UDP-glucose pyrophosphorylase: up-regulation in hypertrophic cartilage and role in hyaluronan synthesis.
Previously, we have performed subtractive hybridization to identify genes up-regulated in hypertrophic chondrocytes of the avian epiphyseal growth plate. In the present study, we report the identification of one of the clones as UDP-glucose pyrophosphorylase (UDPG-PPase) and propose a possible function for this enzyme in regulating hyaluronan (HA) synthesis in hypertrophic cartilage. We have cloned the 2.6 kb full-length cDNA for avian UDPG-PPase and confirmed its up-regulation in hypertrophic versus non-hypertrophic cartilage by Northern-blot analysis. The 6-fold increase in mRNA was paralleled by an equivalent increase in enzymic activity. The enzyme catalyses the conversion of glucose 1-phosphate into UDP-glucose, which is used to synthesize a number of cellular components, including HA. Overexpression of enzymically active UDPG-PPase in non-hypertrophic chondrocytes resulted in a 2-3-fold increase in total HA, as determined by a competitive binding assay and immunohistochemistry. In the developing growth plate, HA synthesis was elevated in the hypertrophic zone along with the up-regulation of the HA synthase (HAS)-2 gene. Our data suggest that an increase in both activities, UDPG-PPase and HAS-2, is required for non-hypertrophic chondrocytes to synthesize an amount of HA comparable with that in hypertrophic chondrocytes. Therefore we conclude that HA synthesis during chondrocyte differentiation is regulated at the level of the substrate-provider gene, UDPG-PPase, as well as the HAS genes.
Magee
C
C
Department of Anatomy and Cellular Biology, Tufts University Medical School, 136 Harrison Avenue, Boston, MA 02111, U.S.A.
Nurminskaya
M
M
Linsenmayer
T F
TF
D000818:Animals; D001483:Base Sequence; D002642:Chick Embryo; D019902:Chondrocytes / Q000201:enzymology* / Q000473:pathology; D003001:Cloning, Molecular; D017931:DNA Primers; D004838:Epiphyses / Q000201:enzymology; D015971:Gene Expression Regulation, Enzymologic; D049452:Green Fluorescent Proteins; D006820:Hyaluronic Acid / Q000096:biosynthesis*; D006984:Hypertrophy; D007700:Kinetics; D008164:Luminescent Proteins / Q000235:genetics; D008969:Molecular Sequence Data; D016133:Polymerase Chain Reaction; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis; D011994:Recombinant Proteins / Q000378:metabolism; D005957:UTP-Glucose-1-Phosphate Uridylyltransferase / Q000235:genetics* / Q000378:metabolism
D017931:DNA Primers; D008164:Luminescent Proteins; D011993:Recombinant Fusion Proteins; D011994:Recombinant Proteins; D049452:Green Fluorescent Proteins; D006820:Hyaluronic Acid; D005957:UTP-Glucose-1-Phosphate Uridylyltransferase