title: The ESAT-6 protein of Mycobacterium tuberculosis interacts with beta-2-microglobulin (β2M) affecting antigen presentation function of macrophage.
abstract: ESAT-6, an abundantly secreted protein of Mycobacterium tuberculosis (M. tuberculosis) is an important virulence factor, inactivation of which leads to reduced virulence of M. tuberculosis. ESAT-6 alone, or in complex with its chaperone CFP-10 (ESAT-6:CFP-10), is known to modulate host immune responses; however, the detailed mechanisms are not well understood. The structure of ESAT-6 or ESAT-6:CFP-10 complex does not suggest presence of enzymatic or DNA-binding activities. Therefore, we hypothesized that the crucial role played by ESAT-6 in the virulence of mycobacteria could be due to its interaction with some host cellular factors. Using a yeast two-hybrid screening, we identified that ESAT-6 interacts with the host protein beta-2-microglobulin (β2M), which was further confirmed by other assays, like GST pull down, co-immunoprecipitation and surface plasmon resonance. The C-terminal six amino acid residues (90-95) of ESAT-6 were found to be essential for this interaction. ESAT-6, in complex with CFP-10, also interacts with β2M. We found that ESAT-6/ESAT-6:CFP-10 can enter into the endoplasmic reticulum where it sequesters β2M to inhibit cell surface expression of MHC-I-β2M complexes, resulting in downregulation of class I-mediated antigen presentation. Interestingly, the ESAT-6:β2M complex could be detected in pleural biopsies of individuals suffering from pleural tuberculosis. Our data highlight a novel mechanism by which M. tuberculosis may undermine the host adaptive immune responses to establish a successful infection. Identification of such novel interactions may help us in designing small molecule inhibitors as well as effective vaccine design against tuberculosis.
authors.affiliation: Laboratory of Molecular Cell Biology, Centre for DNA Fingerprinting and Diagnostics (CDFD), Nampally, Hyderabad, India.
authors.forename: Gopalkrishna
authors.initials: G
authors.lastname: Sreejit
authors.affiliation: Laboratory of Molecular Cell Biology, Centre for DNA Fingerprinting and Diagnostics (CDFD), Nampally, Hyderabad, India.
authors.forename: Asma
authors.initials: A
authors.lastname: Ahmed
authors.affiliation: Laboratory of Molecular Cell Biology, Centre for DNA Fingerprinting and Diagnostics (CDFD), Nampally, Hyderabad, India.
authors.forename: Nazia
authors.initials: N
authors.lastname: Parveen
authors.affiliation: Laboratory of Molecular Cell Biology, Centre for DNA Fingerprinting and Diagnostics (CDFD), Nampally, Hyderabad, India.
authors.forename: Vishwanath
authors.initials: V
authors.lastname: Jha
authors.affiliation: Division of Immunology and Molecular Biology, LEPRA Society-Blue Peter Research Centre, Hyderabad, India.
authors.forename: Vijaya Lakshmi
authors.initials: VL
authors.lastname: Valluri
authors.affiliation: Molecular Biology Unit, National Institute of Nutrition (ICMR), Jamai-Osmania Hyderabad, India.
authors.forename: Sudip
authors.initials: S
authors.lastname: Ghosh
authors.affiliation: Laboratory of Molecular Cell Biology, Centre for DNA Fingerprinting and Diagnostics (CDFD), Nampally, Hyderabad, India.
authors.forename: Sangita
authors.initials: S
authors.lastname: Mukhopadhyay
mesh_terms: D000818:Animals; D017951:Antigen Presentation; D000942:Antigens, Bacterial / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D015723:Gene Library; D017930:Genes, Reporter; D006801:Humans; D008264:Macrophages / Q000276:immunology*; D009169:Mycobacterium tuberculosis / Q000235:genetics / Q000276:immunology* / Q000472:pathogenicity; D011994:Recombinant Proteins; D014376:Tuberculosis / Q000276:immunology* / Q000382:microbiology; D020798:Two-Hybrid System Techniques; D014774:Virulence; D037521:Virulence Factors / Q000235:genetics / Q000378:metabolism; D001613:beta 2-Microglobulin / Q000235:genetics / Q000276:immunology / Q000378:metabolism*
chemical_list: D000942:Antigens, Bacterial; D001426:Bacterial Proteins; C093276:ESAT-6 protein, Mycobacterium tuberculosis; D011994:Recombinant Proteins; D037521:Virulence Factors; D001613:beta 2-Microglobulin