title: FAM20B is a kinase that phosphorylates xylose in the glycosaminoglycan-protein linkage region.
abstract: 2-O-phosphorylation of xylose has been detected in the glycosaminoglycan-protein linkage region, GlcAbeta1-3Galbeta1-3Galbeta1-4Xylbeta1-O-Ser, of proteoglycans. Recent mutant analyses in zebrafish suggest that xylosyltransferase I and FAM20B, a protein of unknown function that shows weak similarity to a Golgi kinase encoded by four-jointed, operate in a linear pathway for proteoglycan production. In the present study, we identified FAM20B as a kinase that phosphorylates the xylose residue in the linkage region. Overexpression of FAM20B increased the amount of both chondroitin sulfate and heparan sulfate in HeLa cells, whereas the RNA interference of FAM20B resulted in a reduction of their amount in the cells. Gel-filtration analysis of the glycosaminoglycan chains synthesized in the overexpressing cells revealed that the glycosaminoglycan chains had a similar length to those in mock-transfected cells. These results suggest that FAM20B regulates the number of glycosaminoglycan chains by phosphorylating the xylose residue in the glycosaminoglycan-protein linkage region of proteoglycans.
authors.affiliation: Department of Biochemistry, Kobe Pharmaceutical University, Higashinada-ku, Kobe 658-8558, Japan.
authors.forename: Toshiyasu
authors.initials: T
authors.lastname: Koike
authors.forename: Tomomi
authors.initials: T
authors.lastname: Izumikawa
authors.forename: Jun-Ichi
authors.initials: J
authors.lastname: Tamura
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Kitagawa
mesh_terms: D000818:Animals; D019556:COS Cells; D002522:Chlorocebus aethiops; D002850:Chromatography, Gel; D018076:DNA, Complementary / Q000378:metabolism; D006025:Glycosaminoglycans / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D008969:Molecular Sequence Data; D010766:Phosphorylation; D010770:Phosphotransferases / Q000235:genetics / Q000378:metabolism*; D034622:RNA Interference; D014162:Transfection; D014994:Xylose / Q000378:metabolism*
chemical_list: D018076:DNA, Complementary; D006025:Glycosaminoglycans; D014994:Xylose; D010770:Phosphotransferases