Expression of recombinant hyaluronan synthase (HAS) isoforms in CHO cells reduces cell migration and cell surface CD44

In the present study we investigated the functional properties of the three recombinant hyaluronan synthases (RAS proteins) HAS1, HAS2, and HAS3. HAS3 -transfected CRO clones exhibited the highest hyaluronan polymerization rat e followed by HAS2 transfectants which were more catalytically active than HAS1 transfectants. In living cells all three RAS proteins synthesized hyal uronan chains of high molecular weight (larger than 3.9 x 10(6)). In vitro, the HAS2 isoform produced hyaluronan chains of a molecular weight larger t han 3.9 x 10(6), whereas HAS3 produced polydisperse hyaluronan (molecular w eight 0.12-1 x 10(6)), and HAS1 synthesized much shorter chains of an avera ge molecular weight of 0.12 x 10(6). Thus, each HAS protein may interact wi th different cytoplasmic proteins which may influence their catalytic activ ity. CNO transfectants with the ability to synthesize about 1 mu g hyaluron an/1 x 10(5) cells/24 h were surrounded by hyaluronan-containing coats, whe reas transfectants generating about Li-fold lower amounts of hyaluronan for med coats only in the presence of chondroitin sulfate proteoglycan. An inve rse correlation between hyaluronan production on the one hand and cell migr ation and cell surface CD44 expression on the other was found; a 4-fold low er migration and a 2-fold decrease of cell surface CD44 receptors was seen when hyaluronan production increased 1000-fold over the level in the untran sfected cells. The inverse relationships between hyaluronan production and migration and CD44 expression of cells are of importance for the regulation of cell-extracellular matrix interactions. (C) 1999 Academic Press.