FORMATION AND MAINTENANCE OF LYSOSOME STRUCTURE-FUNCTION

我研究的长期目标是精确描述 溶酶体的结构和功能。 从生物合成到周转， 溶酶体组装、组织并激活其组成酶， 保护细胞不被自身消化 在这一总体框架内， 拟议的实验将具体问：1）什么蛋白质序列 组织蛋白酶D（一种主要的溶酶体蛋白酶）和胃蛋白酶（一种 分泌的蛋白酶，负责指导这两个高度 同源消化酶不同的细胞隔室; ii）什么 是组织蛋白酶D活性丧失的一般细胞效应， 溶酶体; iii）组织蛋白酶D在溶酶体中的物理分布是什么？ 包括溶酶体在内的各种细胞区室，即它是膜 结合的或可溶的;和iv）什么参数定义组织蛋白酶D周转或 退化？ 为了回答这些问题，有必要从功能上隔离 编码组织蛋白酶D和胃蛋白酶的可表达重组DNA分子， 分离组织蛋白酶D活性有条件缺陷培养细胞。 重组克隆将用于构建缺失和融合 蛋白质，其将依次被测定用于互补的蛋白质， 组织蛋白酶D缺陷细胞。 这种方法将允许快速筛选 随机构建的（即鸟枪法）重组分子，因此， 组织蛋白酶D和胃蛋白酶一级序列的完整搜索 分类信号 为了评估组织蛋白酶D活性丧失的影响， 有条件缺陷的单元将根据它们的 生化缺陷，蛋白质合成和周转的变化，形态学， 和生长特性。 脉冲追踪细胞分离程序将 用于研究组织蛋白酶D的周转，因为它与溶酶体有关 正常培养细胞的结构和功能。 本文所述的溶酶体生理学研究在本质上是基础性的， 将有助于我们理解溶酶体相关的病理学， 细胞和分子水平。

The long term objective of my research is to describe the precise molecular structure and function of lysosomes. From biosynthesis to turnover, how do lysosomes assemble, organize and activate their constituent enzymes, while protecting the cell from autodigestion? Within this general framework, the proposed experiments will specifically ask: 1) what protein sequence determinants of cathepsin D, a major lysosomal protease, and pepsin, a secreted protease, are responsible for directing these two highly homologous digestive enzymes to different cellular compartments; ii) what are the general cellular effects of a loss of cathepsin D activity in lysosomes; iii) what is the physical disposition of cathepsin D in the various cellular compartments including lysosomes, i.e. is it membrane bound or soluble; and iv) what parameters define cathepsin D turnover or degradation? To answer these questions it will be necessary to isolate functionally expressible recombinant DNA molecules coding for cathepsin D and pepsin and isolate cultured cells conditionally defective in cathepsin D activity. The recombinant clones will be used to construct deletion and fusion proteins which will, in turn, be assayed for complementation of the cathepsin D deficient cells. This approach will allow rapid screening of randomly constructed (i.e. shotgun) recombinant molecules and thus, a complete search of cathepsin D and pepsin primary sequence for putative sorting signals. To evaluate the effect of a loss of cathepsin D activity, the conditionally defective cells will be characterized in terms of their biochemical defect, changes in protein synthesis and turnover, morphology, and growth characteristics. Pulse-chase cell fractionation procedures will be used to study the turnover of cathepsin D as it relates to lysosome structure and function in normal cultured cells. The studies of lysosome physiology, described here, are basic in nature but will be valuable to our understanding of lysosome related pathologies at the cellular and molecular level.