PROCESSING OF PROINSULIN/INSULIN BY B-CELL ORGANELLES

胰腺B细胞产生的胰岛素涉及许多密切的 综合步骤。理解胰岛素产生的唯一途径是 整体，从而确定与以下项目相关的潜在缺陷 对糖尿病的责任，是为了更好地了解 这些单独步骤的分子机制。这就是我们的目标 目前的研究。为此，有必要对B细胞亚细胞进行研究 组分(高尔基亚组分、颗粒亚组分和溶酶体)。 因为亚细胞分离需要更多的组织 利用分离的胰岛，大鼠胰岛素瘤细胞将很容易获得 使用。胰岛素瘤细胞将首先从以下方面进行表征 胰岛素原生物合成和转化，以及胰岛素释放，以验证 作为研究B细胞功能的模型。为了改变密度或 目的细胞器在再分馏前的其他性质， 从而提高再分馏过程的分辨率， 产品(包括胰岛素原)通过高尔基复合体的运输将 用莫能菌素或特里斯阻断。胰岛素原向胰岛素的转化将是 通过掺入精氨酸和赖氨酸类似物而被阻断；这导致 包衣颗粒到未包衣颗粒成熟过程中的伴生阻塞 (笼状蛋白包衣颗粒是最早的未成熟形式)。 选择用于详细研究的生化/超微结构转化 提出的问题是：1)高尔基复合体对胰岛素原的处理： 胰岛素原必须以某种方式被高尔基复合体识别，从而 集中在选定的高尔基地区，用于通向和最终 包装成分泌颗粒。识别过程可以是 受体介导的。高尔基体膜上可能存在的胰岛素原受体 被研究。2)胰岛素原转化为异糖：胰岛素原的确切位置 高尔基综合体的转换将是本地化的， 胰岛素原和转换酶的产生机制 与研究人员进行接触。3)颗粒异构性：功能性 将研究包衣和未包衣颗粒的意义， 特别提到负责优惠的机制 释放新合成的胰岛素。4)胰岛素储备的退化： 这一途径的机制和调控将被研究。嗜酒者 是最受欢迎的途径，但尚未得到生化证实。其影响 胰岛素晶体对胰岛素对体内降解敏感性的影响 将对溶酶体进行评估。

Insulin production by the pancreatic B-cell involves a number of closely integrated steps. The only way to understand insulin production as a whole, and thus identify the potential defects associated with, or responsible for, diabetes, is to gain a better understanding of the molecular mechanism of these individual steps. This is the goal of the present study. For this it will be necessary to study B-cell subcellular fractions (Golgi subfractions, granule subpopulations, and lysosomes). Since subcellular fractionation demands larger amounts of tissue than are readily available using isolated islets, rat insulinoma cells will be used. The insulinoma cells will first be characterized in terms of proinsulin biosynthesis and conversion, and insulin release, to validate them as a model for B-cell function. In order to modify the density or other properties of the organelles of interest before subfractionation, thereby improving the resolution of the subfractionation procedure, the transport of products (including proinsulin) across the Golgi complex will be blocked with monensin or Tris. Proinsulin conversion to insulin will be blocked by incorporation of arginine and lysine analogs; this results in an associated block in the maturation of coated to mature uncoated granules (the clathrin-coated granule being the earliest immature form). The biochemical/ultrastructural transformations selected for detailed study and the issues raised are: 1) Proinsulin processing by the Golgi comlex: proinsulin must in some way be recognized by the Golgi complex and thereby concentrated in select Golgi regions for channeling towards, and ultimate packaging into, secretory granules. The recognition process could be receptor mediated. Putative proinsulin receptors on Golgi membranes will be studied. 2) Proinsulin conversion to isulin: the precise site of initiation of conversion in the Golgi complex will be localized, and the mechanism responsible for bringing proinsulin and the conversion enzyme into contact studied. 3) Granule heterogeneity: the functional significance of coated and uncoated granules will be studied, with particular reference to the mechanism responsible for the preferential release of newly synthesized insulin. 4) Degradation of insulin stores: the mechanism and regulation of this pathway will be studied. Crinophagy is the favored path but has not been confirmed biochemically. The impact of the insulin crystal on sensitivity of insulin to degradation within lysosomes will be evaluated.