title: Chondroitin sulfate N-acetylgalactosaminyltransferase-1 plays a critical role in chondroitin sulfate synthesis in cartilage.
abstract: Cartilage destruction leads to severe joint diseases, such as osteoarthritis and spinal disorders with back pain, and cartilage regeneration is very inefficient. A major component of the cartilage extracellular matrix is the proteoglycan aggrecan that contains approximately 100 chondroitin sulfate (CS) chains, which impart water absorption and resistance to compression. Here, we demonstrate that chondroitin sulfate N-acetylgalactosaminyltransferase-1 (CSGalNAcT-1) plays a critical role in CS biosynthesis in cartilage. By in situ hybridization and real time reverse transcription-PCR of developing cartilage, CSGalNAcT-1 exhibited the highest level of expression. Its expression in chondrogenic ATDC5 cells correlated well with that of aggrecan core protein. In heterozygote and homozygote aggrecan-null cartilage where aggrecan transcription is decreased, CSGalNAcT-1 transcription diminished accordingly. Overexpression of the enzyme in chondrocytic cells further enhanced CS biosynthesis but not that of the aggrecan core protein, indicating that the enzyme activity is not saturated in the cells and that aggrecan synthesized in the overexpressing cells is heavier than the native molecule. Analysis of the CS chains synthesized in the overexpressing cells by gel chromatography and that of disaccharide composition revealed that the CS chains had similar length and sulfation patterns. Furthermore, adenoviral gene delivery of the enzyme into intervertebral discs displayed a substantial increase in the level of CS biosynthesis. These observations indicate that CSGalNAcT-1 overexpression increases the number of CS chains attached to aggrecan core protein. Our studies may lead to a new therapeutic intervention, ameliorating the outcome of cartilage degenerative diseases.
authors.affiliation: Institute for Molecular Science of Medicine, Aichi Medical University, Nagakute, Aichi 480-1195, Japan.
authors.forename: Kenichiro
authors.initials: K
authors.lastname: Sakai
authors.forename: Koji
authors.initials: K
authors.lastname: Kimata
authors.forename: Takashi
authors.initials: T
authors.lastname: Sato
authors.forename: Masanori
authors.initials: M
authors.lastname: Gotoh
authors.forename: Hisashi
authors.initials: H
authors.lastname: Narimatsu
authors.forename: Kenichi
authors.initials: K
authors.lastname: Shinomiya
authors.forename: Hideto
authors.initials: H
authors.lastname: Watanabe
mesh_terms: D000818:Animals; D002358:Cartilage, Articular / Q000201:enzymology* / Q000378:metabolism; D002460:Cell Line; D045744:Cell Line, Tumor; D002809:Chondroitin Sulfates / Q000096:biosynthesis*; D006801:Humans; D051379:Mice; D008813:Mice, Inbred ICR; D017350:N-Acetylgalactosaminyltransferases / Q000008:administration & dosage / Q000235:genetics / Q000502:physiology*; D051381:Rats; D014161:Transduction, Genetic; D014162:Transfection
chemical_list: D002809:Chondroitin Sulfates; D017350:N-Acetylgalactosaminyltransferases; C472559:chondroitin sulfate N-acetylgalactosaminyltransferase-1