Calcium regulation of secretion in neuroendocrine cells

描述（申请人提供）：神经肽、生物胺和神经营养因子通过调节突触前和突触后功能影响突触传递。这些神经调质的调节释放是由致密核心囊泡（DCV）与质膜的Ca 2+依赖性融合介导的。虽然调节的DCV胞吐作用类似于介导突触递质释放的突触囊泡（SV）的Ca 2+依赖性胞吐作用，但这些过程在速度、潜伏期、Ca 2+调节和位置上不同。更全面地了解Ca2+触发的DCV融合的分子机制将揭示两种囊泡融合途径的相似性和差异，这两种途径可以确定选择性抑制调节剂分泌而不抑制突触传递的独特药物靶点。蛋白CAPS（分泌中的Ca2+依赖性激活蛋白）似乎是DCV而不是SV胞吐所需的。我们将阐明CAPS在调节DCV融合中的分子机制，并确定这种蛋白在神经系统中的生理作用。CAPS是一种PIP2结合蛋白，与SNARE融合机制的关键组分syntaxin具有高亲和力相互作用。这些相互作用可能在DCV胞吐中的后期融合前步骤介导CAPS的功能。CAPS还结合rabphilin，其可以部分介导CAPS与DCV的相互作用。我们的具体目标是：1。确定CAPS-突触融合蛋白相互作用对DCV胞吐的功能意义; 2.确定CAPS是否在DCV胞吐中作为PIP2效应子起作用; 3.确定CAPS在DCV胞吐中的选择性作用的基础以及这是否通过rabphilin相互作用介导;和4.确定CAPS在介导神经肽、生物胺和神经营养因子分泌的神经运输通路中的一般作用。这项工作的结果将有助于了解神经运输途径和分泌囊泡与质膜融合的分子基础。

DESCRIPTION (provided by applicant): Neuropeptides, biogenic amines, and neurotrophins affect synaptic transmission by regulating pre- and postsynaptic function. The regulated release of these neuromodulators is mediated by the Ca2+-dependent fusion of dense-core vesicles (DCVs) with the plasma membrane. Although regulated DCV exocytosis is similar to the Ca2+-dependent exocytosis of synaptic vesicles (SVs) that mediate synaptic transmitter release, these processes differ in speed, latency, Ca2+ regulation and location. A fuller understanding of molecular mechanisms underlying Ca2+-triggered DCV fusion will reveal similarities and differences in the two vesicle fusion pathways that could identify unique drug targets for the selective inhibition of modulator secretion without inhibiting synaptic transmission. The protein CAPS (Ca2+-dependent activator protein in secretion) appears to be required for DCV but not SV exocytosis. We will elucidate the molecular mechanism of CAPS function in regulated DCV fusion and determine the physiological role of this protein in the nervous system. CAPS is a PIP2-binding protein that exhibits high affinity interactions with syntaxin, a key component of the SNARE fusion machinery. These interactions may mediate the function of CAPS at a late pre-fusion step in DCV exocytosis. CAPS also binds rabphilin, which may in part mediate CAPS interactions with DCVs. Our specific aims will be: 1. To determine the functional significance of CAPS-syntaxin interactions for DCV exocytosis; 2. To determine if CAPS functions as a PIP2 effector in DCV exocytosis; 3. To determine the basis for the selective role of CAPS in DCV exocytosis and whether this is mediated through rabphilin interactions; and 4. To determine the general role of CAPS in neural trafficking pathways that mediate neuropeptide, biogenic amine and neurotrophin secretion. The results from this work will contribute to understanding neural trafficking pathways and to the molecular basis for secretory vesicle fusion with the plasma membrane.