Calcium regulation of secretion in neuroendocrine cells

描述(申请人提供)：突触传递由 通过突触小泡(SV)释放突触上的快速递质 胞吐。相反，突触的调节是通过释放 致密核心囊泡(DCV)的调制递质，作用于 在突触后改变突触传递。对这一问题的理解 快速钙依赖的SV胞吐的分子机制有 在过去的十年中增加了，并且需要相同的分子组成 用于DCV胞吐。然而，SV的生理调节不同 和DCV的胞吐作用表明，也有不同的分子机制 每个人。我们发现CAPS(依赖于钙离子的分泌激活蛋白) 驻留在DCV上，而不是SVS上，DCV需要，但SV胞吐不需要。在……里面 我们的继续研究，我们将通过 哪种CAPS可促进依赖于钙的DCV与血浆的融合 薄膜。这将通过识别CAP上的域来实现 它与血浆和DCV膜的相互作用(目标1)。这些研究将 定义DCV的基础-CAPS功能的选择性。为了进一步澄清 CAPS的作用机制及其相互作用的功能重要性 将测定合成素、狂犬素和Muncl8等蛋白质(AIM 2)。这些研究将为CAPS如何调控提供分子解释。 融合机制有助于DCV的胞吐作用。要进一步定义的域 功能所需的CAPS，我们将描述功能缺失的CAPS突变体 以及通过X射线结晶学研究确定帽子结构(目标3)。 为了将CAPS的分子相互作用与其在DCV胞吐中的作用联系起来，我们 将研究具有改进的CAPS功能的细胞中的融合孔动力学(目标4)。 这些研究的完成将为我们提供有关监管 融合机制以及DCV和SV胞吐作用的分子差异。 研究结果可应用于神经系统和内分泌的治疗。 涉及单胺类递质分泌过少或过多的疾病 多肽激素。

DESCRIPTION (provided by applicant): Synaptic transmission is mediated by release of fast-acting transmitters at synapses via synaptic vesicle (SV) exocytosis. Synaptic modulation is, in contrast, mediated by release from dense-core vesicles (DCVs) of modulatory transmitters that act pre- and postsynaptically to modify synaptic transmission. The understanding of the molecular mechanisms that underlie rapid Ca2+-dependent SV exocytosis has increased over the past decade and the same molecular constituents are required for DCV exocytosis. However, differences in the physiological regulation of SV and DCV exocytosis suggest that there are also molecular mechanisms distinct to each. We discovered that CAPS (ca2+-dependent activator protein for secretion) resides on DCVs but not SVs and is required for DCV but not SV exocytosis. In our continuation studies, we will determine the molecular mechanism through which CAPS acts to facilitate Ca2-dependent DCV fusion with the plasma membrane. This will be accomplished by identifying domains on CAPS that mediate its interactions with plasma and DCV membranes (Aim 1). These studies will define the basis of the DCV-selectivity of CAPS function. To further elucidate the mechanism of CAPS action, the functional importance of its interactions with proteins such as syntaxin, rabphilin and Muncl8 will be determined (Aim 2). These studies will provide a molecular explanation of how CAPS regulates the fusion machinery to facilitate DCV exocytosis. To further define domains of CAPS required for function, we will characterize loss-of-function CAPS mutants as well as determine CAPS structure by X-ray crystallographic studies (Aim 3). To relate the molecular interactions of CAPS to its role in DCV exocytosis, we will study fusion pore dynamics in cells with modified CAPS function (Aim 4). Completion of these studies will provide insight on the regulation of the fusion machinery and on molecular differences between DCV and SV exocytosis. The results may find application in the therapy of nervous system and endocrine disorders that involve hypo- or hypersecretion of monoamine transmitters or peptide hormones.