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Gene Review

STE50  -  Ste50p

Saccharomyces cerevisiae S288c

Synonyms: Protein STE50, YCL032W, YCL32W
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High impact information on STE50

  • Adaptor protein Ste50p links the Ste11p MEKK to the HOG pathway through plasma membrane association [1].
  • We propose that Opy2p can serve as a membrane anchor for the Ste50p/Ste11p module in the activation of the HOG pathway [1].
  • Adaptor functions of Cdc42, Ste50, and Sho1 in the yeast osmoregulatory HOG MAPK pathway [2].
  • We found that strains with mutations in the STE50 gene, in combination with ssk2Delta ssk22Delta mutations, were unable to induce HOG1 phosphorylation after osmotic stress [3].
  • Requirement of STE50 for osmostress-induced activation of the STE11 mitogen-activated protein kinase kinase kinase in the high-osmolarity glycerol response pathway [3].

Biological context of STE50

  • STE50 has been shown to be involved in this pheromone signal-transduction pathway [4].
  • A new gene, STE50, which plays an essential role in cell differentiation in Saccharomyces cerevisiae was detected and analysed [5].
  • When present on a high copy number plasmid, STE50 causes supersensitivity to alpha-pheromone, and increases the level of alpha-pheromone-induced transcription of FUS1 in haploid a cells [5].
  • These data indicate that inactivation of STE50 influences stress tolerance in mutants of the Ras-cAMP pathway, which is a major determinant of intrinsic stress tolerance and cell survival of the Saccharomyces cerevisiae [6].
  • By pde2Delta-dependent increase of the Ras-cAMP pathway activity, inactivation of STE50 results in an extreme shortening of life span and oxidative stress sensitivity of sch9Delta mutants [6].

Anatomical context of STE50


Associations of STE50 with chemical compounds

  • It was concluded that STE50 fulfills an essential role in the activation of the high-osmolarity glycerol response pathway by acting as an integral subunit of the STE11 MAPKKK [3].
  • Replacement of T42 with a phosphorylation-mimetic aspartic acid residue (T42D) permits wild-type function in all assays of Ste50p function [8].
  • Here, we show that Ste50p is phosphorylated on multiple serine/threonine residues in vivo [8].

Physical interactions of STE50

  • Both two-hybrid analyses and coprecipitation assays demonstrated that the N-terminal domain of STE50 binds strongly to the N-terminal domain of STE11 [3].

Enzymatic interactions of STE50


Regulatory relationships of STE50

  • Overexpression of STE11 also suppresses the mating defects of ste50 mutants [10].
  • RA domain function can be replaced by the nine C-terminal, plasma membrane-targeting residues (KKSKKCAIL) of Cdc42, and membrane-targeted Ste50 also suppresses the signaling deficiency of cdc42 alleles specifically defective in invasive growth [7].
  • Moreover, when exposed to hyperosmolarity, these Ste50p-SAM mutants activate genes in the mating (FUS1) and filamentous-growth (FLO11) pathways to higher levels than does the wild type [11].
  • This mutation abolishes the ability of overexpressed Ste50p to suppress either the mating defect of a ste20 ste50 deletion mutant or the mating defect of a strain with a Ste11p deleted from its sterile-alpha motif domain [8].

Other interactions of STE50

  • We have found that L73A and L75A abrogate the Ste50p interaction with Ste11p, and we compare these data with the known interaction sites defined for other SAM domain interactions [12].
  • Interestingly, these two Ste50p-SAM mutants were associated with increased activation of the mating and filamentous-growth pathways, but a reduction in the SHO1-dependent growth response to hyperosmolarity, relative to the wild-type Ste50p [11].
  • Ste4 has regions of homology with STE50, an S. cerevisiae protein required for sexual differentiation that we show can bind to STE11 [13].
  • In contrast, the constitutive activation of the pheromone response pathway caused by disruption of GPA1 (G alpha) is not suppressed in ste50-2 mutants [5].

Analytical, diagnostic and therapeutic context of STE50


  1. Adaptor protein Ste50p links the Ste11p MEKK to the HOG pathway through plasma membrane association. Wu, C., Jansen, G., Zhang, J., Thomas, D.Y., Whiteway, M. Genes Dev. (2006) [Pubmed]
  2. Adaptor functions of Cdc42, Ste50, and Sho1 in the yeast osmoregulatory HOG MAPK pathway. Tatebayashi, K., Yamamoto, K., Tanaka, K., Tomida, T., Maruoka, T., Kasukawa, E., Saito, H. EMBO J. (2006) [Pubmed]
  3. Requirement of STE50 for osmostress-induced activation of the STE11 mitogen-activated protein kinase kinase kinase in the high-osmolarity glycerol response pathway. Posas, F., Witten, E.A., Saito, H. Mol. Cell. Biol. (1998) [Pubmed]
  4. Ste50p sustains mating pheromone-induced signal transduction in the yeast Saccharomyces cerevisiae. Xu, G., Jansen, G., Thomas, D.Y., Hollenberg, C.P., Ramezani Rad, M. Mol. Microbiol. (1996) [Pubmed]
  5. STE50, a novel gene required for activation of conjugation at an early step in mating in Saccharomyces cerevisiae. Rad, M.R., Xu, G., Hollenberg, C.P. Mol. Gen. Genet. (1992) [Pubmed]
  6. Ste50 adaptor protein influences Ras/cAMP-driven stress-response and cell survival in Saccharomyces cerevisiae. Poplinski, A., Hopp, C., Ramezani-Rad, M. Curr. Genet. (2007) [Pubmed]
  7. The RA domain of Ste50 adaptor protein is required for delivery of Ste11 to the plasma membrane in the filamentous growth signaling pathway of the yeast Saccharomyces cerevisiae. Truckses, D.M., Bloomekatz, J.E., Thorner, J. Mol. Cell. Biol. (2006) [Pubmed]
  8. Phosphorylation of the MAPKKK regulator Ste50p in Saccharomyces cerevisiae: a casein kinase I phosphorylation site is required for proper mating function. Wu, C., Arcand, M., Jansen, G., Zhong, M., Iouk, T., Thomas, D.Y., Meloche, S., Whiteway, M. Eukaryotic Cell (2003) [Pubmed]
  9. Control of MAPK specificity by feedback phosphorylation of shared adaptor protein Ste50. Hao, N., Zeng, Y., Elston, T.C., Dohlman, H.G. J. Biol. Chem. (2008) [Pubmed]
  10. Ste50p is involved in regulating filamentous growth in the yeast Saccharomyces cerevisiae and associates with Ste11p. Ramezani Rad, M., Jansen, G., Bühring, F., Hollenberg, C.P. Mol. Gen. Genet. (1998) [Pubmed]
  11. Mutations in the SAM domain of STE50 differentially influence the MAPK-mediated pathways for mating, filamentous growth and osmotolerance in Saccharomyces cerevisiae. Jansen, G., Bühring, F., Hollenberg, C.P., Ramezani Rad, M. Mol. Genet. Genomics (2001) [Pubmed]
  12. Structure of the sterile alpha motif (SAM) domain of the Saccharomyces cerevisiae mitogen-activated protein kinase pathway-modulating protein STE50 and analysis of its interaction with the STE11 SAM. Grimshaw, S.J., Mott, H.R., Stott, K.M., Nielsen, P.R., Evetts, K.A., Hopkins, L.J., Nietlispach, D., Owen, D. J. Biol. Chem. (2004) [Pubmed]
  13. Identification of Ste4 as a potential regulator of Byr2 in the sexual response pathway of Schizosaccharomyces pombe. Barr, M.M., Tu, H., Van Aelst, L., Wigler, M. Mol. Cell. Biol. (1996) [Pubmed]
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