Cdc37p is involved in osmoadaptation and controls high osmolarity-induced cross-talk via the MAP kinase Kss1p.

Cdc37p, the p50 homolog of Saccharomyces cerevisiae, is an Hsp90 cochaperone involved in the targeting of protein kinases to Hsp90. Here we report a role for Cdc37p in osmoadaptive signalling in this yeast. The osmosensitive phenotype that is displayed by the cdc37-34 mutant strain appears not to be the consequence of deficient signalling through the high osmolarity glycerol (HOG) MAP kinase pathway. Rather, Cdc37p appears to play a role in the filamentous growth (FG) pathway, which mediates adaptation to high osmolarity parallel to the HOG pathway. The osmosensitive phenotype of the cdc37-34 mutant strain is aggravated upon the deletion of the HOG gene. We report that the hyper-osmosensitive phenotype of the cdc37-34, hog1 mutant correlates to a reduced of activity of the FG pathway. We utilized this phenotype to isolate suppressor genes such as KSS1 that encodes a MAP kinase that functions in the FG pathway. We report that Kss1p interacts physically with Cdc37p. Like Kss1p, the second suppressor that we isolated, Dse1p, is involved in cell wall biogenesis or maintenance, suggesting that Cdc37p controls osmoadapation by regulating mitogen-activated protein kinase signalling aimed at adaptive changes in cell wall organization.