Identification of putative negative regulators of XXXX signaling through a screening for protein phosphatases acting on cell wall integrity and mating MAPK pathways.

@entity71626 @entity9793 @entity42731 @entity42730 @entity9791 @entity71627 @entity9794 @entity375 @entity4149 @entity65054 @entity19624 @entity71625
UNASSIGNED: The lack of signaling through MAPK pathways leads to a defective cellular response to the corresponding stimulus, but an improper hyperactivation of these routes results in deleterious effects as well. Protein phosphorylation is an activating modification for signal transmission through components of MAPK pathways and thus, protein phosphatases are key negative regulators of these cellular routes by limiting excessive signaling activity. However, in contrast to most of the protein kinases operating in MAPK pathways, protein phosphatases usually exhibit redundancy and promiscuity, which has limited the identification of their function. In order to identify new putative phosphatases operating in @entity375 MAPK signaling, we have taken advantage of growth inhibition promoted by overproduction of constitutively active components of the mating and cell wall integrity (CWI) pathways to perform a screen with a collection of 43 protein phosphatases or phosphatase-regulatory proteins. The phosphatases able to alleviate the induced growth inhibition when overproduced were further studied by testing their capacity to downregulate expression of mating and CWI responsive promoters and the consequences of their removal on MAPK signaling. Epistasis analysis placed the Ser/Thr protein phosphatase @entity71625 as a regulator of the mating MAPK module downstream the MAPKKK Ste11. The dual specificity phosphatase @entity9791 was found to be important for the maintenance of cell wall integrity and appropriate signaling through the CWI pathway. Moreover, we have found that @entity9794 and @entity65054 bind to the CWI MAPK @entity19624 . Together with known phosphatases of the mating and CWI pathway, as @entity9793 or @entity42731 , other putative negative regulators of both pathways that came up in the screening were @entity9794 , @entity71626 and @entity71627 . We show that @entity71627 physically interacts with @entity19624 and the mating MAPK Fus3. Elimination of @entity71627 results in increased signaling through these pathways, suggesting that this @entity4149 phosphatase, like @entity42731 and @entity42730 , plays a downregulatory role on both MAPKs.
