title: Yeast Lrg1p acts as a specialized RhoGAP regulating 1,3-beta-glucan synthesis.
abstract: Selection of an extragenic suppressor of fks1-1154 Deltafks2, mutations in the catalytic subunits of yeast 1,3-beta-glucan synthase (GS) conferring temperature-sensitivity, led to the LRG1 gene, which was originally identified as a LIM-RhoGAP homologous gene. Mutations in the LRG1 gene restore impaired 1,3-beta-glucan synthesis in the fks1-1154 Deltafks2 mutant as well as that in rho1-2, a temperature-sensitive mutant of Rho-type GTPase that functions as a regulatory subunit of GS. Two-hybrid analyses of Lrg1p, which contains a sequence conserved among Rho GTPase-activating proteins (GAPs), revealed its specific interactions with the active form of Rho1p. Among eight potential yeast RhoGAPs, Lrg1p is the only member that negatively regulates GS activity: mutations in the rest of GAPs, including bem2, Deltabem3, Deltasac7, Deltabag7, Deltarga1, Deltarga2 and Deltargd1, do not suppress impairment of 1,3-beta-glucan synthesis. Analyses of Mpk1p phosphorylation revealed the inability of Lrg1p to regulate the Pkc1p-MAP kinase cascade, a distinct Rho1p-regulating signalling pathway known to be affected by the GAPs, Bem2p and Sac7p. Thus, different groups of Rho1p GAPs control the activity of different Rho1p-effector proteins.
authors.affiliation: Department of Integrated Biosciences, Graduate School of Frontier Science, University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
authors.forename: D
authors.initials: D
authors.lastname: Watanabe
authors.forename: M
authors.initials: M
authors.lastname: Abe
authors.forename: Y
authors.initials: Y
authors.lastname: Ohya
mesh_terms: D004268:DNA-Binding Proteins / Q000378:metabolism*; D054714:Echinocandins; D005656:Fungal Proteins; D020690:GTPase-Activating Proteins / Q000378:metabolism*; D015966:Gene Expression Regulation, Fungal; D005936:Glucans / Q000096:biosynthesis*; D005964:Glucosyltransferases; D008565:Membrane Proteins; D011493:Protein Kinase C; D012441:Saccharomyces cerevisiae / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins; D047071:beta-Glucans; D020741:rho GTP-Binding Proteins / Q000378:metabolism*
chemical_list: D004268:DNA-Binding Proteins; D054714:Echinocandins; D005656:Fungal Proteins; D020690:GTPase-Activating Proteins; D005936:Glucans; C088938:LRG1 protein, S cerevisiae; D008565:Membrane Proteins; D029701:Saccharomyces cerevisiae Proteins; D047071:beta-Glucans; C085379:rho GTPase-activating protein; C033363:beta-1,3-glucan; D005964:Glucosyltransferases; C091618:FKS1 protein, S cerevisiae; C097993:Pkc1 protein, Trichoderma reesei; D011493:Protein Kinase C; C051302:RHO1 protein, S cerevisiae; D020741:rho GTP-Binding Proteins