Section 46
Chapter 45,601

Compartmentalization of the mitogen-activated protein kinase (MAPK) in hepatic endosomes: association with the internalized epidermal growth factor (EGF) receptor

Faure, R.; Gaulin, J.F.; Bourgoin, S.; Fortier, S.

Molecular cell biology research communications MCBRC 1(2): 132-139


ISSN/ISBN: 1522-4724
PMID: 10356362
DOI: 10.1006/mcbr.1999.0120
Accession: 045600708

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A pool of MAPK was found in hepatic plasma membrane (PM) and endosomes (ENs). After injection of a single dose of EGF (10 microg/100 g body weight), MAPK was detected in EGF receptor (EGFR) immunoprecipitates prepared from ENs. MAPK was detected in a time-dependent manner in EGFR immunoprecipitates that was coincident with the progressive concentration of the EGFR. The EGFR-associated MAPK was also detected by using an anti-phospho-MAPK suggesting that it was active. MAPK was present in wheat-germ agglutinin (WGA) eluates prepared from ENs and was maximally tyrosine-phosphorylated at the time peak of EGFR internalization. MAPK therefore is compartmentalized in PM and ENs of rat liver. A fraction of the endosomal MAPK was found to be associated with the internalized EGFR complexes, suggesting that it plays a role in the control of the EGFR activity at this locus.

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