title: Biosynthesis of proteoglycans and hyaluronic acid by rat oral epithelial cells (keratinocytes) in vitro.
abstract: Biosynthesis of complex carbohydrates, including sulfated glycoproteins, hyaluronic acid (HA), and proteoglycans (PGs), synthesized by rat oral epithelial cells (keratinocytes) in culture were studied by metabolic labeling protocols using [35S]sulfate and [3H]glucosamine in combination with differential enzymatic digestion and analytical gel filtration. The epithelial cells synthesized a major sulfated glycoprotein species with an apparent molecular size approximately 50 kDa, which accounted for approximately 46% of the total 35S incorporation. HA was a relatively minor component of 3H-labeled macromolecules (approximately 4% of the total 3H incorporation), and almost all of it was secreted into the medium. PGs accounted for approximately half of the 35S incorporation, of which about 30% was secreted into the medium and the remainder associated with the cell layer. The majority of PGs (75% of the secreted and 97% of the cell-associated) contained heparan sulfate (HS) and had an apparent molecular weight of approximately 150,000. Cell-associated HSPGs had a core protein of approximately 70 kDa with HS chains of approximately 64 kDa, while HSPG in the medium had a core protein of approximately 50 kDa with HS chains of the same average size as those of the cell-associated HSPG. Of the total cell-associated HSPGs, glycosylphosphatidyl inositol-anchored forms, plasma membrane intercalated forms and those associated with basolateral pericellular matrix accounted for approximately 3%, 56% and approximately 4% of the total, respectively. Approximately one third of the cell-associated HSPGs were intracellular components most likely generated through intracellular degradation processes following endocytosis. Cell surface HSPGs synthesized by keratinocytes may be involved in some biological roles such as the regulation of normal epithelial turnover and defense mechanisms involving interactions with various oral pathogens.
authors.affiliation: Bone Research Branch, National Institute of Dental Research, National Institutes of Health, Bethesda, Maryland 20892.
authors.forename: M
authors.initials: M
authors.lastname: Hashimoto-Uoshima
authors.forename: V C
authors.initials: VC
authors.lastname: Hascall
authors.forename: D K
authors.initials: DK
authors.lastname: MacCallum
authors.forename: M
authors.initials: M
authors.lastname: Yanagishita
mesh_terms: D000818:Animals; D002460:Cell Line; D002462:Cell Membrane / Q000737:chemistry / Q000378:metabolism; D002850:Chromatography, Gel; D004847:Epithelial Cells; D004848:Epithelium / Q000648:ultrastructure; D005109:Extracellular Matrix / Q000737:chemistry / Q000378:metabolism; D017261:Glycosylphosphatidylinositols / Q000032:analysis; D006820:Hyaluronic Acid / Q000096:biosynthesis*; D007553:Isotope Labeling; D015603:Keratinocytes / Q000378:metabolism* / Q000648:ultrastructure; D010159:Palate / Q000166:cytology / Q000648:ultrastructure; D011509:Proteoglycans / Q000096:biosynthesis*; D051381:Rats; D013462:Sulfur Radioisotopes; D014316:Tritium
chemical_list: D017261:Glycosylphosphatidylinositols; D011509:Proteoglycans; D013462:Sulfur Radioisotopes; D014316:Tritium; D006820:Hyaluronic Acid