RESUMEN
Methicillin-resistant Staphylococcus aureus, or MRSA, is one of the major causative agents of hospital-acquired infections worldwide. Novel antimicrobial strategies efficient against antibiotic-resistant strains are necessary and not only against S. aureus. Among those, strategies that aim at blocking or dismantling proteins involved in the acquisition of essential nutrients, helping the bacteria to colonize the host, are intensively studied. A major route for S. aureus to acquire iron from the host organism is the Isd (iron surface determinant) system. In particular, the hemoglobin receptors IsdH and IsdB located on the surface of the bacterium are necessary to acquire the heme moiety containing iron, making them a plausible antibacterial target. Herein, we obtained an antibody of camelid origin that blocked heme acquisition. We determined that the antibody recognized the heme-binding pocket of both IsdH and IsdB with nanomolar order affinity through its second and third complementary-determining regions. The mechanism explaining the inhibition of acquisition of heme in vitro could be described as a competitive process in which the complementary-determining region 3 from the antibody blocked the acquisition of heme by the bacterial receptor. Moreover, this antibody markedly reduced the growth of three different pathogenic strains of MRSA. Collectively, our results highlight a mechanism for inhibiting nutrient uptake as an antibacterial strategy against MRSA.
Asunto(s)
Anticuerpos Antibacterianos , Staphylococcus aureus Resistente a Meticilina , Receptores de Superficie Celular , Anticuerpos de Dominio Único , Humanos , Antibacterianos/farmacología , Hemo/metabolismo , Staphylococcus aureus Resistente a Meticilina/efectos de los fármacos , Receptores de Superficie Celular/metabolismo , Receptores de Superficie Celular/uso terapéutico , Anticuerpos de Dominio Único/biosíntesis , Anticuerpos de Dominio Único/química , Anticuerpos de Dominio Único/metabolismo , Anticuerpos de Dominio Único/farmacología , Infecciones Estafilocócicas/tratamiento farmacológico , Antígenos Bacterianos/inmunología , Anticuerpos Antibacterianos/genética , Anticuerpos Antibacterianos/inmunología , Camélidos del Nuevo Mundo , Animales , Unión Proteica/efectos de los fármacos , Modelos Moleculares , Simulación de Dinámica MolecularRESUMEN
Cation diffusion facilitators (CDFs) are a large family of divalent metal transporters with broad specificities that contribute to intracellular metal homeostasis and toxicity in bacterial pathogens. Streptococcus pyogenes (Group A Streptococcus [GAS]) expresses two homologous CDF efflux transporters, MntE and CzcD, which selectively transport Mn and Zn, respectively. We discovered that the MntE- and CzcD-deficient strains exhibited a marked decrease in the viability of macrophage-differentiated THP-1 cells and neutrophils. In addition, the viability of mice infected with both deficient strains markedly increased. Consistent with a previous study, our results suggest that MntE regulates the PerR-dependent oxidative stress response by maintaining intracellular Mn levels and contributing to the growth of GAS. The maturation and proteolytic activity of streptococcal cysteine protease (SpeB), an important virulence factor in GAS, has been reported to be abrogated by zinc and copper. Zn inhibited the maturation and proteolytic activity of SpeB in the culture supernatant of the CzcD-deficient strain. Furthermore, Mn inhibited SpeB maturation and proteolytic activity in a MntE-deficient strain. Since the host pathogenicity of the SpeB-deficient strain was significantly reduced, maintenance of intracellular manganese and zinc levels in the GAS via MntE and CzcD may not only confer metal resistance to the bacterium, but may also play an essential role in its virulence. These findings provide new insights into the molecular mechanisms of pathogenicity, which allow pathogens to survive under stressful conditions associated with elevated metal ion concentrations during host infection.
Asunto(s)
Evasión Inmune , Streptococcus pyogenes , Animales , Ratones , Streptococcus pyogenes/metabolismo , Metales/metabolismo , Zinc/metabolismo , Proteínas de Transporte de Membrana/metabolismo , Cationes Bivalentes/metabolismo , Proteínas Bacterianas/genética , Proteínas Bacterianas/metabolismo , Regulación Bacteriana de la Expresión GénicaRESUMEN
Streptococcus pyogenes causes a wide range of human infections. Currently, antibiotics are the main treatment for S. pyogenes infection, but serious anti-microbial resistance requires alternative treatment options. To develop a novel strategy for treatment, we physicochemically characterized SPs0871, a putative maltose/maltodextrin-binding protein that is thought to have important roles in the pathogenesis of invasive streptococci. We obtained a variable domain of heavy chain of heavy-chain antibody, the smallest unit of an antibody, which specifically binds to SPs0871. Although the VHH completely inhibited the binding of maltodextrins to SPs0871, the inhibition did not lead to growth suppression of the bacteria. Our results provide important insights for development of VHH as an anti-streptococcal therapeutic.
Asunto(s)
Antibacterianos/farmacología , Proteínas Bacterianas/antagonistas & inhibidores , Cadenas Pesadas de Inmunoglobulina/farmacología , Polisacáridos/antagonistas & inhibidores , Streptococcus pyogenes/efectos de los fármacos , Antibacterianos/química , Proteínas Bacterianas/química , Cadenas Pesadas de Inmunoglobulina/química , Pruebas de Sensibilidad Microbiana , Polisacáridos/química , Streptococcus pyogenes/químicaRESUMEN
Streptococcus pyogenes (Group A Streptococcus, GAS) causes a range of human diseases, including life-threatening and severe invasive GAS infections, such as streptococcal toxic shock syndrome (STSS). Several antibiotics, including penicillin, are effective against GAS. Still, invasive GAS diseases have a high mortality rate (>30%). Clinical isolates from STSS patients show higher expression of pore-forming streptolysin O (SLO). Thus, SLO is an important pathogenic factor for GAS and may be an effective target for treatment of GAS disease. We succeeded in obtaining a single-chain variable fragment (scFv) SLO-I4 capable of recognizing SLO, which significantly inhibited GAS-induced cell lytic activity in erythrocytes, macrophages, and epithelial cells. In epithelial cells, SLO-I4 significantly reduced SLO-mediated endosomal membrane damage, which consequently prevented bacterial escape from the endosome. The effectiveness of anti-SLO scFv in counteracting SLO function suggests that it might be beneficial against GAS infections.
Asunto(s)
Anticuerpos de Cadena Única/inmunología , Infecciones Estreptocócicas/inmunología , Streptococcus pyogenes/inmunología , Estreptolisinas/inmunología , Proteínas Bacterianas/inmunología , Células HeLa , Hemólisis , HumanosRESUMEN
Autophagy is a cellular self-catabolic process wherein organelles, macromolecules, and invading microbes are sequestered in autophagosomes that fuse with lysosomes. In this study, we uncover the role of nitric oxide (NO) as a signaling molecule for autophagy induction via its downstream mediator, 8-nitroguanosine 3',5'-cyclic monophosphate (8-nitro-cGMP). We found that 8-nitro-cGMP-induced autophagy is mediated by Lys63-linked polyubiquitination and that endogenous 8-nitro-cGMP promotes autophagic exclusion of invading group A Streptococcus (GAS) from cells. 8-nitro-cGMP can modify Cys residues by S-guanylation of proteins. We showed that intracellular GAS is modified with S-guanylation extensively in autophagosomes-like vacuoles, suggesting the role of S-guanylation as a marker for selective autophagic degradation. This finding is supported by the fact that S-guanylated bacteria were selectively marked with polyubiquitin, a known molecular tag for selective transport to autophagosomes. These results collectively indicate that 8-nitro-cGMP plays a crucial role in cytoprotection during bacterial infections or inflammations via autophagy upregulation.
Asunto(s)
Autofagia , GMP Cíclico/análogos & derivados , Inmunidad Innata , Macrófagos/metabolismo , Streptococcus pyogenes/metabolismo , Animales , Proteína 5 Relacionada con la Autofagia , Proteínas Bacterianas/metabolismo , GMP Cíclico/metabolismo , Células HeLa , Humanos , Interferón gamma/farmacología , Lipopolisacáridos/farmacología , Proteínas Luminiscentes/biosíntesis , Proteínas Luminiscentes/genética , Macrófagos/efectos de los fármacos , Macrófagos/inmunología , Macrófagos/microbiología , Ratones , Ratones Noqueados , Proteínas Asociadas a Microtúbulos/deficiencia , Proteínas Asociadas a Microtúbulos/genética , Proteínas Asociadas a Microtúbulos/metabolismo , Óxido Nítrico/metabolismo , Poliubiquitina/metabolismo , Transporte de Proteínas , Transducción de Señal , Streptococcus pyogenes/inmunología , Streptococcus pyogenes/patogenicidad , Factores de Tiempo , Transfección , UbiquitinaciónRESUMEN
Xenophagy, also known as antibacterial autophagy, plays a role in host defence against invading pathogens such as Group A Streptococcus (GAS) and Salmonella. In xenophagy, autophagy receptors are used in the recognition of invading pathogens and in autophagosome maturation and autolysosome formation. However, the mechanism by which autophagy receptors are regulated during bacterial infection remains poorly elucidated. In this study, we identified LAMTOR2 and LAMTOR1, also named p14 and p18, respectively, as previously unrecognised xenophagy regulators that modulate the autophagy receptor TAX1BP1 in response to GAS and Salmonella invasion. LAMTOR1 was localized to bacterium-containing endosomes, and LAMTOR2 was recruited to bacterium-containing damaged endosomes in a LAMTOR1-dependent manner. LAMTOR2 was dispensable for the formation of autophagosomes targeting damaged membrane debris surrounding cytosolic bacteria, but it was critical for autolysosome formation, and LAMTOR2 interacted with the autophagy receptors NBR1, TAX1BP1, and p62 and was necessary for TAX1BP1 recruitment to pathogen-containing autophagosomes. Notably, knockout of TAX1BP1 caused a reduction in autolysosome formation and subsequent bacterial degradation. Collectively, our findings demonstrated that the LAMTOR1/2 complex is required for recruiting TAX1BP1 to autophagosomes and thereby facilitating autolysosome formation during bacterial infection.
Asunto(s)
Péptidos y Proteínas de Señalización Intracelular/metabolismo , Macroautofagia/fisiología , Proteínas de Neoplasias/metabolismo , Salmonella/patogenicidad , Western Blotting , Sistemas CRISPR-Cas/genética , Línea Celular , Células HeLa , Humanos , Inmunoprecipitación , Péptidos y Proteínas de Señalización Intracelular/genética , Macroautofagia/genética , Microscopía Fluorescente , Proteínas de Neoplasias/genéticaRESUMEN
BACKGROUND: Group A Streptococcus (GAS) is a major human pathogen, which is associated with a wide spectrum of invasive diseases, such as pharyngitis, scarlet fever, rheumatic fever, and streptococcal toxic shock syndrome (STSS). It is hypothesized that differences in GAS pathogenicity are related to the acquisition of diverse bacteriophages (phages). Nevertheless, the GAS genome also harbors clustered regularly interspaced short palindromic repeats (CRISPR) and CRISPR-associated (cas) genes, which play an important role in eliminating foreign DNA, including those of phages. However, the structure of prophages in GAS strains is mosaic, and the phylogenetic relationship between prophages and CRISPR is not clear. In this study, we analyzed CRISPR and prophage structure using 118 complete genome sequences of GAS strains to elucidate the relationship between two genomic elements. Additionally, phylogenetic and M-type analyses were performed. RESULTS: Of the 118 GAS strains, 80 harbored type I-C and/or II-A CRISPR/cas loci. A total of 553 spacer sequences were identified from CRISPR/cas loci and sorted into 229 patterns. We identified and classified 373 prophages into 14 groups. Some prophage groups shared a common integration site, and were related to M-type. We further investigated the correlation between spacer sequences and prophages. Of the 229 spacer sequence patterns, 203 were similar to that of other GAS prophages. No spacer showed similarity with that of a specific prophage group with mutL integration site. Moreover, the average number of prophages in strains with type II-A CRISPR was significantly less than that in type I-C CRISPR and non-CRISPR strains. However, there was no statistical difference between the average number of prophages in type I-C strains and that in non-CRISPR strains. CONCLUSIONS: Our results indicated that type II-A CRISPR may play an important role in eliminating phages and that the prophage integration site may be an important criterion for the acceptance of foreign DNA by GAS. M type, spacer sequence, and prophage group data were correlated with the phylogenetic relationships of GAS. Therefore, we hypothesize that genetic characteristics and/or phylogenetic relationships of GAS may be estimated by analyzing its spacer sequences.
Asunto(s)
Repeticiones Palindrómicas Cortas Agrupadas y Regularmente Espaciadas , Filogenia , Profagos/clasificación , Streptococcus pyogenes/genética , Evolución Molecular , Genoma Bacteriano , Streptococcus pyogenes/virología , Integración ViralRESUMEN
Streptococcus pyogenes, an important pathogen that causes a wide range of diseases, possesses the sia gene cluster, which encodes proteins involved in the heme acquisition system. Although this system was previously described, the molecular mechanism of effective heme transfer remains to be elucidated. Here, we have characterized the interactions between heme and each domain of Streptococcal hemoprotein receptor (Shr) and Streptococcal heme-binding protein (Shp). Our kinetic and thermodynamic analyses suggested that effective heme transfer within this system is achieved not only by affinity-based transfer but also by the difference of the binding driving force. The biophysical characterization of the above-mentioned interaction will lead to an indication for the selection of the target for a chemical screening of inhibitors as novel antibacterial agents based on biophysical approaches.
Asunto(s)
Proteínas Bacterianas/metabolismo , Proteínas Portadoras/metabolismo , Hemo/metabolismo , Hemoproteínas/metabolismo , Hemoglobinas/metabolismo , Infecciones Estreptocócicas/metabolismo , Streptococcus pyogenes/fisiología , Proteínas de Unión al Hemo , Humanos , Modelos Moleculares , Unión Proteica , Infecciones Estreptocócicas/microbiología , TermodinámicaRESUMEN
BACKGROUND: Group A Streptococcus (GAS; Streptococcus pyogenes) causes a range of mild to severe infections in humans. It can also colonize healthy persons asymptomatically. Therefore, it is important to study GAS carriage in healthy populations, as carriage of it might lead to subsequent disease manifestation, clonal spread in the community, and/or diversification of the organism. Throat swab culture is the gold standard method for GAS detection. Advanced culture-independent methods provide rapid and efficient detection of microorganisms directly from clinical samples. We investigated the presence of GAS in throat swab samples from healthy adults in Japan using culture-dependent and culture-independent methods. RESULTS: Two throat swab samples were collected from 148 healthy volunteers. One was cultured on selective medium, while total DNA extracted from the other was polymerase chain reaction (PCR) amplified with two GAS-specific primer pairs: one was a newly designed 16S rRNA-specific primer pair, the other a previously described V-Na+-ATPase primer pair. Although only 5 (3.4 %) of the 148 samples were GAS-positive by the culture-dependent method, 146 (98.6 %) were positive for the presence of GAS DNA by the culture-independent method. To obtain serotype information by emm typing, we performed nested PCR using newly designed emm primers. We detected the four different emm types in 25 (16.9 %) samples, and these differed from the common emm types associated with GAS associated diseases in Japan. The different emm types detected in the healthy volunteers indicate that the presence of unique emm types might be associated with GAS carriage. CONCLUSIONS: Our results suggest that culture-independent methods should be considered for profiling GAS in the healthy hosts, with a view to obtaining better understanding of these organisms. The GAS-specific primers (16S rRNA and V-Na+-ATPase) used in this study can be used to estimate the maximum potential GAS carriage in people.
Asunto(s)
Faringe/microbiología , Streptococcus pyogenes/genética , Streptococcus pyogenes/aislamiento & purificación , Adulto , Proteínas Bacterianas/genética , Técnicas de Tipificación Bacteriana/métodos , Cartilla de ADN , ADN Bacteriano/análisis , Genotipo , Humanos , Japón , Persona de Mediana Edad , Tipificación Molecular/métodos , Reacción en Cadena de la Polimerasa/métodos , ARN Ribosómico 16S/genética , Serotipificación , Infecciones Estreptocócicas/diagnóstico , Infecciones Estreptocócicas/microbiología , Adulto JovenRESUMEN
Autophagy plays a crucial role in host defence by facilitating the degradation of invading bacteria such as Group A Streptococcus (GAS). GAS-containing autophagosome-like vacuoles (GcAVs) form when GAS-targeting autophagic membranes entrap invading bacteria. However, the membrane origin and the precise molecular mechanism that underlies GcAV formation remain unclear. In this study, we found that Rab17 mediates the supply of membrane from recycling endosomes (REs) to GcAVs. We showed that GcAVs contain the RE marker transferrin receptor (TfR). Colocalization analyses demonstrated that Rab17 colocalized effectively with GcAV. Rab17 and TfR were visible as punctate structures attached to GcAVs and the Rab17-positive dots were recruited to the GAS-capturing membrane. Overexpression of Rab17 increased the TfR-positive GcAV content, whereas expression of the dominant-negative Rab17 form (Rab17 N132I) caused a decrease, thereby suggesting the involvement of Rab17 in RE-GcAV fusion. The efficiency of GcAV formation was lower in Rab17 N132I-overexpressing cells. Furthermore, knockdown of Rabex-5, the upstream activator of Rab17, reduced the GcAV formation efficiency. These results suggest that Rab17 and Rab17-mediated REs are involved in GcAV formation. This newly identified function of Rab17 in supplying membrane from REs to GcAVs demonstrates that RE functions as a primary membrane source during antibacterial autophagy.
Asunto(s)
Endosomas/metabolismo , Células Epiteliales/inmunología , Células Epiteliales/microbiología , Interacciones Huésped-Patógeno , Fagosomas/metabolismo , Streptococcus pyogenes/crecimiento & desarrollo , Proteínas de Unión al GTP rab/metabolismo , Autofagia , Factores de Intercambio de Guanina Nucleótido/metabolismo , Células HeLa , Humanos , Streptococcus pyogenes/inmunologíaRESUMEN
In recent years, reported cases of salmonellosis in cattle and horses in Hokkaido, Japan, have increased. To optimize antimicrobial therapy, we assessed the antimicrobial susceptibility of Salmonella isolates from these animals. Among 112 bovine isolates, high resistance rates were observed for streptomycin (92.0%), ampicillin (88.4%), and tetracycline (79.5%), while resistance rates for kanamycin (8.9%), ciprofloxacin (1.8%), gentamicin (0.0%), and colistin (0.0%) were low. Additionally, 18.8% of the bovine isolates were resistant to cefotaxime, and all of these cefotaxime-resistant isolates carried blaCMY-2. Among 16 equine isolates, no resistance was observed to cefazolin, cefotaxime, gentamicin, nalidixic acid, ciprofloxacin, colistin, or chloramphenicol. Gentamicin and kanamycin are recommended as the first-line treatment for salmonellosis in cattle, with fluoroquinolones as the second choice.
RESUMEN
Biparatopic antibodies (bpAbs) are engineered antibodies that bind to multiple different epitopes within the same antigens. bpAbs comprise diverse formats, including fragment-based formats, and choosing the appropriate molecular format for a desired function against a target molecule is a challenging task. Moreover, optimizing the design of constructs requires selecting appropriate antibody modalities and adjusting linker length for individual bpAbs. Therefore, it is crucial to understand the characteristics of bpAbs at the molecular level. In this study, we first obtained single-chain variable fragments and camelid heavy-chain variable domains targeting distinct epitopes of the metal binding protein MtsA and then developed a novel format single-chain bpAb connecting these fragment antibodies with various linkers. The physicochemical properties, binding activities, complex formation states with antigen, and functions of the bpAb were analyzed using multiple approaches. Notably, we found that the assembly state of the complexes was controlled by a linker and that longer linkers tended to form more compact complexes. These observations provide detailed molecular information that should be considered in the design of bpAbs.
Asunto(s)
Anticuerpos de Cadena Única , Anticuerpos de Cadena Única/química , Anticuerpos de Cadena Única/genética , Anticuerpos de Cadena Única/inmunología , Animales , Humanos , Ingeniería de Proteínas/métodos , Epítopos/química , Epítopos/inmunología , Cadenas Pesadas de Inmunoglobulina/química , Cadenas Pesadas de Inmunoglobulina/genética , Cadenas Pesadas de Inmunoglobulina/inmunologíaRESUMEN
Autophagy mediates the degradation of cytoplasmic contents in the lysosome and plays a significant role in immunity. Here we identified the small GTPases Rab9A and Rab23 as novel autophagy regulators during Group A streptococcus (GAS) infection. Rab9A was recruited to GAS-containing autophagosome-like vacuoles (GcAVs) after autophagosomal maturation and its activity was required for GcAV enlargement and eventual lysosomal fusion. GcAV enlargement appeared to be related to homotypic fusion of GcAVs with Rab9A. Rab23 was recruited to GAS-capturing forming autophagosomes. Knockdown of Rab23 expression decreased both LC3- and Atg5-positive GAS formation and caused the accumulation of LC3-positive structures that did not associate with intracellular GAS. It was suggested, therefore, that Rab23 is required for GcAV formation and is involved in GAS targeting of autophagic vacuoles. Furthermore, knockdown of Rab9A or Rab23 expression impaired the degradation of intracellular GAS. Therefore, our data reveal that the Rab9A and Rab23 GTPases play crucial roles in autophagy of GAS. However, neither Rab9A nor Rab23 were localized to starvation-induced autophagosomes. Not only Rab9A but also Rab23 was dispensable for starvation-induced autophagosome formation. These findings demonstrate that specific Rab proteins function at distinct steps during autophagy in response to GAS infection.
Asunto(s)
Autofagia , Infecciones Estreptocócicas/microbiología , Streptococcus pyogenes/fisiología , Proteínas de Unión al GTP rab/metabolismo , Técnicas de Silenciamiento del Gen , Células HeLa , Interacciones Huésped-Patógeno , Humanos , Lisosomas/enzimología , Lisosomas/microbiología , Fusión de Membrana , Viabilidad Microbiana , Microscopía Confocal , Fagosomas/enzimología , Fagosomas/microbiología , Transporte de Proteínas , Interferencia de ARN , Vacuolas/enzimología , Proteínas de Unión al GTP rab/genética , Proteínas de Unión al GTP rab/fisiologíaRESUMEN
Streptococcus mutans is the major pathogen of dental caries and occasionally causes infective endocarditis. Here we report the complete genome sequence of serotype k S. mutans strain LJ23, which was recently isolated from the oral cavity of a Japanese patient.
Asunto(s)
Genoma Bacteriano , Streptococcus mutans/clasificación , Streptococcus mutans/genética , Humanos , Datos de Secuencia Molecular , Boca/microbiología , SerotipificaciónRESUMEN
Streptococcus pyogenes (group A streptococcus (GAS)) is a pathogen that invades non-phagocytic host cells, and causes a variety of acute infections such as pharyngitis. Our group previously reported that intracellular GAS is effectively degraded by the host-cell autophagic machinery, and that a cholesterol-dependent cytolysin, streptolysin O (SLO), is associated with bacterial escape from endosomes in epithelial cells. However, the details of both the intracellular behavior of GAS and the process leading to its autophagic degradation remain unknown. In this study, we found that two host small G proteins, Rab5 and Rab7, were associated with the pathway of autophagosome formation and the fate of intracellular GAS. Rab5 was involved in bacterial invasion and endosome fusion. Rab7 was clearly multifunctional, with roles in bacterial invasion, endosome maturation, and autophagosome formation. In addition, this study showed that the bacterial cytolysin SLO supported the escape of GAS into the cytoplasm from endosomes, and surprisingly, a SLO-deficient mutant of GAS was viable longer than the wild-type strain although it failed to escape the endosomes. This intracellular behavior of GAS is unique and distinct from that of other types of bacterial invaders. Our results provide a new picture of GAS infection and host-cell responses in epithelial cells.
Asunto(s)
Autofagia , Espacio Intracelular/microbiología , Estreptolisinas/metabolismo , Proteínas de Unión al GTP rab/metabolismo , Proteínas de Unión al GTP rab5/metabolismo , Proteínas Bacterianas/metabolismo , Biomarcadores/metabolismo , Endosomas/microbiología , Endosomas/ultraestructura , Células HeLa , Humanos , Espacio Intracelular/metabolismo , Lisosomas/microbiología , Lisosomas/ultraestructura , Viabilidad Microbiana , Modelos Biológicos , Proteínas Mutantes/metabolismo , Fagosomas/metabolismo , Fagosomas/microbiología , Fagosomas/ultraestructura , Transporte de Proteínas , Streptococcus pyogenes/citología , Streptococcus pyogenes/metabolismo , Streptococcus pyogenes/ultraestructura , Factores de Tiempo , Proteínas de Unión a GTP rab7RESUMEN
Streptococcus pyogenes (group A streptococcus, GAS), one of the most common pathogens of humans, attaches and invades into human pharyngeal or skin epithelial cells. We have previously reported that induction of apoptosis is associated with GAS invasion, which induces mitochondrial dysfunction and apoptotic cell death. We demonstrate here that GAS-induced apoptosis is mediated by reactive oxygen species (ROS) production. Both the induction of apoptosis and ROS production markedly increased upon invasion of wild-type GAS strain JRS4 into HeLa cells; however, the apoptotic response was not observed in fibronectin-binding protein F1-disrupted mutant SAM1-infected cells. In Bcl-2-overexpressing HeLa cells (HBD98-2-4), the induction of apoptosis, ROS production and mitochondrial dysfunction were significantly suppressed, whereas the numbers of invaded GAS was not different between HeLa (mock cells) and the HeLa HBD98-2-4 cells. Whereas Rac1 activation occurred during GAS invasion, ROS production in GAS-infected cells was clearly inhibited by transfection with the Rac1 mutants (L37 or V12L37), but not by the dominant active mutant (V12L61) or by the dominant negative mutant (N17). These observations indicate that GAS invasion triggers ROS production through Rac1 activation and generated ROS induced mitochondrial dysfunction leading to cellular apoptosis.
Asunto(s)
Apoptosis , Células Epiteliales/microbiología , Especies Reactivas de Oxígeno/metabolismo , Especies Reactivas de Oxígeno/toxicidad , Streptococcus pyogenes/patogenicidad , Proteína de Unión al GTP rac1/metabolismo , Células HeLa , HumanosRESUMEN
Most bacteria naturally release spherical lipid-bilayered extracellular vesicles (EVs) containing proteins, nucleic acids, and virulence-related molecules, thus contributing to diverse biological functions including transport of virulence factors. The group A streptococcus, Streptococcus pyogenes (GAS), a major human pathogen, also releases EVs; however, it remains unclear how GAS EVs interact physiologically and pathologically with host cells, and what the differences are between invasive and non-invasive strains. The proteome profile in this study revealed that GAS EVs enclosed many virulence-related proteins such as streptolysin O and NAD-glycohydrolase, facilitating their pathogenicity, and invasive GAS EVs were more abundant than non-invasive counterparts. In terms of biological effects, invasive GAS EVs showed slo-dependent cytotoxic activity and the induction of cytokine expression, contributing to GAS pathogenicity directly. Although non-invasive GAS EVs did not show cytotoxic activity, they may be utilized as a means to prevent antibacterial mechanisms such as autophagy, leading to enhancement of their own survival in the intracellular environment after the infection. These results suggest that invasive and non-invasive GAS EVs play different roles in GAS infection strategy and pathogenicity. Our findings also indicate that EVs could be a key factor for GAS pathogenicity in GAS-host interactions.
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Vesículas Extracelulares , Monocitos/microbiología , Streptococcus pyogenes , Proteínas Bacterianas , Humanos , Inflamación , NAD+ Nucleosidasa , Virulencia , Factores de VirulenciaRESUMEN
Group A Streptococcus (GAS; Streptococcus pyogenes) is a major human pathogen that causes streptococcal pharyngitis, skin and soft tissue infections, and life-threatening conditions such as streptococcal toxic-shock syndrome. During infection, GAS not only invades diverse host cells but also injects effector proteins such as NAD-glycohydrolase (Nga) into the host cells through a streptolysin O (SLO)-dependent mechanism without invading the cells; Nga and SLO are two major virulence factors that are associated with increased bacterial virulence. Here, we have shown that the invading GAS induces fragmentation of the Golgi complex and inhibits anterograde transport in the infected host cells through the secreted toxins SLO and Nga. GAS infection-induced Golgi fragmentation required both bacterial invasion and SLO-mediated Nga translocation into the host cytosol. The cellular Golgi network is critical for the sorting of surface molecules and is thus essential for the integrity of the epithelial barrier and for the immune response of macrophages to pathogens. In epithelial cells, inhibition of anterograde trafficking by invading GAS and Nga resulted in the redistribution of E-cadherin to the cytosol and an increase in bacterial translocation across the epithelial barrier. Moreover, in macrophages, interleukin-8 secretion in response to GAS infection was found to be suppressed by intracellular GAS and Nga. Our findings reveal a previously undescribed bacterial invasion-dependent function of Nga as well as a previously unrecognized GAS-host interaction that is associated with GAS pathogenesis.IMPORTANCE Two prominent virulence factors of group A Streptococcus (GAS), streptolysin O (SLO) and NAD-glycohydrolase (Nga), are linked to enhanced pathogenicity of the prevalent GAS strains. Recent advances show that SLO and Nga are important for intracellular survival of GAS in epithelial cells and macrophages. Here, we found that invading GAS disrupts the Golgi complex in host cells through SLO and Nga. We show that GAS-induced Golgi fragmentation requires bacterial invasion into host cells, SLO pore formation activity, and Nga NADase activity. GAS-induced Golgi fragmentation results in the impairment of the epithelial barrier and chemokine secretion in macrophages. This immune inhibition property of SLO and Nga by intracellular GAS indicates that the invasion of GAS is associated with virulence exerted by SLO and Nga.
Asunto(s)
Células Epiteliales/microbiología , Aparato de Golgi/patología , Interacciones Huésped-Patógeno/genética , NAD+ Nucleosidasa/genética , Streptococcus pyogenes/patogenicidad , Estreptolisinas/genética , Células A549 , Proteínas Bacterianas/genética , Proteínas Bacterianas/metabolismo , Citoplasma/microbiología , Aparato de Golgi/genética , Aparato de Golgi/microbiología , Células HeLa , Interacciones Huésped-Patógeno/inmunología , Humanos , Interleucina-8/inmunología , NAD+ Nucleosidasa/metabolismo , Infecciones Estreptocócicas/microbiología , Streptococcus pyogenes/inmunología , Estreptolisinas/metabolismo , Células THP-1 , Factores de VirulenciaRESUMEN
Autophagy selectively targets invading bacteria to defend cells, whereas bacterial pathogens counteract autophagy to survive in cells. The initiation of canonical autophagy involves the PIK3C3 complex, but autophagy targeting Group A Streptococcus (GAS) is PIK3C3-independent. We report that GAS infection elicits both PIK3C3-dependent and -independent autophagy, and that the GAS effector NAD-glycohydrolase (Nga) selectively modulates PIK3C3-dependent autophagy. GAS regulates starvation-induced (canonical) PIK3C3-dependent autophagy by secreting streptolysin O and Nga, and Nga also suppresses PIK3C3-dependent GAS-targeting-autophagosome formation during early infection and facilitates intracellular proliferation. This Nga-sensitive autophagosome formation involves the ATG14-containing PIK3C3 complex and RAB1 GTPase, which are both dispensable for Nga-insensitive RAB9A/RAB17-positive autophagosome formation. Furthermore, although MTOR inhibition and subsequent activation of ULK1, BECN1, and ATG14 occur during GAS infection, ATG14 recruitment to GAS is impaired, suggesting that Nga inhibits the recruitment of ATG14-containing PIK3C3 complexes to autophagosome-formation sites. Our findings reveal not only a previously unrecognized GAS-host interaction that modulates canonical autophagy, but also the existence of multiple autophagy pathways, using distinct regulators, targeting bacterial infection.Abbreviations: ATG5: autophagy related 5; ATG14: autophagy related 14; ATG16L1: autophagy related 16 like 1; BECN1: beclin 1; CALCOCO2: calcium binding and coiled-coil domain 2; GAS: group A streptococcus; GcAV: GAS-containing autophagosome-like vacuole; LAMP1: lysosomal associated membrane protein 1; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; MTORC1: mechanistic target of rapamycin kinase complex 1; Nga: NAD-glycohydrolase; PIK3C3: phosphatidylinositol 3-kinase catalytic subunit type 3; PtdIns3P: phosphatidylinositol-3-phosphate; PtdIns4P: phosphatidylinositol-4-phosphate; RAB: RAB, member RAS oncogene GTPases; RAB1A: RAB1A, member RAS oncogene family; RAB11A: RAB11A, member RAS oncogene family; RAB17: RAB17, member RAS oncogene family; RAB24: RAB24, member RAS oncogene family; RPS6KB1: ribosomal protein S6 kinase B1; SLO: streptolysin O; SQSTM1: sequestosome 1; ULK1: unc-51 like autophagy activating kinase 1; WIPI2: WD repeat domain, phosphoinositide interacting 2.
Asunto(s)
Autofagia , Fosfatidilinositol 3-Quinasas Clase III/metabolismo , Streptococcus pyogenes/metabolismo , Proteínas de Unión al GTP rab1/metabolismo , Autofagosomas/efectos de los fármacos , Autofagosomas/metabolismo , Autofagia/efectos de los fármacos , Proteínas Bacterianas/metabolismo , Células HeLa , Humanos , Viabilidad Microbiana/efectos de los fármacos , Proteínas Asociadas a Microtúbulos/metabolismo , NAD+ Nucleosidasa/metabolismo , Agregado de Proteínas/efectos de los fármacos , Pliegue de Proteína/efectos de los fármacos , Puromicina/farmacología , Estreptolisinas/metabolismo , Proteínas de Unión al GTP rab/metabolismoRESUMEN
Streptococcus pyogenes (group A Streptococcus [GAS]) is a major human pathogen that occasionally causes severe and life-threatening invasive diseases. Here, we report the complete genome sequences of four GAS strains of three M types, which were isolated from patients with severe invasive disease in Japan.