title: Involvement of cdc2-mediated phosphorylation in the cell cycle-dependent regulation of p185neu.
abstract: We previously reported cell cycle-dependent negative regulation of p185neu (decreased tyrosine phosphorylation and kinase activity, with electrophoretic mobility retarded by serine/threonine phosphorylation) in M phase and the escape of mutation-activated p185neu* from this regulation. Our present results showed that retardation of electrophoretic mobility occurs independently of the cells' transformed status. We found that normal p185neu lost its ability to dimerize in the M phase. We demonstrated a physical association between cdc2 (a serine/threonine kinase, active in M phase) and p185neu. We showed that the carboxy terminal portion of p185neu is phosphorylated in vitro by cdc2. Many phosphopeptides (at least three phosphoserine residues) unique to the M phase were identified, and the in vivo and in vitro phosphopeptide patterns were superimposable. In contrast, mutation-activated p185neu* dimerized in the M phase with no changes in electrophoretic mobility, failed to associate with cdc2 and no unique phosphoserine residues could be identified in the M phase (data not shown), consistent with the escape of p185neu* from cell cycle-dependent regulation. Our results suggest that this escape is an intrinsic property of the mutation-activated p185neu* independent of its ability to transform cells. Our results also suggest the involvement of serine/threonine kinases such as cdc2 in the cell cycle-dependent negative regulation of p185neu.
authors.affiliation: Department of Tumor Biology, The University of Texas M.D. Anderson Cancer Center, Houston 77030, USA.
authors.forename: N
authors.initials: N
authors.lastname: Kiyokawa
authors.forename: D
authors.initials: D
authors.lastname: Karunagaran
authors.forename: E K
authors.initials: EK
authors.lastname: Lee
authors.forename: Y
authors.initials: Y
authors.lastname: Xie
authors.forename: D H
authors.initials: DH
authors.lastname: Yan
authors.forename: M C
authors.initials: MC
authors.lastname: Hung
mesh_terms: D000818:Animals; D016203:CDC2 Protein Kinase / Q000378:metabolism*; D002453:Cell Cycle / Q000235:genetics*; D002471:Cell Transformation, Neoplastic; D003432:Cross-Linking Reagents / Q000737:chemistry; D019281:Dimerization; D051379:Mice; D008938:Mitosis / Q000235:genetics; D009154:Mutation; D010766:Phosphorylation; D011233:Precipitin Tests / Q000379:methods; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*
chemical_list: D016203:CDC2 Protein Kinase; D003432:Cross-Linking Reagents; D018719:Erb-b2 Receptor Tyrosine Kinases