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Gene Review

FKS1  -  1,3-beta-D-glucan synthase

Saccharomyces cerevisiae S288c

Synonyms: 1,3-beta-D-glucan-UDP glucosyltransferase, 1,3-beta-glucan synthase component FKS1, CND1, CWH53, Calcineurin dependent protein 1, ...
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Disease relevance of FKS1

  • We and others have defined the Saccharomyces cerevisiae FKS1 gene by recessive mutations resulting in 100-1000-fold hypersensitivity to FK506 and CsA (as compared to wild type), but which do not affect sensitivity to a variety of other antifungal drugs [1].
  • The clinical C. albicans mutants were less susceptible to caspofungin in the disseminated candidiasis model, and GS inhibition profiles and DNA sequence analyses were consistent with a homozygous fks1 mutation [2].

High impact information on FKS1


Chemical compound and disease context of FKS1


Biological context of FKS1

  • Yeast GS is composed of a putative catalytic subunit encoded by FKS1 and FKS2 and a regulatory subunit encoded by RHO1 [6].
  • Analysis of fks1 delta mutants showed a partial K1 killer toxin-resistant phenotype and a 30% reduction in alkali-soluble beta-1,3-glucan that was accompanied by a modest reduction in beta-1,6-glucan [7].
  • Up-regulation of genes encoding glycosylphosphatidylinositol (GPI)-attached proteins in response to cell wall damage caused by disruption of FKS1 in Saccharomyces cerevisiae [8].
  • Deletion and replacement analysis of the promoter regions identified Rlm1-binding sequences as being responsible for the up-regulation following disruption of FKS1 [8].
  • Removal of the cell wall does not inhibit internalization, suggesting that the function of Rho1 and Fks1 in endocytosis is not through cell wall synthesis or structural integrity [9].

Anatomical context of FKS1

  • FKS1 and FKS2 are alternative subunits of the glucan synthase complex, which is responsible for synthesizing 1,3-beta-glucan chains, the major structural polymer of the Saccharomyces cerevisiae cell wall [10].

Associations of FKS1 with chemical compounds

  • Previous work has shown that the FKS1 gene encodes a 215-kDa integral membrane protein (Fks1p) which mediates sensitivity to the echinocandin class of antifungal glucan synthase inhibitors and is a subunit of this enzyme [11].
  • Induction of FKS2 expression in response to pheromone, CaCl2, or loss of FKS1 function requires the Ca2+/calmodulin-dependent protein phosphatase calcineurin [10].
  • Alternatively, Fks1p and Fks2p could actively participate in the biosynthesis of both polymers as beta-glucan transporters [7].
  • The remaining two genes were up-regulated by doxycycline, suggesting that a transcription factor other than Rlm1 is involved in their response to disruption of FKS1 [8].
  • We have previously shown that growth of fks1 null mutants is highly sensitive to the calcineurin inhibitors FK506 and cyclosporin A [11].

Physical interactions of FKS1

  • Gel overlay analysis indicated that an unmodified form of GST-Rho1p fails to interact with Fks1p [12].

Other interactions of FKS1

  • PXL1 also displays genetic interactions with the Rho1 effector FKS1 [13].
  • These results suggest that distinct networks regulate the two effector proteins of Rho1p, Fks1p and Pkc1p [6].
  • Fks1p and Fks2p are related proteins thought to be catalytic subunits of the beta-1,3-glucan synthase [7].
  • Therefore, a double mutant in calcineurin (CNB1) and FKS1 is inviable due to a deficiency in FKS2 expression [10].
  • Disruption of FKS1 reduces the glucan content of the cell wall, increases chitin content and activates the expression of CWP1, which encodes a glycosylphosphatidylinositol (GPI)-dependent cell wall protein [8].

Analytical, diagnostic and therapeutic context of FKS1

  • The CND1 gene was cloned, and sequence analysis predicts that it encodes a novel protein 1,876 amino acids in length with multiple membrane-spanning domains [14].
  • Northern blotting demonstrated that C. albicans GSC1 and GSL1 but not GSL2 mRNAs were expressed in the growing yeast-phase cells [15].
  • In order to identify essential amino acid residues responsible for the sensitivity, each of the 10 non-conserved amino acids of Fks1p was substituted into the corresponding amino acid of Fks2p by site-directed mutagenesis [16].


  1. The yeast FKS1 gene encodes a novel membrane protein, mutations in which confer FK506 and cyclosporin A hypersensitivity and calcineurin-dependent growth. Eng, W.K., Faucette, L., McLaughlin, M.M., Cafferkey, R., Koltin, Y., Morris, R.A., Young, P.R., Johnson, R.K., Livi, G.P. Gene (1994) [Pubmed]
  2. Specific substitutions in the echinocandin target Fks1p account for reduced susceptibility of rare laboratory and clinical Candida sp. isolates. Park, S., Kelly, R., Kahn, J.N., Robles, J., Hsu, M.J., Register, E., Li, W., Vyas, V., Fan, H., Abruzzo, G., Flattery, A., Gill, C., Chrebet, G., Parent, S.A., Kurtz, M., Teppler, H., Douglas, C.M., Perlin, D.S. Antimicrob. Agents Chemother. (2005) [Pubmed]
  3. Identification of yeast Rho1p GTPase as a regulatory subunit of 1,3-beta-glucan synthase. Qadota, H., Python, C.P., Inoue, S.B., Arisawa, M., Anraku, Y., Zheng, Y., Watanabe, T., Levin, D.E., Ohya, Y. Science (1996) [Pubmed]
  4. Cell wall stress depolarizes cell growth via hyperactivation of RHO1. Delley, P.A., Hall, M.N. J. Cell Biol. (1999) [Pubmed]
  5. The Saccharomyces cerevisiae FKS1 (ETG1) gene encodes an integral membrane protein which is a subunit of 1,3-beta-D-glucan synthase. Douglas, C.M., Foor, F., Marrinan, J.A., Morin, N., Nielsen, J.B., Dahl, A.M., Mazur, P., Baginsky, W., Li, W., el-Sherbeini, M. Proc. Natl. Acad. Sci. U.S.A. (1994) [Pubmed]
  6. Dissection of upstream regulatory components of the Rho1p effector, 1,3-beta-glucan synthase, in Saccharomyces cerevisiae. Sekiya-Kawasaki, M., Abe, M., Saka, A., Watanabe, D., Kono, K., Minemura-Asakawa, M., Ishihara, S., Watanabe, T., Ohya, Y. Genetics (2002) [Pubmed]
  7. Mutations in Fks1p affect the cell wall content of beta-1,3- and beta-1,6-glucan in Saccharomyces cerevisiae. Dijkgraaf, G.J., Abe, M., Ohya, Y., Bussey, H. Yeast (2002) [Pubmed]
  8. Up-regulation of genes encoding glycosylphosphatidylinositol (GPI)-attached proteins in response to cell wall damage caused by disruption of FKS1 in Saccharomyces cerevisiae. Terashima, H., Yabuki, N., Arisawa, M., Hamada, K., Kitada, K. Mol. Gen. Genet. (2000) [Pubmed]
  9. Receptor internalization in yeast requires the Tor2-Rho1 signaling pathway. deHart, A.K., Schnell, J.D., Allen, D.A., Tsai, J.Y., Hicke, L. Mol. Biol. Cell (2003) [Pubmed]
  10. Temperature-induced expression of yeast FKS2 is under the dual control of protein kinase C and calcineurin. Zhao, C., Jung, U.S., Garrett-Engele, P., Roe, T., Cyert, M.S., Levin, D.E. Mol. Cell. Biol. (1998) [Pubmed]
  11. Differential expression and function of two homologous subunits of yeast 1,3-beta-D-glucan synthase. Mazur, P., Morin, N., Baginsky, W., el-Sherbeini, M., Clemas, J.A., Nielsen, J.B., Foor, F. Mol. Cell. Biol. (1995) [Pubmed]
  12. Prenylation of Rho1p is required for activation of yeast 1, 3-beta-glucan synthase. Inoue, S.B., Qadota, H., Arisawa, M., Watanabe, T., Ohya, Y. J. Biol. Chem. (1999) [Pubmed]
  13. The PXL1 gene of Saccharomyces cerevisiae encodes a paxillin-like protein functioning in polarized cell growth. Mackin, N.A., Sousou, T.J., Erdman, S.E. Mol. Biol. Cell (2004) [Pubmed]
  14. Calcineurin, the Ca2+/calmodulin-dependent protein phosphatase, is essential in yeast mutants with cell integrity defects and in mutants that lack a functional vacuolar H(+)-ATPase. Garrett-Engele, P., Moilanen, B., Cyert, M.S. Mol. Cell. Biol. (1995) [Pubmed]
  15. Cloning of the Candida albicans homolog of Saccharomyces cerevisiae GSC1/FKS1 and its involvement in beta-1,3-glucan synthesis. Mio, T., Adachi-Shimizu, M., Tachibana, Y., Tabuchi, H., Inoue, S.B., Yabe, T., Yamada-Okabe, T., Arisawa, M., Watanabe, T., Yamada-Okabe, H. J. Bacteriol. (1997) [Pubmed]
  16. Differential sensitivity between Fks1p and Fks2p against a novel beta -1,3-glucan synthase inhibitor, aerothricin3 [corrected]. Kondoh, O., Takasuka, T., Arisawa, M., Aoki, Y., Watanabe, T. J. Biol. Chem. (2002) [Pubmed]
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