Effect of EGF on the intracellular distribution of heat-shock proteins in A431 cells

The intracellular distribution of hsp70 and hdj1 was studied using immunofluorescent method. In nonstimulated cells hsp70 and hdj1 were observed in the cytoplasm of A431 cells. When 100 ng/ml EGF was added for 15 min, both hsp70 and hdj1 were accumulated in the nuclei. Later on (up to 1 h) hsp70 was exported from the nuclei to be observed mainly in the cytoplasm, whereas hdj1 remained in the nuclei. In cells exposed to tyrphostin AG1478, this inhibitor of tyrosine kinase activity of EGF receptor prevented EGF-dependent accumulation of hsp70 and hdj1 in the nuclei. U73122, an inhibitor of phospholipase C activity, induced tyrosine phosphorylation of EGF receptor without EGF stimulation. In cells treated with U73122, both hsp70 and hdj1 were detected in the nuclei of non-stimulated cells. It is concluded that the intracellular distribution of heat shock proteins in A431 cells depends on tyrosine kinase activity of EGF receptor. Here we report for the first time the influence of EGF on the intracellular redistribution of heat shock proteins.