title: Interferon-gamma regulates cathepsin G activity in microglia-derived lysosomes and controls the proteolytic processing of myelin basic protein in vitro.
abstract: The serine protease cathepsin (Cat) G dominates the proteolytic processing of the multiple sclerosis (MS)-associated autoantigen myelin basic protein (MBP) in lysosomes from primary human B cells and dendritic cells. This is in contrast to B-lymphoblastoid cell lines, where the asparagine endopeptidase (AEP) is responsible for this task. We have analysed microglia-derived lysosomal proteases for their ability to process MBP in vitro. In lysosomes derived from primary murine microglia, CatD, CatS, AEP and CatG were involved in the processing of MBP. Interestingly, when microglia were treated with interferon-gamma to mimic a T helper type 1-biased cytokine milieu in MS, CatG was drastically down-regulated, in contrast to CatS, CatB, CatL, CatD or AEP. This resulted in significantly increased stability of MBP and a selective lack of CatG-derived proteolytic fragments; however, it did not affect the gross pattern of MBP processing. Inhibition of serine proteases eliminated the processing differences between lysosomal extracts from resting microglia compared to interferon-stimulated microglia. Thus, the cytokine environment modulates lysosomal proteases in microglia by a selective down-regulation of CatG, leading to decreased MBP-processing by microglia-derived lysosomal proteases in vitro.
authors.affiliation: Department of Medicine II, University of Tübingen, Germany. tburster@stanford.edu
authors.forename: Timo
authors.initials: T
authors.lastname: Burster
authors.forename: Alexander
authors.initials: A
authors.lastname: Beck
authors.forename: Simone
authors.initials: S
authors.lastname: Poeschel
authors.forename: Anita
authors.initials: A
authors.lastname: Øren
authors.forename: Daniel
authors.initials: D
authors.lastname: Baechle
authors.forename: Michael
authors.initials: M
authors.lastname: Reich
authors.forename: Olaf
authors.initials: O
authors.lastname: Roetzschke
authors.forename: Kirsten
authors.initials: K
authors.lastname: Falk
authors.forename: Bernhard O
authors.initials: BO
authors.lastname: Boehm
authors.forename: Sawsan
authors.initials: S
authors.lastname: Youssef
authors.forename: Hubert
authors.initials: H
authors.lastname: Kalbacher
authors.forename: Herman
authors.initials: H
authors.lastname: Overkleeft
authors.forename: Eva
authors.initials: E
authors.lastname: Tolosa
authors.forename: Christoph
authors.initials: C
authors.lastname: Driessen
mesh_terms: D000818:Animals; D017951:Antigen Presentation / Q000276:immunology*; D001324:Autoantigens / Q000378:metabolism; D056649:Cathepsin G; D002403:Cathepsins / Q000378:metabolism*; D015536:Down-Regulation / Q000276:immunology; D007371:Interferon-gamma / Q000276:immunology*; D008247:Lysosomes / Q000276:immunology; D051379:Mice; D008815:Mice, Inbred Strains; D017628:Microglia / Q000276:immunology*; D004676:Myelin Basic Protein / Q000378:metabolism*; D010664:Phenylmethylsulfonyl Fluoride / Q000494:pharmacology; D011480:Protease Inhibitors / Q000494:pharmacology; D012697:Serine Endopeptidases / Q000276:immunology / Q000378:metabolism*
chemical_list: D001324:Autoantigens; D004676:Myelin Basic Protein; D011480:Protease Inhibitors; D010664:Phenylmethylsulfonyl Fluoride; D007371:Interferon-gamma; D002403:Cathepsins; D012697:Serine Endopeptidases; C534094:CTSG protein, human; D056649:Cathepsin G; C534096:Ctsg protein, mouse