A positive feedback loop between protein kinase CKII and Cdc37 promotes the activity of multiple protein kinases.
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 alpha' 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 degrees 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.
Bandhakavi
Sricharan
S
Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia 30602-7229, USA.
McCann
Richard O
RO
Hanna
David E
DE
Glover
Claiborne V C
CV
D000595:Amino Acid Sequence; D047390:Casein Kinase II; D018797:Cell Cycle Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D029721:Drosophila Proteins; D005246:Feedback; D005838:Genotype; D018841:HSP90 Heat-Shock Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D007700:Kinetics; D018832:Molecular Chaperones / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D010766:Phosphorylation; D011494:Protein Kinases / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D021122:Protein Subunits / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000201:enzymology* / Q000235:genetics; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity
C513270:CDC37 protein, S cerevisiae; D018797:Cell Cycle Proteins; D029721:Drosophila Proteins; D018841:HSP90 Heat-Shock Proteins; D018832:Molecular Chaperones; D021122:Protein Subunits; D011994:Recombinant Proteins; D029701:Saccharomyces cerevisiae Proteins; D011494:Protein Kinases; D047390:Casein Kinase II; D017346:Protein Serine-Threonine Kinases