title: Matrix metalloproteinase proteolysis of the myelin basic protein isoforms is a source of immunogenic peptides in autoimmune multiple sclerosis.
abstract: BACKGROUND
  Matrix metalloproteinases (MMPs) play a significant role in the fragmentation of myelin basic protein (MBP) and demyelination leading to autoimmune multiple sclerosis (MS) and experimental autoimmune encephalomyelitis (EAE). The classic MBP isoforms are predominantly expressed in the oligodendrocytes of the CNS. The splice variants of the single MBP gene (Golli-MBP BG21 and J37) are widely expressed in the neurons and also in the immune cells. The relative contribution of the individual MMPs to the MBP cleavage is not known.
  
  
  RESULTS
  To elucidate which MMP plays the primary role in cleaving MBP, we determined the efficiency of MMP-2, MMP-8, MMP-9, MMP-10, MMP-12, MT1-MMP, MT2-MMP, MT3-MMP, MT4-MMP, MT5-MMP and MT6-MMP in the cleavage of the MBP, BG21 and J37 isoforms in the in vitro cleavage reactions followed by mass-spectroscopy analysis of the cleavage fragments. As a result, we identified the MMP cleavage sites and the sequence of the resulting fragments. We determined that MBP, BG21 and J37 are highly sensitive to redundant MMP proteolysis. MT6-MMP (initially called leukolysin), however, was superior over all of the other MMPs in cleaving the MBP isoforms. Using the mixed lymphocyte culture assay, we demonstrated that MT6-MMP proteolysis of the MBP isoforms readily generated, with a near quantitative yield, the immunogenic N-terminal 1-15 MBP peptide. This peptide selectively stimulated the proliferation of the PGPR7.5 T cell clone isolated from mice with EAE and specific for the 1-15 MBP fragment presented in the MHC H-2(U) context.
  
  
  CONCLUSIONS
  In sum, our biochemical observations led us to hypothesize that MT6-MMP, which is activated by furin and associated with the lipid rafts, plays an important role in MS pathology and that MT6-MMP is a novel and promising drug target in MS especially when compared with other individual MMPs.
authors.affiliation: Inflammatory and Infectious Disease Center, Burnham Institute for Medical Research, La Jolla, California, United States of America.
authors.forename: Sergey A
authors.initials: SA
authors.lastname: Shiryaev
authors.forename: Alexei Y
authors.initials: AY
authors.lastname: Savinov
authors.forename: Piotr
authors.initials: P
authors.lastname: Cieplak
authors.forename: Boris I
authors.initials: BI
authors.lastname: Ratnikov
authors.forename: Khatereh
authors.initials: K
authors.lastname: Motamedchaboki
authors.forename: Jeffrey W
authors.initials: JW
authors.lastname: Smith
authors.forename: Alex Y
authors.initials: AY
authors.lastname: Strongin
mesh_terms: D017398:Alternative Splicing; D000595:Amino Acid Sequence; D000818:Animals; D006801:Humans; D008213:Lymphocyte Activation; D020782:Matrix Metalloproteinases / Q000235:genetics / Q000378:metabolism*; D000090023:Metallothionein 3; D051379:Mice; D008969:Molecular Sequence Data; D009103:Multiple Sclerosis / Q000235:genetics / Q000276:immunology*; D004676:Myelin Basic Protein / Q000235:genetics / Q000378:metabolism*; D010455:Peptides / Q000235:genetics / Q000276:immunology*; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism*; D016415:Sequence Alignment; D013601:T-Lymphocytes / Q000276:immunology
chemical_list: D000090023:Metallothionein 3; C000715430:Mt3 protein, mouse; D004676:Myelin Basic Protein; D010455:Peptides; D020033:Protein Isoforms; D020782:Matrix Metalloproteinases