Effect of tunicamycin on the metabolism of low-density lipoproteins by control and low-density-lipoprotein-receptor-deficient human skin fibroblasts

Preincubation of normal human skin fibroblasts with tunicamycin, which inhibits N-glycosylation of glycoproteins, resulted in a dose-dependent and reversible inhibition of binding and internalization of homologous low-density lipoproteins by the cells. The degradation of the internalized lipoproteins was not affected by the drug. Comparative studies with fibroblasts deficient in low-density-lipoprotein receptors indicated that tunicamycin exerts its inhibitory effect only via the receptor-mediated high-affinity binding and uptake of lipoproteins. These results suggest that expression of low-density-lipoprotein receptors on the cell surface of human skin fibroblasts depends on intact N-glycosylation.