CHROMOGRANIN A--NICOTINIC SIGNALING AND DESENSITIZATION

嗜铬粒蛋白A：烟碱信号和脱敏。尼古丁是一种 烟草中的一种成分，尽管有害， 方面的影响.从儿茶酚胺能细胞释放的儿茶酚胺被触发 通过烟碱胆碱能刺激，促进胞吐共释放 储存囊泡成分：儿茶酚胺，神经肽，和酸性 嗜铬粒蛋白，主要成分是嗜铬粒蛋白A（CgA）。CGA 被切割成生物活性肽，例如新的片段 （CgA 344 -364，我们发现并命名为“catestatin”）， 反馈抑制儿茶酚胺释放。我们发现， 神经元烟碱受体引起儿茶酚胺的分泌， CgA转录上调CgA的生物合成， 儿茶酚胺，并脱敏（产生耐受性）进一步 烟碱反应，分泌和转录。初步 研究中，我们发现catestatin拮抗所有这些胆碱能 应答因此，CgA（及其片段catestatin）似乎发挥了重要作用。 神经元烟碱胆碱能信号传导的中心作用， 对尼古丁有积极反应（分泌和转录），以及 在阻断所有已知的刺激（分泌或转录）或 尼古丁的脱敏作用CgA的这些特征和 catestatin的反应和作用表明， 反馈作用。在这里，我们将探讨CgA的这些功能， catestatin，使用培养的嗜铬细胞。两大领域将 表征了I.烟碱胆碱能刺激对引起 分泌（儿茶酚胺和CgA），CgA生物合成，和 进一步分泌或转录的脱敏（耐受性） 尼古丁的反应我们已经表征了CgA启动子 结构域（顺式），其介导对尼古丁的反应，并具有 开始建立信号转导通路， 转录及其脱敏。二. Catestatin拮抗 烟碱反应（分泌、转录和脱敏 其中）。我们描述了catestatin对分泌的抑制作用， 特别是作为非竞争性烟碱胆碱能拮抗剂，和 确定了其对烟碱信号转导的影响，以及 对先前烟碱脱敏的保护。这些研究可能 建立一种新的自我平衡（负反馈）机制， 内源性肽拮抗烟碱刺激 儿茶酚胺释放，CgA基因转录，和脱敏 分泌和转录。 这种保护， 脱敏可能对生物体有利， 长时间的压力，也许是为了防止 提前终止分泌和转录反应， 生理性烟碱刺激

Chromogranin A: nicotinic signaling and desensitization. Nicotine is a component of tobacco that motivates continued abuse despite harmful effects. Catecholamine release from catecholaminergic cells is triggered by nicotinic cholinergic stimulation, prompting exocytotic co-release of storage vesicle constituents: catecholamines, neuropeptides, and acidic chromogranins, the major component being chromogranin A (CgA). CgA is cleaved to biologically active peptides, such as a novel fragment (CgA344-364, which we discovered and named "catestatin") that feedback-inhibits catecholamine release. We found that stimulation of neuronal nicotinic receptors causes secretion of catecholamines and CgA, transcriptionally upregulates the biosynthesis of CgA and catecholamines, and desensitizes (creates tolerance to) further nicotinic responses, both secretory and transcriptional. In preliminary studies, we found that catestatin antagonized all of these cholinergic responses. Thus, CgA (and its fragment catestatin) seem to play a central role in neuronal nicotinic cholinergic signaling, both in responding positively to nicotine (in secretion and transcription), and in blocking all known stimulatory (secretory or transcriptional) or desensitizing action of nicotine. These features of CgA's and catestatin's responses and action suggest a homeostatic, negative feedback role. Here we will explore these functions of CgA and catestatin, using cultured chromaffin cells. Two general areas will be characterized. I. Effects of nicotinic cholinergic stimulation to cause secretion (of catecholamines and CgA), CgA biosynthesis, and desensitization of (tolerance to) further secretion or transcriptional responses to nicotine. We have already characterized CgA promoter domains (in cis) which mediate the response to nicotine, and have begun to establish signal transduction pathways involved in transcription and its desensitization. II. Catestatin's antagonism of nicotinic responses (secretion, transcription, and desensitization thereof). We characterized catestatin's inhibitory effects on secretion, specifically as a non-competitive nicotinic cholinergic antagonist, and established its effect on nicotinic signal transduction, as well as protection against prior nicotinic desensitization. These studies may establish a novel homeostatic (negative feedback) mechanism by which an endogenous peptide antagonizes nicotinic stimulation of catecholamine release, CgA gene transcription, and desensitization of both secretion and transcription. Such protection against desensitization may be advantageous to an organism during circumstances of prolonged stress, perhaps guarding against premature termination of secretory and transcriptional responses to physiological nicotinic stimulation.