Important insights concerning the molecular basis of skeletal muscle disuse-atrophy and aging related muscle loss have been obtained in cell culture and animal models, but these regulatory signaling ...pathways have not previously been studied in aging human muscle. In the present study, muscle atrophy was induced by immobilization in healthy old and young individuals to study the time-course and transcriptional factors underlying human skeletal muscle atrophy. The results reveal that irrespectively of age, mRNA expression levels of MuRF-1 and Atrogin-1 increased in the very initial phase (2-4 days) of human disuse-muscle atrophy along with a marked reduction in PGC-1α and PGC-1β (1-4 days) and a ~10% decrease in myofiber size (4 days). Further, an age-specific decrease in Akt and S6 phosphorylation was observed in young muscle within the first days (1-4 days) of immobilization. In contrast, Akt phosphorylation was unchanged in old muscle after 2 days and increased after 4 days of immobilization. Further, an age-specific down-regulation of MuRF-1 and Atrogin-1 expression levels was observed following 2 weeks of immobilization, along with a slowing atrophy response in aged skeletal muscle. Neither the immediate loss of muscle mass, nor the subsequent age-differentiated signaling responses could be explained by changes in inflammatory mediators, apoptosis markers or autophagy indicators. Collectively, these findings indicate that the time-course and regulation of human skeletal muscle atrophy is age dependent, leading to an attenuated loss in aging skeletal muscle when exposed to longer periods of immobility-induced disuse.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The PfEMP1 family of surface proteins is central for Plasmodium falciparum virulence and must retain the ability to bind to host receptors while also diversifying to aid immune evasion. The ...interaction between CIDRα1 domains of PfEMP1 and endothelial protein C receptor (EPCR) is associated with severe childhood malaria. We combine crystal structures of CIDRα1:EPCR complexes with analysis of 885 CIDRα1 sequences, showing that the EPCR-binding surfaces of CIDRα1 domains are conserved in shape and bonding potential, despite dramatic sequence diversity. Additionally, these domains mimic features of the natural EPCR ligand and can block this ligand interaction. Using peptides corresponding to the EPCR-binding region, antibodies can be purified from individuals in malaria-endemic regions that block EPCR binding of diverse CIDRα1 variants. This highlights the extent to which such a surface protein family can diversify while maintaining ligand-binding capacity and identifies features that should be mimicked in immunogens to prevent EPCR binding.
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•EPCR binding is retained by PfEMP1 CIDRα1 domains despite huge sequence variation•Diverse CIDRα1 domains retain structural and chemical features to bind to EPCR•CIDRα1 domains mimic features of a natural ligand of EPCR and block its binding•Patient sera contain neutralizing antibodies that prevent parasite binding to EPCR
PfEMP1 proteins of Plasmodium must retain binding to host receptor EPCR while diversifying for immune evasion. Using structural studies, Lau et al. show that EPCR-binding surfaces of PfEMP1 are conserved in shape and bonding potential, despite sequence diversity, and identify features that should be mimicked in immunogens preventing EPCR binding.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Sequestration of Plasmodium falciparum‐infected erythrocytes (IE) within the brain microvasculature is a hallmark of cerebral malaria (CM). Using a microchannel flow adhesion assay with TNF‐activated ...primary human microvascular endothelial cells, we demonstrate that IE isolated from Malawian paediatric CM cases showed increased binding to brain microvascular endothelial cells compared to IE from uncomplicated malaria (UM) cases. Further, UM isolates showed significantly greater adhesion to dermal than to brain microvascular endothelial cells. The major mediator of parasite adhesion is P. falciparum erythrocyte membrane protein 1, encoded by var genes. Higher levels of var gene transcripts predicted to bind host endothelial protein C receptor (EPCR) and ICAM‐1 were detected in CM isolates. These data provide further evidence for differential tissue binding in severe and uncomplicated malaria syndromes, and give additional support to the hypothesis that CM pathology is based on increased cytoadherence of IE in the brain microvasculature.
Synopsis
Cytoadherence of Plasmodium falciparum‐infected erythrocytes (IE) to the endothelial cells lining brain vessels is a hallmark of cerebral malaria (CM). This study shows that the ability of IE to cytoadhere in the brain of patients with CM and uncomplicated malaria is associated with the disease.
IE from children with uncomplicated malaria do not bind well to brain endothelial cells, whereas IE from CM patients show high levels of binding.
Significant associations in IE binding to brain endothelial cells were seen for both ICAM‐1 and EPCR.
PfEMP1 variants containing EPCR‐binding motifs were associated with cerebral malaria.
Cytoadherence of Plasmodium falciparum‐infected erythrocytes (IE) to the endothelial cells lining brain vessels is a hallmark of cerebral malaria (CM). This study shows that the ability of IE to cytoadhere in the brain of patients with CM and uncomplicated malaria is associated with the disease.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Overexpression of the transcriptional coactivator peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α), like exercise, increases mitochondrial content and inhibits muscle atrophy. To ...understand these actions, we tested whether PGC-1α or its close homolog, PGC-1β, influences muscle protein turnover. In myotubes, overexpression of either coactivator increased protein content by decreasing overall protein degradation without altering protein synthesis rates. Elevated PGC-1α or PGC-1β also prevented the acceleration of proteolysis induced by starvation or FoxO transcription factors and prevented the induction of autophagy and atrophy-specific ubiquitin ligases by a constitutively active FoxO3. In mouse muscles, overexpression of PGC-1β (like PGC-1α) inhibited denervation atrophy, ubiquitin ligase induction, and transcription by NFκB. However, increasing muscle PGC-1α levels pharmacologically by treatment of mice with 5-aminoimidazole-4-carboxamide 1-β-d-ribofuranoside failed to block loss of muscle mass or induction of ubiquitin ligases upon denervation atrophy, although it prevented loss of mitochondria. This capacity of PGC-1α and PGC-1β to inhibit FoxO3 and NFκB actions and proteolysis helps explain how exercise prevents muscle atrophy.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Sequestration of Plasmodium falciparum-infected erythrocytes in host blood vessels is a key triggering event in the pathogenesis of severe childhood malaria, which is responsible for about one ...million deaths every year. Sequestration is mediated by specific interactions between members of the P. falciparum erythrocyte membrane protein 1 (PfEMP1) family and receptors on the endothelial lining. Severe childhood malaria is associated with expression of specific PfEMP1 subtypes containing domain cassettes (DCs) 8 and 13 (ref. 3), but the endothelial receptor for parasites expressing these proteins was unknown. Here we identify endothelial protein C receptor (EPCR), which mediates the cytoprotective effects of activated protein C, as the endothelial receptor for DC8 and DC13 PfEMP1. We show that EPCR binding is mediated through the amino-terminal cysteine-rich interdomain region (CIDRα1) of DC8 and group A PfEMP1 subfamilies, and that CIDRα1 interferes with protein C binding to EPCR. This PfEMP1 adhesive property links P. falciparum cytoadhesion to a host receptor involved in anticoagulation and endothelial cytoprotective pathways, and has implications for understanding malaria pathology and the development of new malaria interventions.
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DOBA, IJS, IZUM, KILJ, KISLJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The clinical outcome of Plasmodium falciparum infections ranges from asymptomatic parasitemia to severe malaria syndromes associated with high mortality. The virulence of P. falciparum infections is ...associated with the type of P. falciparum erythrocyte membrane protein 1 (PfEMP1) expressed on the surface of infected erythrocytes to anchor these to the vascular lining. Although var2csa , the var gene encoding the PfEMP1 associated with placental malaria, was discovered in 2003, the identification of the var /PfEMP1 variants associated with severe malaria in children has remained elusive. To identify var /PfEMP1 variants associated with severe disease outcome, we compared var transcript levels in parasites from 88 children with severe malaria and 40 children admitted to the hospital with uncomplicated malaria. Transcript analysis was performed by RT-quantitative PCR using a set of 42 primer pairs amplifying var subtype-specific loci covering most var /PfEMP1 subtypes. In addition, we characterized the near-full-length sequence of the most prominently expressed var genes in three patients diagnosed with severe anemia and/or cerebral malaria. The combined analysis showed that severe malaria syndromes, including severe anemia and cerebral malaria, are associated with high transcript levels of PfEMP1 domain cassette 8-encoding var genes. Transcript levels of group A var genes, including genes encoding domain cassette 13, were also significantly higher in patients with severe syndromes compared with those with uncomplicated malaria. This study specifies the var /PfEMP1 types expressed in severe malaria in children, and thereby provides unique targets for future efforts to prevent and treat severe malaria infections.
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BFBNIB, NMLJ, NUK, PNG, SAZU, UL, UM, UPUK
Interpretation of the colossal number of genetic variants identified from sequencing applications is one of the major bottlenecks in clinical genetics, with the inference of the effect of amino ...acidsubstituting missense variations on protein structure and function being especially challenging. Here we characterize the three-dimensional (3D) amino acid positions affected in pathogenic and population variants from 1,330 disease-associated genes using over 14,000 experimentally solved human protein structures. By measuring the statistical burden of variations (i.e., point mutations) from all genes on 40 3D protein features, accounting for the structural, chemical, and functional context of the variations’ positions, we identify features that are generally associated with pathogenic and population missense variants. We then perform the same amino acid-level analysis individually for 24 protein functional classes, which reveals unique characteristics of the positions of the altered amino acids: We observe up to 46% divergence of the class-specific features from the general characteristics obtained by the analysis on all genes, which is consistent with the structural diversity of essential regions across different protein classes. We demonstrate that the function-specific 3D features of the variants match the readouts of mutagenesis experiments for BRCA1 and PTEN, and positively correlate with an independent set of clinically interpreted pathogenic and benign missense variants. Finally, we make our results available through a web server to foster accessibility and downstream research. Our findings represent a crucial step toward translational genetics, from highlighting the impact of mutations on protein structure to rationalizing the variants’ pathogenicity in terms of the perturbed molecular mechanisms.
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BFBNIB, NMLJ, NUK, PNG, SAZU, UL, UM, UPUK
We report a genome-wide association study of venous thromboembolism (VTE) incorporating 81,190 cases and 1,419,671 controls sampled from six cohorts. We identify 93 risk loci, of which 62 are ...previously unreported. Many of the identified risk loci are at genes encoding proteins with functions converging on the coagulation cascade or platelet function. A VTE polygenic risk score (PRS) enabled effective identification of both high- and low-risk individuals. Individuals within the top 0.1% of PRS distribution had a VTE risk similar to homozygous or compound heterozygous carriers of the variants G20210A (c.*97 G > A) in F2 and p.R534Q in F5. We also document that F2 and F5 mutation carriers in the bottom 10% of the PRS distribution had a risk similar to that of the general population. We further show that PRS improved individual risk prediction beyond that of genetic and clinical risk factors. We investigated the extent to which venous and arterial thrombosis share clinical risk factors using Mendelian randomization, finding that some risk factors for arterial thrombosis were directionally concordant with VTE risk (for example, body mass index and smoking) whereas others were discordant (for example, systolic blood pressure and triglyceride levels).
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GEOZS, IJS, IMTLJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBMB, UL, UM, UPUK, ZAGLJ
Cerebral malaria is a deadly outcome of infection by Plasmodium falciparum, occurring when parasite-infected erythrocytes accumulate in the brain. These erythrocytes display parasite proteins of the ...PfEMP1 family that bind various endothelial receptors. Despite the importance of cerebral malaria, a binding phenotype linked to its symptoms has not been identified. Here, we used structural biology to determine how a group of PfEMP1 proteins interacts with intercellular adhesion molecule 1 (ICAM-1), allowing us to predict binders from a specific sequence motif alone. Analysis of multiple Plasmodium falciparum genomes showed that ICAM-1-binding PfEMP1s also interact with endothelial protein C receptor (EPCR), allowing infected erythrocytes to synergistically bind both receptors. Expression of these PfEMP1s, predicted to bind both ICAM-1 and EPCR, is associated with increased risk of developing cerebral malaria. This study therefore reveals an important PfEMP1-binding phenotype that could be targeted as part of a strategy to prevent cerebral malaria.
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•Structural basis for P. falciparum PfEMP1 binding to endothelial receptor ICAM-1defined•A sequence motif derived from structure predicts group A PfEMP1 binding to ICAM-1•These ICAM-1-binding PfEMP1s also all bind to endothelial protein C receptor (EPCR)•Expression of dual ICAM-1- and EPCR-binding PfEMP1 is associated with cerebral malaria
Plasmodium falciparum-infected erythrocytes display PfEMP1 proteins that bind various endothelial receptors, including ICAM-1. Lennartz et al. structurally characterize PfEMP1 binding to ICAM-1, allowing them to identify a PfEMP1 family that simultaneously binds to both ICAM-1 and EPCR. Dual-binding PfEMP1s display stronger endothelial adhesion and are associated with cerebral malaria.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Plasmodium falciparum erythrocyte membrane protein-1 (PfEMP-1) is a highly polymorphic adherence receptor expressed on the surface of infected erythrocytes. Based on sequence homology PfEMP-1 ...variants have been grouped into three major groups A-C, the highly conserved VAR2CSA variants, and semi-conserved types defined by tandem runs of specific domains ("domain cassettes" (DC)). The PfEMP-1 type expressed determines the adherence phenotype, and is associated with clinical outcome of infection.
Parasite isolates from Beninese children or women presenting with, respectively, CM or PAM were collected along with samples from patients with uncomplicated malaria (UM). We assessed the transcript level of var genes by RT-qPCR and the expression of PfEMP-1 proteins by LC-MS/MS.
Var genes encoding DC8 and Group A PfEMP-1 were transcribed more often and at higher levels in cerebral malaria vs. uncomplicated malaria patients. LC-MS/MS identified peptides from group A, DC8 PfEMP-1 more frequently in cerebral malaria than in uncomplicated malaria and pregnancy-associated malaria samples.
This is the first study to show association between PfEMP-1 subtype and disease outcome by direct analysis of parasites proteome. The results corroborate that group A and specifically the PfEMP-1 types DC8 are universally associated with cerebral malaria. This is a crucial observation for promoting studies on malaria pathogenesis.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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