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Crenarchaeal CdvA Forms Double-Helical Filaments Containing DNA and Interacts with ESCRT-III-Like CdvB  [PDF]
Christine Moriscot,Simonetta Gribaldo,Jean-Michel Jault,Mart Krupovic,Julie Arnaud,Marc Jamin,Guy Schoehn,Patrick Forterre,Winfried Weissenhorn,Patricia Renesto
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0021921
Abstract: The phylum Crenarchaeota lacks the FtsZ cell division hallmark of bacteria and employs instead Cdv proteins. While CdvB and CdvC are homologues of the eukaryotic ESCRT-III and Vps4 proteins, implicated in membrane fission processes during multivesicular body biogenesis, cytokinesis and budding of some enveloped viruses, little is known about the structure and function of CdvA. Here, we report the biochemical and biophysical characterization of the three Cdv proteins from the hyperthermophilic archaeon Metallospherae sedula.
Un-“ESCRT”-ed Budding  [PDF]
Mark Yondola,Carol Carter
Viruses , 2011, DOI: 10.3390/v3010026
Abstract: In their recent publication, Rossman et al. [1] describe how the inherent budding capability of its M2 protein allows influenza A virus to bypass recruitment of the cellular ESCRT machinery enlisted by several other enveloped RNA and DNA viruses, including HIV, Ebola, rabies, herpes simplex type 1 and hepatitis B. Studies from the same laboratory [2] and other laboratories [3–6] indicate that budding of plasmid-derived virus-like particles can be mediated by the influenza virus hemagglutinin and neuraminidase proteins in the absence of M2. These events are also independent of canonical ESCRT components [2,7]. Understanding how intrinsic properties of these influenza virus proteins permit ESCRT-independent budding expands our understanding of the budding process?itself.
A Unique Role for the Host ESCRT Proteins in Replication of Tomato bushy stunt virus  [PDF]
Daniel Barajas,Yi Jiang,Peter D. Nagy
PLOS Pathogens , 2009, DOI: 10.1371/journal.ppat.1000705
Abstract: Plus-stranded RNA viruses replicate in infected cells by assembling viral replicase complexes consisting of viral- and host-coded proteins. Previous genome-wide screens with Tomato bushy stunt tombusvirus (TBSV) in a yeast model host revealed the involvement of seven ESCRT (endosomal sorting complexes required for transport) proteins in viral replication. In this paper, we show that the expression of dominant negative Vps23p, Vps24p, Snf7p, and Vps4p ESCRT factors inhibited virus replication in the plant host, suggesting that tombusviruses co-opt selected ESCRT proteins for the assembly of the viral replicase complex. We also show that TBSV p33 replication protein interacts with Vps23p ESCRT-I and Bro1p accessory ESCRT factors. The interaction with p33 leads to the recruitment of Vps23p to the peroxisomes, the sites of TBSV replication. The viral replicase showed reduced activity and the minus-stranded viral RNA in the replicase became more accessible to ribonuclease when derived from vps23Δ or vps24Δ yeast, suggesting that the protection of the viral RNA is compromised within the replicase complex assembled in the absence of ESCRT proteins. The recruitment of ESCRT proteins is needed for the precise assembly of the replicase complex, which might help the virus evade recognition by the host defense surveillance system and/or prevent viral RNA destruction by the gene silencing machinery.
Noncanonical Role for the Host Vps4 AAA+ ATPase ESCRT Protein in the Formation of Tomato Bushy Stunt Virus Replicase  [PDF]
Daniel Barajas equal contributor,Isabel Fernández de Castro Martín equal contributor,Judit Pogany,Cristina Risco ,Peter D. Nagy
PLOS Pathogens , 2014, DOI: doi/10.1371/journal.ppat.1004087
Abstract: Assembling of the membrane-bound viral replicase complexes (VRCs) consisting of viral- and host-encoded proteins is a key step during the replication of positive-stranded RNA viruses in the infected cells. Previous genome-wide screens with Tomato bushy stunt tombusvirus (TBSV) in a yeast model host have revealed the involvement of eleven cellular ESCRT (endosomal sorting complexes required for transport) proteins in viral replication. The ESCRT proteins are involved in endosomal sorting of cellular membrane proteins by forming multiprotein complexes, deforming membranes away from the cytosol and, ultimately, pinching off vesicles into the lumen of the endosomes. In this paper, we show an unexpected key role for the conserved Vps4p AAA+ ATPase, whose canonical function is to disassemble the ESCRT complexes and recycle them from the membranes back to the cytosol. We find that the tombusvirus p33 replication protein interacts with Vps4p and three ESCRT-III proteins. Interestingly, Vps4p is recruited to become a permanent component of the VRCs as shown by co-purification assays and immuno-EM. Vps4p is co-localized with the viral dsRNA and contacts the viral (+)RNA in the intracellular membrane. Deletion of Vps4p in yeast leads to the formation of crescent-like membrane structures instead of the characteristic spherule and vesicle-like structures. The in vitro assembled tombusvirus replicase based on cell-free extracts (CFE) from vps4Δ yeast is highly nuclease sensitive, in contrast with the nuclease insensitive replicase in wt CFE. These data suggest that the role of Vps4p and the ESCRT machinery is to aid building the membrane-bound VRCs, which become nuclease-insensitive to avoid the recognition by the host antiviral surveillance system and the destruction of the viral RNA. Other (+)RNA viruses of plants and animals might also subvert Vps4p and the ESCRT machinery for formation of VRCs, which require membrane deformation and spherule formation.
Protein–Protein Interaction Network and Subcellular Localization of the Arabidopsis Thaliana ESCRT Machinery  [PDF]
Lynn G. L. Richardson,Robert T. Mullen
Frontiers in Plant Science , 2011, DOI: 10.3389/fpls.2011.00020
Abstract: The endosomal sorting complex required for transport (ESCRT) consists of several multi-protein subcomplexes which assemble sequentially at the endosomal surface and function in multivesicular body (MVB) biogenesis. While ESCRT has been relatively well characterized in yeasts and mammals, comparably little is known about ESCRT in plants. Here we explored the yeast two-hybrid protein interaction network and subcellular localization of the Arabidopsis thaliana ESCRT machinery. We show that the Arabidopsis ESCRT interactome possesses a number of protein–protein interactions that are either conserved in yeasts and mammals or distinct to plants. We show also that most of the Arabidopsis ESCRT proteins examined at least partially localize to MVBs in plant cells when ectopically expressed on their own or co-expressed with other interacting ESCRT proteins, and some also induce abnormal MVB phenotypes, consistent with their proposed functional role(s) as part of the ESCRT machinery in Arabidopsis. Overall, our results help define the plant ESCRT machinery by highlighting both conserved and unique features when compared to ESCRT in other evolutionarily diverse organisms, providing a foundation for further exploration of ESCRT in plants.
TRPC3 and TRPC6 Contribute to the Pathogenesis of Hypertension  [PDF]
Qin Zou, Cui Zhang, Yuqing Guo
American Journal of Molecular Biology (AJMB) , 2015, DOI: 10.4236/ajmb.2015.54011
Abstract: Recently studies found that TRPC3 and TRPC6 played an important role in cardiovascular disease. Hypertension, as a cardiovascular disease causing the highest morbidity and mortality, has close relationship with the expressions of TRPC3 and TRPC6. Unbalanced calcium homeostasis is the major factor of pathogenesis of hypertension. Changes of intracellular calcium concentration depend on calcium transmembrane transportation, intracellular calcium store releasing and other processes. TRPC3, TRPC6 molecules, as non-selective cation channels on the cell membranes, are involved in the processes. This review illustrated the functions of TRPC3 and TRPC6 on myocardial cells, smooth muscle cells and inflammatory cells in the development of hypertension, and the effects of drugs like sildenafil to provide a new way for the prevention and treatment of hypertension.
A Novel TRPC6 Mutation That Causes Childhood FSGS  [PDF]
Saskia F. Heeringa,Clemens C. M?ller,Jianyang Du,Lixia Yue,Bernward Hinkes,Gil Chernin,Christopher N. Vlangos,Peter F. Hoyer,Jochen Reiser,Friedhelm Hildebrandt
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0007771
Abstract: TRPC6, encoding a member of the transient receptor potential (TRP) superfamily of ion channels, is a calcium-permeable cation channel, which mediates capacitive calcium entry into the cell. Until today, seven different mutations in TRPC6 have been identified as a cause of autosomal-dominant focal segmental glomerulosclerosis (FSGS) in adults.
The Serine 814 of TRPC6 Is Phosphorylated under Unstimulated Conditions  [PDF]
Simon M. Bousquet,Michael Monet,Guylain Boulay
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0018121
Abstract: TRPC are nonselective cation channels involved in calcium entry. Their regulation by phosphorylation has been shown to modulate their routing and activity. TRPC6 activity increases following phosphorylation by Fyn, and is inhibited by protein kinase G and protein kinase C. A previous study by our group showed that TRPC6 is phosphorylated under unstimulated conditions in a human embryonic kidney cells line (HEK293). To investigate the mechanism responsible for this phosphorylation, we used a MS/MS approach combined with metabolic labeling and showed that the serine at position 814 is phosphorylated in unstimulated cells. The mutation of Ser814 into Ala decreased basal phosphorylation but did not modify TRPC6 activity. Even though Ser814 is within a consensus site for casein kinase II (CK2), we showed that CK2 is not involved in the phosphorylation of TRPC6 and does not modify its activity. In summary, we identified a new basal phosphorylation site (Ser814) on TRPC6 and showed that CK2 is not responsible for the phosphorylation of this site.
Involvement of ESCRT-II in Hepatitis B Virus Morphogenesis  [PDF]
Jens T. Stieler, Reinhild Prange
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0091279
Abstract: The hepatitis B virus (HBV) is an enveloped DNA virus that replicates via reverse transcription of its pregenomic RNA (pgRNA). Budding of HBV is supposed to occur at intracellular membranes and requires scission functions of the endosomal sorting complex required for transport (ESCRT) provided by ESCRT-III and VPS4. Here, we have investigated the impact of the upstream-acting ESCRT-I and ESCRT-II complexes in HBV morphogenesis. RNA interference knockdown of the ESCRT-I subunits TSG101 and VPS28 did not block, but rather stimulate virus release. In contrast, RNAi-mediated depletion of the ESCRT-II components EAP20, EAP30 and EAP45 greatly reduced virus egress. By analyzing different steps of the HBV maturation pathway, we find that the knockdown of ESCRT-II not only inhibited the production and/or release of enveloped virions, but also impaired intracellular nucleocapsid formation. Transcription/translation studies revealed that the depletion of ESCRT-II neither affected the synthesis and nuclear export of HBV-specific RNAs nor the expression of the viral core and envelope proteins. Moreover, the absence of ESCRT-II had no effects on the assembly capability and integrity of HBV core/capsids. However, the level of encapsidated pgRNA was significantly reduced in ESCRT-II-depleted cells, implicating that ESCRT-II directs steps accompanying the formation of replication-competent nucleocapsids, like e.g. assisting in RNA trafficking and encapsidation. In support of this, the capsid protein was found to interact and colocalize with ESCRT-II subunits in virus-producing cells. Together, these results indicate an essential role for ESCRT-II in the HBV life cycle and suggest that ESCRT-II functions prior to the final HBV budding reaction.
TRPC6 Single Nucleotide Polymorphisms and Progression of Idiopathic Membranous Nephropathy  [PDF]
Julia M. Hofstra, Marieke J. H. Coenen, Mascha M. V. A. P. Schijvenaars, Jo H. M. Berden, Johan van der Vlag, Lies H. Hoefsloot, Nine V. A. M. Knoers, Jack F. M. Wetzels, Tom Nijenhuis
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0102065
Abstract: Background Activating mutations in the Transient Receptor Potential channel C6 (TRPC6) cause autosomal dominant focal segmental glomerular sclerosis (FSGS). TRPC6 expression is upregulated in renal biopsies of patients with idiopathic membranous glomerulopathy (iMN) and animal models thereof. In iMN, disease progression is characterized by glomerulosclerosis. In addition, a context-dependent TRPC6 overexpression was recently suggested in complement-mediated podocyte injury in e.g. iMN. Hence, we hypothesized that genetic variants in TRPC6 might affect susceptibility to development or progression of iMN. Methods & Results Genomic DNA was isolated from blood samples of 101 iMN patients and 292 controls. By direct sequencing of the entire TRPC6 gene, 13 single nucleotide polymorphisms (SNPs) were identified in the iMN cohort, two of which were causing an amino acid substitution (rs3802829; Pro15Ser and rs36111323, Ala404Val). No statistically significant differences in genotypes or allele frequencies between patients and controls were observed. Clinical outcome in patients was determined (remission n = 26, renal failure n = 46, persistent proteinuria n = 29, follow-up median 80 months {range 51–166}). The 13 identified SNPs showed no association with remission or renal failure. There were no differences in genotypes or allele frequencies between patients in remission and progressors. Conclusions Our data suggest that TRPC6 polymorphisms do not affect susceptibility to iMN, or clinical outcome in iMN.
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