RESUMEN
Chlamydia invasion of epithelial cells is a pathogen-driven process involving two functionally distinct effectors - TarP and TmeA. They collaborate to promote robust actin dynamics at sites of entry. Here, we extend studies on the molecular mechanism of invasion by implicating the host GTPase dynamin 2 (Dyn2) in the completion of pathogen uptake. Importantly, Dyn2 function is modulated by TarP and TmeA at the levels of recruitment and activation through oligomerization, respectively. TarP-dependent recruitment requires phosphatidylinositol 3-kinase and the small GTPase Rac1, while TmeA has a post-recruitment role related to Dyn2 oligomerization. This is based on the rescue of invasion duration and efficiency in the absence of TmeA by the Dyn2 oligomer-stabilizing small molecule activator Ryngo 1-23. Notably, Dyn2 also regulated turnover of TarP- and TmeA-associated actin networks, with disrupted Dyn2 function resulting in aberrant turnover dynamics, thus establishing the interdependent functional relationship between Dyn2 and the effectors TarP and TmeA.
Asunto(s)
Actinas , Chlamydia trachomatis , Dinamina II , Chlamydia trachomatis/metabolismo , Chlamydia trachomatis/fisiología , Humanos , Dinamina II/metabolismo , Dinamina II/genética , Células HeLa , Actinas/metabolismo , Proteína de Unión al GTP rac1/metabolismo , Proteínas Bacterianas/metabolismo , Proteínas Bacterianas/genética , Infecciones por Chlamydia/microbiología , Infecciones por Chlamydia/metabolismo , Interacciones Huésped-Patógeno , Células Epiteliales/microbiología , Células Epiteliales/metabolismoRESUMEN
Chlamydia trachomatis is a clinically important bacterium that infects epithelial cells of the genitourinary and respiratory tracts and the eye. These differentiated cells are in a quiescent growth state and have a surface organelle called a primary cilium, but the standard Chlamydia cell culture infection model uses cycling cells that lack primary cilia. To investigate if these differences are relevant, we performed infections with host cells that have a primary cilium. We found that C. trachomatis caused progressive loss of the primary cilium that was prevented by disrupting Aurora A (AurA), HDAC6 or calmodulin, which are components of the cellular cilia disassembly pathway. Stabilization of the primary cilium by targeting this pathway caused a large reduction in infectious progeny although there were no changes in chlamydial inclusion growth, chlamydial replication or the ultrastructural appearance of dividing and infectious forms (RBs and EBs, respectively). Thus, the presence of a primary cilium interfered with the production of infectious EBs at a late step in the developmental cycle. C. trachomatis infection also induced quiescent cells to re-enter the cell cycle, as detected by EdU incorporation in S-phase, and Chlamydia-induced cilia disassembly was necessary for cell cycle re-entry. This study therefore describes a novel host-pathogen interaction in which the primary cilium limits a productive Chlamydia infection, and the bacterium counteracts this host cell defense by activating the cellular cilia disassembly pathway.
Asunto(s)
Infecciones por Chlamydia , Chlamydia trachomatis , Cilios , Chlamydia trachomatis/fisiología , Cilios/microbiología , Cilios/metabolismo , Infecciones por Chlamydia/microbiología , Infecciones por Chlamydia/metabolismo , Infecciones por Chlamydia/patología , Humanos , Células Epiteliales/microbiología , Células Epiteliales/metabolismoRESUMEN
Toll-like receptor 9 (TLR9) is an innate immune receptor that localizes to endosomes in antigen presenting cells and recognizes single stranded unmethylated CpG sites on bacterial genomic DNA (gDNA). Previous bioinformatic studies have demonstrated that the genome of the human pathogen Chlamydia trachomatis contains TLR9 stimulatory motifs, and correlative studies have implied a link between human TLR9 (hTLR9) genotype variants and susceptibility to infection. Here, we present our evaluation of the stimulatory potential of C. trachomatis gDNA and its recognition by hTLR9- and murine TLR9 (mTLR9)-expressing cells. Utilizing reporter cell lines, we demonstrate that purified gDNA from C. trachomatis can stimulate hTLR9 signaling, albeit at lower levels than gDNA prepared from other Gram-negative bacteria. Interestingly, we found that while C. trachomatis is capable of signaling through hTLR9 and mTLR9 during live infections in HEK293 reporter cell lines, signaling only occurs at later developmental time points. Chlamydia-specific induction of hTLR9 is blocked when protein synthesis is inhibited prior to the RB-to-EB conversion, exacerbated by the inhibition of lipooligosaccharide biosynthesis, and is significantly altered during the induction of aberrance/persistence. Our observations support the hypothesis that chlamydial gDNA is released during the conversion between the pathogen's replicative and infectious forms and during treatment with antibiotics targeting peptidoglycan assembly. Given that C. trachomatis inclusions do not co-localize with TLR9-containing vacuoles in the pro-monocytic cell line U937, our findings also hint that chlamydial gDNA is capable of egress from the inclusion, and traffics to TLR9-containing vacuoles via an as yet unknown pathway.
Asunto(s)
Infecciones por Chlamydia , Chlamydia trachomatis , Transducción de Señal , Receptor Toll-Like 9 , Chlamydia trachomatis/inmunología , Chlamydia trachomatis/metabolismo , Chlamydia trachomatis/genética , Humanos , Receptor Toll-Like 9/metabolismo , Receptor Toll-Like 9/genética , Animales , Ratones , Infecciones por Chlamydia/microbiología , Infecciones por Chlamydia/inmunología , Infecciones por Chlamydia/metabolismo , Células HEK293 , ADN Bacteriano/genética , Línea CelularRESUMEN
Chlamydia trachomatis infection can be regulated by autophagy-related genes. LncRNA CYTOR has been proven to be involved in autophagy. In this research, we investigated the role of CYTOR in autophagy induced by C. trachomatis and the potential mechanisms. After C. trachomatis infection, CYTOR and MAPK1 were up-regulated and miR-206 was down-regulated, meanwhile, the autophagy-related protein Beclin1 and LC3-â ¡/LC3-â ratio were increased. Interference with CYTOR or overexpression with miR-206 downregulated the autophagy-related protein Beclin1 and the number of autophagic spots LC3, decreased the protein ratio of LC3-II/LC3-I, and upregulated the expression of P62 protein. The luciferase reporter assay confirmed that CYTOR acted as a sponge for miR-206 to target MAPK1. In addition, CYTOR promoted autophagy induced by C. trachomatis infection through the MAPK1/ERK signaling pathway activation. Taken together, we have identified a novel molecular mechanism that the CYTOR/miR-206/MAPK1 axis was involved in the regulation of autophagy in C. trachomatis infection. This work provides an experimental basis for elucidating the pathogenesis of C. trachomatis for the treatment, prevention and control of related infectious diseases.
Asunto(s)
Autofagia , Chlamydia trachomatis , MicroARNs , Proteína Quinasa 1 Activada por Mitógenos , ARN Largo no Codificante , Chlamydia trachomatis/genética , MicroARNs/genética , MicroARNs/metabolismo , Humanos , ARN Largo no Codificante/genética , ARN Largo no Codificante/metabolismo , Proteína Quinasa 1 Activada por Mitógenos/metabolismo , Proteína Quinasa 1 Activada por Mitógenos/genética , Infecciones por Chlamydia/microbiología , Infecciones por Chlamydia/metabolismo , Células HeLa , Regulación hacia Arriba , Beclina-1/metabolismo , Beclina-1/genéticaRESUMEN
Chlamydia infection is an important cause of public health diseases, and no effective vaccine is currently available. Owing to its unique intracellular lifestyle, Chlamydia requires a variety of nutrients and substrates from host cells, particularly sphingomyelin, cholesterol, iron, amino acids, and the mannose-6-phosphate receptor, which are essential for inclusion development. Here, we summarize the recent advances in Chlamydia nutrient acquisition mechanism by hijacking host cell vesicular transport, which plays an important role in chlamydial growth and development. Chlamydia obtains the components necessary to complete its intracellular developmental cycle by recruiting Rab proteins (major vesicular trafficking regulators) and Rab effector proteins to the inclusion, interfering with Rab-mediated multivesicular trafficking, reorienting the nutrition of host cells, and reconstructing the intracellular niche environment. Consequently, exploring the role of vesicular transport in nutrient acquisition offers a novel perspective on new approaches for preventing and treating Chlamydia infection.
Asunto(s)
Infecciones por Chlamydia , Chlamydia , Interacciones Huésped-Patógeno , Nutrientes , Humanos , Infecciones por Chlamydia/microbiología , Infecciones por Chlamydia/metabolismo , Chlamydia/metabolismo , Chlamydia/fisiología , Chlamydia/patogenicidad , Nutrientes/metabolismo , Animales , Transporte BiológicoRESUMEN
The obligate intracellular bacterium, Chlamydia trachomatis, has evolved to depend on its human host for many metabolites, including most amino acids and three of the four nucleotides. Given this, it is not surprising that depletion of a single amino acid in the host cell growth medium blocks chlamydial replication. Paradoxically, supra-normal levels of some amino acids also block productive replication of Chlamydia. Here, we have determined how elevated serine levels, generated by exogenous supplementation, impede chlamydial inclusion development and reduce the generation of infectious progeny. Our findings reveal that human serine racemase, which is broadly expressed in multiple tissues, potentiates the anti-chlamydial effect of elevated serine concentrations. In addition to reversibly converting l-serine to d-serine, serine racemase also deaminates serine via ß-elimination. We have determined that d-serine does not directly impact Chlamydia; rather, ammonia generated by serine deamination limits the productive chlamydial replication. Our findings imply that ammonia produced within host cells can traverse the chlamydial inclusion membrane. Further, this property of serine deaminase can be exploited to sensitize Chlamydia to concentrations of doxycycline that are otherwise not bactericidal. Because exogenously elevated levels of serine can be tolerated over extended periods, the broad expression pattern of serine racemase indicates it to be a host enzyme whose activity can be directed against multiple intracellular bacterial pathogens. From a therapeutic perspective, demonstrating host metabolism can be skewed to generate an anti-bacterial metabolite that synergizes with antibiotics, we believe our results provide a new approach to target intracellular pathogens.
Asunto(s)
Antibacterianos , Chlamydia trachomatis , Serina , Humanos , Chlamydia trachomatis/metabolismo , Chlamydia trachomatis/efectos de los fármacos , Serina/metabolismo , Antibacterianos/farmacología , Células HeLa , Racemasas y Epimerasas/metabolismo , Desaminación , Infecciones por Chlamydia/metabolismo , Infecciones por Chlamydia/tratamiento farmacológico , Infecciones por Chlamydia/microbiologíaRESUMEN
Chlamydia trachomatis is the leading cause of bacterial sexually transmitted infections in the USA and of preventable blindness worldwide. This obligate intracellular pathogen replicates within a membrane-bound inclusion, but how it acquires nutrients from the host while avoiding detection by the innate immune system is incompletely understood. C. trachomatis accomplishes this in part through the translocation of a unique set of effectors into the inclusion membrane, the inclusion membrane proteins (Incs). Incs are ideally positioned at the host-pathogen interface to reprogram host signaling by redirecting proteins or organelles to the inclusion. Using a combination of co-affinity purification, immunofluorescence confocal imaging, and proteomics, we characterize the interaction between an early-expressed Inc of unknown function, Tri1, and tumor necrosis factor receptor-associated factor 7 (TRAF7). TRAF7 is a multi-domain protein with a RING finger ubiquitin ligase domain and a C-terminal WD40 domain. TRAF7 regulates several innate immune signaling pathways associated with C. trachomatis infection and is mutated in a subset of tumors. We demonstrate that Tri1 and TRAF7 specifically interact during infection and that TRAF7 is recruited to the inclusion. We further show that the predicted coiled-coil domain of Tri1 is necessary to interact with the TRAF7 WD40 domain. Finally, we demonstrate that Tri1 displaces the native TRAF7 binding partners, mitogen-activated protein kinase kinase kinase 2 (MEKK2), and MEKK3. Together, our results suggest that by displacing TRAF7 native binding partners, Tri1 has the capacity to alter TRAF7 signaling during C. trachomatis infection.IMPORTANCEChlamydia trachomatis is the leading cause of bacterial sexually transmitted infections in the USA and preventable blindness worldwide. Although easily treated with antibiotics, the vast majority of infections are asymptomatic and therefore go untreated, leading to infertility and blindness. This obligate intracellular pathogen evades the immune response, which contributes to these outcomes. Here, we characterize the interaction between a C. trachomatis-secreted effector, Tri1, and a host protein involved in innate immune signaling, TRAF7. We identified host proteins that bind to TRAF7 and demonstrated that Tri1 can displace these proteins upon binding to TRAF7. Remarkably, the region of TRAF7 to which these host proteins bind is often mutated in a subset of human tumors. Our work suggests a mechanism by which Tri1 may alter TRAF7 signaling and has implications not only in the pathogenesis of C. trachomatis infections but also in understanding the role of TRAF7 in cancer.
Asunto(s)
Proteínas Bacterianas , Infecciones por Chlamydia , Chlamydia trachomatis , Interacciones Huésped-Patógeno , Humanos , Chlamydia trachomatis/metabolismo , Chlamydia trachomatis/genética , Chlamydia trachomatis/inmunología , Células HeLa , Proteínas Bacterianas/metabolismo , Proteínas Bacterianas/genética , Infecciones por Chlamydia/microbiología , Infecciones por Chlamydia/metabolismo , Infecciones por Chlamydia/inmunología , Transducción de Señal , Péptidos y Proteínas Asociados a Receptores de Factores de Necrosis Tumoral/metabolismo , Péptidos y Proteínas Asociados a Receptores de Factores de Necrosis Tumoral/genética , Inmunidad Innata , Unión Proteica , Proteínas de la Membrana/metabolismo , Proteínas de la Membrana/genética , Células HEK293RESUMEN
BACKGROUND: The pathogenesis of Chlamydia trachomatis is associated with the induction of the host inflammatory response; however, the precise underlying molecular mechanisms remain poorly understood. METHODS: CT622, a T3SS effector protein, has an important role in the pathogenesis of C trachomatis; however, whether CT622 can induce a host inflammatory response is not understood. Our findings demonstrate that CT622 induces the expression of interleukins 6 and 8 (IL-6 and IL-8). Mechanistically, these effects involve the activation of the MAPK/NF-κB signaling pathways (mitogen-activated protein kinase/nuclear factor κB). RESULTS: Interestingly, we demonstrated that the suppression of toll-like receptor 4 using small interfering RNA markedly reduced the phosphorylation of ERK, p38, JNK, and IκBα, concomitant with a significant decrease in IL-6 and IL-8 secretion. Conversely, disruption of toll-like receptor 2 abrogated the CT622-induced upregulation of IL-8 and activation of ERK, whereas IL-6 expression and p38, JNK, and IκBα phosphorylation were unaffected. CONCLUSIONS: Taken together, these results indicate that CT622 contributes to the inflammatory response through the toll-like receptor 2/4-mediated MAPK/NF-κB pathways, which provides insight into the molecular pathology of C trachomatis infection.