scholarly journals Incorporation of CD55 into the Zika Viral Envelope Contributes to Its Stability against Human Complement

Viruses ◽  
2021 ◽  
Vol 13 (3) ◽  
pp. 510
Author(s):  
Zahra Malekshahi ◽  
Sarah Bernklau ◽  
Britta Schiela ◽  
Iris Koske ◽  
Zoltan Banki ◽  
...  
Keyword(s):  
Serum Concentration ◽  
Human Cells ◽  
Viral Envelope ◽  
Human Complement ◽  
Western Blots ◽  
Capture Assay ◽  
Mucosal Surfaces ◽  
Regulator Protein ◽  
Complement Regulator ◽  
The Stability

The rapid spread of the virus in Latin America and the association of the infection with microcephaly in newborns or Guillain–Barré Syndrome in adults prompted the WHO to declare the Zika virus (ZIKV) epidemic to be an international public health emergency in 2016. As the virus was first discovered in monkeys and is spread not only by mosquitos but also from human to human, we investigated the stability to the human complement of ZIKV derived from mosquito (ZIKVInsect), monkey (ZIKVVero), or human cells (ZIKVA549 and ZIKVFibro), respectively. At a low serum concentration (10%), which refers to complement concentrations found on mucosal surfaces, the virus was relatively stable at 37 °C. At higher complement levels (up to 50% serum concentration), ZIKV titers differed significantly depending on the cell line used for the propagation of the virus. While the viral titer of ZIKVInsect decreased about two orders in magnitude, when incubated with human serum, the virus derived from human cells was more resistant to complement-mediated lysis (CML). By virus-capture assay and Western blots, the complement regulator protein CD55 was identified to be incorporated into the viral envelope. Blocking of CD55 by neutralizing Abs significantly increased the sensitivity to human complement. Taken together, these data indicate that the incorporation of CD55 from human cells contributes to the stability of ZIKV against complement-mediated virolysis.

Mechanism of complement regulator Factor H mediated pneumococcal uptake by human cells

2010 ◽  
Vol 47 (13) ◽  
pp. 2242-2242
Author(s):  
Vaibhav Agarwal ◽  
Tauseef Asmat ◽  
Shanshan Luo ◽  
Peter F. Zipfel ◽  
Sven Hammerschmidt
Keyword(s):  
Human Cells ◽  
Factor H ◽  
Complement Regulator

scholarly journals Temperature Regulation of the Hemin Storage (Hms+) Phenotype of Yersinia pestis Is Posttranscriptional

2004 ◽  
Vol 186 (6) ◽  
pp. 1638-1647 ◽  
Author(s):  
Robert D. Perry ◽  
Alexander G. Bobrov ◽  
Olga Kirillina ◽  
Heather A. Jones ◽  
Lisa Pedersen ◽  
...  
Keyword(s):  
Membrane Proteins ◽  
Yersinia Pestis ◽  
Growth Temperature ◽  
Temperature Regulation ◽  
Iron Status ◽  
Outer Membrane Proteins ◽  
Western Blots ◽  
Protein Levels ◽  
The Stability ◽  
In Cells

ABSTRACT In Yersinia pestis, the Congo red (and hemin) binding that is characteristic of the Hms+ phenotype occurs at temperatures up to 34°C but not at higher temperatures. Manifestation of the Hms+ phenotype requires at least five proteins (HmsH, -F, -R, -S, and -T) that are organized into two separate operons: hmsHFRS and hmsT. HmsH and HmsF are outer membrane proteins, while HmsR, HmsS, and HmsT are predicted to be inner membrane proteins. We have used transcriptional reporter constructs, RNA dot blots, and Western blots to examine the expression of hms operons and proteins. Our studies indicate that transcription from the hmsHFRS and hmsT promoters is not regulated by the iron status of the cells, growth temperature, or any of the Hms proteins. In addition, the level of mRNA for both operons is not significantly affected by growth temperature. However, protein levels of HmsH, HmsR, and HmsT in cells grown at 37°C are very low compared to those in cells grown at 26°C, while the amounts of HmsF and HmsS show only a moderate reduction at the higher growth temperature. Neither the Pla protease nor a putative endopeptidase (Y2360) encoded upstream of hmsH is essential for temperature regulation of the Hms+ phenotype. However, HmsT at 37°C is sensitive to degradation by Lon and/or ClpPX. Thus, the stability of HmsH, HmsR, and HmsT proteins likely plays a role in temperature regulation of the Hms+ phenotype of Y. pestis.

230 Leptospira Immunoglobulin-like proteins bind human complement regulator Factor H

2010 ◽  
Vol 47 (13) ◽  
pp. 2248-2248
Author(s):  
Mónica M. Castiblanco Valencia ◽  
Tatiana R. Fraga ◽  
Ludmila B. Silva ◽  
Patrícia A.E. Abreu ◽  
Angela S. Barbosa ◽  
...  
Keyword(s):  
Factor H ◽  
Human Complement ◽  
Complement Regulator

A novel strategy for preventing PERV transmission to human cells by remodeling the viral envelope glycoprotein

2006 ◽  
Vol 13 (3) ◽  
pp. 258-263 ◽  
Author(s):  
Shuji Miyagawa ◽  
Shino Nakatsu ◽  
Kenji Hazama ◽  
Takatoshi Nakagawa ◽  
Akihiro Kondo ◽  
...  
Keyword(s):  
Envelope Glycoprotein ◽  
Human Cells ◽  
Viral Envelope ◽  
Viral Envelope Glycoprotein ◽  
Novel Strategy ◽  
Perv Transmission

scholarly journals Differential localization of tropomyosin isoforms in cultured nonmuscle cells.

1988 ◽  
Vol 107 (2) ◽  
pp. 563-572 ◽  
Author(s):  
J J Lin ◽  
T E Hegmann ◽  
J L Lin
Keyword(s):  
Molecular Mass ◽  
Chicken Embryo Fibroblast ◽  
Polyclonal Antiserum ◽  
Western Blots ◽  
Tropomyosin Isoforms ◽  
Lower Molecular Mass ◽  
Nonmuscle Cells ◽  
Double Label ◽  
Sequential Absorption ◽  
The Stability

We have previously shown that chicken embryo fibroblast (CEF) cells and human bladder carcinoma (EJ) cells contain multiple isoforms of tropomyosin, identified as a, b, 1, 2, and 3 in CEF cells and 1, 2, 3, 4, and 5 in human EJ cells by one-dimensional SDS-PAGE (Lin, J. J.-C., D. M. Helfman, S. H. Hughes, and C.-S. Chou. 1985. J. Cell Biol. 100: 692-703; and Lin, J. J.-C., S. Yamashiro-Matsumura, and F. Matsumura. 1984. Cancer Cells 1:57-65). Both isoform 3 (TM-3) of CEF and isoforms 4,5 (TM-4,-5) of human EJ cells are the minor isoforms found respectively in normal chicken and human cells. They have a lower apparent molecular mass and show a weaker affinity to actin filaments when compared to the higher molecular mass isoforms. Using individual tropomyosin isoforms immobilized on nitrocellulose papers and sequential absorption of polyclonal antiserum on these papers, we have prepared antibodies specific to CEF TM-3 and to CEF TM-1,-2. In addition, two of our antitropomyosin mAbs, CG beta 6 and CG3, have now been demonstrated by Western blots, immunoprecipitation, and two-dimensional gel analysis to have specificities to human EJ TM-3 and TM-5, respectively. By using these isoform-specific reagents, we are able to compare the intracellular localizations of the lower and higher molecular mass isoforms in both CEF and human EJ cells. We have found that both lower and higher molecular mass isoforms of tropomyosin are localized along stress fibers of cells, as one would expect. However, the lower molecular mass isoforms are also distributed in regions near ruffling membranes. Further evidence for this different localization of different tropomyosin isoforms comes from double-label immunofluorescence microscopy on the same CEF cells with affinity-purified antibody against TM-3, and monoclonal CG beta 6 antibody against TM-a, -b, -1, and -2 of CEF tropomyosin. The presence of the lower molecular mass isoform of tropomyosin in ruffling membranes may indicate a novel way for the nonmuscle cell to control the stability and organization of microfilaments, and to regulate the cell motility.

scholarly journals Loss of Factor H family proteins associates with meningococcal disease severity

2021 ◽  
Author(s):  
Anna E. van Beek ◽  
Richard B. Pouw ◽  
Victoria J. Wright ◽  
Neneh Sallah ◽  
David Inwald ◽  
...  
Keyword(s):  
Renal Failure ◽  
Meningococcal Disease ◽  
Tissue Injury ◽  
Protein Family ◽  
Factor H ◽  
Host Tissue ◽  
Human Complement ◽  
Complement Regulator ◽  
Circulating Levels ◽  
Over Time

ABSTRACTNeisseria meningitidis, the causative agent of meningococcal disease (MD), evades complement-mediated clearance upon infection by ‘hijacking’ the human complement regulator factor H (FH). The FH protein family also comprises the homologous FH-related (FHR) proteins, hypothesized to act as antagonists of FH, and FHR-3 has recently been implicated to play a major role in MD susceptibility. Here, we show that, next to FH and FHR-3, the circulating levels of all FH family proteins are equally decreased during pediatric MD. We did not observe a specific consumption of FH or FHR-3 by N. meningitidis during the first days of infection and the levels recovered over time. MD severity associated predominantly with a loss of FH. Strikingly, loss of FH and FHRs associated strongly with renal failure, suggesting insufficient protection of host tissue by the FH protein family. Retaining higher levels of FH family proteins may thus limit tissue injury during MD.

scholarly journals Entamoeba histolytica develops resistance to complement deposition and lysis after acquisition of human complement regulatory proteins through trogocytosis

2021 ◽  
Author(s):  
Hannah W. Miller ◽  
Tammie S.Y. Tam ◽  
Katherine S. Ralston
Keyword(s):  
Entamoeba Histolytica ◽  
Regulatory Protein ◽  
Human Cells ◽  
Jurkat Cells ◽  
Human Complement ◽  
Complement Regulatory Proteins ◽  
Complement Regulators ◽  
Novel Strategy ◽  
Complement Deposition ◽  
Complement Lysis

Entamoeba histolytica is the cause of amoebiasis. The trophozoite (amoeba) form of this parasite is capable of invading the intestine, and can disseminate through the bloodstream to other organs. The mechanisms that allow amoebae to evade complement deposition during dissemination have not been well characterized. We previously discovered a novel complement-evasion mechanism employed by E. histolytica. E. histolytica ingests small bites of living human cells in a process termed trogocytosis. We demonstrated that amoebae were protected from lysis by human serum following trogocytosis of human cells, and that amoebae acquired and displayed human membrane proteins from the cells they ingested. Here, we aimed to define how amoebae are protected from complement lysis after performing trogocytosis. We found that amoebae were protected from complement lysis after ingestion of both human Jurkat T cells and red blood cells, and that the level of protection correlated with the amount of material ingested. Trogocytosis of human cells led to a reduction in deposition of C3b on the surface of amoebae. We asked whether display of human complement regulators is involved in amoebic protection, and found that CD59 was displayed by amoebae after trogocytosis. Deletion of a single complement regulatory protein, CD59 or CD46, from Jurkat cells was not sufficient to alter amoebic protection. Removal of all GPI-anchored proteins, including CD59 and CD55, from the surface of amoebae that had undergone trogocytosis suggested that multiple, redundant complement regulators mediate amoebic protection. These studies shed light on a novel strategy for immune evasion by a pathogen.

scholarly journals The RAD51 recombinase protects mitotic chromatin in human cells

2020 ◽  
Author(s):  
Isabel E. Wassing ◽  
Xanita Saayman ◽  
Lucia Rampazzo ◽  
Christine Ralf ◽  
Andrew Bassett ◽  
...  
Keyword(s):  
Dna Damage ◽  
Spindle Assembly Checkpoint ◽  
De Novo ◽  
Human Cells ◽  
Replication Forks ◽  
Chromosomal Replication ◽  
Anaphase Onset ◽  
The Stability ◽  
Stalled Replication Forks ◽  
Mitotic Chromatin

AbstractThe RAD51 recombinase plays critical roles in safeguarding genome integrity, which is fundamentally important for all living cells. While interphase functions of RAD51 in repairing broken DNA and protecting stalled replication forks are well characterised, its role in mitosis remains contentious. In this study, we show that RAD51 protects under-replicated DNA in mitotic human cells and, in this way, promotes mitotic DNA synthesis (MiDAS) and successful chromosome segregation. MiDAS was globally detectable irrespective of DNA damage and was promoted by de novo RAD51 recruitment, RAD51-mediated fork protection, and RAD51 phosphorylation by the key mitotic regulator Polo-like kinase 1. Importantly, acute inhibition of RAD51-promoted MiDAS led to mitotic DNA damage, delayed anaphase onset and induced centromere fragility, revealing a mechanism that prevents the satisfaction of the spindle assembly checkpoint when chromosomal replication remains incomplete. This study hence identifies an unexpected function of RAD51 in promoting the stability of mitotic chromatin.

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