Negative functional interaction between cell integrity MAPK pathway and Rho1 GTPase in fission yeast.
Rho1 GTPase is the main activator of cell wall glucan biosynthesis and regulates actin cytoskeleton in fungi, including Schizosaccharomyces pombe. We have obtained a fission yeast thermosensitive mutant strain carrying the rho1-596 allele, which displays reduced Rho1 GTPase activity. This strain has severe cell wall defects and a thermosensitive growth, which is partially suppressed by osmotic stabilization. In a global screening for rho1-596 multicopy suppresors the pmp1+ gene was identified. Pmp1 is a dual specificity phosphatase that negatively regulates the Pmk1 mitogen-activated protein kinase (MAPK) cell integrity pathway. Accordingly, elimination of Pmk1 MAPK partially rescued rho1-596 thermosensitivity, corroborating the unexpected antagonistic functional relationship of these genes. We found that rho1-596 cells displayed increased basal activation of the cell integrity MAPK pathway and therefore were hypersensitive to MgCl2 and FK506. Moreover, the absence of calcineurin was lethal for rho1-596. We found a higher level of calcineurin activity in rho1-596 than in wild-type cells, and overexpression of constitutively active calcineurin partially rescued rho1-596 thermosensitivity. All together our results suggest that loss of Rho1 function causes an increase in the cell integrity MAPK activity, which is detrimental to the cells and turns calcineurin activity essential.
Instituto de Biología Funcional y Genómica, Consejo Superior de Investigaciones Científicas/Departamento de Microbiología y Genética, Universidad de Salamanca, 37007 Salamanca, Spain.
Raul A
RA
Viana
Mario
M
Pinar
Teresa
T
Soto
Pedro M
PM
Coll
Jose
J
Cansado
Pilar
P
Pérez
D000595:Amino Acid Sequence; D019703:Calcineurin / Q000378:metabolism*; D002473:Cell Wall / Q000378:metabolism*; D054638:Dual Specificity Phosphatase 1 / Q000235:genetics* / Q000378:metabolism; D015966:Gene Expression Regulation, Fungal / Q000187:drug effects; D005936:Glucans / Q000096:biosynthesis; D020935:MAP Kinase Signaling System; D015636:Magnesium Chloride / Q000494:pharmacology; D020928:Mitogen-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism; D009154:Mutation; D009997:Osmotic Pressure; D010766:Phosphorylation / Q000187:drug effects; D029702:Schizosaccharomyces pombe Proteins / Q000235:genetics* / Q000378:metabolism; D016559:Tacrolimus / Q000494:pharmacology; D020741:rho GTP-Binding Proteins / Q000235:genetics* / Q000378:metabolism
D005936:Glucans; D029702:Schizosaccharomyces pombe Proteins; D015636:Magnesium Chloride; D020928:Mitogen-Activated Protein Kinases; C516338:Pmk1 protein, S pombe; C110459:Pmp1 protein, S pombe; D019703:Calcineurin; D054638:Dual Specificity Phosphatase 1; D020741:rho GTP-Binding Proteins; C511156:rho1 protein, S pombe; D016559:Tacrolimus
FK506; MAPK, phosphatase; Rho GTPase; calcineurin; cell integrity