title: Mammalian p50Cdc37 is a protein kinase-targeting subunit of Hsp90 that binds and stabilizes Cdk4.
abstract: CDC37, an essential gene in Saccharomyces cerevisiae, interacts genetically with multiple protein kinases and is required for production of Cdc28p/cyclin complexes through an unknown mechanism. We have identified mammalian p50Cdc37 as a protein kinase-targeting subunit of the molecular chaperone Hsp90. Previously, p50 was observed in complexes with pp60v-src and Raf-1, but its identity and function have remained elusive. In mouse fibroblasts, a primary target of Cdc37 is Cdk4. This kinase is activated by D-type cyclins and functions in passage through G1. In insect cells, Cdc37 is sufficient to target Hsp90 to Cdk4 and both in vitro and in vivo, Cdc37/Hsp90 associates preferentially with the fraction of Cdk4 not bound to D-type cyclins. Cdc37 is coexpressed with cyclin Dl in cells undergoing programmed proliferation in vivo, consistent with a positive role in cell cycle progression. Pharmacological inactivation of Cdc37/Hsp90 function decreases the half-life of newly synthesized Cdk4, indicating a role for Cdc37/Hsp90 in Cdk4 stabilization. This study suggests a general role for p50Cdc37 in signaling pathways dependent on intrinsically unstable protein kinases and reveals a previously unrecognized chaperone-dependent step in the production of Cdk4/cyclin D complexes.
authors.affiliation: Verna and Marrs McLean Department of Biochemistry, Baylor College of Medicine, Houston, Texas 77030, USA.
authors.forename: L
authors.initials: L
authors.lastname: Stepanova
authors.forename: X
authors.initials: X
authors.lastname: Leng
authors.forename: S B
authors.initials: SB
authors.lastname: Parker
authors.forename: J W
authors.initials: JW
authors.lastname: Harper
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D018797:Cell Cycle Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D018833:Chaperonins; D003001:Cloning, Molecular; D056741:Cyclin D; D051358:Cyclin-Dependent Kinase 4; D018844:Cyclin-Dependent Kinases / Q000235:genetics / Q000378:metabolism*; D016213:Cyclins / Q000096:biosynthesis; D003593:Cytoplasm / Q000737:chemistry / Q000201:enzymology; D029721:Drosophila Proteins; D004795:Enzyme Stability; D005347:Fibroblasts / Q000378:metabolism; D005786:Gene Expression Regulation; D018841:HSP90 Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D051379:Mice; D018832:Molecular Chaperones; D008969:Molecular Sequence Data; D008970:Molecular Weight; D011518:Proto-Oncogene Proteins; D029701:Saccharomyces cerevisiae Proteins; D017386:Sequence Homology, Amino Acid
chemical_list: C513270:CDC37 protein, S cerevisiae; C498362:CDC37 protein, human; C513271:Cdc37 protein, mouse; D018797:Cell Cycle Proteins; C534694:CycD protein, Drosophila; D056741:Cyclin D; D016213:Cyclins; D029721:Drosophila Proteins; D018841:HSP90 Heat-Shock Proteins; D018832:Molecular Chaperones; D011518:Proto-Oncogene Proteins; D029701:Saccharomyces cerevisiae Proteins; C495900:CDK4 protein, human; C495902:Cdk4 protein, mouse; D051358:Cyclin-Dependent Kinase 4; D018844:Cyclin-Dependent Kinases; D018833:Chaperonins