title: Suppression of dendritic cell-mediated responses by genes in calcium and cysteine protease pathways during Mycobacterium tuberculosis infection.
abstract: With rising incidence of acquired drug resistance among life-threatening pathogens, alternative approaches to improve therapy and vaccination have taken center stage. To this end, genome-wide and pathway-specific siRNA libraries are being employed increasingly to identify genes that regulate immune responses against a number of pathogens. In this study using calcium and cysteine protease pathway-specific siRNA libraries, we identified genes that play critical roles in modulating diverse functions of dendritic cells (DCs) during Mycobacterium tuberculosis infection. Knockdown of many of these genes in the two pathways resulted in reduced bacterial burden within DCs. These included genes that regulated activation of transcription factors, ubiquitin-specific peptidases, and genes that are involved in autophagy and neddylation. Knockdown of certain genes increased the expression of IL-12p40 and surface densities of costimulatory molecules in an antigen- and receptor-specific manner. Increased IL-12p40 and costimulatory molecules on DCs also promoted the development of Th1 responses from a Th2 inducing antigen. Furthermore, modulation of autophagy and oxidative burst appeared to be one of the mechanisms by which these genes regulated survival of M. tuberculosis within DCs. Although some genes regulated specific responses, others regulated multiple responses that included IL-12 production, T cell priming, as well as intracellular survival of M. tuberculosis. Further dissection of the mechanisms such as neddylation, by which these genes regulate immune responses, would improve our understanding of host parameters that are modulated during M. tuberculosis infection.
authors.affiliation: Infectious Disease Immunology Laboratory, Dr. B. R. Ambedkar Centre for Biomedical Research, University of Delhi, Delhi 110007, India.
authors.forename: Jhalak
authors.initials: J
authors.lastname: Singhal
authors.forename: Neha
authors.initials: N
authors.lastname: Agrawal
authors.forename: Mohit
authors.initials: M
authors.lastname: Vashishta
authors.forename: N Gayatri
authors.initials: NG
authors.lastname: Priya
authors.forename: Brijendra K
authors.initials: BK
authors.lastname: Tiwari
authors.forename: Yogendra
authors.initials: Y
authors.lastname: Singh
authors.forename: Rajagopal
authors.initials: R
authors.lastname: Raman
authors.forename: Krishnamurthy
authors.initials: K
authors.lastname: Natarajan
mesh_terms: D000818:Animals; D001343:Autophagy / Q000235:genetics / Q000276:immunology; D002118:Calcium / Q000378:metabolism*; D002147:Calmodulin / Q000378:metabolism; D015815:Cell Adhesion Molecules / Q000378:metabolism; D057056:Cysteine Proteases / Q000378:metabolism*; D003713:Dendritic Cells / Q000166:cytology / Q000276:immunology* / Q000378:metabolism / Q000382:microbiology*; D005260:Female; D055785:Gene Knockdown Techniques; D007109:Immunity / Q000235:genetics*; D053762:Interleukin-12 Subunit p40 / Q000096:biosynthesis; D051379:Mice; D009169:Mycobacterium tuberculosis / Q000502:physiology*; D034741:RNA, Small Interfering / Q000235:genetics; D017382:Reactive Oxygen Species / Q000378:metabolism; D016897:Respiratory Burst / Q000235:genetics / Q000276:immunology; D013482:Superoxide Dismutase / Q000378:metabolism; D000072105:Superoxide Dismutase-1; D013601:T-Lymphocytes / Q000166:cytology / Q000276:immunology / Q000378:metabolism / Q000382:microbiology; D051195:Toll-Like Receptor 2 / Q000378:metabolism
chemical_list: D002147:Calmodulin; D015815:Cell Adhesion Molecules; D053762:Interleukin-12 Subunit p40; D034741:RNA, Small Interfering; D017382:Reactive Oxygen Species; C493486:Tlr2 protein, mouse; D051195:Toll-Like Receptor 2; C000606291:Sod1 protein, mouse; D013482:Superoxide Dismutase; D000072105:Superoxide Dismutase-1; D057056:Cysteine Proteases; D002118:Calcium