Calcium regulation of secretion in neuroendocrine cells

描述（由申请人提供）：突触传递由 通过突触囊泡（SV）在突触处释放快速作用递质 胞吐作用相反，突触调节是通过释放 致密核心囊泡（DCV）的调节递质，作用于前， 突触后改变突触传递。的理解 作为快速Ca2+依赖性SV胞吐作用基础的分子机制， 在过去的十年中增加，需要相同的分子成分 用于DCV胞吐。然而，SV的生理调节差异 和DCV胞吐作用表明，也有不同的分子机制， 每个.我们发现CAPS（Ca2+依赖性分泌激活蛋白） 存在于DCV而不是SV上，并且是DCV而不是SV胞吐所需的。在 我们的后续研究，我们将确定分子机制，通过 CAPS的作用是促进Ca2依赖性DCV与血浆融合， 膜的这将通过识别CAPS上介导 其与血浆和DCV膜的相互作用（目的1）。这些研究将 定义了CAPS函数的DCV选择性的基础。进一步阐明 CAPS的作用机制，其相互作用的功能重要性 与蛋白质如突触融合蛋白、rabphilin和Muncl8的结合将被确定（Aim 2）。这些研究将为CAPS如何调节 促进DCV胞吐的融合机制。为了进一步定义 CAPS所需的功能，我们将表征功能丧失的CAPS突变体 以及通过X射线晶体学研究确定CAPS结构（Aim 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 将研究具有修饰的CAPS功能的细胞中的融合孔动力学（目的4）。 这些研究的完成将使人们了解到 DCV和SV胞吐作用之间的分子差异。 本研究结果可用于神经系统和内分泌治疗 涉及单胺递质分泌不足或分泌过多的疾病，或 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.