DCVs have been known to be prominent post-Golgi carriers for almost 50 years, the exact mechanism of how DCVs maturation and its specific components recycled back to TGN remains largely unknown.In search for mutants with high-temperature-induced dauer formation (Hid) phenotype in C. elegans, a mutation in hid-1 gene was identified. The hid-1 gene encodes a novel protein with a single homolog in Drosophila melanogaster, mouse and Homo sapiens and bioinformatic analysis of HID-1 suggests no known functional domain. In addition to Hid phenotype, hid-1 mutants show pleiotropic phenotypes such as mildly uncoordinated movement (Unc), moderately resistant to the paralytic effects of aldicarb (Ric) and constipated phenotype (Aex). Here we used C. elegans as the research model to study the molecular mechanism and function of HID-1 protein.First, we introduced the functional mechanisms of DCVs, the neural circuits and molecular mechanisms underlying the sensory integration and a great animal model to study above mysteries, C. elegans.Animals integrate various environmental stimuli within the nervous system to generate proper behavioral response and plasticity. The neural circuits and molecular mechanisms underlying the sensory integration are largely unknown. Here in the second part, we identified protein HID-1 that functions in the sensory integration across modalities and associative learning in C. elegans. hid-1 mutants display defects in sensory integration between taste and olfactory signals and in two types of associative learning. We propose that HID-1 functions in neurons by regulating DCVs, which constitutes an essential component in sensory integration and behavior plasticity.In the third part, we studied HID-1, a highly conserved protein, involved in DCVs maturation and specific protein recycling thereafter. The subcellular distribution of HID-1 was localized to Golgi. Deletion of HID-1 reduced not only the number of readily releasable DCVs but also the amount of soluble peptides, but not the dense core peptides. On the contrary, the DCV-specific membrane proteins were incresed in the absence of HID-1. We propose that HID-1 participates in DCVs soluble cargo and membrane protein recycling from early endosome back to Golgi and hence affects the DCVs maturationThe last part presentsα-latrotoxin (α-LTX), a neurotoxin from black-widow spider, causes vesicles release in presynapse of nerve terminal after binding to specific membrane receptors. We found thatα-LTX inserts into the plasma membrane and forms stable non-selective cation channels, the influx of extracellular Ca2+ through the channels causes massive Ca2+-dependent exocytosis of insulin-containing vesicles. Whereas,α-LTXN4C, binding with its receptor CIRL in extracellular divalent cation-dependent way, increases [Ca2+]i by mobilization of the intracellular calcium stores.更多还原