- A binding motif for Hsp90 in the A chains of ADP-ribosylating toxins that move from the endoplasmic reticulum to the cytosol. [Journal Article]
- CMCell Microbiol 2019 Jun 24; :e13074
- Cholera toxin (Ctx) is an AB-type protein toxin that acts as an ADP-ribosyltransferase to disrupt intracellular signaling in the target cell. It moves by vesicle carriers from the cell surface to the…
Cholera toxin (Ctx) is an AB-type protein toxin that acts as an ADP-ribosyltransferase to disrupt intracellular signaling in the target cell. It moves by vesicle carriers from the cell surface to the endoplasmic reticulum (ER) of an intoxicated cell. The catalytic CtxA1 subunit then dissociates from the rest of the toxin, unfolds, and activates the ER-associated degradation system for export to the cytosol. Translocation occurs through an unusual ratchet mechanism in which the cytosolic chaperone Hsp90 couples CtxA1 refolding with CtxA1 extraction from the ER. Here, we report that Hsp90 recognizes two peptide sequences from CtxA1: an N-terminal RPPDEI sequence (residues 11-16) and an LDIAPA sequence in the C-terminal region (residues 153-158) of the 192 amino acid protein. Peptides containing either sequence effectively blocked Hsp90 binding to full-length CtxA1. Both sequences were necessary for the ER-to-cytosol export of CtxA1. Mutagenesis studies further demonstrated that the RPP residues in the RPPDEI motif are required for CtxA1 translocation to the cytosol. The LDIAPA sequence is unique to CtxA1, but we identified an RPPDEI-like motif at the N- or C-termini of the A chains from four other ER-translocating toxins that act as ADP-ribosyltransferases: pertussis toxin, Escherichia coli heat-labile toxin, Pseudomonas aeruginosa exotoxin A, and Salmonella enterica serovar Typhimurium ADP-ribosylating toxin. Hsp90 plays a functional role in the intoxication process for most, if not all, of these toxins. Our work has established a defined RPPDEI binding motif for Hsp90 that is required for the ER-to-cytosol export of CtxA1 and possibly other toxin A chains as well.
- Reconstructing disasters and adaptation scenario of nineteenth-century Kashmir. [Journal Article]
- DDisasters 2019 Jun 24
- Realistic disaster scenarios are constructed by integrating both natural hazard phenomena and human science sources of information. We profiled 51 historical natural hazard events of nineteenth-centu…
Realistic disaster scenarios are constructed by integrating both natural hazard phenomena and human science sources of information. We profiled 51 historical natural hazard events of nineteenth-century Kashmir, which provide us much better insight into what people were subjected to under severe natural and deprived socioeconomic conditions. Moreover, critical evaluation of historical data revealed that nineteenth-century was stressed with a series of environmental hazards intersected with socioeconomic and political factors which influenced adaptation and augmented the consequences of resulting disasters. Consequently, sequence of disasters over the century led Kashmir society to learn how to live with disasters and minimize risk and more importantly brought about cultural transformation. The very understanding of the natural hazard vulnerability of Kashmir Valley can help to reduce risk arising out of such processes; much needed to guide regional design, planning and can help to direct future policy responses. This article is protected by copyright. All rights reserved.
- Mr.Vc: a database of microarray and RNA-seq of Vibrio cholerae. [Journal Article]
- DDatabase (Oxford) 2019 Jan 01; 2019
- Gram-negative bacterium Vibrio cholerae is the causative agent of cholera, a life-threatening diarrheal disease. During its infectious cycle, V. cholerae routinely switches niches between aquatic env…
Gram-negative bacterium Vibrio cholerae is the causative agent of cholera, a life-threatening diarrheal disease. During its infectious cycle, V. cholerae routinely switches niches between aquatic environment and host gastrointestinal tract, in which V. cholerae modulates its transcriptome pattern accordingly for better survival and proliferation. A comprehensive resource for V. cholerae transcriptome will be helpful for cholera research, including prevention, diagnosis and intervention strategies. In this study, we constructed a microarray and RNA-seq database of V. cholerae (Mr.Vc), containing gene transcriptional expression data of 145 experimental conditions of V. cholerae from various sources, covering 25 937 entries of differentially expressed genes. In addition, we collected relevant information including gene annotation, operons they may belong to and possible interaction partners of their protein products. With Mr.Vc, users can easily find transcriptome data they are interested in, such as the experimental conditions in which a gene of interest was differentially expressed in, or all genes that were differentially expressed in an experimental condition. We believe that Mr.Vc database is a comprehensive data repository dedicated to V. cholerae and could be a useful resource for all researchers in related fields. Mr.Vc is available for free at http://bioinfo.life.hust.edu.cn/mrvc.
- Multimerization and Retention of the Scavenger Receptor SR-B1 in the Plasma Membrane. [Journal Article]
- DCDev Cell 2019 Jun 04
- Scavenger receptor B1 (SR-B1), the main receptor for high-density lipoprotein (HDL), is key in preventing atherosclerosis. It removes cholesterol from HDL, returning the lipid-poor lipoprotein to the…
Scavenger receptor B1 (SR-B1), the main receptor for high-density lipoprotein (HDL), is key in preventing atherosclerosis. It removes cholesterol from HDL, returning the lipid-poor lipoprotein to the circulation. To study the mechanisms controlling SR-B1 dynamics at the plasma membrane and its internalization rate, we developed a single-chain variable fragment (ScFv) antibody to image the receptor in live cells and track the behavior of single SR-B1 molecules. Unlike transferrin receptors, cholera-toxin-binding gangliosides, and bulk membrane markers, SR-B1 was internalized only marginally over hours. Plasmalemmal retention was not attributable to its C-terminal PDZ-binding domain or to attachment to the cortical cytoskeleton. Instead, SR-B1 undergoes multimerization into large metastable clusters that, despite being mobile in the membrane, fail to enter endocytic pathways. SR-B1 multimerization was impaired by mutating its C-terminal leucine zipper and by disrupting actin polymerization, causing rapid receptor internalization. Multimerization and plasmalemmal retention are critical for SR-B1 function.
- Human Peripheral Blood Mononuclear Cells Express High Levels of the Vitamin a Transport Protein, Stimulated by Retinoic Acid 6 (P19-004-19). [Journal Article]
- CDCurr Dev Nutr 2019; 3(Suppl 1)
- CONCLUSIONS: These results provide preliminary data in which to target vitamin A signaling, through cellular uptake of retinol, in immune cells to improve immune homeostasis in diverse populations.
- Streptococcus pneumoniae Acquisition and Carriage in Vaccine Naïve Indian Children with HIV and their Parents: A Longitudinal Household Study. [Journal Article]
- IJIndian J Pediatr 2019 Jun 20
- CONCLUSIONS: While the rate of pneumococcal carriage and acquisition did not differ between CLH and HUC, HIV affected families had exposure to a wider range of serotypes including non-vaccine type serotypes and antibiotic resistant serotypes, than HIV unaffected families.
- Cholera toxin perturbs the paracellular barrier in the small intestinal epithelium of rats by affecting claudin-2 and tricellulin. [Journal Article]
- PAPflugers Arch 2019 Jun 20
- Cholera toxin is commonly known to induce chloride secretion of the intestine. In recent years, effects on epithelial barrier function have been reported, indicating synergistic co-regulation of tran…
Cholera toxin is commonly known to induce chloride secretion of the intestine. In recent years, effects on epithelial barrier function have been reported, indicating synergistic co-regulation of transporters and tight junction proteins. Our current study focused on the analysis of cholera toxin effects on transepithelial resistance and on tight junction proteins, the latter known as structural correlates of barrier function. Ligated segments of the rat jejunum were injected with buffered solution containing cholera toxin (1 μg/ml) and incubated for 4 h. Subsequently, selfsame tissue specimens were mounted in Ussing chambers, and cholera toxin (1 μg/ml) was added on the apical side. Transepithelial resistance and permeability of sodium fluorescein (376 Da) were analyzed. Subsequently, tissues were removed, expression and localization of claudins were analyzed, and morphological studies were performed employing transmission electron microscopy and confocal laser scanning microscopy. Cholera toxin induced a marked decrease in transepithelial resistance in the rat jejunal epithelium and an increase in paracellular permeability for sodium fluorescein. Immunoblotting of tight junction proteins revealed an increase in claudin-2 signals, which was verified by confocal laser scanning immunofluorescence microscopy, and a decrease in tricellulin, whereas other tight junction proteins remained unchanged. Transmission electron microscopy showed a reduction in the number of microvilli after incubation with cholera toxin. Moreover, cholera toxin led to a widening of the intercellular space between enterocytes. In accordance with the commonly known prosecretory effect of cholera toxin, our study revealed a complementary effect on small intestinal barrier function and integrity, which might constitute a pathomechanism with high relevance for prevention and therapeutic approaches.
- Correction to: Structural analysis and proteomics studies on the Myoviridae vibriophage M4. [Published Erratum]
- AVArch Virol 2019 Jun 21
- Unfortunately, the original article was published with an incorrect figure. Figure 11 contains errors and needs to be withdrawn.
Unfortunately, the original article was published with an incorrect figure. Figure 11 contains errors and needs to be withdrawn.
- Adjuvant Allergen Fusion Proteins as Novel Tools for the Treatment of Type I Allergies. [Review]
- AIArch Immunol Ther Exp (Warsz) 2019 Jun 20
- While acute allergic symptoms can be managed by emergency medication, to date, allergen-specific immunotherapy (SIT) with allergen extracts is the only available curative treatment option. However, t…
While acute allergic symptoms can be managed by emergency medication, to date, allergen-specific immunotherapy (SIT) with allergen extracts is the only available curative treatment option. However, the risk of anaphylactic reactions, long treatment duration, varying extract quality, and underrepresentation of certain allergens currently prevent many patients from successfully undergoing SIT. Novel strategies are needed to enhance efficacy, safety, and convenience of allergy treatment. Fusion proteins combining allergen and adjuvant into a single molecule can efficiently induce immune responses by targeting the allergen to the relevant immune cells in vivo. Simultaneous co-delivery of both antigen and adjuvant to the same cell in a fixed molecular ratio triggers the uptake and presentation of the conjugated allergen in the context of the adjuvant-induced immune cell activation. This review summarizes the published strategies to improve the treatment of type I allergies using fusion proteins consisting of allergen (peptides) and either (1) immune-activating bacterial (flagellin, MPLA, S-layer, cholera-, and tetanus toxin), (2) viral (PreS, VP-1, TAT), or (3) fungal (FIP-fve) components, (4) immune-activating DNA motifs, (5) forced delivery of allergens to the MHC-II loading pathway, and (6) killing of immune cells expressing allergen-specific IgE by fusion of the allergen to diphtheria toxin.
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- HSC70 and HSP90 chaperones perform complementary roles in translocation of the cholera toxin A1 subunit from the endoplasmic reticulum to the cytosol. [Journal Article]
- JBJ Biol Chem 2019 Jun 20
- Cholera toxin (CT) travels by vesicle carriers from the cell surface to the endoplasmic reticulum (ER) where the catalytic A1 subunit of CT (CTA1) dissociates from the rest of the toxin, unfolds, and…
Cholera toxin (CT) travels by vesicle carriers from the cell surface to the endoplasmic reticulum (ER) where the catalytic A1 subunit of CT (CTA1) dissociates from the rest of the toxin, unfolds, and moves through a membrane-spanning translocon pore to reach the cytosol. Heat shock protein 90 (HSP90) binds to the N-terminal region of CTA1 and facilitates its ER-to-cytosol export by refolding the toxin as it emerges at the cytosolic face of the ER membrane. HSP90 also refolds some endogenous cytosolic proteins as part of a foldosome complex containing heat shock cognate 71 kDa protein (HSC70) and the HSC70/HSP90-organizing protein (HOP) linker which anchors HSP90 to HSC70. We accordingly predicted that HSC70 and HOP also function in CTA1 translocation. Inactivation of HSC70 by drug treatment disrupted CTA1 translocation to the cytosol and generated a toxin-resistant phenotype. In contrast, the depletion of HOP did not disrupt CT activity against cultured cells. HSC70 and HSP90 could bind independently to disordered CTA1, even in the absence of HOP. This indicated HSP90 and HSC70 recognize distinct regions of CTA1, which was confirmed by the identification of a YYIYVI binding motif for HSC70 that spans residues 83-88 of the 192 amino acid CTA1 polypeptide. Refolding of disordered CTA1 occurred in the presence of HSC70 alone, indicating that HSC70 and HSP90 can each independently refold CTA1. Our work suggests a novel translocation mechanism in which sequential interactions with HSP90 and HSC70 drive the N- to C-terminal extraction of CTA1 from the ER.