Cdc37p is required for stress-induced high-osmolarity glycerol and protein kinase C mitogen-activated protein kinase pathway functionality by interaction with Hog1p and Slt2p -Mpk1p--
Department of Biochemistry and Molecular Biology, Faculty of Science, Vrije Universiteit, De Boelelaan 1083, 1081 HV Amsterdam, The Netherlands-
Abstract: The yeast Saccharomyces cerevisiae utilizes rapidly responding mitogen-activated protein kinase -MAPK- signaling cascades to adapt efficiently to a changing environment- Here we report that phosphorylation of Cdc37p, an Hsp90 cochaperone, by casein kinase 2 controls the functionality of two MAPK cascades in yeast- These pathways, the high-osmolarity glycerol -HOG- pathway and the cell integrity -protein kinase C- MAPK pathway, mediate adaptive responses to high osmotic and cell wall stresses, respectively- Mutation of the phosphorylation site Ser14 in Cdc37p renders cells sensitive to osmotic stress and cell wall perturbation by calcofluor white- We found that levels of the MAPKs Hog1p and Slt2p -Mpk1p- in cells are reduced in a cdc37-S14A mutant, and consequently downstream responses mediated by Hog1p and Slt2p are compromised- Furthermore, we present evidence that Hog1p and Slt2p both interact in a complex with Cdc37p in vivo, something that has not been reported previously- The interaction of Hsp90, Slt2p, and Hog1p with Cdc37p depends on the phosphorylation status of Cdc37p- In fact, our biochemical data show that the osmosensitive phenotype of the cdc37-S14A mutant is due to the loss of the interaction between Cdc37p, Hog1p, and Hsp90- Likewise, during cell wall stress, the interaction of Slt2p with Cdc37p and Hsp90 is crucial for Slt2p-dependent downstream responses, such as the activation of the transcription factor Rlm1p- Interestingly, phosphorylated Slt2p, but not phosphorylated Hog1p, has an increased affinity for Cdc37p- Together these observations suggest that Cdc37p acts as a regulator of MAPK signaling-