Response of stratified cultures of human keratinocytes to disruption of proteoglycan synthesis by p‐nitrophenyl‐β‐D‐xylopyranoside

Abstract

Proteoglycans play a role in regulating proliferation and adhesion of cells to each other and to the basal lamina. Synthesis of proteoglycans is disrupted by β-xylosides, which serve as alternate substrate sites for glycosaminoglycan chain attachment and therefore prevent glycosylation of the core protein. We have investigated the effects of p-nitrophenyl-β-D-xylopyranoside (PNP-xyloside) on cultured human keratinocytes. Stratified cultures were incubated for 7 days with PNP-xyloside (0.05–2.0 mM). Concentrations as low as 0.05 mM increased the secretion of free chondroitin sulfate by 10–15-fold over untreated cultures. Cellassociated proteoglycan decreased as PNP-xyloside concentration increased. At 2 mM PNP-xyloside, heparan sulfate as well as chondroitin sulfate addition to core proteins was disrupted: the core protein of epican, a heparan sulfate form of CD44 found on keratinocytes, was detected immunologically but lacked heparan sulfate. 2.0 mM PNP-xyloside reduced the number of attached cells by 20–25% after 7 days, but had little effect on morphology or protein synthesis. These results indicate that intact proteoglycans are not critical for maintaining epidermal keratinocyte stratification, cell-cell adhesion, or growth.