Yeast osmoregulation
Download
1 / 40

Yeast Osmoregulation - PowerPoint PPT Presentation


  • 103 Views
  • Uploaded on

Yeast Osmoregulation. Content. Introduction Sensing osmotic changing HOG signaling pathways Transcriptional Responses Response To Hyperosmotic Shock Quantitative analyses. Introduction. The osmoregulatory system in the yeast Saccharomyces cerevisiae is particularly well understood.

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about ' Yeast Osmoregulation' - naoko


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript

Content
Content

  • Introduction

  • Sensing osmotic changing

  • HOG signaling pathways

  • Transcriptional Responses

  • Response To Hyperosmotic Shock

  • Quantitative analyses


Introduction
Introduction

  • The osmoregulatory system in the yeast Saccharomyces cerevisiae is particularly well understood.

  • Key to yeast osmoregulation is the production and accumulation of the compatible solute glycerol, which is partly controlled by the high osmolarity glycerol (HOG) signaling system.


Sensing osmotic changing
Sensing Osmotic Changing

  • Sln1

    Sln1p is a protein of 1,220 amino acids.

    Sln1p is the only sensor histidine kinase in the S. cerevisiae proteome.



  • Sho1p

    Sho1p is a protein of 367 amino acids consisting of four predicted transmembrane domains within the N-terminal part, a linker domain, and an SH3 domain for protein-protein interaction.



  • Hkr1 and Msb2: Putative Osmosensors?

    Recent studies have shown that mucin-like transmembrane proteins Hkr1 and Msb2 are the potential osmosensors and the most upstream elements know so far in the SHO1 branch.




Hog signaling pathways
HOG Signaling Pathways

  • The HOG pathway is one of the best understood and most intensively studied MAPK systems.

  • Two branches of the HOG pathways: SHO1 branch and the SLN1 branch.



The sln1 branch
The SLN1 Branch

  • Under low osmolarity, Sln1p constantly autophosphorylates itself on His576. Then transferred to Asp1144, within the receiver domain of Sln1p.

  • The phosphate group is transferred to His64 on Ypd1p and further to Asp554 on Ssk1p.

  • Dephosphorylated Ssk1p activates the MAPKKKs Ssk2p and Ssk22p.




The sho1 branch
The SHO1 Branch pathway

  • Activation of the Sho1 branch of the HOG pathway involves rapid and transient formation of a protein complex at the cell surface, specifically at places of cell growth.




  • Pbs2p is activated by phosphorylation on Ser514 and Thr518 by any of the three MAPKKKs Ssk2p/Ssk22p and Ste11p.

  • Dual phosphorylation on the conserved Thr174 and Tyr176 activates the MAP kinase Hog1p.

  • Under hyperosmotic stress, Hog1p is rapidly phosphorylated and translocated immediately to the nucleus, and transcriptional responses are observed.

  • Both phosphorylation of Hog1p and nuclear localization are transient effects.




  • The Hog1 MAPK in the HOG pathway is negatively regulated jointly by the protein tyrosine phosphatases Ptp2/Ptp3 and the type 2 protein phosphatases Ptc1/Ptc2/Ptc3.

  • Specificities of these phosphatases are determined by docking interactions as well as their cellular localizations.




Transcriptional responses
Transcriptional Responses Hog1

  • Several studies have reported global gene expression analyses following a hyperosmotic shock of different intensity.

  • It appears that about 200 to 400 genes are upregulated and that some 150 to 250 genes are downregulated.

  • Several transcription factors seem to be involved in Hog1-dependent responses: Hot1, Sko1, Msn2/Msn4, Msn1, and Smp1.




SKO1 Hog1

  • Sko1 binds to cAMP response element sites in targets promoters.

  • Active Hog1 converts Sko1 from a repressor to an activator.

  • It appears that Sko1 controls the expression of several regulators of the osmoresponse systems, such as the Msn2 transcription factor and the Ptp3 protein phosphatase.



R esponse t o hyperosmotic s hock
R stress response. Msn2/Msn4 nuclear localization is negatively controlled by protein kinase A.esponse ToHyperosmotic Shock

  • Metabolism and Transport of Glycerol

  • Metabolism of Trehalose and Glycogen

  • Transport systems involved in osmoadptation


Metabolism and transport of glycerol
Metabolism and Transport of Glycerol stress response. Msn2/Msn4 nuclear localization is negatively controlled by protein kinase A.

  • Glycerol metabolic pathway.

  • Control of glycerol production under

    osmotic stress

  • Transmembrane flux of glycerol



Control of glycerol production under osmotic stress
Control of glycerol production under osmotic stress glycogen

  • Expression is rapidly and transiently stimulated by an osmotic upshift.

  • The mRNA profile of GPD1 and GPP2 depends greatly on the severity of the stress.

  • The rapid and transient transcriptional response to osmotic stress of GPD1 and GPP2 expression is highly dependent on the HOG pathway.


Transmembrane flux of glycerol
Transmembrane flux of glycerol glycogen

  • Upon osmoshock, expression changes of several genes encoding enzymes in lipid metabolism have been observed by global gene expression analysis.

  • Lower levels of ergosterol could make the membrane more compact and less flexible and hence lead to diminished transmembrane flux of glycerol.


Transport systems involved in osmoadptation
Transport systems involved in osmoadptation glycogen

  • MIP Channels

  • Ion Transport

  • Osmolyte Uptake

  • Possible Roles of the Vacuole in Osmoadaptation


Mip channels fps1
MIP Channels: Fps1 glycogen

  • These type of proteins are characterized by six transmembrane domains andtwo loops, B and E, that dip into the membrane from both sides, essentially forming a seventh transmembrane domain.

  • It appears that three regions play a role in Fps1 gating: the B loop, the region of about 40 amino acids proximal to the first transmembrane domain, and the 10 amino acids immediately distal to the sixth transmembrane domain.



Thank you
Thank you! of response mechanisms


ad