Lateral diffusion of epidermal growth factor complexed to its surface receptors does not account for the thermal sensitivity of patch formation and endocytosis

Publisher Website
Google Scholar
Abstract
The patching and endocytosis of EGF (epidermal growth factor) bound to A-431 cells (a human epidermoid carcinoma line) are temperature-sensitive processes which are completely inhibited at 4.degree. C. Receptor-mediated endocytosis generally occurs through coated regions, and EGF bound to its membrane receptor must diffuse laterally to these points of internalization. In this work the thermal sensitivity of the lateral diffusion of EGF receptor complexes and the thermal sensitivity of the patching and endocytosis of the hormone receptor complexes were investigated. Using the fluorescence photobleach recovery technique, the lateral diffusion coefficients [D] of a fluorescent derivative of EGF as a function of temperature were measured. D increased gradually from 2.8 .times. 10-10 cm2/s at 5.degree. C to 8.5 .times. 10-10 cm2/s at 37.degree. C, and no phase transition was detected. Neither was a phase transition detected when the diffusion coefficient of fluorescent lipid probes was measured over this temperature range. From a calculation of the collision frequency of the occupied EGF receptors with coated regions using the measured values of D at 5.degree. and 37.degree. C, diffusion apparently is not the rate-limiting step for either endocytosis or patching.

This publication has 31 references indexed in Scilit: