MOLECULAR-CLONING OF A PHOSPHATIDYLINOSITOL-ANCHORED MEMBRANE HEPARAN-SULFATE PROTEOGLYCAN FROM HUMAN LUNG FIBROBLASTS

Two mAbs raised against the 64-kD core protein of a membrane heparan sulfate proteoglycan from human lung fibroblasts also recognize a non-hydrophobic proteoglycan which accumulates in the culture medium of the cells. Pulse-chase studies suggest that the hydrophobic cell-associated forms act as precursors for the nonhydrophobic medium-released species. The core proteins of the medium-released proteoglycans are slightly smaller than those of the hydrophobic cell-associated species, but the NH2- terminal amino acid sequences of both forms are identical. The characterization of human lung fibroblast cDNAs that encode the message for these core proteins and the effect of bacterial phosphatidylinosi-tol-specific phospholipase C suggest that the hydrophobic proteoglycan is membrane-anchored through a phospholipid tail. These data identify a novel membrane proteoglycan in human lung fibroblasts and imply that the shedding of this proteoglycan in human lung fibroblasts and imply that the shedding of this proteoglycan may be related to the presence of the phospholipid anchor.