REGULATION OF LYSOSOMAL ENZYME TRAFFICKING

摘要溶酶体在真核细胞中起着重要的作用。 细胞内和细胞外大分子的降解部位。 选择性地将蛋白质输送到溶酶体包括添加一种 蛋白质的共同地址标记(甘露糖6-磷酸标记)，以及 结合标记物并介导的膜相关受体 蛋白质转位到溶酶体室。最新研究 建议在某些情况下可以更改此目标确定过程 这样，通常指定给溶酶体的酶从 手机。这种调节机制在生理上可能很重要，因为 细胞外溶酶体酶可能在肿瘤生长中发挥重要作用 在正常细胞生长和转移中也是如此。 这项提议的长期目标是确定分子基础 用于溶酶体酶的正常和受控制的运输。建议数 研究将涉及MEP的分子和细胞生物学研究，a 溶酶体半胱氨酸蛋白酶的运输受生长调节 因子和细胞转化，以及被认为是中介的受体 溶酶体转运：依赖于阳离子的甘露糖6-磷酸(Man-6-P) 受体和Man-6-P/IGF-II受体。 MEP基因的定点突变和表达将用于 确定蛋白质上的结构决定因素，负责增加 Man-6-P记分器。海藻中蛋白质和碳水化合物部分的分析 MEP，并检测生长因子对合成和表达的影响。 两个受体的贩运，将进行，以进一步 确定MEP调节分泌的基础。 这些研究将提供信息，从而确定 负责选择性磷酸化的识别结构 溶酶体蛋白，将有助于阐明参与的机制 受控制的溶酶体蛋白的运输。

The lysosome plays an important role in eukaryotic cells as the primary site of degradation of both cellular and extracellular macromolecules. Selective delivery of proteins to the lysosome involves addition of a common address marker (the mannose 6-phosphate marker) to the proteins, and membrane-associated receptors that bind the marker and mediate translocation of the proteins to the lysosomal compartment. Recent studies suggest that under certain conditions this targeting process can be altered such that enzymes normally destined for lysosomes are secreted from the cell. This regulatory mechanism may be important physiologically since extracellular lysosomal enzymes may play important roles in tumor growth and metastasis as well as in normal cell growth. The long range goal of this proposal is to determine the molecular basis for normal and regulated trafficking of lysosomal enzymes. The proposed studies will involve molecular and cellular biological studies on MEP, a lysosomal cysteine proteinase whose trafficking is regulated by growth factors and cellular transformation, and the receptors thought to mediate lysosomal trafficking: the cation dependent mannose 6-phosphate (Man-6-P) receptor and the Man-6-P/IGF-II receptor. Site-specific mutagenesis and expression of MEP cDNA will be used to identify structural determinants on the protein responsible for addition of the Man-6-P marker. Analysis of the protein and carbohydrate portions of MEP, and examination of the effects of growth factors on the synthesis and trafficking of the two receptors, will be carried out in order to further define the basis for MEP's regulated secretion. These studies will provide information leading to determination of the recognition structure responsible for selective phosphorylation of lysosomal proteins and will help elucidate the mechanisms involved in regulated trafficking of lysosomal proteins.