A Positive Feedback Loop between Protein Kinase CKII and Cdc37 Promotes the Activity of Multiple Protein Kinases

Abstract

We report here the identification of CDC37, which encodes a putative Hsp90 co-chaperone, as a multicopy suppressor of a temperature-sensitive allele (cka2-13 ts ) of the CKA2 gene encoding the ␣ catalytic subunit of protein kinase CKII. Unlike wild-type cells, cka2-13 cells were sensitive to the Hsp90-specific inhibitor geldanamycin, and this sensitivity was suppressed by overexpression of either Hsp90 or Cdc37. However, only CDC37 was capable of suppressing the temperature sensitivity of a cka2-13 strain, implying that Cdc37 is the limiting component. Immunoprecipitation of metabolically labeled Cdc37 from wild-type versus cka2-13 strains revealed that Cdc37 is a physiological substrate of CKII, and Ser-14 and/or Ser-17 were identified as the most likely sites of CKII phosphorylation in vivo. A cdc37-S14,17A strain lacking these phosphorylation sites exhibited severe growth and morphological defects that were partially reversed in a cdc37-S14,17E strain. Reduced CKII activity was observed in both cdc37-S14A and cdc37-S17A mutants at 37°C, and cdc37-S14A or cdc37-S14,17A overexpression was incapable of protecting cka2-13 mutants on media containing geldanamycin. Additionally, CKII activity was elevated in cells arrested at the G 1 and G 2 /M phases of the cell cycle, the same phases during which Cdc37 function is essential. Collectively, these data define a positive feedback loop between CKII and Cdc37. Additional genetic assays demonstrate that this CKII/Cdc37 interaction positively regulates the activity of multiple protein kinases in addition to CKII.Protein kinase CKII is an essential, ubiquitous serine/threonine/tyrosine protein kinase of unknown function. From most sources, the enzyme is composed of two polypeptide subunits, ␣ (35-44 kDa) and ␤ (24 -28 kDa), which combine to form an ␣ 2 ␤ 2 tetramer (for review, see Refs.

Novel Interaction between the Co-chaperone Cdc37 and Rho GTPase Exchange Factor Vav3 Promotes Androgen Receptor Activity and Prostate Cancer Growth*

“…Although Vav3 resides with AR in transcriptional complexes of the PSA enhancer (11), Cdc37 did not. Mutation of Cdc37 at Ser-13 disrupts Cdc37 co-chaperone activity (37)(38)(39)(40). However, Cdc37 S13A was not compromised in promotion of Vav3 coactivation of AR.…”

“…The phosphorylation of Cdc37 at serine 13 is involved in the regulation of Cdc37 co-chaperone activity for protein kinases (37)(38)(39)(40). To determine whether Cdc37 potentiation of Vav3 co-activation of AR requires Cdc37 serine 13 phosphorylation, we examined a Cdc37 (S13A) mutant.…”

The complementation of yeast with human or Plasmodium falciparum Hsp90 confers differential inhibitor sensitivities

“…Whether that is the case for yeast, human and Pf Hsp90 is not known since, to the best of our knowledge, they have not yet been measured side by side. Furthermore, the binding affinities of Hsp90 for inhibitors can be influenced by its interactions with co-chaperones [17,22,[37][38][39][40][41], which in turn may be modulated by posttranslational modifications of Hsp90 (see for example refs. [42][43][44]).…”

Structural and functional basis of protein phosphatase 5 substrate specificity

“…3C). A positive feedback loop between CK2 and Cdc37 regulates the activation of the former and the phosphorylation of the latter (18,19). His9, Glu11, and Asp14 form part of the highly conserved N-terminal region of Cdc37 (Fig.…”