scholarly journals Cyclic Dimeric GMP Signaling Regulates Intracellular Aggregation, Sessility, and Growth of Ehrlichia chaffeensis

2011 ◽  
Vol 79 (10) ◽  
pp. 3905-3912 ◽  
Author(s):  
Yumi Kumagai ◽  
Junji Matsuo ◽  
Zhihui Cheng ◽  
Yoshihiro Hayakawa ◽  
Yasuko Rikihisa

ABSTRACTCyclic dimeric GMP (c-di-GMP), a bacterial second messenger, is known to regulate bacterial biofilm and sessility. Replication of an obligatory intracellular pathogen,Ehrlichia chaffeensis, is characterized by formation of bacterial aggregates called morulae inside membrane-bound inclusions. WhenE. chaffeensismatures into an infectious form, morulae become loose to allow bacteria to exit from host cells to infect adjacent cells.E. chaffeensisexpresses a sensor kinase, PleC, and a cognate response regulator, PleD, which can produce c-di-GMP. A hydrophobic c-di-GMP antagonist, 2′-O-di(tert-butyldimethysilyl)-c-di-GMP (CDGA) inhibitsE. chaffeensisinternalization into host cells by facilitating degradation of some bacterial surface proteins via endogenous serine proteases. In the present study, we found that PleC and PleD were upregulated synchronously during exponential growth of bacteria, concomitant with increased morula size. While CDGA did not affect host cells, when infected cells were treated with CDGA, bacterial proliferation was inhibited, morulae became less compact, and the intracellular movement of bacteria was enhanced. Concurrently, CDGA treatment facilitated the extracellular release of bacteria with lower infectivity than those spontaneously released from sham-treated cells. Addition of CDGA to isolated inclusions induced dispersion of the morulae, degradation of an inclusion matrix protein TRP120, and bacterial intrainclusion movement, all of which were blocked by a serine protease inhibitor. These results suggest that c-di-GMP signaling regulates aggregation and sessility ofE. chaffeensiswithin the inclusion through stabilization of matrix proteins by preventing the serine protease activity, which is associated with bacterial intracellular proliferation and maturation.

2018 ◽  
Vol 87 (1) ◽  
Author(s):  
Kashif S. Haleem ◽  
Youssif M. Ali ◽  
Hasan Yesilkaya ◽  
Thomas Kohler ◽  
Sven Hammerschmidt ◽  
...  

ABSTRACTComplement is a critical component of antimicrobial immunity. Various complement regulatory proteins prevent host cells from being attacked. Many pathogens have acquired the ability to sequester complement regulators from host plasma to evade complement attack. We describe here howStreptococcus pneumoniaeadopts a strategy to prevent the formation of the C3 convertase C4bC2a by the rapid conversion of surface bound C4b and iC4b into C4dg, which remains bound to the bacterial surface but no longer forms a convertase complex. Noncapsular virulence factors on the pneumococcus are thought to facilitate this process by sequestering C4b-binding protein (C4BP) from host plasma. WhenS. pneumoniaeD39 was opsonized with human serum, the larger C4 activation products C4b and iC4b were undetectable, but the bacteria were liberally decorated with C4dg and C4BP. With targeted deletions of either PspA or PspC, C4BP deposition was markedly reduced, and there was a corresponding reduction in C4dg and an increase in the deposition of C4b and iC4b. The effect was greatest when PspA and PspC were both knocked out. Infection experiments in mice indicated that the deletion of PspA and/or PspC resulted in the loss of bacterial pathogenicity. Recombinant PspA and PspC both bound serum C4BP, and both led to increased C4b and reduced C4dg deposition onS. pneumoniaeD39. We conclude that PspA and PspC help the pneumococcus to evade complement attack by binding C4BP and so inactivating C4b.


2004 ◽  
Vol 32 (1) ◽  
pp. 21-27 ◽  
Author(s):  
R.B. Sim ◽  
S.A. Tsiftsoglou

The complement system is a group of about 35 soluble and cell-surface proteins which interact to recognize, opsonize and clear or kill invading micro-organisms or altered host cells (e.g. apoptotic or necrotic cells). Complement is a major part of the innate immune system. Recognition proteins such as C1q, MBL (mannan-binding lectin) and ficolins bind to targets via charge or sugar arrays. Binding causes activation of a series of serine protease proenzymes, such as C1r, C1s and MASP2 (MBL-associated serine protease 2), which in turn activate the atypical serine proteases factor B and C2, which then activate the major opsonin of the system, C3. Activated C3 binds covalently to targets, and is recognized by receptors on phagocytic cells. Two of the complement proteases, factors D and I, circulate not as proenzymes, but in activated form, and they have no natural inhibitors; their substrates are transient protein complexes (e.g. C3bB and C3bH) which form during complement activation. Factor B and C2 also have no natural inhibitor; they are active only when proteolytically cleaved and bound in an unstable, short-lived complex with C3b or C4b. C1r, C1s and the MASPs, in contrast, are regulated more conventionally by the natural serpin, C1-inhibitor. Complement proteases in general have very narrow specificity, and low substrate turnover with both natural and synthetic substrates. Excessive activation of complement is inflammatory, and causes tissue damage (e.g. in rheumatoid arthritis, or in ischaemia/reperfusion injury). Substances that regulate complement activation are likely to be useful in the regulation of inflammation. Complement activation might potentially be controlled at many different steps. Much attention has been focused on controlling the formation or activity of the protease complexes C3bBb and C4b2a (containing activated factor B and C2 respectively), as these generate the inflammatory peptides C3a and C5a.


2007 ◽  
Vol 98 (09) ◽  
pp. 488-496 ◽  
Author(s):  
Patric Nitsche-Schmitz ◽  
Manfred Rohde ◽  
Gursharan Chhatwal

SummaryGram-positive cocci are important human pathogens. Streptococci and staphylococci in particular are a major threat to human health,since they cause a variety of serious invasive infections. Their invasion into normally sterile sites of the host depends on elaborated bacterial mechanisms that involve adhesion to the host tissue, its degradation, internalisation by host cells, and passage through epithelia and endothelia. Interactions of bacterial surface proteins with proteins of the host’s extracellular matrix as well as with cell surface receptors are crucial factors in these processes, and some of the key mechanisms are similar in many pathogenic Gram-positive cocci.Therapies that interfere with these mechanisms may become efficient alternatives to today’s antibiotic treatments.


mSphere ◽  
2020 ◽  
Vol 5 (4) ◽  
Author(s):  
Lei-Jie Jia ◽  
Thomas Krüger ◽  
Matthew G. Blango ◽  
Ferdinand von Eggeling ◽  
Olaf Kniemeyer ◽  
...  

ABSTRACT Aspergillus fumigatus is one of the most common airborne molds capable of causing mycoses and allergies in humans. During infection, fungal surface proteins mediate the first contact with the human immune system to evade immune responses or to induce hypersensitivity. Several methods have been established for surface proteomics (surfomics). Biotinylation coupled with liquid chromatography-tandem mass spectrometry (LC-MS/MS) identification of peptides is a particularly efficient method to identify the surface-exposed regions of proteins that potentially mediate interaction with the host. After biotinylation of surface proteins during spore germination, we detected 231 different biotinylated surface proteins (including several well-known proteins such as RodA, CcpA, and DppV; allergens; and heat shock proteins [HSPs]), as well as some previously undescribed surface proteins. The dynamic change of the surface proteome was illustrated by detection of a relatively high number of proteins exclusively at one developmental stage. Using immunofluorescence microscopy, we confirmed the surface localization of several HSPs of the HSP70 family, which may have moonlighting functions. Collectively, by comparing our data with data representative of previously published A. fumigatus surface proteomes, our study generated a comprehensive data set corresponding to the A. fumigatus surfome and uncovered the surface-exposed regions of many proteins on the surface of conidia or hyphae. These surface-exposed regions are candidates for direct interaction with host cells and may represent antigenic epitopes that either induce protective immune responses or mediate immune evasion. Thus, our data sets provided and compiled here represent reasonable immunotherapy and diagnostic targets for future investigations. IMPORTANCE Aspergillus fumigatus is the most important airborne human-pathogenic mold, capable of causing both life-threatening invasive pulmonary aspergillosis in immunocompromised patients and allergy-inducing infections in individuals with atopic allergy. Despite its obvious medical relevance, timely diagnosis and efficient antifungal treatment of A. fumigatus infection remain major challenges. Proteins on the surface of conidia (asexually produced spores) and mycelium directly mediate host-pathogen interaction and also may serve as targets for diagnosis and immunotherapy. However, the similarity of protein sequences between A. fumigatus and other organisms, sometimes even including the human host, makes selection of targets for immunological-based studies difficult. Here, using surface protein biotinylation coupled with LC-MS/MS analysis, we identified hundreds of A. fumigatus surface proteins with exposed regions, further defining putative targets for possible diagnostic and immunotherapeutic design.


2018 ◽  
Vol 200 (8) ◽  
Author(s):  
Roberto E. Bruna ◽  
María Victoria Molino ◽  
Martina Lazzaro ◽  
Javier F. Mariscotti ◽  
Eleonora García Véscovi

ABSTRACTPrtA is the major secreted metalloprotease ofSerratia marcescens. Previous reports implicate PrtA in the pathogenic capacity of this bacterium. PrtA is also clinically used as a potent analgesic and anti-inflammatory drug, and its catalytic properties attract industrial interest. Comparatively, there is scarce knowledge about the mechanisms that physiologically govern PrtA expression inSerratia. In this work, we demonstrate that PrtA production is derepressed when the bacterial growth temperature decreases from 37°C to 30°C. We show that this thermoregulation occurs at the transcriptional level. We determined that upstream ofprtA, there is a conserved motif that is directly recognized by the CpxR transcriptional regulator. This feature is found alongSerratiastrains irrespective of their isolation source, suggesting an evolutionary conservation of CpxR-dependent regulation of PrtA expression. We found that inS. marcescens, the CpxAR system is more active at 37°C than at 30°C. In good agreement with these results, in acpxRmutant background,prtAis derepressed at 37°C, while overexpression of the NlpE lipoprotein, a well-known CpxAR-inducing condition, inhibits PrtA expression, suggesting that the levels of the activated form of CpxR are increased at 37°C over those at 30°C. In addition, we establish that PrtA is involved in the ability ofS. marcescensto develop biofilm. In accordance, CpxR influences the biofilm phenotype only when bacteria are grown at 37°C. In sum, our findings shed light on regulatory mechanisms that fine-tune PrtA expression and reveal a novel role for PrtA in the lifestyle ofS. marcescens.IMPORTANCEWe demonstrate thatS. marcescensmetalloprotease PrtA expression is transcriptionally thermoregulated. While strongly activated below 30°C, its expression is downregulated at 37°C. We found that inS. marcescens, the CpxAR signal transduction system, which responds to envelope stress and bacterial surface adhesion, is activated at 37°C and able to downregulate PrtA expression by direct interaction of CpxR with a binding motif located upstream of theprtAgene. Moreover, we reveal that PrtA expression favors the ability ofS. marcescensto develop biofilm, irrespective of the bacterial growth temperature. In this context, thermoregulation along with a highly conserved CpxR-dependent modulation mechanism gives clues about the relevance of PrtA as a factor implicated in the persistence ofS. marcescenson abiotic surfaces and in bacterial host colonization capacity.


2011 ◽  
Vol 79 (11) ◽  
pp. 4370-4381 ◽  
Author(s):  
Bing Zhu ◽  
Jeeba A. Kuriakose ◽  
Tian Luo ◽  
Efren Ballesteros ◽  
Sharu Gupta ◽  
...  

ABSTRACTEhrlichia chaffeensisis an obligately intracellular bacterium that modulates host cell gene transcription in the mononuclear phagocyte, but the host gene targets and mechanisms involved in transcriptional modulation are not well-defined. In this study, we identified a novel tandem repeat DNA-binding domain in theE. chaffeensis120-kDa tandem repeat protein (TRP120) that directly binds host cell DNA. TRP120 was observed by immunofluorescent microscopy in the nucleus ofE. chaffeensis-infected host cells and was detected in nuclear extracts by Western immunoblotting with TRP120-specific antibody. The TRP120 binding sites and associated host cell target genes were identified using high-throughput deep sequencing (Illumina) of immunoprecipitated DNA (chromatin immunoprecipitation and high-throughput DNA sequencing). Multiple em motif elicitation (MEME) analysis of the most highly enriched TRP120-bound sequences revealed a G+C-rich DNA motif, and recombinant TRP120 specifically bound synthetic oligonucleotides containing the motif. TRP120 target gene binding sites were mapped most frequently to intersecting regions (intron/exon; 49%) but were also identified in upstream regulatory regions (25%) and downstream locations (26%). Genes targeted by TRP120 were most frequently associated with transcriptional regulation, signal transduction, and apoptosis. TRP120 targeted inflammatory chemokine genes, CCL2, CCL20, and CXCL11, which were strongly upregulated duringE. chaffeensisinfection and were also upregulated by direct transfection with recombinant TRP120. This study reveals that TRP120 is a novel DNA-binding protein that is involved in a host gene transcriptional regulation strategy.


2021 ◽  
Vol 6 (1) ◽  
pp. 55-74
Author(s):  
Nurit P Azouz ◽  
Andrea Klingler ◽  
Victoria Callahan ◽  
Ivan Akhrymuk ◽  
Katarina Elez ◽  
...  

Background: Host proteases have been suggested to be crucial for dissemination of MERS, SARS-CoV, and SARS-CoV-2 coronaviruses, but the relative contribution of membrane versus intracellular proteases remains controversial. Transmembrane serine protease 2 (TMPRSS2) is regarded as one of the main proteases implicated in the coronavirus S protein priming, an important step for binding of the S protein to the angiotensin-converting enzyme 2 (ACE2) receptor before cell entry.  Methods: We developed a cell-based assay to identify TMPRSS2 inhibitors. Inhibitory activity was established in SARS-CoV-2 viral load systems. Results: We identified the human extracellular serine protease inhibitor (serpin) alpha 1 antitrypsin (A1AT) as a novel TMPRSS2 inhibitor. Structural modeling revealed that A1AT docked to an extracellular domain of TMPRSS2 in a conformation that is suitable for catalysis, resembling similar serine protease inhibitor complexes. Inhibitory activity of A1AT was established in a SARS-CoV-2 viral load system. Notably, plasma A1AT levels were associated with COVID-19 disease severity.  Conclusions: Our data support the key role of extracellular serine proteases in SARS CoV-2 infections and indicate that treatment with serpins, particularly the FDA-approved drug A1AT, may be effective in limiting SARS-CoV-2 dissemination by affecting the surface of the host cells.


mBio ◽  
2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Calvin K. Lee ◽  
Jérémy Vachier ◽  
Jaime de Anda ◽  
Kun Zhao ◽  
Amy E. Baker ◽  
...  

ABSTRACT What are bacteria doing during “reversible attachment,” the period of transient surface attachment when they initially engage a surface, besides attaching themselves to the surface? Can an attaching cell help any other cell attach? If so, does it help all cells or employ a more selective strategy to help either nearby cells (spatial neighbors) or its progeny (temporal neighbors)? Using community tracking methods at the single-cell resolution, we suggest answers to these questions based on how reversible attachment progresses during surface sensing for Pseudomonas aeruginosa strains PAO1 and PA14. Although PAO1 and PA14 exhibit similar trends of surface cell population increase, they show unanticipated differences when cells are considered at the lineage level and interpreted using the quantitative framework of an exactly solvable stochastic model. Reversible attachment comprises two regimes of behavior, processive and nonprocessive, corresponding to whether cells of the lineage stay on the surface long enough to divide, or not, before detaching. Stark differences between PAO1 and PA14 in the processive regime of reversible attachment suggest the existence of two surface colonization strategies. PAO1 lineages commit quickly to a surface compared to PA14 lineages, with early c-di-GMP-mediated exopolysaccharide (EPS) production that can facilitate the attachment of neighbors. PA14 lineages modulate their motility via cyclic AMP (cAMP) and retain memory of the surface so that their progeny are primed for improved subsequent surface attachment. Based on the findings of previous studies, we propose that the differences between PAO1 and PA14 are potentially rooted in downstream differences between Wsp-based and Pil-Chp-based surface-sensing systems, respectively. IMPORTANCE The initial pivotal phase of bacterial biofilm formation known as reversible attachment, where cells undergo a period of transient surface attachment, is at once universal and poorly understood. What is more, although we know that reversible attachment culminates ultimately in irreversible attachment, it is not clear how reversible attachment progresses phenotypically, as bacterial surface-sensing circuits fundamentally alter cellular behavior. We analyze diverse observed bacterial behavior one family at a time (defined as a full lineage of cells related to one another by division) using a unifying stochastic model and show that our findings lead to insights on the time evolution of reversible attachment and the social cooperative dimension of surface attachment in PAO1 and PA14 strains.


2012 ◽  
Vol 80 (6) ◽  
pp. 2008-2018 ◽  
Author(s):  
Archana Vaithilingam ◽  
Jose E. Teixeira ◽  
Peter J. Miller ◽  
Bradley T. Heron ◽  
Christopher D. Huston

ABSTRACTPhagocytosis of host cells is characteristic of tissue invasion by the intestinal amebaEntamoeba histolytica, which causes amebic dysentery and liver abscesses.Entamoeba histolyticainduces host cell apoptosis and uses ligands, including C1q, on apoptotic cells to engulf them. Two mass spectrometry analyses identified calreticulin in amebic phagosome preparations, and, in addition to its function as an endoplasmic reticulum chaperone, calreticulin is believed to be the macrophage receptor for C1q. The purpose of this study was to determine if calreticulin functions as anE. histolyticaC1q receptor during phagocytosis of host cells. Calreticulin was localized to the surface ofE. histolyticaduring interaction with both Jurkat lymphocytes and erythrocytes and was present in over 75% of phagocytic cups during amebic erythrophagocytosis. Presence of calreticulin on the cell surface was further demonstrated using a method that selectively biotinylated cell surface proteins and by flow cytometry using trophozoites overexpressing epitope-tagged calreticulin. Regulated overexpression of calreticulin increasedE. histolytica's ability to phagocytose apoptotic lymphocytes and calcium ionophore-treated erythrocytes but had no effect on amebic adherence to or destruction of cell monolayers or surface expression of the GalNAc lectin and serine-richE. histolyticaprotein (SREHP) receptors. Finally,E. histolyticacalreticulin bound specifically to apoptotic lymphocytes and to human C1q. Collectively, these data implicate cell surface calreticulin as a receptor for C1q duringE. histolyticaphagocytosis of host cells.


2021 ◽  
Author(s):  
Gaohui Sun ◽  
Yaqun Sui ◽  
Yang Zhou ◽  
Junlin Ya ◽  
Cai Yuan ◽  
...  

SARS-CoV-2 is the viral pathogen causing the COVID19 global pandemic. No effective treatment for COVID-19 has been established yet. TMPRSS2 is essential for viral spread and pathogenicity by facilitating the entry of SARS-CoV-2 onto host cells. The protease inhibitor camostat, an anticoagulant used in the clinic, has potential anti-inflammatory and anti-viral activities against COVID-19. However, the potential mechanisms of viral resistance and antiviral activity of camostat are unclear. Herein, we demonstrate high inhibitory potencies of camostat for a panel of serine proteases, indicating the camostat is a broad-spectrum inhibitor of serine proteases. In addition, we determined the crystal structure of camostat in complex with a serine protease (uPA), which reveals that camostat insert to the S1 pocket of uPA but was hydrolyzed by uPA, and the cleaved camostat covalently binds to the Ser195. We also generated the homology model of the structure of the TMPRSS2 serine protease domain. The model showed that camostat used the same inhibitory mechanism to inhibit the activity of TMPRSS2, and subsequently preventing SARS-CoV-2 spread. Importance section Serine proteases are a large family of enzymes critical for multiple physiological processes and proven diagnostic and therapeutic targets in several clinical indications. A serine protease transmembrane protease serine 2 (TMPRSS2) was recently found to mediate SARS-coronavirus 2 (SARS-CoV-2) entry into the host. camostat mesylate (FOY 305), a serine protease inhibitor active against TMPRSS2 and used for the treatment of oral squamous cell carcinoma and chronic pancreatitis, inhibits SARS-CoV-2 infection of human lung cells. However, the direct inhibition mechanism of camostat mesylate for TMPRSS2 is unclear. Herein, we demonstrate camostat used the same inhibitory mechanism to inhibit the activity of TMPRSS2 as uPA, and subsequently preventing SARS-CoV-2 spread.


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