Calmodulin may decrease cell surface sialic acid and be involved in the expression of fibronectin during liver regeneration

The decrease of sialic acid in plasma membrane glycoproteins and the expression of cell surface fibronectin were studied during the pre-replicative phase of liver regeneration. The aim of this study was to correlate these cell-surface events to the intracellular surge of calmodulin observed a few hours after partial hepatectomy. The fact that calmodulin decreased the specific activity of UDP-N-acetyl-D-glucosamine 2'-epimerase, a key regulatory enzyme in the biosynthesis of glycoprotein sialic acids, and that trifluoperazine prevented the desialylation indicates that the membrane desialylation is a calmodulin-dependent process. On the other hand, Western blotting using anti-rat fibronectin antibody in trifluoperazine-treated animals suggests that calmodulin may also be involved in the surface expression of fibronectin in regenerating hepatocytes.