Identification of decorin proteoglycan in bovine tracheal serous cells in culture and localization of decorin mRNA in situ.

: Bovine tracheal submucosal gland serous cells in culture synthesize and secrete proteoglycans and not mucin glycoconjugates. We are interested in the characterization and role of these proteoglycans in airway secretions. The major [35S]methionine-labeled proteoglycan present is identified as the small chondroitin/dermatan sulfate proteoglycan decorin (PG II. PG40). Consistent with its identity as decorin this proteoglycan showed average apparent molecular weights of 75,000 to 130,000 with a core protein of an average, M(r) of about 40,000 and with glycosaminoglycan chains sensitive to chondroitinase ABC lyase of an average M(r) of about 25,000. These data were obtained from gel chromatographic and SDS-PAGE analyses. Northern blot analysis and partial amino acid sequencing of the purified protein further confirmed its identity as decorin. In situ hybridization studies using a decorin riboprobe revealed no expression of decorin in the surface epithelium and only low levels of expression in submucosal gland epithelial cells of bovine tracheal tissue. However, high levels of expression were localized to cells which are peripheral to tracheal submucosal gland epithelial cells and which contact with the extracellular matrix.