CONTROL OF SYNTHESIS OF A TRANSFORMATION-DEPENDENT SECRETED GLYCOPROTEIN

培养的小鼠成纤维细胞被RNA病毒转化， 病毒或化学试剂，都分泌39，000 Mr-磷酸糖蛋白 （主要排泄蛋白，MEP）。 非转化鼠 成纤维细胞在用肿瘤促进剂如TPA或 生长因子如PDGF。 分泌的MEP似乎是前体形式 一种特异性很强的酸性蛋白酶 我们已经纯化了MEP， 单特异性亲和纯化的抗血清，并克隆了一个cDNA， 编码来自中国仓鼠和小鼠细胞的MEP。 该蛋白含有 甘露糖6-磷酸，溶酶体识别标记。 进行处理 在转化的和非转化的细胞中细胞内进行，以得到两个 特定的较低分子量形式，其中最低分子量具有 主要是溶酶体定位。 转化、TPA和PDGF 通过增加MEP特异性mRNA水平刺激MEP合成。 的 MEP mRNA水平增加的机制是转录增加， 在核径流实验中测量。 我们正在研究这个系统， 溶酶体蛋白酶合成、加工和 分泌，因为它受到转化和模拟转化的试剂的影响。 转化状态，如肿瘤促进剂和生长因子。

Cultured mouse fibroblasts which are transformed by RNA viruses, a DNA virus or a chemical agent, all secrete a 39,000 Mr-phosphoglycoprotein (major excreted protein, MEP) in large amounts. Nontransformed murine fibroblasts secrete MEP after treatment with tumor promoters such as TPA or growth fators such as PDGF. Secreted MEP appears to be the precursor form of an acid protease with broad specificity. We have purified MEP, prepared monospecific affinity-purified antisera against it and cloned a cDNA which codes for MEP from Chinese hamster and mouse cells. The protein contains mannose 6-phosphate, thelysosomal recognition marker. It is processed intracellularly in both transformed and nontransformed cells to give two specific lower molecular weight forms, the lowest of which has a predominantly lysosomal localization. Transformation, TPA and PDGF stimulate MEP synthesis by increasing levels of MEP specific mRNA. The mechanism of the increase in MEP mRNA levels is increased transcription as measured in nuclear run-off experiments. We are studying this system as a model of regulation of lysosomal protease synthesis, processing and secretion as it is affected by transformation and agents which mimic the transformed state, such as tumor promoters and growth factors.