Synthesis, turnover, and down-regulation of epidermal growth factor receptors in human A431 epidermoid carcinoma cells and skin fibroblasts.

摘要: Epidermal growth factor (EGF) receptors extracted with Triton X-100 from human skin fibroblasts and A431 epidermoid carcinoma cells rapidly lose EGF-binding activity precipitable polyethylene glycol. The presence of concanavalin A which can cross-link and, thereby, aggregate the receptors, allowed quantitative recovery lost activity. Scatchard analysis EGF binding X-100-solubilized showed that possess approximately 1.5 X 10(6) 7 10(4) sites/cell, respectively, exhibit similar affinities for ligand. heavy isotope density-shift method was employed to determine whether differences in rates receptor synthesis or decay account large difference number receptors/cell between two cell types. After shifting medium containing (15N, 13C, 2H) amino acids, light solubilized total cellular membranes, were resolved by isopycnic banding on density gradients then quantitated. It demonstrated synthesize at a rate 12 times faster than half-life is somewhat longer (t1/2 = 16 h) 9 fibroblasts. Down-regulation surface capacity occurs t1/2 2-3 h results 70-83% decrease level h. revealed these changes due an alteration not affinity. Rates inactivation/decay determined method. No change occurred as consequence down-regulation. Down-regulation, however, caused 4.5 These indicate EGF-dependent regulation involves inactivation.