Browsing by Author "Martin, Rebecca K."

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    Functional inhibition of acid sphingomyelinase disrupts infection by intracellular bacterial pathogens
    (Life Science Alliance, 2019-03-22) Cockburn, Chelsea L.; Green, Ryan S.; Damle, Sheela R.; Martin, Rebecca K.; Ghahrai, Naomi N.; Colonne, Punsiri M.; Fullerton, Marissa S.; Conrad, Daniel H.; Chalfant, Charles E.; Voth, Daniel E.; Rucks, Elizabeth A.; Gilk, Stacey D.; Carlyon, Jason A.; Department of Microbiology and Immunology, Indiana University School of Medicine
    Intracellular bacteria that live in host cell-derived vacuoles are significant causes of human disease. Parasitism of low-density lipoprotein (LDL) cholesterol is essential for many vacuole-adapted bacteria. Acid sphingomyelinase (ASM) influences LDL cholesterol egress from the lysosome. Using functional inhibitors of ASM (FIASMAs), we show that ASM activity is key for infection cycles of vacuole-adapted bacteria that target cholesterol trafficking-Anaplasma phagocytophilum, Coxiella burnetii, Chlamydia trachomatis, and Chlamydia pneumoniae. Vacuole maturation, replication, and infectious progeny generation by A. phagocytophilum, which exclusively hijacks LDL cholesterol, are halted and C. burnetii, for which lysosomal cholesterol accumulation is bactericidal, is killed by FIASMAs. Infection cycles of Chlamydiae, which hijack LDL cholesterol and other lipid sources, are suppressed but less so than A. phagocytophilum or C. burnetii A. phagocytophilum fails to productively infect ASM-/- or FIASMA-treated mice. These findings establish the importance of ASM for infection by intracellular bacteria and identify FIASMAs as potential host-directed therapies for diseases caused by pathogens that manipulate LDL cholesterol.
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    The Il9 CNS-25 Regulatory Element Controls Mast Cell and Basophil IL-9 Production
    (American Association of Immunologists, 2019-09-01) Qayum, Amina Abdul; Koh, Byunghee; Martin, Rebecca K.; Kenworthy, Blake T.; Kharwadkar, Rakshin; Fu, Yongyao; Wu, Wenting; Conrad, Daniel H.; Kaplan, Mark H.; Microbiology and Immunology, School of Medicine
    Interleukin 9 (IL-9) is an important mediator of allergic disease that is critical for mast cell driven diseases. IL-9 is produced by many cell types including T cells, basophils, and mast cells. Yet, how IL-9 is regulated in mast cells or basophils is not well characterized. In this report we tested the effects of deficiency of a mouse Il9 gene regulatory element (Il9 CNS-25) in these cells in vivo and in vitro. In mast cells stimulated with IL-3 and IL-33, the Il9 CNS-25 enhancer is a potent regulator of mast cell Il9 gene transcription and epigenetic modification at the Il9 locus. Our data show preferential binding of STAT5 and GATA1 to CNS-25 over the Il9 promoter in mast cells, and that T cells and mast cells have differing requirements for the induction of IL-9 production. Il9 CNS-25 is required for IL-9 production from T cells, basophils, and mast cells in a food allergy model, and deficiency in IL-9 expression results in decreased mast cell expansion. In a Nippostrongylus brasiliensis infection model we observed a similar decrease in mast cell accumulation. Although decreased mast cells correlated with higher parasite egg burden and delayed clearance in vivo, T cell-deficiency in IL-9 also likely contributes to the phenotype. Thus, our data demonstrate IL-9 production in mast cells and basophils in vivo requires Il9 CNS-25, and that Il9 CNS-25-dependent IL-9 production is required for mast cell expansion during allergic intestinal inflammation.