title: Dephosphorylation on tyrosine of epidermal growth factor receptor is inhibited by Ca2+ pretreatment in isolated liver membrane.
abstract: The autophosphorylation of epidermal growth factor receptor of the liver membrane was enhanced by pretreatment with 1 mM Ca2+. This enhancement was blocked by 30 microM genistein, but not by 30 microM H-7. In immunoblotting analysis, the amount of phosphotyrosine increased in the Ca(2+)-pretreated membrane. When dephosphorylation processes were studied, receptor dephosphorylation occurred in a time-dependent manner in the untreated membrane, but not in the Ca(2+)-pretreated membrane. In the presence of sodium vanadate, receptor phosphorylation increased in the untreated membrane, but not in the Ca(2+)-pretreated membrane. Inhibition of dephosphorylation did not occur in the membrane pretreated with Ca2+ in the presence of monodansylcadaverine, a transglutaminase (TGase) inhibitor. These results suggest that Ca2+ pretreatment causes the inhibition of some protein tyrosine phosphatase via a Ca(2+)-involved mechanism such as activation of TGase and results in the enhancement of receptor phosphorylation.
authors.affiliation: Department of Radiopharmacy, Tohoku College of Pharmacy, Sendai, Japan.
authors.forename: S
authors.initials: S
authors.lastname: Katoh
authors.forename: A
authors.initials: A
authors.lastname: Funayama
authors.forename: H
authors.initials: H
authors.lastname: Kohno
authors.forename: Y
authors.initials: Y
authors.lastname: Ohkubo
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D002103:Cadaverine / Q000031:analogs & derivatives / Q000494:pharmacology; D002118:Calcium / Q000494:pharmacology*; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D066246:ErbB Receptors / Q000187:drug effects / Q000302:isolation & purification / Q000378:metabolism*; D015151:Immunoblotting; D007700:Kinetics; D008099:Liver / Q000378:metabolism*; D010766:Phosphorylation; D019000:Phosphotyrosine; D014443:Tyrosine / Q000031:analogs & derivatives* / Q000032:analysis / Q000378:metabolism; D014638:Vanadates / Q000494:pharmacology
chemical_list: D019000:Phosphotyrosine; D014638:Vanadates; D014443:Tyrosine; D000255:Adenosine Triphosphate; D066246:ErbB Receptors; C008542:monodansylcadaverine; D002103:Cadaverine; D002118:Calcium