Cell wall perturbation in yeast results in dual phosphorylation of the Slt2/Mpk1 MAP kinase and in an Slt2-mediated increase in FKS2-lacZ expression,glucanase resistance and thermotolerance

The protein kinase C (PKC1) pathway is essential for maintaining cell integ rity in yeast. Here it is shown that various forms of cell wall damage resu lt in activation of the downstream MAP kinase Slt2/Mpk1. Several cell wall mutants displayed enhanced FKS2-lacZ expression, a known output of Slt2 act ivation. A similar response was obtained with wild-type cells grown in the presence of the cell wall perturbants Calcofluor white and Zymolyase. Upreg ulation of FKS2-lacZ in response to sublethal concentrations of these agent s fully in dual threonine and tyrosine phosphorylation of Slt2. Both Slt2 p hosphorylation and FKS2-lacZ induction could be largely prevented by provid ing osmotic support to the plasma membrane. Interestingly, Slt2 phosphoryla tion in response to cell wall damage required the putative plasmamembrane-l ocated sensor Mid2 but not Hcs77/Wsc1. Finally, cell wall perturbation gave rise to cells with increased resistance to glucanase digestion and heat sh ock. These responses depended on the presence of Slt2. These results indica te that weakening of the cell wall activates the Slt2/Mpk1 MAP kinase pathw ay and results in compensatory changes in the cell wall.