CROSSTALK BETWEEN cAMP-PKA AND HOG-MAPK PATHWAYS IN THE REGULATION OF THE OSMOTIC STRESS RESPONSE IN S. CEREVISIAE

GULIAS F; ROSSI S; ORTOLA M; BERMUDEZ M; OJEDA L; GALELLO F; PORTELA P

Salta

Congreso; SAIB-SAIGE 2021; 2021

S.cerevisiae osmoadaptation response involves several signaling mechanisms that couple stimuli to coordinate responses, thereby ensuring its homeostasis. Previously, we have described a crosstalk between the cAMP-PKA and HOG-MAPK signaling pathways on the cell survival response to osmotic stress. Under osmotic stress, TPK2 gene deletion improves the defective cellular growth showed by HOG1 deleted strain. Here, we perform several experiments to elucidate the interplay between the two catalytic subunits of PKA, Tpk2 and Tpk1, and Hog1 kinase on the osmotic stress adaptation program.We compared the glycogen and trehalose accumulation- two important glucose stores- in the PKA and Hog1 mutant strains growing under normal and osmotic stress conditions. HOG1 deletion promotes a high glycogen accumulation in response to osmotic stress. Both double mutant strains, hog1Δtpk1Δ and hog1Δtpk2Δ, show a similar glycogen accumulation to wild-type cells. Under normal growth conditions, the hog1Δ strain shows low trehalose content in comparison to wild-type cells, though both strains similarly increase the trehalose levels under osmotic stress. When trehalose level is compared between the different strains under osmotic stress conditions, the following order is apparent: tpk2Δ > hog1Δtpk2Δ > hog1Δtpk1Δ> hog1Δ = tpk1Δ= wild-type.The hog1Δ mutant cells shmoo-like growth form under osmotic stress is inhibited by TPK2 gene deletion but not by TPK1 gene deletion. HOG1 deletion promotes the invasive growth in high salt-containing medium. Here, the double mutant hog1Δtpk1Δ abolish the phenotype, whereas hog1Δtpk2Δ mutant strain increases the invasive growth under osmotic stress conditions. In addition, we analyzed the role of PKA and HOG-MAPK pathways on chronological lifespan (CLS). TPK2 deletion, but not HOG1 or TPK1, produces a reduction in CLS. HOG1 deletion suppresses the tpk2Δ reduced CLS, revealing a PKA isoform-specific role on CLS. Previously, we described that Tpk2 and Hog1 are recruited to the promoter regions of osmostress responsive genes as HSP42 and RPS29B and its kinase activity are required to gene expression pattern in response to stress. Now, we analyzed the in vivo kinetic recruitment of the Snf2-catalytic subunit of the SWI/SNF complex and stress-responsive transcription factor, Msn2, to the HSP42, RPS29B, and STL1 promoter regions. ChIP assays, using tpk2Δ, hog1Δ and hog1Δtpk2Δ strains, indicate a crosstalk between both Tpk2 and Hog1 kinases activity on Snf2 and Msn2 recruitment to the analyzed gene promoters. Our results contribute to the question of how signals from multiple pathways become integrated into a coordinated response. cAMP-PKA pathway specificity- via Tpk1 or Tpk2 catalytic isoforms - and HOG-MAPK pathway have an opposite role during the cellular adaptation to osmotic stresses.