Dataset Information

Cytosolic entry of Shiga-like toxin a chain from the yeast endoplasmic reticulum requires catalytically active Hrd1p.

ABSTRACT: Escherichia coli Shiga-like toxin 1 normally traffics to the endoplasmic reticulum (ER) in sensitive mammalian cells from where the catalytic A chain (SLTxA1) dislocates to the cytosol to inactivate ribosomes. Currently, no molecular details of the dislocation process are available. To investigate the mechanism of the dislocation step we expressed SLTxA1 in the ER of Saccharomyces cerevisiae.Using a combination of growth studies and biochemical tracking in yeast knock-out strains we show that SLTxA1 follows an ER-associated degradation (ERAD) pathway to enter the cytosol in a step mediated by the transmembrane Hrd1p ubiquitin ligase complex. ER-to-cytosol dislocation of the bulk population of SLTxA1 requires Cdc48p and its ubiquitin-handling co-factor Npl4p, and this population of toxin is terminally dispatched by proteasomal degradation. A small sub-population of SLTxA1 uncouples from this classical ERAD pathway and recovers catalytic activity in the cytosol. The pathway that leads to toxicity is also Hrd1p-dependent but, unlike that for the related ricin A chain toxin, SLTxA1 dislocation does require the catalytic cysteine of Hrd1p. However it does not depend on canonical ubiquitylation since toxin variants lacking endogenous lysyl residues also utilize this pathway, and furthermore there is no requirement for a number of Cdc48p co-factors.The fraction of SLTxA1 that disengages from the ERAD pathway thus does so upstream of Cdc48p interactions and downstream of Hrd1p interactions, in a step that possibly involves de-ubiquitylation. Mechanistically therefore, the dislocation of this toxin is quite distinct from that of conventional ERAD substrates that are normally degraded, and the toxins partially characterised to date that do not require the catalytic cysteine of the major Hrd1p component of the dislocation apparatus.

SUBMITTER: Li S

PROVIDER: S-EPMC3400632 | biostudies-literature | 2012

REPOSITORIES: biostudies-literature

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Cytosolic entry of Shiga-like toxin a chain from the yeast endoplasmic reticulum requires catalytically active Hrd1p.

Li Shuyu S Spooner Robert A RA Hampton Randolph Y RY Lord J Michael JM Roberts Lynne M LM

PloS one 20120719 7

<h4>Background</h4>Escherichia coli Shiga-like toxin 1 normally traffics to the endoplasmic reticulum (ER) in sensitive mammalian cells from where the catalytic A chain (SLTxA1) dislocates to the cytosol to inactivate ribosomes. Currently, no molecular details of the dislocation process are available. To investigate the mechanism of the dislocation step we expressed SLTxA1 in the ER of Saccharomyces cerevisiae.<h4>Methodology and principal findings</h4>Using a combination of growth studies and b ...[more]

PMID: 22829918

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Project description:Aim and experimental set-up: Sequencing of small RNA from total RNA fractions. The aim of this experiment was to compare profiles of miRNA expression between the following genetic backgrounds: Col-0 (wild type), era1-2 (farnesyl transferase mutant), j2-2/j3-2 + pJ3:J3 (j2/j3 double knockout expressing transgenic J3 under the control of the endogenous J3 promoter), j2-2/j3-2 + pJ3:J3C417S (j2/j3 double knockout expressing transgenic J3 mutated in the farnesylation site (C417S) under the control of the endogenous J3 promoter). Seedlings were grown under sterile conditions for 16 days. Two biological replicates of each genotype were harvested, and total RNA was prepared by Trizol extraction. Small RNA libraries were constructed using NEBNext Small RNA Library Prep Set and sequenced on an Illumina platform. Sequencing of small RNA bound to AGO1 in membrane fractions The aim of this experiment was to characterize AGO1-bound small RNAs in membrane fractions, and to answer two specific questions: Can miRNAs be identified whose association with membrane-bound AGO1 is different between the following four genotypes: Col-0 (wild type), era1-2 (farnesyl transferase mutant), j2-2/j3-2 + pJ3:J3 (j2/j3 double knockout expressing transgenic J3 under the control of the endogenous J3 promoter), j2-2/j3-2 + pJ3:J3C417S (j2/j3 double knockout expressing transgenic J3 mutated in the farnesylation site (C417S) under the control of the endogenous J3 promoter) Is the ratio between reads matching miRNA and miRNA* different between the above four genotypes? Seedlings were grown under sterile conditions for 16 days. Two biological replicates of each genotype were harvested. Microsomes were prepared from 2g of seedling tissue, solubilized by 1% deoxycholate and AGO1 was immunoprecipitated with specific antibodies (Agrisera). Immunopurified AGO1 was eluted from Protein A sepharose beads by competitive elution with antigenic AGO1 peptide. Small RNA was extracted by Trizol extraction from eluted AGO1. Small RNA libraries were constructed using NEBNext Small RNA Library Prep Set and sequenced on an Illumina platform.

Dataset Information

Cytosolic entry of Shiga-like toxin a chain from the yeast endoplasmic reticulum requires catalytically active Hrd1p.

Publications

Cytosolic entry of Shiga-like toxin a chain from the yeast endoplasmic reticulum requires catalytically active Hrd1p.

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