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：10
页码：5025-5029
DOI：10.1073/pnas.75.10.5025
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Using a quantitative electron microscopic autoradiographic technique, we have localized the initial binding step of 125I-labeled epidermal growth factor (125I-EGF) to the plasma membrane of the human fibroblast. After initial binding, labeled EGF is internalized progressively by the cell in a time- and temperature-dependent fashion; when cell-associated radioactivity comes to steady state, approximately 1/3 of the autoradiographic grains are related to the plasma membrane and approximately 2/3 have been internalized. Under these conditions the internalized grains are almost exclusively related to lysosomal structures. When 125I-EGF associates with the cells for 2 hr at 4 degrees or 2 min at 37 degrees, 34% of grains localize to coated regions of the membrane. These coated regions make up less than 2% of the membrane surface. These data directly confirm kinetic studies and suggest that saturable binding of EGF is followed by adsorptive pinocytosis and cellular degradation of the ligand and possibly its cell surface receptor.
