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Calcium effects on epidermal growth factor receptor‐mediated endocytosis in normal and SV40‐transformed human fibroblasts
Author(s) -
Tupper Joseph T.,
Bodine Peter V.
Publication year - 1983
Publication title -
journal of cellular physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.529
H-Index - 174
eISSN - 1097-4652
pISSN - 0021-9541
DOI - 10.1002/jcp.1041150209
Subject(s) - internalization , endocytosis , epidermal growth factor , extracellular , microbiology and biotechnology , receptor , cell surface receptor , cell , cell growth , biology , growth factor , cell membrane , calmodulin , cell culture , calcium , chemistry , biochemistry , enzyme , genetics , organic chemistry
Lowering of extracellular Ca 2+ levels will reversibly arrest the growth of human fibroblasts (WI38). Simian virus 40 (SV 40 )‐transformed WI38 cells do not exhibit this Ca 2+ ‐dependent arrest. One possibility for this difference in Ca 2+ requirement is that extracellular or surface membrane‐bound Ca 2+ may be required for growth factor receptor‐mediated endocytosis and this Ca 2+ requirement may differ in normal versus transformed cells. In this study we have evaluated the role of Ca 2+ in the binding, internalization, and degradation of epidermal growth factor (EGF) in the WI38 and SV 40 WI38 cell. The binding of [ 125 I]EGF to the cell surface is not significantly altered by lowering of Ca 2+ to 10 −5 ‐M levels in either the normal or transformed cell. At this Ca 2+ level, growth of the normal cell is inhibited. The subsequent internalization of EGF is reduced nearly threefold in the normal cell but not in the transformed cell following Ca 2+ deprivation. Degradation of the EGF‐receptor complex is also sensitive to Ca 2+ . A twofold reduction in the rate of release of acid‐soluble 125 I occurs in the normal but not the transformed cell under conditions of lowered medium Ca 2+ . In contrast, 2‐chloro‐10‐3‐aminopropyl phenothiazine (CP), an inhibitor of the Ca 2+ ‐dependent regulator protein calmodulin, causes an inhibition of [ 125 I]EGF internalization and degradation in both the normal and transformed WI38 cell, and a marked inhibition of [ 125 I]EGF binding to the cell surface receptor of the transformed cell but not the normal cell.