title: The recently identified hexosaminidase D enzyme substantially contributes to the elevated hexosaminidase activity in rheumatoid arthritis.
abstract: Since the 1970s, numerous reports have described elevated hexosaminidase activities in rheumatoid arthritis. However, due to the overlapping substrate specificities of different hexosaminidases, identification of the exact enzyme(s) responsible for the elevated activity remains incomplete. In this work we tested if the recently described enzyme, hexosaminidase D was expressed in human arthritic joints, and could contribute to the elevated hexosaminidase activity in rheumatoid arthritis. Thermostable β-d-N-acetyl-galactosaminidase (hexosaminidase D) activities were determined in synovial fluid samples, synovial membranes, synovial fibroblast cell strains and synovial fibroblast-derived extracellular vesicles of patients with rheumatoid arthritis and osteoarthritis using chromogenic substrates. Expression of the HEXDC gene was detected both in steady state and in TGF-β treated synovial fibroblasts by real time PCR. Strikingly, hexosaminidase D accounted for approximately 50% of the total β-N-acetyl-galactosaminidase activity in synovial membranes and synovial fibroblasts, and it was responsible for the vast majority of the β-d-N-acetyl-galactosaminidase activity in synovial fluid samples. TGF-β downregulated the expression of hexosaminidase D in synovial fibroblasts dose-dependently. Of note, significant activity of hexosaminidase D was also found in association with extracellular vesicles released by synovial fibroblasts. This first study that describes the expression and disease relevance of the HEXDC gene in humans demonstrates the expression of this novel enzyme within the joints, and suggests that its activity may significantly contribute to the overall local exoglycosidase activity.
authors.affiliation: Department of Genetics, Cell and Immunobiology, Semmelweis University, Nagyvárad tér 4, Budapest, H-1089, Hungary. maria.pasztoi@gmail.com
authors.forename: Mária
authors.initials: M
authors.lastname: Pásztói
authors.forename: Barbara
authors.initials: B
authors.lastname: Sódar
authors.forename: Petra
authors.initials: P
authors.lastname: Misják
authors.forename: Krisztina
authors.initials: K
authors.lastname: Pálóczi
authors.forename: Ágnes
authors.initials: Á
authors.lastname: Kittel
authors.forename: Kálmán
authors.initials: K
authors.lastname: Tóth
authors.forename: Károly
authors.initials: K
authors.lastname: Wellinger
authors.forename: Pál
authors.initials: P
authors.lastname: Géher
authors.forename: György
authors.initials: G
authors.lastname: Nagy
authors.forename: Tamás
authors.initials: T
authors.lastname: Lakatos
authors.forename: András
authors.initials: A
authors.lastname: Falus
authors.forename: Edit Irén
authors.initials: EI
authors.lastname: Buzás
mesh_terms: D000328:Adult; D000368:Aged; D001172:Arthritis, Rheumatoid / Q000201:enzymology* / Q000276:immunology / Q000473:pathology; D002460:Cell Line; D005260:Female; D005347:Fibroblasts / Q000201:enzymology / Q000276:immunology / Q000473:pathology; D015971:Gene Expression Regulation, Enzymologic; D006801:Humans; D008297:Male; D008875:Middle Aged; D013582:Synovial Fluid / Q000201:enzymology* / Q000276:immunology; D013583:Synovial Membrane / Q000201:enzymology* / Q000276:immunology / Q000473:pathology; D001619:beta-N-Acetylhexosaminidases / Q000096:biosynthesis* / Q000276:immunology
chemical_list: D001619:beta-N-Acetylhexosaminidases