Showing papers by "Denise M. Monack published in 1997"
TL;DR: The ability of Y. pseudotuberculosis to promote apoptosis of macrophages in cell culture suggests that this process is important for the establishment of infection in the host and for evasion of the host immune response.
Abstract: Pathogenic Yersinia spp. carry a large common plasmid that encodes a number of essential virulence determinants. Included in these factors are the Yersinia-secreted proteins called Yops. We analyzed the consequences of wild-type and mutant strains of Yersinia pseudotuberculosis interactions with the macrophage cell line RAW264.7 and murine bone marrow-derived macrophages. Wild-type Y. pseudotuberculosis kills ≈70% of infected RAW264.7 macrophages and marrow-derived macrophages after an 8-h infection. We show that the cell death mediated by Y. pseudotuberculosis is apoptosis. Mutant Y. pseudotuberculosis that do not make any Yop proteins no longer cause host cell death. Attachment to host cells via invasin or YadA is necessary for the cell death phenotype. Several Yop mutant strains that fail to express one or more Yop proteins were engineered and then characterized for their ability to cause host cell death. A mutant with a polar insertion in YpkA Ser/Thr kinase that does not express YpkA or YopJ is no longer able to cause apoptosis. In contrast, a mutant no longer making YopE or YopH (a tyrosine phosphatase) induces apoptosis in macrophages similar to wild type. When yopJ is added in trans to the ypkAyopJ mutant, the ability of this strain to signal programmed cell death in macrophages is restored. Thus, YopJ is necessary for inducing apoptosis. The ability of Y. pseudotuberculosis to promote apoptosis of macrophages in cell culture suggests that this process is important for the establishment of infection in the host and for evasion of the host immune response.
420 citations
TL;DR: It is shown that the invasion defect is correlated with a lack of SipC in culture supernatants of these mutant strains of Salmonella typhimurium, which raises the possibility of an interaction between the two type III secretion systems.
Abstract: Summary We have investigated the structure and transcriptional organization of 13 genes of Salmonella Pathogenicity Island 2 (SPI2) that encode components of the second type III secretion apparatus of Salmonella typhimurium. ssaK, L, M, V, N, O, P, Q, R, S, T, U constitute one operon of 10 kb. ssaJ lies upstream of ssaK and is the terminal gene of another operon. The deduced products of ssaJ, ssaK, ssaV, ssaN, ssaO, ssaQ, ssaR, ssaS, ssaT, and ssaU show greatest similarity to the Yersinia spp. genes yscJ ,y scL, lcrD, yscN, yscO, yscQ, yscR, yscS, yscT ,a ndyscU, respectively. The products of the ssaL, ssaM and ssaP genes do not have significant similarity to products of other type III secretion systems, and might be important for the specific function of the SPI2 type III secretion system. Bacterial strains carrying different ssa mutations display minor alterations in terms of serum sensitivity when compared with the wild-type strain, but none are defective in replication within macrophage-like RAW 264.7 cells. However, some of the ssa mutant strains invade HEp2 cells less efficiently and are less cytotoxic to RAW 264.7 macrophages than the wild-type strain. We show that the invasion defect is correlated with a lack of SipC in culture supernatants of these mutant strains. SipC is a product of the SPI1 type III secretion system of S. typhimurium, and is important for epithelial cell invasion. Therefore, mutations in SPI2 can affect the SPI1 secretion system, which raises the possibility of an interaction between the two type III secretion systems.
191 citations
01 Jan 1997
TL;DR: In this article, the consequences of wild-type and mutant strains of Yersinia pseudotuberculosis interactions with the macrophage cell line RAW264.7 and murine bone marrow-derived macrophages were analyzed.
Abstract: Pathogenic Yersinia spp. carry a large com- mon plasmid that encodes a number of essential virulence determinants. Included in these factors are the Yersinia- secreted proteins called Yops. We analyzed the consequences of wild-type and mutant strains of Yersinia pseudotuberculosis interactions with the macrophage cell line RAW264.7 and murine bone marrow-derived macrophages. Wild-type Y. pseudotuberculosis kills '70% of infected RAW264.7 macro- phages and marrow-derived macrophages after an 8-h infec- tion. We show that the cell death mediated by Y. pseudotuber- culosis is apoptosis. Mutant Y. pseudotuberculosis that do not make any Yop proteins no longer cause host cell death. Attachment to host cells via invasin or YadA is necessary for the cell death phenotype. Several Yop mutant strains that fail to express one or more Yop proteins were engineered and then characterized for their ability to cause host cell death. A mutant with a polar insertion in YpkA SeryThr kinase that does not express YpkA or YopJ is no longer able to cause apoptosis. In contrast, a mutant no longer making YopE or YopH (a tyrosine phosphatase) induces apoptosis in macro- phages similar to wild type. When yopJ is added in trans to the ypkAyopJ mutant, the ability of this strain to signal pro- grammed cell death in macrophages is restored. Thus, YopJ is necessary for inducing apoptosis. The ability of Y. pseudotu- berculosis to promote apoptosis of macrophages in cell culture suggests that this process is important for the establishment of infection in the host and for evasion of the host immune response.
47 citations