期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：1978
卷号：75
期号：6
页码：2644-2648
DOI：10.1073/pnas.75.6.2644
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：An affinity labeling technique used previously for identification of a membrane receptor for epidermal growth factor (EGF) was exploited to investigate the physiological fate of receptor after binding of EGF. Incubation of affinity-labeled cells at 37{degrees} resulted in a time-dependent loss of radioactivity from the EGF-receptor covalent complex (Mr 190,000). Ninety percent of the radioactivity lost from the band of Mr 190,000 during a 1-hr incubation at 37{degrees} appeared in three bands of Mr 62,000, 47,000, and 37,000. The crosslinked EGF-receptor complex (Mr 190,000) on intact cells was accessible to the action of trypsin at 4{degrees} and cofractionated with the plasmalemmal fraction. The proteolytic processing products of receptor were inaccessible to trypsin and banded with the lysosomal fraction upon subcellular fractionation. The rate of internalization and proteolytic processing of radiolabeled receptor was the same as the rate of reduction of binding activity induced by EGF. A study of the relationship between EGF-induced receptor internalization and processing, and stimulation of DNA synthesis, showed that both these processes were half-maximally stimulated at approximately 0.1 nM EGF, a concentration at which only 10% of the receptor sites are occupied. These data indicate that at concentrations of EGF subsaturating for binding but optimal for biological activity, there is a slow, continuous process of receptor internalization and degradation which could be limiting for EGF-induced mitogenesis.
关键词：radiolabeled hormone receptors ; down regulation of hormone receptors ; receptor internalization ; DNA synthesis ; mitogenic hormone
