Guanylate Binding Proteins promote anti-Leishmania Host Cell Defense

SUMMARYHeparin-binding proteins (HBPs) play a key role in Trypanosoma cruzi-host cell interactions. HBPs recognize heparan sulfate (HS) at the host cell surface and are able to induce the cytoadherence and invasion of this parasite. Herein, we analysed the biochemical properties of the HBPs and also evaluated the expression and subcellular localization of HBPs in T. cruzi trypomastigotes. A flow cytometry analysis revealed that HBPs are highly expressed at the surface of trypomastigotes, and their peculiar localization mainly at the flagellar membrane, which is known as an important signalling domain, may enhance their binding to HS and elicit the parasite invasion. The plasmon surface resonance results demonstrated the stability of HBPs and their affinity to HS and heparin. Additionally, gelatinolytic activities of 70 kDa, 65·8 kDa and 59 kDa HBPs over a broad pH range (5·5–8·0) were revealed using a zymography assay. These proteolytic activities were sensitive to serine proteinase inhibitors, such as aprotinin and phenylmethylsulfonyl fluoride, suggesting that HBPs have the properties of trypsin-like proteinases.

Download Full-text

Truncation of Fibronectin-Binding Proteins in Staphylococcus aureus Strain Newman Leads to Deficient Adherence and Host Cell Invasion Due to Loss of the Cell Wall Anchor Function

Infection and Immunity ◽

10.1128/iai.72.12.7155-7163.2004 ◽

2004 ◽

Vol 72 (12) ◽

pp. 7155-7163 ◽

Cited By ~ 106

Author(s):

Matthias Grundmeier ◽

Muzaffar Hussain ◽

Petra Becker ◽

Christine Heilmann ◽

Georg Peters ◽

...

Keyword(s):

Staphylococcus Aureus ◽

Cell Wall ◽

Host Cell ◽

Cell Invasion ◽

Binding Proteins ◽

Stop Codon ◽

Aureus Strain ◽

Host Cell Invasion ◽

Fibronectin Receptor ◽

Fibronectin Binding

ABSTRACT Staphylococcus aureus fibronectin-binding proteins (FnBPs) play a critical role in S. aureus pathogenesis. FnBPs mediate adhesion to fibronectin and invasion of mammalian cells, including epithelial, endothelial, and fibroblastic cells, by fibronectin bridging to the host cell fibronectin receptor integrin (α5)β1. Strain Newman is a laboratory strain frequently used for genetic, functional, and in vivo studies. However, despite pronounced production of FnBPs, strain Newman is only weakly adherent to immobilized Fn and weakly invasive. We examined whether these effects are due to a structural difference of FnBPs. Here, we show that both fnbA Newman and fnbB Newman contain a centrally located point mutation resulting in a stop codon. This leads to a truncation of both FnBPs at the end of the C domain at identical positions. Most likely, the stop codon occurred first in fnbB Newman and was subsequently transferred to fnbA Newman by replacement of the entire region encompassing the C, D, and W domains with the respective sequence of fnbB Newman. Using heterologous expression in Staphylococcus carnosus, we found that truncated FnBPs were completely secreted into the culture medium and not anchored to the cell wall, since they lack the sortase motif (LPETG). Consequently, this led to a loss of FnBP-dependent functions, such as strong adhesion to immobilized fibronectin, binding of fibrinogen, and host cell invasion. This mutation may explain some of the earlier reported conflicting data with strain Newman. Thus, care should be taken when drawing negative conclusions about the role of FnBPs as a virulence factor in a given model.

Download Full-text

Rotavirus RNAs sponge host cell RNA binding proteins and interfere with their subcellular localization

Virology ◽

10.1016/j.virol.2018.09.013 ◽

2018 ◽

Vol 525 ◽

pp. 96-105 ◽

Cited By ~ 5

Author(s):

Alfonso Oceguera ◽

Andrea V. Peralta ◽

Gustavo Martínez-Delgado ◽

Carlos F. Arias ◽

Susana López

Keyword(s):

Subcellular Localization ◽

Host Cell ◽

Binding Proteins ◽

Rna Binding ◽

Rna Binding Proteins

Download Full-text

Leishmania: manipulation of signaling pathways to inhibit host cell apoptosis

Therapeutic Advances in Infectious Disease ◽

10.1177/20499361211014977 ◽

2021 ◽

Vol 8 ◽

pp. 204993612110149

Author(s):

Sandra-Georgina Solano-Gálvez ◽

Diego-Abelardo Álvarez-Hernández ◽

Laila Gutiérrez-Kobeh ◽

Rosalino Vázquez-López

Keyword(s):

Cell Death ◽

Host Cell ◽

Signaling Pathways ◽

Defense Mechanism ◽

Morphological Changes ◽

Wide Spectrum ◽

Chromatin Condensation ◽

Mitogen Activated Protein Kinase ◽

Type I ◽

Cell Defense

The maintenance of homeostasis in living systems requires the elimination of unwanted cells which is performed, among other mechanisms, by type I cell death or apoptosis. This type of programmed cell death involves several morphological changes such as cytoplasm shrinkage, chromatin condensation (pyknosis), nuclear fragmentation (karyorrhexis), and plasma membrane blebbing that culminate with the formation of apoptotic bodies. In addition to the maintenance of homeostasis, apoptosis also represents an important defense mechanism for cells against intracellular microorganisms. In counterpart, diverse intracellular pathogens have developed a wide array of strategies to evade apoptosis and persist inside cells. These strategies include the manipulation of signaling pathways involved in the inhibition of apoptosis where mitogen-activated protein kinase (MAPK) and phosphoinositide 3-kinase (PI3K) play a key role. Leishmania is an intracellular protozoan parasite that causes a wide spectrum of diseases known as leishmaniasis. This parasite displays different strategies, including apoptosis inhibition, to down-regulate host cell defense mechanisms in order to perpetuate infection.

Download Full-text

The Secreted Acid Phosphatase Domain-Containing GRA44 from Toxoplasma gondii Is Required for c-Myc Induction in Infected Cells

mSphere ◽

10.1128/msphere.00877-19 ◽

2020 ◽

Vol 5 (1) ◽

Cited By ~ 6

Author(s):

William J. Blakely ◽

Michael J. Holmes ◽

Gustavo Arrizabalaga

Keyword(s):

Acid Phosphatase ◽

Toxoplasma Gondii ◽

Host Cell ◽

Secretory Pathway ◽

Parasitophorous Vacuole ◽

Severe Disease ◽

Immune Recognition ◽

Phosphatase Domain ◽

Content Type ◽

Cell Defense

ABSTRACT During host cell invasion, the eukaryotic pathogen Toxoplasma gondii forms a parasitophorous vacuole to safely reside within the cell, while it is partitioned from host cell defense mechanisms. From within this safe niche, parasites sabotage multiple host cell systems, including gene expression, apoptosis, and intracellular immune recognition, by secreting a large arsenal of effector proteins. Many parasite proteins studied for active host cell manipulative interactions have been kinases. The translocation of effectors from the parasitophorous vacuole into the host cell is mediated by a putative translocon complex, which includes the proteins MYR1, MYR2, and MYR3. Whether other proteins are involved in the structure or regulation of this putative translocon is not known. We have discovered that the secreted protein GRA44, which contains a putative acid phosphatase domain, interacts with members of this complex and is required for host cell effects downstream of effector secretion. We have determined that GRA44 is processed in a region with homology to sequences targeted by protozoan proteases of the secretory pathway and that both major cleavage fragments are secreted into the parasitophorous vacuole. Immunoprecipitation experiments showed that GRA44 interacts with a large number of secreted proteins, including MYR1. Importantly, conditional knockdown of GRA44 resulted in a lack of host cell c-Myc upregulation, which mimics the phenotype seen when members of the translocon complex are genetically disrupted. Thus, the putative acid phosphatase GRA44 is crucial for host cell alterations during Toxoplasma infection and is associated with the translocon complex which Toxoplasma relies upon for success as an intracellular pathogen. IMPORTANCE Approximately one-third of humans are infected with the parasite Toxoplasma gondii. Toxoplasma infections can lead to severe disease in those with a compromised or suppressed immune system. Additionally, infections during pregnancy present a significant health risk to the developing fetus. Drugs that target this parasite are limited, have significant side effects, and do not target all disease stages. Thus, a thorough understanding of how the parasite propagates within a host is critical in the discovery of novel therapeutic targets. Toxoplasma replication requires that it enter the cells of the infected organism. In order to survive the environment inside a cell, Toxoplasma secretes a large repertoire of proteins, which hijack a number of important cellular functions. How these Toxoplasma proteins move from the parasite into the host cell is not well understood. Our work shows that the putative phosphatase GRA44 is part of a protein complex responsible for this process.

Download Full-text

Picornavirus Modification of a Host mRNA Decay Protein

mBio ◽

10.1128/mbio.00431-12 ◽

2012 ◽

Vol 3 (6) ◽

Cited By ~ 41

Author(s):

Janet M. Rozovics ◽

Amanda J. Chase ◽

Andrea L. Cathcart ◽

Wayne Chou ◽

Paul D. Gershon ◽

...

Keyword(s):

Host Cell ◽

Mrna Decay ◽

Binding Proteins ◽

Rna Binding ◽

Rna Binding Proteins ◽

Binding Protein ◽

Rna Binding Protein ◽

Rna Replication ◽

Human Rhinovirus ◽

Genomic Rnas

ABSTRACTDue to the limited coding capacity of picornavirus genomic RNAs, host RNA binding proteins play essential roles during viral translation and RNA replication. Here we describe experiments suggesting that AUF1, a host RNA binding protein involved in mRNA decay, plays a role in the infectious cycle of picornaviruses such as poliovirus and human rhinovirus. We observed cleavage of AUF1 during poliovirus or human rhinovirus infection, as well as interaction of this protein with the 5′ noncoding regions of these viral genomes. Additionally, the picornavirus proteinase 3CD, encoded by poliovirus or human rhinovirus genomic RNAs, was shown to cleave all four isoforms of recombinant AUF1 at a specific N-terminal sitein vitro. Finally, endogenous AUF1 was found to relocalize from the nucleus to the cytoplasm in poliovirus-infected HeLa cells to sites adjacent to (but distinct from) putative viral RNA replication complexes.IMPORTANCEThis study derives its significance from reporting how picornaviruses like poliovirus and human rhinovirus proteolytically cleave a key player (AUF1) in host mRNA decay pathways during viral infection. Beyond cleavage of AUF1 by the major viral proteinase encoded in picornavirus genomes, infection by poliovirus results in the relocalization of this host cell RNA binding protein from the nucleus to the cytoplasm. The alteration of both the physical state of AUF1 and its cellular location illuminates how small RNA viruses manipulate the activities of host cell RNA binding proteins to ensure a faithful intracellular replication cycle.

Download Full-text

Ehrlichia chaffeensis TRP32 Interacts with Host Cell Targets That Influence Intracellular Survival

Infection and Immunity ◽

10.1128/iai.00154-12 ◽

2012 ◽

Vol 80 (7) ◽

pp. 2297-2306 ◽

Cited By ~ 33

Author(s):

Tian Luo ◽

Jere W. McBride

Keyword(s):

Host Cell ◽

Defense Mechanisms ◽

Ring Finger ◽

Elongation Factor ◽

Intracellular Survival ◽

Mononuclear Phagocytes ◽

Ehrlichia Chaffeensis ◽

Content Type ◽

Cell Defense

ABSTRACTEhrlichia chaffeensisis an obligately intracellular bacterium that exhibits tropism for mononuclear phagocytes and survives by evading host cell defense mechanisms. Recently, molecular interactions ofE. chaffeensistandem repeat proteins 47 and 120 (TRP47 and -120) and the eukaryotic host cell have been described. In this investigation, yeast two-hybrid analysis demonstrated that anE. chaffeensistype 1 secretion system substrate, TRP32, interacts with a diverse group of human proteins associated with major biological processes of the host cell, including protein synthesis, trafficking, degradation, immune signaling, cell signaling, iron metabolism, and apoptosis. Eight target proteins, including translation elongation factor 1 alpha 1 (EF1A1), deleted in azoospermia (DAZ)-associated protein 2 (DAZAP2), ferritin light polypeptide (FTL), CD63, CD14, proteasome subunit beta type 1 (PSMB1), ring finger and CCCH-type domain 1 (RC3H1), and tumor protein p53-inducible protein 11 (TP53I11) interacted with TRP32 as determined by coimmunoprecipitation assays, colocalization with TRP32 in HeLa and THP-1 cells, and/or RNA interference. Interactions between TRP32 and host targets localized to theE. chaffeensismorulae or in the host cell cytoplasm adjacent to morulae. Common or closely related interacting partners ofE. chaffeensisTRP32, TRP47, and TRP120 demonstrate a molecular convergence on common cellular processes and molecular cross talk betweenEhrlichiaTRPs and host targets. These findings further support the role of TRPs as effectors that promote intracellular survival.

Download Full-text

Late Endosomal/Lysosomal Cholesterol Accumulation Is a Host Cell-Protective Mechanism Inhibiting Endosomal Escape of Influenza A Virus

mBio ◽

10.1128/mbio.01345-18 ◽

2018 ◽

Vol 9 (4) ◽

Cited By ~ 13

Author(s):

Alexander Kühnl ◽

Agnes Musiol ◽

Nicole Heitzig ◽

Danielle E. Johnson ◽

Christina Ehrhardt ◽

...

Keyword(s):

Host Cell ◽

Influenza A Virus ◽

Influenza A ◽

Membrane Lipids ◽

Endosomal Escape ◽

Host Cells ◽

Protective Mechanism ◽

Cholesterol Accumulation ◽

Protective Function ◽

Cell Defense

ABSTRACTTo transfer the viral genome into the host cell cytoplasm, internalized influenza A virus (IAV) particles depend on the fusion of the IAV envelope with host endosomal membranes. The antiviral host interferon (IFN) response includes the upregulation of interferon-induced transmembrane protein 3 (IFITM3), which inhibits the release of the viral content into the cytosol. Although IFITM3 induction occurs concomitantly with late endosomal/lysosomal (LE/L) cholesterol accumulation, the functional significance of this process is not well understood. Here we report that LE/L cholesterol accumulation itself plays a pivotal role in the early antiviral defense. We demonstrate that inducing LE/L cholesterol accumulation is antiviral in non-IFN-primed cells, restricting incoming IAV particles and impairing mixing of IAV/endosomal membrane lipids. Our results establish a protective function of LE/L cholesterol accumulation and suggest endosomal cholesterol balance as a possible antiviral target.IMPORTANCEWith annual epidemics occurring in all parts of the world and the risk of global outbreaks, influenza A virus (IAV) infections remain a major threat to public health. Infected host cells detect viral components and mount an interferon (IFN)-mediated response to restrict virus propagation and spread of infection. Identification of cellular factors and underlying mechanisms that establish such an antiviral state can provide novel strategies for the development of antiviral drugs. The contribution of LE/L cholesterol levels, especially in the context of the IFN-induced antiviral response, has remained controversial so far. Here, we report that accumulation of cholesterol in the LE/L compartment contributes to the IFN-induced host cell defense against incoming IAV. Our results establish cholesterol accumulation in LE/Lper seas a novel antiviral barrier and suggest the endosomal cholesterol balance as a putative druggable host cell factor in IAV infection.

Download Full-text

Functional BvgAS Virulence Control System in Bordetella bronchiseptica Is Necessary for Induction of Ca2+ Transients in Ciliated Tracheal Epithelial Cells

Infection and Immunity ◽

10.1128/iai.71.12.7208-7210.2003 ◽

2003 ◽

Vol 71 (12) ◽

pp. 7208-7210 ◽

Cited By ~ 5

Author(s):

Nathan A. Groathouse ◽

Robert A. Heinzen ◽

Scott Boitano

Keyword(s):

Host Cell ◽

Cell System ◽

Cell Interactions ◽

Bordetella Bronchiseptica ◽

Avirulent Strain ◽

Wild Type ◽

Tracheal Epithelial Cells ◽

Cell Defense ◽

Host Cell Interactions ◽

Tracheal Epithelial

ABSTRACT To study initial Bordetella bronchiseptica-tracheal epithelial cell interactions, we coincubated B. bronchiseptica with rabbit tracheal explant cultures and assayed bacterial adherence and host cell Ca2+ signaling. Wild-type B. bronchiseptica (RB50) preferentially adhered to cilia and induced ciliated host cell Ca2+ transients within 2 min of coincubation, whereas coincubation with an avirulent strain (RB57) resulted in limited binding and Ca2+ signaling. The described cell system allows for assessment of initial B. bronchiseptica-host cell interactions that can contribute to pathogenicity or to host cell defense.

Download Full-text