| Abstract: | It has been first shown that EGF regulates a proteolytic activity of proteasomes. Following a 15 min action with 100 ng/ml EGF, three types of peptidase activity of both cytoplasmic and nuclear proteasomes were induced in A431 cells, although, this effect on different populations of proteasomes was selective. EGF preferentially stimulates chymotrypsin-like activity of cytoplasmic proteasomes, and induces a similar increase of chymotrypsin-like, trypsin-like and peptydylglutamyl peptide hydrolase activities of nuclear particles. Tyrphostin, an inhibitor of tyrosine kinase activity of EGF receptor, prevents the EGF effect on both proteolytic and RNase activity of nuclear and cytoplasmic proteasomes. It is concluded that EGF may rapidly and selectively stimulate enzymatic activity of EGF receptor. |
