PKA AND HOG1 ROLE IN GENE EXPRESSION AND CELL SURVIVAL IN RESPONSE TO OSMOSTRESS IN SACCHAROMYCES CEREVISIAE

OJEDA, LUCAS E; COLMAN-LERNER, A; ROSSI, S; DUNAYEVICH, P; PORTELA, PAULA

Salta

Congreso; LV Annual SAIB Meeting and XIV PABMB Congress; 2019

The stress-adaptation response involves several signaling pathways that combine stimuli to coordinate responses ensuring cellular homeostasis.We focus on crosstalk between HOG1-MAPK and cAMP-PKA pathways in osmostress cellular responses. We compared the growth rate, glucoseconsumption rate and osmotic stress survival of the WT, hog1∆, tpk2∆ and tpk1∆, hog1∆tpk2∆ and hog1∆tpk1∆ strains. The hog1∆ strain showsgrowth defects, reduced efficiency of glucose metabolism, and cell viability under osmotic stress. The hog1∆tpk2∆ double mutant shows higherduplication time than hog1∆ and hog1∆tpk1∆ strains and similar to WT cells. However, under osmotic stress, the hog1∆tpk2∆ double mutant strainshows a maximum growth level similar to hog1∆ and hog1∆tpk1∆ that was about 50% less than the WT strain. The hog1∆tpk2∆ double mutantimproved the glucose consumption rate and cell viability compared to the hog1∆ strain. These results indicate that TPK2 deletion improves thestress tolerance of hog1∆ mutant strain. An increase in external osmolarity causes loss of turgor pressure and cell volume due to water efflux,which triggers a homeostatic response activated by the HOG pathway. Consequently, there are glycerol accumulation and cell volume recoveryduring osmostress-adaptation. HOG pathway activation requires transient phosphorylation of the activation loop and the subsequent nuclearaccumulation of Hog1. In the nucleus, Hog1 controls the expression of several stress-response genes. TPK2 deletion did not affect the levels ofHog1 activation loop phosphorylation, neither Hog1 nuclear accumulation, nor HOG transcriptional reporter induction, nor cell volume recoveryin response to osmotic stress. These results indicate that osmostress activation of HOG-MAPKwas not affected by the Tpk2 catalytic subunit. Thein vivo kinetic recruitment of Hog1 to the STL1 (an osmostress-activated gene) promoter was slightly affected in strains lacking Tpk2. Then, weanalyzed the Hog1 contribution on gene expression of two osmostress genes, HSP42 and RPS29B, that were previously described as targets ofPKA binding. Analysis of the transcriptional time curse was performed in WT, hog1Δ, tpk2Δ, tpk2Δhog1Δ strains. Our results suggest that theadaptive response to transient stress could be regulated by the opposite roles of Hog1 and PKA. Tpk2 recruitment on HSP42 coding region andRPS29B promoter was also assessed in response to osmotic stress. Tpk2 binding was affected in cells lacking Hog1, suggesting crosstalk betweenthe chromatin recruitment of Tpk2 and Hog1. Altogether, our results suggest that both Tpk2 and Hog1 are key regulators in osmostress adaptationthat could act in parallel in order to perform opposite roles in this stress response