| 1. |
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- 2019
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Tidskriftsartikel (refereegranskat)
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| 2. |
- Hudson, Lawrence N, et al.
(författare)
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The database of the PREDICTS (Projecting Responses of Ecological Diversity In Changing Terrestrial Systems) project
- 2017
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Ingår i: Ecology and Evolution. - : John Wiley & Sons. - 2045-7758. ; 7:1, s. 145-188
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Tidskriftsartikel (refereegranskat)abstract
- The PREDICTS project-Projecting Responses of Ecological Diversity In Changing Terrestrial Systems (www.predicts.org.uk)-has collated from published studies a large, reasonably representative database of comparable samples of biodiversity from multiple sites that differ in the nature or intensity of human impacts relating to land use. We have used this evidence base to develop global and regional statistical models of how local biodiversity responds to these measures. We describe and make freely available this 2016 release of the database, containing more than 3.2 million records sampled at over 26,000 locations and representing over 47,000 species. We outline how the database can help in answering a range of questions in ecology and conservation biology. To our knowledge, this is the largest and most geographically and taxonomically representative database of spatial comparisons of biodiversity that has been collated to date; it will be useful to researchers and international efforts wishing to model and understand the global status of biodiversity.
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| 3. |
- Navarro, Claudia D.C., et al.
(författare)
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Aging-dependent mitochondrial bioenergetic impairment in the skeletal muscle of NNT-deficient mice
- 2024
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Ingår i: Experimental Gerontology. - 0531-5565. ; 193
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Tidskriftsartikel (refereegranskat)abstract
- Overall health relies on features of skeletal muscle that generally decline with age, partly due to mechanisms associated with mitochondrial redox imbalance and bioenergetic dysfunction. Previously, aged mice genetically devoid of the mitochondrial NAD(P)+ transhydrogenase (NNT, encoded by the nicotinamide nucleotide transhydrogenase gene), an enzyme involved in mitochondrial NADPH supply, were shown to exhibit deficits in locomotor behavior. Here, by using young, middle-aged, and older NNT-deficient (Nnt−/−) mice and age-matched controls (Nnt+/+), we aimed to investigate how muscle bioenergetic function and motor performance are affected by NNT expression and aging. Mice were subjected to the wire-hang test to assess locomotor performance, while mitochondrial bioenergetics was evaluated in fiber bundles from the soleus, vastus lateralis and plantaris muscles. An age-related decrease in the average wire-hang score was observed in middle-aged and older Nnt−/− mice compared to age-matched controls. Although respiratory rates in the soleus, vastus lateralis and plantaris muscles did not significantly differ between the genotypes in young mice, the rates of oxygen consumption did decrease in the soleus and vastus lateralis muscles of middle-aged and older Nnt−/− mice. Notably, the soleus, which exhibited the highest NNT expression level, was the muscle most affected by aging, and NNT loss. Additionally, histology of the soleus fibers revealed increased numbers of centralized nuclei in older Nnt−/− mice, indicating abnormal morphology. In summary, our findings suggest that NNT expression deficiency causes locomotor impairments and muscle dysfunction during aging in mice.
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| 4. |
- Amer, Ayad, 1980-, et al.
(författare)
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Functional consequences of site-directed mutagenesis in the C-terminus of YopN, a Yersinia pseudotuberculosis regulator of Yop secretion
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Pathogenic Yersinia spp. utilizes the Ysc-Yop type III secretion system to targetYop effector proteins into the cytosol of host immune cells. Internalizedeffectors alter specific signaling pathways to neutralize immune cell-dependentphagocytosis, killing and pro-inflammatory responsiveness. This enablesextracellular bacterial multiplication and survival in immune tissue. Central tothe temporal control of Yop type III secretion is the regulator YopN. Incomplex with TyeA, YopN acts to plug the inner face of the type III secretionchannel, denying entry to other Yop substrates until after YopN has beensecreted. A +1 frameshift event in the 3-prime end of yopN results in thesynthesis of a singular secreted YopN-TyeA polypeptide chimera that retainssome regulatory function. As the C-terminal coding sequence of YopN in thishybrid product differs greatly from native sequence, we used site-directedmutagenesis to determine the functional significance of this segment. YopNtruncated at residue 287 or containing a shuffled sequence covering 288 to 293retains full function both in vitro and in vivo. Thus, the extreme C-terminus isapparently superfluous to YopN function. In contrast, a YopN varianttruncated after residue 278 was completely unstable, and these bacteria hadlost all control of T3S activity, and failed to defend against immune cell killing.Interestingly, inclusion of a shuffled sequence from residues 279 to 287recovered some T3S control over function. Hence, the YopN segmentencompassing 279 to 287 is essential for full function, although the exact aminoacid sequence is less important.
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| 5. |
- Amer, Ayad, 1980-, et al.
(författare)
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Genetically engineered frameshifted YopN-TyeA chimeras influence type III secretion system function in Yersinia pseudotuberculosis
- 2013
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Ingår i: PLOS ONE. - San Francisco : Public Library of Science. - 1932-6203. ; 8:10
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Tidskriftsartikel (refereegranskat)abstract
- Type III secretion is a tightly controlled virulence mechanism utilized by many gram negative bacteria to colonize their eukaryotic hosts. To infect their host, human pathogenic Yersinia spp. translocate protein toxins into the host cell cytosol through a preassembled Ysc-Yop type III secretion device. Several of the Ysc-Yop components are known for their roles in controlling substrate secretion and translocation. Particularly important in this role is the YopN and TyeA heterodimer. In this study, we confirm that Y. pseudotuberculosis naturally produce a 42 kDa YopN-TyeA hybrid protein as a result of a +1 frame shift near the 3 prime of yopN mRNA, as has been previously reported for the closely related Y. pestis. To assess the biological role of this YopN-TyeA hybrid in T3SS by Y. pseudotuberculosis, we used in cis site-directed mutagenesis to engineer bacteria to either produce predominately the YopN-TyeA hybrid by introducing +1 frame shifts to yopN after codon 278 or 287, or to produce only singular YopN and TyeA polypeptides by introducing yopN sequence from Y. enterocolitica, which is known not to produce the hybrid. Significantly, the engineered 42 kDa YopN-TyeA fusions were abundantly produced, stable, and were efficiently secreted by bacteria in vitro. Moreover, these bacteria could all maintain functionally competent needle structures and controlled Yops secretion in vitro. In the presence of host cells however, bacteria producing the most genetically altered hybrids (+1 frameshift after 278 codon) had diminished control of polarized Yop translocation. This corresponded to significant attenuation in competitive survival assays in orally infected mice, although not at all to the same extent as Yersinia lacking both YopN and TyeA proteins. Based on these studies with engineered polypeptides, most likely a naturally occurring YopN-TyeA hybrid protein has the potential to influence T3S control and activity when produced during Yersinia-host cell contact.
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| 6. |
- Amer, Ayad, et al.
(författare)
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YopN and TyeA Hydrophobic Contacts Required for Regulating Ysc-Yop Type III Secretion Activity by Yersinia pseudotuberculosis
- 2016
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Ingår i: Frontiers in Cellular and Infection Microbiology. - : Frontiers Media SA. - 2235-2988. ; 6
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Tidskriftsartikel (refereegranskat)abstract
- Yersinia bacteria target Yop effector toxins to the interior of host immune cells by the Ysc-Yop type III secretion system. A YopN-TyeA heterodimer is central to controlling Ysc-Yop targeting activity. A + 1 frameshift event in the 3-prime end of yopN can also produce a singular secreted YopN-TyeA polypeptide that retains some regulatory function even though the C-terminal coding sequence of this YopN differs greatly from wild type. Thus, this YopN C-terminal segment was analyzed for its role in type III secretion control. Bacteria producing YopN truncated after residue 278, or with altered sequence between residues 279 and 287, had lost type III secretion control and function. In contrast, YopN variants with manipulated sequence beyond residue 287 maintained full control and function. Scrutiny of the YopN-TyeA complex structure revealed that residue W279 functioned as a likely hydrophobic contact site with TyeA. Indeed, a YopNW279G mutant lost all ability to bind TyeA. The TyeA residue F8 was also critical for reciprocal YopN binding. Thus, we conclude that specific hydrophobic contacts between opposing YopN and TyeA termini establishes a complex needed for regulating Ysc-Yop activity.
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| 7. |
- Costa, Tiago, et al.
(författare)
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Measurement of Yersinia translocon pore formation in erythrocytes
- 2019
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Ingår i: Pathogenic Yersinia. - New York, NY, U.S.A. : Humana Press. - 9781493995400 ; , s. 211-229
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Bokkapitel (refereegranskat)abstract
- Many Gram-negative pathogens produce a type III secretion system capable of intoxicating eukaryotic cells with immune-modulating effector proteins. Fundamental to this injection process is the prior secretion of two translocator proteins destined for injectisome translocon pore assembly within the host cell plasma membrane. It is through this pore that effectors are believed to travel to gain access to the host cell interior. Yersinia species especially pathogenic to humans and animals assemble this translocon pore utilizing two hydrophobic translocator proteins-YopB and YopD. Although a full molecular understanding of the biogenesis, function and regulation of this translocon pore and subsequent effector delivery into host cells remains elusive, some of what we know about these processes can be attributed to studies of bacterial infections of erythrocytes. Herein we describe the methodology of erythrocyte infections by Yersinia, and how analysis of the resultant contact-dependent hemolysis can serve as a relative measurement of YopB- and YopD-dependent translocon pore formation.
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| 8. |
- Costa, Tiago R. D., et al.
(författare)
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Active type III translocon assemblies that attenuate Yersinia virulence
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Type III secretion enables bacteria to intoxicate eukaryotic cells with anti-host effectors. A class of secreted cargo are the two hydrophobic translocators that form a translocon pore in the host cell plasma membrane through which the translocated effectors may gain cellular entry. In pathogenic Yersinia, YopB and YopD shape this translocon pore. Here, four in cis yopD mutations were constructed to disrupt a predicted a-helix motif at the C-terminus. Mutants YopDI262P and YopDK267P poorly localised Yop effectors into target eukaryotic cells and failed to resist uptake and killing by immune cells. These defects were due to deficiencies in host-membrane insertion of the YopD-YopB translocon. Mutants YopDA263P and YopDA270P had no measurable in vitro translocation defect, even though they formed smaller translocon pores in erythrocyte membranes. Despite this, all four mutants were attenuated in a mouse infection model. Hence, YopD variants have been generated that can spawn translocons capable of targeting effectors in vitro, yet were bereft of any lethal effect in vivo. It is therefore probable that an active translocon makes a range of contributions during bacteria-host cell contact that extends beyond effector delivery per se.
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| 9. |
- Costa, Tiago R. D., et al.
(författare)
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Coiled-coils in the YopD translocator family : A predicted structure unique to the YopD N-terminus contributes to full virulence of Yersinia pseudotuberculosis
- 2012
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Ingår i: Infection, Genetics and Evolution. - : Elsevier. - 1567-1348 .- 1567-7257. ; 12:8, s. 1729-1742
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Tidskriftsartikel (refereegranskat)abstract
- Pathogenic Yersinia all harbor a virulence plasmid-encoded Ysc–Yop T3SS. In this system, translocator function is performed by the hydrophobic proteins YopB and YopD. With the goal to better understand how YopD orchestrates yop-regulatory control, translocon pore formation and Yop effector translocation, we performed an in silico prediction of coiled-coil motifs in YopD and YopD-like sequences from other bacteria. Of interest was a predicted N-terminal coiled-coil that occurred solely in Yersinia YopD sequences. To investigate if this unique feature was biologically relevant, two in cis point mutations were generated with a view to disrupting this putative structure. Both mutants maintained full T3SS function in vitro in terms of environmental control of Yops synthesis and secretion, effector toxin translocation and evasion of phagocytosis and killing by cultured immune cells. However, these same mutants were attenuated for virulence in a murine oral-infection model. The cause of this tardy disease progression is unclear. However, these data indicate that any structural flaw in this element unique to the N-terminus will subtly compromise an aspect of YopD biology. Sub-optimal T3SSs are then formed that are unable to fortify Yersinia against attack by the host innate and adaptive immune response.
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| 10. |
- Costa, Tiago R. D., et al.
(författare)
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Influence of the LcrH chaperone on type III secretion system regulation in Yersinia pseudotuberculosis
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Human pathogenic Yersiniae share a common virulence plasmid that encodes for the Ysc-Yop type III secretion system (T3SS). Control of yop expression involves several pathways in which their cross-talk is not completely understood. LcrF, an AraC-like transcriptional activator, is required for temperature-dependent yop-transcription. In contrast, a repressive effect of the T3S chaperone LcrH and the cognate translocator substrate YopD occurs through binding to yop mRNA and inhibiting translation; a process that is also thought to involve LcrQ. Several homologous members of the LcrH family of translocator-class of T3S chaperones can act as a cofactor to amplify the activity of transcriptional activators analogous to LcrF. However, we show here in Y. pseudotuberculosis that LcrH does not induce LcrF-dependent transcription of target genes. Moreover, a full length DlcrH null mutant in which YopB and YopD are rapidly degraded is totally de-repressed for Yop synthesis even though the anti-activator LcrQ is forced to accumulate in the cytoplasm through rendering the Ysc-Yop T3SS non-functional or ectopically producing LcrQ in trans. Typically, this mutant cannot grow at 37°C. Thus, in all respects, the DlcrH null mutant mirrors the regulatory defects established for Yersinia lacking the translocator and anti-activator YopD. On the other hand, Y. pseudotuberculosis producing the LcrHE30G point mutant that is defective for YscY chaperone binding exhibits a mild regulatory defect that permits some growth at 37°C, but is blind to the cytoplasmic accumulation of LcrQ. Critically however, this mutant still responds to repression caused by YopD accumulation, which is stably produced and efficiently secreted by this strain. Thus, our work with LcrHE30G indicates an additional regulatory function of this versatile T3S chaperone that is independent of the LcrF transcription factor and the YopD anti-activator.
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