Phosphorelay Signaling in Yeast in Response to Changes in Osmolarity

Jennifer L. Santos, and Kazuhiro Shiozaki^*

¹Biochemistry and Molecular Biology Graduate Program, University of California, Davis, Davis, CA. K. Shiozaki is also in the Section of Microbiology, University of California, Davis, Davis, CA 95616, USA.

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*Corresponding author. E-mail, kshiozaki{at}ucdavis.edu

Description

In the yeast, Saccharomyces cerevesiae, phosphorelay signaling systems that involve a three-step His-Asp-His-Asp phosphotransfer are involved in transmitting signals in response to cellular stress. The animation shows one example of such a phosphorelay system involved in yeast responses to changes in osmolarity. Under conditions of low osmolarity, a histidine-aspartate phosphorelay pathway transmits information that deactivates one signaling pathway and activates gene expression through another pathway. In response to high osmolarity, the Sln1 kinase that initiates the phosphorelay is inhibited and the high osmolarity glycerol 1 (Hog1) mitogen-activated protein kinase (MAPK) cascade is active. Thus, Sln1 acts as a molecular switch controlling the flow of information through the Hog1 MAPK cascade and gene expression stimulated by Skn7.

Sln1 is a histidine kinase that is active under low osmolarity conditions (click "Low Osmolarity"). Ypd1 contains the histidine phosphotransfer (Hpt) domain, which mediates the transfer of the phosphoryl group from Sln1 to the response regulators Ssk1 and Skn7. Aspartate phosphorylated Ssk1 cannot activate the Hog1 MAPK cascade, whereas aspartate phosphorylated Skn7 stimulates gene expression by Skn7. In contrast, high osmolarity stress (click "High Osmolarity") inhibits the Sln1 kinase, and the unphosphorylated form of Ssk1 activates the Hog1 cascade. Sln1 is shown as a monomer for simplicity, although dimerization may necessary for Sln1 activation. Abbreviations used in the animation include H, histidine; A, aspartate; and P, phosphate.

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Educational Details

Learning Resource Type: Animation

Context: Undergraduate upper division, graduate, professional (degree program)

Intended Users: Teacher, learner

Intended Educational Use: Teach, learn

Discipline: Microbiology, cell biology, biochemistry

Keywords: Histidine transfer protein, MAPK, transcription, stress

Technical Details

Format: Shockwave Flash Object (swf)

Size: 16 kb

Requirements: Macromedia Flash Player http://www.macromedia.com/downloads/

Related Resources

Resource Citation Review: J. L. Santos, K. Shiozaki, Fungal histidine kinases. Sci. STKE 2001, re1 (2001). [Gloss] [Abstract] [Full Text]

Connections Map: P. J. Westfall, D. R. Ballon, J. Thorner, High osmolarity glycerol (HOG) pathway in yeast. Sci. STKE (Connections Map. as seen December 2004), http://stke.sciencemag.org/cgi/cm/stkecm;CMP_14620. [Specific Pathway]

Limits for Use

Cost: Free

Rights: This material may be downloaded, printed, linked to, and/or redistributed without modification for noncommercial, course-teaching purposes only, provided credit to STKE is included by listing the citation for the teaching resource.

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Citation: J. L. Santos, K. Shiozaki, Phosphorelay signaling in yeast in response to changes in osmolarity. Sci. STKE 2004, tr12

© 2004 American Association for the Advancement of Science