title: Bfl-1/A1 acts as a negative regulator of autophagy in mycobacteria infected macrophages.
abstract: Expression of Bcl-2 family protein, Bfl-1/A1 has been found to differ considerably amongst macrophages infected with virulent Mycobacterium tuberculosis H37Rv or with avirulent M. tuberculosis H37Ra. Present work was undertaken to deduce the significance of differential expression of Bfl-1/A1 in the outcome of mycobacterial infection. We have studied the role of Bfl-1/A1 particularly in autophagy formation in tubercle bacilli infected cells since autophagy has been recognized as a component of innate immunity against pathogenic mycobacteria. First, we have confirmed that upon infection virulent strain H37Rv retain Bfl-1/A1 for longer period and impose autophagosome maturation block within infected cells as evident from confocal microscopy. Moreover, down regulation of Bfl-1/A1 by siRNA induced autophagy formation and reduced bacterial growth. Furthermore, even the avirulent strain H37Ra resist autophagosome maturation and survive if the cellular level of Bfl-1 is maintained in THP-1 cells by stable transfection (Bfl-1 overexpressing cells). No noteworthy difference in mTOR expression was observed between normal THP-1 and Bfl-1 overexpressing THP-1 cells infected with either strain of mycobacteria. Interestingly, we found that not only mTOR but also Bfl-1/A1 is involved in rapamycin induced autophagy in mycobacteria infected macrophages. We have found that Bfl-1 physically interacts with Beclin 1 in Bfl-1 overexpressing THP-1 as well as in H37Rv infected THP-1 cells as they co-precipitated. Taken together, our results clearly demonstrated that Bfl-1/A1 negatively regulates autophagy and expression of Bfl-1/A1 in H37Rv infected macrophages provides the bacteria a survival strategy to overcome host defense.
authors.affiliation: Division of Cell Biology and Immunology, Institute of Microbial Technology (CSIR), Chandigarh 160 036, India.
authors.forename: Mahesh
authors.initials: M
authors.lastname: Kathania
authors.forename: Chaaya Iyengar
authors.initials: CI
authors.lastname: Raje
authors.forename: Manoj
authors.initials: M
authors.lastname: Raje
authors.forename: Rajesh Kumar
authors.initials: RK
authors.lastname: Dutta
authors.forename: Sekhar
authors.initials: S
authors.lastname: Majumdar
mesh_terms: D051017:Apoptosis Regulatory Proteins / Q000378:metabolism; D001343:Autophagy / Q000187:drug effects; D000071186:Beclin-1; D002460:Cell Line; D015536:Down-Regulation / Q000235:genetics; D055785:Gene Knockdown Techniques; D006801:Humans; D042541:Intracellular Space / Q000187:drug effects / Q000382:microbiology; D008264:Macrophages / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism / Q000382:microbiology*; D008565:Membrane Proteins / Q000378:metabolism; D050296:Microbial Viability / Q000187:drug effects; D015778:Minor Histocompatibility Antigens; D009169:Mycobacterium tuberculosis / Q000187:drug effects / Q000472:pathogenicity / Q000502:physiology*; D010588:Phagosomes / Q000187:drug effects / Q000378:metabolism; D021381:Protein Transport / Q000187:drug effects; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000235:genetics; D020123:Sirolimus / Q000494:pharmacology; D058570:TOR Serine-Threonine Kinases / Q000378:metabolism
chemical_list: D051017:Apoptosis Regulatory Proteins; C096816:BCL2-related protein A1; C491997:BECN1 protein, human; D000071186:Beclin-1; D008565:Membrane Proteins; D015778:Minor Histocompatibility Antigens; D019253:Proto-Oncogene Proteins c-bcl-2; D034741:RNA, Small Interfering; D058570:TOR Serine-Threonine Kinases; D020123:Sirolimus