title: Matrix metalloproteinase proteolysis of the mycobacterial HSP65 protein as a potential source of immunogenic peptides in human tuberculosis.
abstract: Mycobacterium tuberculosis is the causative agent of human tuberculosis (TB). Mycobacterial secretory protein ESAT-6 induces matrix metalloproteinase (MMP)-9 in epithelial cells neighboring infected macrophages. MMP-9 then enhances recruitment of uninfected macrophages, which contribute to nascent granuloma maturation and bacterial growth. Disruption of MMP-9 function attenuates granuloma formation and bacterial growth. The abundant mycobacterial 65 kDa heat shock protein (HSP65) chaperone is the major target for the immune response and a critical component in M. tuberculosis adhesion to macrophages. We hypothesized that HSP65 is susceptible to MMP-9 proteolysis and that the resulting HSP65 immunogenic peptides affect host adaptive immunity. To identify MMPs that cleave HSP65, we used MMP-2 and MMP-9 gelatinases, the simple hemopexin domain MMP-8, membrane-associated MMP-14, MMP-15, MMP-16 and MMP-24, and glycosylphosphatidylinositol-linked MMP-17 and MMP-25. We determined both the relative cleavage efficiency of MMPs against the HSP65 substrate and the peptide sequence of the cleavage sites. Cleavage of the unstructured PAGHG474L C-terminal region initiates the degradation of HSP65 by MMPs. This initial cleavage destroys the substrate-binding capacity of the HSP65 chaperone. Multiple additional cleavages of the unfolded HSP65 then follow. MMP-2, MMP-8, MMP-14, MMP-15 and MMP-16, in addition to MMP-9, generate the known highly immunogenic N-terminal peptide of HSP65. Based on our biochemical data, we now suspect that MMP proteolysis of HSP65 in vivo, including MMP-9 proteolysis, also results in the abundant generation of the N-terminal immunogenic peptide and that this peptide, in addition to intact HSP65, contributes to the complex immunomodulatory interplay in the course of TB infection.
authors.affiliation: Infectious and Inflammatory Disease Center, Sanford-Burnham Medical Research Institute, La Jolla, CA 92037, USA.
authors.forename: Sergey A
authors.initials: SA
authors.lastname: Shiryaev
authors.forename: Piotr
authors.initials: P
authors.lastname: Cieplak
authors.forename: Alexander E
authors.initials: AE
authors.lastname: Aleshin
authors.forename: Qing
authors.initials: Q
authors.lastname: Sun
authors.forename: Wenhong
authors.initials: W
authors.lastname: Zhu
authors.forename: Khatereh
authors.initials: K
authors.lastname: Motamedchaboki
authors.forename: Alexander
authors.initials: A
authors.lastname: Sloutsky
authors.forename: Alex Y
authors.initials: AY
authors.lastname: Strongin
mesh_terms: D056704:Adaptive Immunity; D000595:Amino Acid Sequence; D000942:Antigens, Bacterial / Q000737:chemistry / Q000378:metabolism*; D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism*; D020134:Catalytic Domain; D018834:Chaperonin 60 / Q000737:chemistry / Q000378:metabolism*; D000939:Epitopes / Q000737:chemistry / Q000378:metabolism; D006801:Humans; D006868:Hydrolysis / Q000187:drug effects; D056747:Immunomodulation; D007527:Isoenzymes / Q000037:antagonists & inhibitors / Q000378:metabolism; D020780:Matrix Metalloproteinase 9 / Q000235:genetics / Q000378:metabolism; D061965:Matrix Metalloproteinase Inhibitors; D020782:Matrix Metalloproteinases / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D009169:Mycobacterium tuberculosis / Q000276:immunology*; D010446:Peptide Fragments / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011480:Protease Inhibitors / Q000494:pharmacology; D011994:Recombinant Proteins / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000378:metabolism; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D013379:Substrate Specificity; D014376:Tuberculosis / Q000276:immunology* / Q000517:prevention & control
chemical_list: D000942:Antigens, Bacterial; D001426:Bacterial Proteins; D018834:Chaperonin 60; D000939:Epitopes; D007527:Isoenzymes; D061965:Matrix Metalloproteinase Inhibitors; D010446:Peptide Fragments; D011480:Protease Inhibitors; D011994:Recombinant Proteins; C074119:heat-shock protein 65, Mycobacterium; D020782:Matrix Metalloproteinases; D020780:Matrix Metalloproteinase 9