Compartmentalization of the mitogen-activated protein kinase (MAPK) in hepatic endosomes: association with the internalized epidermal growth factor (EGF) receptor.
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.
Faure
R
R
Département de médecine, Centre de Recherche du CHUL, Université Laval, Ste-Foy, Québec, Canada. Robert.Faure@crchul.ulaval.ca
Gaulin
J F
JF
Bourgoin
S
S
Fortier
S
S
D000818:Animals; D002451:Cell Compartmentation; D002462:Cell Membrane / Q000378:metabolism; D011992:Endosomes / Q000201:enzymology / Q000378:metabolism*; D066246:ErbB Receptors / Q000378:metabolism*; D005260:Female; D015151:Immunoblotting; D008099:Liver / Q000201:enzymology / Q000378:metabolism* / Q000648:ultrastructure; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D010766:Phosphorylation; D011233:Precipitin Tests; D051381:Rats; D017207:Rats, Sprague-Dawley; D014443:Tyrosine / Q000378:metabolism; D014909:Wheat Germ Agglutinins
D014909:Wheat Germ Agglutinins; D014443:Tyrosine; D066246:ErbB Receptors; D020928:Mitogen-Activated Protein Kinases