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CK2 controls multiple protein kinases by phosphorylating a kinase-targeting molecular chaperone, Cdc37.

ABSTRACT: Cdc37 is a kinase-associated molecular chaperone whose function in concert with Hsp90 is essential for many signaling protein kinases. Here, we report that mammalian Cdc37 is a pivotal substrate of CK2 (casein kinase II). Purified Cdc37 was phosphorylated in vitro on a conserved serine residue, Ser13, by CK2. Moreover, Ser13 was the unique phosphorylation site of Cdc37 in vivo. Crucially, the CK2 phosphorylation of Cdc37 on Ser13 was essential for the optimal binding activity of Cdc37 toward various kinases examined, including Raf1, Akt, Aurora-B, Cdk4, Src, MOK, MAK, and MRK. In addition, nonphosphorylatable mutants of Cdc37 significantly suppressed the association of Hsp90 with protein kinases, while the Hsp90-binding activity of the mutants was unchanged. The treatment of cells with a specific CK2 inhibitor suppressed the phosphorylation of Cdc37 in vivo and reduced the levels of Cdc37 target kinases. These results unveil a regulatory mechanism of Cdc37, identify a novel molecular link between CK2 and many crucial protein kinases via Cdc37, and reveal the molecular basis for the ability of CK2 to regulate pleiotropic cellular functions.

SUBMITTER: Miyata Y

PROVIDER: S-EPMC387775 | biostudies-literature | 2004 May

REPOSITORIES: biostudies-literature

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CK2 controls multiple protein kinases by phosphorylating a kinase-targeting molecular chaperone, Cdc37.

Miyata Yoshihiko Y Nishida Eisuke E

Molecular and cellular biology 20040501 9

Cdc37 is a kinase-associated molecular chaperone whose function in concert with Hsp90 is essential for many signaling protein kinases. Here, we report that mammalian Cdc37 is a pivotal substrate of CK2 (casein kinase II). Purified Cdc37 was phosphorylated in vitro on a conserved serine residue, Ser13, by CK2. Moreover, Ser13 was the unique phosphorylation site of Cdc37 in vivo. Crucially, the CK2 phosphorylation of Cdc37 on Ser13 was essential for the optimal binding activity of Cdc37 toward var ...[more]

PMID: 15082798

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Project description:CK2, a serine/threonine (Ser/Thr) kinase present in eukaryotic cells, is known to have a vast number of substrates. We have recently shown that it localizes to nuclei and at pores between hyphal compartments in Magnaporthe oryzae We performed a pulldown proteomics analysis of M. oryzae CK2 catalytic subunit MoCKa to detect interacting proteins. The MoCKa pulldown was enriched for septum and nucleolus proteins and intrinsically disordered proteins (IDPs) containing a CK2 phosphorylation motif that is proposed to destabilize and unfold α-helices. This points to a function for CK2 phosphorylation and corresponding phosphatase dephosphorylation in the formation of functional protein-protein aggregates and protein-RNA/DNA binding. To test this as widely as possible, we used secondary data downloaded from databases from a large range of M. oryzae experiments, as well as data for a relatively closely related plant-pathogenic fungus, Fusarium graminearum We found that CKa expression was strongly positively correlated with Ser/Thr phosphatases, as well as with disaggregases (HSP104, YDJ1, and SSA1) and an autophagy-indicating protein (ATG8). The latter points to increased protein aggregate formation at high levels of CKa expression. Our results suggest a general role for CK2 in chaperoning aggregation and disaggregation of IDPs and their binding to proteins, DNA, and RNA.IMPORTANCE CK2 is a eukaryotic conserved kinase enzyme complex that phosphorylates proteins. CK2 is known to phosphorylate a large number of proteins and is constitutively active, and thus a "normal" role for a kinase in a signaling cascade might not be the case for CK2. Previous results on localization and indications from the literature point to a function for CK2 phosphorylation in shaping and folding of proteins, especially intrinsically disordered proteins, which constitute about 30% of eukaryotic proteins. We used pulldown of interacting proteins and data downloaded from a large range of transcriptomic experiments in M. oryzae and complemented these with data downloaded from a large range of transcriptomic experiments in Fusarium graminearum We found support for a general role for CK2 in aggregation and disaggregation of IDPs and their binding to proteins, DNA, and RNA-interactions that could explain the importance of CK2 in eukaryotic cell function and disease.

Project description:The overarching goal of delineating molecular principles underlying differentiation of protein kinase clients and chaperone-based modulation of kinase activity is fundamental to understanding activity of many oncogenic kinases that require chaperoning of Hsp70 and Hsp90 systems to attain a functionally competent active form. Despite structural similarities and common activation mechanisms shared by cyclin-dependent kinase (CDK) proteins, members of this family can exhibit vastly different chaperone preferences. The molecular determinants underlying chaperone dependencies of protein kinases are not fully understood as structurally similar kinases may often elicit distinct regulatory responses to the chaperone. The regulatory divergences observed for members of CDK family are of particular interest as functional diversification among these kinases may be related to variations in chaperone dependencies and can be exploited in drug discovery of personalized therapeutic agents. In this work, we report the results of a computational investigation of several members of CDK family (CDK5, CDK6, CDK9) that represented a broad repertoire of chaperone dependencies-from nonclient CDK5, to weak client CDK6, and strong client CDK9. By using molecular simulations of multiple crystal structures we characterized conformational ensembles and collective dynamics of CDK proteins. We found that the elevated dynamics of CDK9 can trigger imbalances in cooperative collective motions and reduce stability of the active fold, thus creating a cascade of favorable conditions for chaperone intervention. The ensemble-based modeling of residue interaction networks and community analysis determined how differences in modularity of allosteric networks and topography of communication pathways can be linked with the client status of CDK proteins. This analysis unveiled depleted modularity of the allosteric network in CDK9 that alters distribution of communication pathways and leads to impaired signaling in the client kinase. According to our results, these network features may uniquely define chaperone dependencies of CDK clients. The perturbation response scanning and rigidity decomposition approaches identified regulatory hotspots that mediate differences in stability and cooperativity of allosteric interaction networks in the CDK structures. By combining these synergistic approaches, our study revealed dynamic and network signatures that can differentiate kinase clients and rationalize subtle divergences in the activation mechanisms of CDK family members. The therapeutic implications of these results are illustrated by identifying structural hotspots of pathogenic mutations that preferentially target regions of the increased flexibility to enable modulation of activation changes. Our study offers a network-based perspective on dynamic kinase mechanisms and drug design by unravelling relationships between protein kinase dynamics, allosteric communications and chaperone dependencies.

Dataset Information

CK2 controls multiple protein kinases by phosphorylating a kinase-targeting molecular chaperone, Cdc37.

Publications

CK2 controls multiple protein kinases by phosphorylating a kinase-targeting molecular chaperone, Cdc37.

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