PP2A-Rts1 antagonizes Rck2-mediated hyperosmotic stress signaling in yeast
In Saccharomyces cerevisiae impairment of protein phosphatase PP2ARts1 leads to temperature and hyperosmotic stress sensitivity, yet the underlying mechanism and the scope of action of the phosphatase in the stress response remain elusive. Using quantitative mass spectrometry-based approaches we have identified a set of putative substrate proteins that show both, hyperosmotic stress- and PP2ARts1-dependent changes in their phosphorylation pattern. A comparative analysis with published MS-shotgun data revealed that the phosphorylation status of many of these sites is regulated by the MAPKAP kinase Rck2, suggesting a node of regulation. Detailed gel mobility shift assays and protein-protein interaction analysis strongly suggest that Rck2 activity is directly regulated by PP2ARts1 via a SLiM B56-family interaction motif, uncovering a previously unknown mechanism of how PP2A influences the response to hyperosmotic stress in Yeast.