title: Hyaluronan synthase 1 (HAS1) requires higher cellular UDP-GlcNAc concentration than HAS2 and HAS3.
abstract: Mammals have three homologous genes encoding proteins with hyaluronan synthase activity (Has1-3), all producing an identical polymer from UDP-N-acetylglucosamine and UDP-glucuronic acid. To compare the properties of these isoenzymes, COS-1 cells, with minor endogenous hyaluronan synthesis, were transfected with human Has1-3 isoenzymes. HAS1 was almost unable to secrete hyaluronan or form a hyaluronan coat, in contrast to HAS2 and HAS3. This failure of HAS1 to synthesize hyaluronan was compensated by increasing the cellular content of UDP-N-acetyl glucosamine by ∼10-fold with 1 mm glucosamine in the growth medium. Hyaluronan synthesis driven by HAS2 was less affected by glucosamine addition, and HAS3 was not affected at all. Glucose-free medium, leading to depletion of the UDP-sugars, markedly reduced hyaluronan synthesis by all HAS isoenzymes while raising its concentration from 5 to 25 mm had a moderate stimulatory effect. The results indicate that HAS1 is almost inactive in cells with low UDP-sugar supply, HAS2 activity increases with UDP-sugars, and HAS3 produces hyaluronan at high speed even with minimum substrate content. Transfected Has2 and particularly Has3 consumed enough UDP-sugars to reduce their content in COS-1 cells. Comparison of different human cell types revealed ∼50-fold differences in the content of UDP-N-acetylhexosamines and UDP-glucuronic acid, correlating with the expression level of Has1, suggesting cellular coordination between Has1 expression and the content of UDP-sugars.
authors.affiliation: Institute of Biomedicine and the Biocenter Kuopio, University of Eastern Finland, FIN-70211 Kuopio, Finland. kirsi.rilla@uef.fi
authors.forename: Kirsi
authors.initials: K
authors.lastname: Rilla
authors.forename: Sanna
authors.initials: S
authors.lastname: Oikari
authors.forename: Tiina A
authors.initials: TA
authors.lastname: Jokela
authors.forename: Juha M T
authors.initials: JM
authors.lastname: Hyttinen
authors.forename: Riikka
authors.initials: R
authors.lastname: Kärnä
authors.forename: Raija H
authors.initials: RH
authors.lastname: Tammi
authors.forename: Markku I
authors.initials: MI
authors.lastname: Tammi
mesh_terms: D000117:Acetylglucosamine / Q000378:metabolism*; D000818:Animals; D001011:Aorta / Q000166:cytology; D019556:COS Cells; D002522:Chlorocebus aethiops; D042783:Endothelial Cells / Q000166:cytology; D005109:Extracellular Matrix / Q000378:metabolism; D015971:Gene Expression Regulation, Enzymologic; D005944:Glucosamine / Q000378:metabolism; D005947:Glucose / Q000378:metabolism; D014453:Glucuronosyltransferase / Q000378:metabolism*; D006801:Humans; D000076002:Hyaluronan Synthases; D006820:Hyaluronic Acid / Q000378:metabolism; D007249:Inflammation; D007527:Isoenzymes; D008954:Models, Biological; D009369:Neoplasms / Q000201:enzymology; D014530:Uridine Diphosphate / Q000737:chemistry*
chemical_list: D007527:Isoenzymes; D014530:Uridine Diphosphate; D006820:Hyaluronic Acid; D014453:Glucuronosyltransferase; C101754:HAS2 protein, human; C105458:HAS3 protein, human; D000076002:Hyaluronan Synthases; D005947:Glucose; D005944:Glucosamine; D000117:Acetylglucosamine