Morisset M, Capony F, Rochefort H
Endocrinology. 1986 Dec;119(6):2773-82. doi: 10.1210/endo-119-6-2773.
A 52K glycoprotein is secreted by human breast cancer cells in culture after estrogen stimulation. Using monoclonal antibodies, we have quantitated and characterized the corresponding proteins of the cell compartment. Using pulse-chase experiments, we have shown that about 40% of the 52K protein is secreted, the majority being successively processed into a 48K and a 34K protein. This last protein is very stable. The processing is inhibited by lysosomotropic agents and leupeptin, suggesting that it occurs in acidic vesicles, such as lysosomes or endosomes. Estradiol increased the intracellular level of immunoreactive 52K related proteins by 4-fold. Its effect is, however, more obvious in the medium, since there is a constitutive level in the cell. The stimulatory effects of estradiol on [3H]mannose and [35S]methionine incorporation into these proteins were similar and the endoglycosydase H sensitivity of the proteins was not altered, suggesting that estradiol did not modulate the glycosylation step. Antiestrogens did not stimulate synthesis and glycosylation of the 52K related proteins. Estradiol also increased the stability of the 52K precursor as well as that of total proteins. We conclude that the secreted 52K protein is the precursor of two cellular proteins of 48K and 34K. Estradiol stimulates both the intracellular accumulation of these proteins and the secretion of the precursor.
雌激素刺激后，人乳腺癌细胞在培养过程中分泌一种52K糖蛋白。利用单克隆抗体，我们已对细胞区室中的相应蛋白质进行了定量和表征。通过脉冲追踪实验，我们发现52K蛋白约40%被分泌，其中大部分先后加工成48K和34K蛋白。最后一种蛋白非常稳定。这种加工过程受到溶酶体促渗剂和亮抑蛋白酶肽的抑制，这表明其发生在酸性囊泡中，如溶酶体或内体。雌二醇使免疫反应性52K相关蛋白的细胞内水平增加了4倍。然而，其作用在培养基中更为明显，因为细胞中有一个组成性水平。雌二醇对这些蛋白中[3H]甘露糖和[35S]甲硫氨酸掺入的刺激作用相似，且这些蛋白对内切糖苷酶H的敏感性未改变，这表明雌二醇并未调节糖基化步骤。抗雌激素并未刺激52K相关蛋白的合成和糖基化。雌二醇还增加了52K前体以及总蛋白的稳定性。我们得出结论，分泌的52K蛋白是两种48K和34K细胞蛋白的前体。雌二醇刺激这些蛋白在细胞内的积累以及前体的分泌。
