Hsp90-Dependent Activation of Protein Kinases Is Regulated by Chaperone-Targeted Dephosphorylation of Cdc37

Section of Structural Biology, Institute of Cancer Research, Chester Beatty Laboratories, 237 Fulham Road, London SW3 6JB, UK.
Molecular cell (Impact Factor: 14.46). 10/2008; 31(6):886-95. DOI: 10.1016/j.molcel.2008.07.021
Source: PubMed

ABSTRACT Activation of protein kinase clients by the Hsp90 system is mediated by the cochaperone protein Cdc37. Cdc37 requires phosphorylation at Ser13, but little is known about the regulation of this essential posttranslational modification. We show that Ser13 of uncomplexed Cdc37 is phosphorylated in vivo, as well as in binary complex with a kinase (C-K), or in ternary complex with Hsp90 and kinase (H-C-K). Whereas pSer13-Cdc37 in the H-C-K complex is resistant to nonspecific phosphatases, it is efficiently dephosphorylated by the chaperone-targeted protein phosphatase 5 (PP5/Ppt1), which does not affect isolated Cdc37. We show that Cdc37 and PP5/Ppt1 associate in Hsp90 complexes in yeast and in human tumor cells, and that PP5/Ppt1 regulates phosphorylation of Ser13-Cdc37 in vivo, directly affecting activation of protein kinase clients by Hsp90-Cdc37. These data reveal a cyclic regulatory mechanism for Cdc37, in which its constitutive phosphorylation is reversed by targeted dephosphorylation in Hsp90 complexes.

  • [Show abstract] [Hide abstract]
    ABSTRACT: Hsp90 chaperones receive much attention due to their role in cancer and other pathological conditions, and a tremendous effort of many laboratories has contributed in the past decades to considerable progress in the understanding of their functions. Hsp90 chaperones exist as dimers and, with the help of cochaperones, promote the folding of numerous client proteins. Although the original view of these interactions suggested that these dimeric complexes were symmetrical, it is now clear that many features are asymmetrical. In this review we discuss several recent advances that highlight how asymmetric interactions with cochaperones as well as asymmetric posttranslational modifications provide mechanisms to regulate client interactions and the progression through Hsp90's chaperone cycle. Copyright © 2015 Elsevier Inc. All rights reserved.
    Molecular cell 04/2015; 58(1):8-20. DOI:10.1016/j.molcel.2015.02.022 · 14.46 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Abstract Protein phosphatase types 1 α (PP1α/PPP1C) and 5 (PP5/PPP5C) are members of the PPP family of serine/threonine protein phosphatases. PP1 and PP5 share a common catalytic mechanism, and several natural compounds, including okadaic acid, microcystin, and cantharidin, act as strong inhibitors of both enzymes. However, to date there have been no reports of compounds that can selectively inhibit PP1 or PP5, and specific or highly selective inhibitors for either PP1 or PP5 are greatly desired by both the research and pharmaceutical communities. Here we describe the development and optimization of a sensitive and robust (representative PP5C assay data: Z'=0.93; representative PP1Cα assay data: Z'=0.90) fluorescent phosphatase assay that can be used to simultaneously screen chemical libraries and natural product extracts for the presence of catalytic inhibitors of PP1 and PP5.
    Assay and Drug Development Technologies 10/2014; 12(8):481-96. DOI:10.1089/adt.2014.603 · 2.08 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Folding and maturation of most protein kinases require chaperone assistance. In higher eukaryotes, CDC37 is the predominant cochaperone that facilitates the transfer of kinase clients to HSP90. Kinase recognition is thought to occur through the N-terminal domain which has thus far eluded structure determination. Client processing also requires the phosphorylation of the N-terminal tail at Ser13 by protein kinase CK2 (casein kinase 2). How phosphorylation alters the molecular properties of CDC37 is not understood. We show that the phosphorylation at Ser13 induces a large shift towards a more compact structure based on ANS fluorescence while modestly increasing secondary structure. Moreover, this transition requires interactions of the N-terminal domain and the remainder of CDC37. The stabilizing property of the phosphorylation event can be recreated in trans by a (phospho Ser13) peptide derived from the N-terminal tail. However, the phosphorylation induced transition is not dependent on the transferred phosphate group, but rather the loss of serine-like properties at position 13. The complete absence of the N-terminal tail results in reduced secondary structure and unresponsiveness to subsequent addition of peptides. The N-terminal tail may therefore serve as an intramolecular chaperone that ensures that CDC37 assumes one of two readily interconvertible states in a manner that impacts the interaction of the client binding N-domain and the MC-domains, involved in dimerization and HSP90 binding.
    Biochemistry 01/2015; DOI:10.1021/bi501129g · 3.19 Impact Factor

Full-text (3 Sources)

Available from
May 28, 2014

Andrew Truman