EFFECT OF SYNTHETIC PROTEASOMAL INHIBITOR MG132 ON DYNAMICS OF EGF-RECEPTOR COMPLEXES
ENDOCYTOSIS IN A431 CELLS
M. S. Melikova, A. A. Aksyonov, N. N. Nikolsky, E. S. Kornilova1
Institute of Cytology RAS, St. Petersburg, Russia;
1 e-mail: lenkor@mail.cytspb.rssi.ru
The effect of proteasomal activity suppression induced by MG132, a synthetic proteasomal inhibitor of EOF-receptor
complexes endocytosis in human epidermoid carcinoma A431 cell line, was studied. Using sub-cellular fractionation in 17 % Percoll
gradient, it was demonstrated that the addition of MG132 to the cells 15 min following stimulation of EGF endocytosis resulted in a slight
accumulation of 125I-EGF in early endosomes, and in much more significant accumulation of the labeled growth factor in
late endosomes/lysosomes, as compared to untreated cells. The release of 125I-EGF degradation products into the incubation
medium was significantly (3-12-fold) inhibited in the presence of MG132. At the same time biochemical analysis has demonstrated that the
EGF receptor itself is not a direct target of proteasomes, since it is revealed as a full-length protein with native mol. mass (170 kDa) in
fractions of early and late endosomes and lysosomes. Possible mechanisms of the MG132 effect on intracellular processing of
EGF-receptor complexes are discussed.
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