AN ABUNDANTLY SECRETED GLYCOPROTEIN FROM DROSOPHILA-MELANOGASTER IS RELATED TO MAMMALIAN SECRETORY PROTEINS PRODUCED IN RHEUMATOID TISSUES AND BY ACTIVATED MACROPHAGES

An abundantly secreted 47-kDa glycoprotein, DS47, was purified from Dr osophila melanogaster (Dm) Schneider line-a cells, a line exhibiting m acrophage-like properties. DS47 is also secreted from several Dm cell lines resembling S2 but not from lines that are morphologically distin ct. A cDNA clone nias isolated from an S2 cell cDNA library using olig odeoxyribonucleotide probes based on the DS47 amino acid (aa) sequence and found to encode a novel secretory glycoprotein of 452 aa. Analysi s of DS47 protein production and mRNA expression during Ay development indicates that both are present throughout the entire Dm life cycle, suggesting that DS47 may be important at all developmental stages, In larvae, the DS47 message is made in the fat body and by hemocytes, and secreted into the hemolymph. DS47 is related to a human cartilage gly coprotein, HC gp-39, that is secreted from cell types associated with the arthritic joint, such as synovial cells and activated macrophages. Interestingly, the HC gp-39 message is most readily detected in the h uman liver, an organ that is somewhat analogous to the Dm rat body. DS 47 also shares homology to a mouse secretory glycoprotein, YM-1, ident ified in activated macrophages. These homologies extend to the chitina se gene family and include a conserved cysteine aa motif, as well as t wo blocks of aa within the enzymatic active site, although neither DS- 47 nor HC gp-39 exhibit chitinase activity. Potential functions of thi s conserved protein family are discussed.