Identification of homologs of the Chlamydia trachomatis effector CteG reveals a family of Chlamydiaceae type III secreted proteins that can be delivered into host cells.

Chlamydiae are a large group of obligate endosymbionts of eukaryotes that includes the Chlamydiaceae family, comprising several animal pathogens. Among Chlamydiaceae, Chlamydia trachomatis causes widespread ocular and urogenital infections in humans. Like many bacterial pathogens, all Chlamydiae manipulate host cells by injecting them with type III secretion effector proteins.

Spores of Clostridioides difficile are toxin delivery vehicles.

Clostridioides difficile causes a wide range of intestinal diseases through the action of two main cytotoxins, TcdA and TcdB. Ingested spores germinate in the intestine establishing a population of cells that produce toxins and spores. The pathogenicity locus, PaLoc, comprises several genes, including those coding for TcdA/B, for the holin-like TcdE protein, and for TcdR, an auto-regulatory RNA polymerase sigma factor essential for tcdA/B and tcdE expression.

Effector Translocation Assay: Differential Solubilization.

The identification of effector proteins delivered into mammalian host cells by bacterial pathogens possessing syringe-like nanomachines is an important step towards an understanding of the mechanisms underlying virulence of these pathogens. In this chapter, we describe a method based on mammalian tissue culture infection models where incubation with a non-ionic detergent (Triton X-100) enables solubilization of host cell membranes but not of bacterial membranes. This allows the isolation of a Triton-soluble fraction lacking bacteria but enriched in proteins present in the host cell cytoplasm, nucleus, and plasma membrane.

The Chlamydia trachomatis IncM Protein Interferes with Host Cell Cytokinesis, Centrosome Positioning, and Golgi Distribution and Contributes to the Stability of the Pathogen-Containing Vacuole.

Chlamydia trachomatis is an obligate intracellular bacterial pathogen that causes ocular and urogenital infections in humans. The ability of C. trachomatis to grow intracellularly in a pathogen-containing vacuole (known as an inclusion) depends on chlamydial effector proteins transported into the host cell by a type III secretion system.

The Type III Secretion Effector CteG Mediates Host Cell Lytic Exit of .

is an obligate intracellular bacterium causing ocular and urogenital infections in humans that are a significant burden worldwide. The completion of its characteristic infectious cycle relies on the manipulation of several host cell processes by numerous chlamydial type III secretion effector proteins. We previously identified the CteG effector and showed it localizes at the host cell plasma membrane at late stages of infection.

A Search for Novel Effector Proteins Reveals a Strain Specific Nucleotropic Effector.

is an accidental human pathogen that causes the potentially fatal Legionnaires' disease, a severe type of pneumonia. The main virulence mechanism of is a Type 4B Secretion System (T4SS) named Icm/Dot that transports effector proteins into the host cell cytosol. The concerted action of effectors on several host cell processes leads to the formation of an intracellular Legionella-containing vacuole that is replication competent and avoids phagolysosomal degradation.

The Chlamydia trachomatis inclusion membrane protein CT006 associates with lipid droplets in eukaryotic cells.

Chlamydia trachomatis causes genital and ocular infections in humans. This bacterial pathogen multiplies exclusively within host cells in a characteristic vacuole (inclusion) and delivers proteins such as inclusion membrane proteins (Incs) into the host cell. Here, we identified CT006 as a novel C.

The multiple functions of the numerous secreted proteins: the tip of the iceberg.

serovars are obligate intracellular bacterial pathogens mainly causing ocular and urogenital infections that affect millions of people worldwide and which can lead to blindness or sterility. They reside and multiply intracellularly within a membrane-bound vacuolar compartment, known as inclusion, and are characterized by a developmental cycle involving two morphologically and physiologically distinct chlamydial forms. Completion of the developmental cycle involves the secretion of > 70 proteins that function in the host cell cytoplasm and nucleus, in the inclusion membrane and lumen, and in the extracellular milieu.

CteG is a Chlamydia trachomatis effector protein that associates with the Golgi complex of infected host cells.

Chlamydia trachomatis is a bacterial pathogen causing ocular and genital infections in humans. C. trachomatis multiplies exclusively inside host cells within a characteristic vacuole, from where it manipulates host cells by injecting them with type III secretion effector proteins.

SsaV Interacts with SsaL to Control the Translocon-to-Effector Switch in the SPI-2 Type Three Secretion System.

Nonflagellar type III secretion systems (nf T3SSs) form a cell surface needle-like structure and an associated translocon that deliver bacterial effector proteins into eukaryotic host cells. This involves a tightly regulated hierarchy of protein secretion. A switch involving SctP and SctU stops secretion of the needle protein.

The Human Centrosomal Protein CCDC146 Binds Inclusion Membrane Protein CT288 and Is Recruited to the Periphery of the -Containing Vacuole.

is an obligate intracellular human pathogen causing mainly ocular and genital infections of significant clinical and public health impact. multiplies intracellularly in a membrane bound vacuole, known as inclusion. Both extracellularly and from within the inclusion, uses a type III secretion system to deliver several effector proteins into the cytoplasm of host cells.

Effector Translocation Assay: Differential Solubilization.

The identification of effector proteins delivered into mammalian host cells by bacterial pathogens possessing syringelike nanomachines is an important step toward understanding the mechanisms underlying the virulence of these pathogens. In this chapter, we describe a method based on mammalian tissue culture infection models where incubation with a nonionic detergent (Triton X-100) enables solubilization of host cell membranes but not of bacterial membranes. This allows the isolation of a Triton-soluble fraction lacking bacteria but enriched in proteins present in the host cell cytoplasm and plasma membrane.

The Chlamydia trachomatis type III secretion substrates CT142, CT143, and CT144 are secreted into the lumen of the inclusion.

Chlamydia trachomatis is a human bacterial pathogen causing ocular and genital infections. It multiplies exclusively within an intracellular membrane-bound vacuole, the inclusion, and uses a type III secretion system to manipulate host cells by injecting them with bacterially-encoded effector proteins. In this work, we characterized the expression and subcellular localization in infected host cells of the C.

In Vitro Activity of Quaternary Ammonium Surfactants against Streptococcal, Chlamydial, and Gonococcal Infective Agents.

Quaternary ammonium compounds (QAC) are widely used, cheap, and chemically stable disinfectants and topical antiseptics with wide-spectrum antimicrobial activities. Within this group of compounds, we recently showed that there are significant differences between the pharmacodynamics of n-alkyl quaternary ammonium surfactants (QAS) with a short (C12) alkyl chain when in vitro toxicities toward bacterial and mammalian epithelial cells are compared. These differences result in an attractive therapeutic window that justifies studying short-chain QAS as prophylactics for sexually transmitted infections (STI) and perinatal vertically transmitted urogenital infections (UGI).

The Salmonella effector SteA binds phosphatidylinositol 4-phosphate for subcellular targeting within host cells.

Many bacterial pathogens use specialized secretion systems to deliver virulence effector proteins into eukaryotic host cells. The function of these effectors depends on their localization within infected cells, but the mechanisms determining subcellular targeting of each effector are mostly elusive. Here, we show that the Salmonella type III secretion effector SteA binds specifically to phosphatidylinositol 4-phosphate [PI(4)P].

Identification of regions within the Legionella pneumophila VipA effector protein involved in actin binding and polymerization and in interference with eukaryotic organelle trafficking.

The Legionella pneumophila effector protein VipA is an actin nucleator that co-localizes with actin filaments and early endosomes in infected macrophages and which interferes with organelle trafficking when expressed in yeast. To identify the regions of VipA involved in its subcellular localization and functions, we ectopically expressed specific VipA mutant proteins in eukaryotic cells. This indicated that the characteristic punctate distribution of VipA depends on its NH2 -terminal (amino acid residues 1-133) and central coiled-coil (amino acid residues 133-206) regions, and suggested a role for the COOH-terminal (amino acid residues 206-339) region in association with actin filaments and for the NH2 -terminal in co-localization with early endosomes.

Bacterial nucleators: actin' on actin.

The actin cytoskeleton is a key target of numerous microbial pathogens, including protozoa, fungi, bacteria and viruses. In particular, bacterial pathogens produce and deliver virulence effector proteins that hijack actin dynamics to enable bacterial invasion of host cells, allow movement within the host cytosol, facilitate intercellular spread or block phagocytosis. Many of these effector proteins directly or indirectly target the major eukaryotic actin nucleator, the Arp2/3 complex, by either mimicking nucleation promoting factors or activating upstream small GTPases.

Approaches targeting the type III secretion system to treat or prevent bacterial infections.

Introduction: The type III secretion system (T3SS) injectisome is an essential virulence mechanism used by many bacterial pathogens to inject host cells with effector proteins. Bacteria harboring T3SSs can cause significant disease in humans. As bacterial antibiotic resistance is a major concern, alternative prophylaxis and therapeutics are needed and T3SSs are a target for anti-virulence drugs.

The Salmonella effector SteA contributes to the control of membrane dynamics of Salmonella-containing vacuoles.

Salmonella enterica serovar Typhimurium is a bacterial pathogen causing gastroenteritis in humans and a typhoid-like systemic disease in mice. S. Typhimurium virulence is related to its capacity to multiply intracellularly within a membrane-bound compartment, the Salmonella-containing vacuole (SCV), and depends on type III secretion systems that deliver bacterial effector proteins into host cells.

Identification of type III secretion substrates of Chlamydia trachomatis using Yersinia enterocolitica as a heterologous system.

Background: Chlamydia trachomatis is an obligate intracellular human pathogen causing ocular and urogenital infections that are a significant clinical and public health concern. This bacterium uses a type III secretion (T3S) system to manipulate host cells, through the delivery of effector proteins into their cytosol, membranes, and nucleus. In this work, we aimed to find previously unidentified C.

Identification of novel type III secretion chaperone-substrate complexes of Chlamydia trachomatis.

Chlamydia trachomatis is an obligate intracellular bacterial pathogen of humans that uses a type III secretion (T3S) system to manipulate host cells through the delivery of effector proteins into their cytosol and membranes. The function of T3S systems depends on small bacterial cytosolic chaperone-like proteins, which bind T3S substrates and ensure their appropriate secretion. To find novel T3S chaperone-substrate complexes of C.

Salmonella inhibits retrograde trafficking of mannose-6-phosphate receptors and lysosome function.

Salmonella enterica is an intracellular bacterial pathogen that replicates within membrane-bound vacuoles through the action of effector proteins translocated into host cells. Salmonella vacuoles have characteristics of lysosomes but are reduced in hydrolytic enzymes transported by mannose-6-phosphate receptors (MPRs). We found that the effector SifA subverted Rab9-dependent retrograde trafficking of MPRs, thereby attenuating lysosome function.

Polymorphisms in inc proteins and differential expression of inc genes among Chlamydia trachomatis strains correlate with invasiveness and tropism of lymphogranuloma venereum isolates.

Chlamydia trachomatis is a human bacterial pathogen that multiplies only within an intracellular membrane-bound vacuole, the inclusion. C. trachomatis includes ocular and urogenital strains, usually causing infections restricted to epithelial cells of the conjunctiva and genital mucosa, respectively, and lymphogranuloma venereum (LGV) strains, which can infect macrophages and spread into lymph nodes.

Salmonella-induced tubular networks.

Salmonella virulence relies on its capacity to replicate inside various cell types in a membrane-bound compartment, the Salmonella-containing vacuole (SCV). A unique feature of Salmonella-infected cells is the presence of tubular structures originating from and connected to the SCV, which often extend throughout the cell cytoplasm. These tubules include the well-studied Salmonella-induced filaments (SIFs), enriched in lysosomal membrane proteins.