BIOSYNTHESIS, PROCESSING & SECRETION OF NEUROPEPTIDES & PITUITARY PEPTIDE HORMONE

参与蛋白质加工过程的分泌囊泡酶 阿黑皮素原（POMC，促肾上腺皮质激素原/内啡肽）和加压素原 研究了 70，000 mol.重量，成对碱性残基特异性 激素原转化酶（PCE），预先纯化， 其特征在于是一种乙酰基蛋白酶，最近已经显示， 在结构上与组织蛋白酶D相关。 PCE被证明是 与α-MSH一起由牛中间叶分泌， 以一种协调一致的方式。 胃蛋白酶抑制剂A， PCE，阻断小鼠中叶POMC的加工 进一步支持酶在体内的生理作用。 这种酶的克隆正在进行中。 我们之前的发现是，在盐负荷应激期间，小鼠表现出 血浆ACTH和垂体前叶POMC mRNA水平增加， 促使研究确定CRF的参与， 加压素（AVP）介导这种反应。 原位定量 下丘脑促肾上腺皮质激素释放激素和精氨酸加压素mRNA水平杂交分析 神经元显示CRF mRNA无变化，但AVP增加 盐负荷后的mRNA。 中位CRFi含量 隆起的是，CRF的释放部位也没有变化， 盐负荷 血浆AVP增加，AVP似乎是 促肾上腺皮质激素分泌的主要调节因子，在基础 CRF水平，在盐负荷应激。 研究使用 分离的小鼠垂体前叶细胞显示AVP是 在低剂量的CRF下增强CRF作用是非常有效的。 细胞凋亡信号转导的分子机制分析 CRF和AVP表明CRF通过cAMP依赖性起作用，而AVP 通过环磷酸腺苷的增加通过磷酸肌醇，就像在大鼠中一样， 但也许是通过增加磷酸化的功效 参与分泌过程的蛋白质。

Pituitary secretory vesicle enzymes involved in the processing of pro-opiomelanocortin (POMC, pro-ACTH/endorphin) and pro-vasopressin were studied. A 70,000 mol. wt., paired basic residue specific prohormone converting enzyme (PCE), previously purified and characterized as an aspartyl protease, has recently been shown to be structurally related to Cathepsin D. PCE was shown to be secreted from bovine intermediated lobe together with alpha-MSH, in a co-ordinately regulated manner. Pepstatin A, an inhibitor of PCE, blocked processing of POMC in the mouse intermediate lobe further supporting a physiologic role of the enzyme in vivo. Cloning of this enzyme is in progress. Our previous finding that mice, during salt-loading stress, exhibit an increase in plasma ACTH and anterior pituitary POMC mRNA levels, prompted studies to determine the involvement of CRF and vasopressin (AVP) in mediating this response. Quantitative in situ hybridization analyses of CRF and AVP mRNA levels in hypothalamic neurons indicate no changes in CRF mRNA, but an increase in AVP mRNA after salt-loading. The content of CRFi in the median eminence, the site of release of CRF also showed no change after salt-loading. Plasma AVP was increased, and AVP appears to be the primary regulator of ACTH secretion, in the presence of basal levels of CRF, during salt-loading stress. Studies using dissociated mouse anterior pituitary cells reveal that AVP is highly effective in potentiating CRF action at low doses of CRF. Analysis of the molecular mechanism for the signal transduction of CRF and AVP indicate that CRF acts through cAMP-dependent, and AVP through a phosphoinositol by an increase in cAMP, as in the rat, but perhaps through an increase in the efficacy of phosphorylation of proteins involved in the secretory process.