Synthesis, secretion, and subcellular localization of serglycin proteoglycan in human endothelial cells

The serglycin proteoglycan is best known as a hematopoietic cell granule pr oteoglycan, It has been found that serglycin is synthesized by endothelial cells, is localized to cytoplasmic vesicles, and is constitutively secreted . Serglycin messenger RNA in human umbilical vein endothelial cells (HUVECs ) and cultured human aortic endothelial cells was detected by reverse trans cription-polymerase chain reaction. S-35-sulfate-labeled secreted and intra cellular proteoglycans were analyzed. It was found that 85% of the proteogl ycans synthesized during culture were secreted, A core protein of the appro priate size for serglycin was detected by analysis of the chondroitinase-di gested S-35-sulfate-labeled HUVEC proteoglycans. This was the major core pr otein of the secreted chondroitin sulfate proteoglycans. Recombinant sergly cin core protein was used to generate an antibody in chickens. A core prote in identified by Western blotting of chondroitinase digests of HUVEC proteo glycans corresponded to the major S-35-sulfate-labeled core protein. Identi cal results were obtained with 2 hematopoietic cell lines. Cyto-immunofluor escence showed cytoplasmic vesicular and perinuclear labeling in hematopoie tic cells and HUVECs. The serglycin-containing vesicles in HUVECs are disti nct from the Weibel-Palade bodies, which contain von Willebrand factor. Con focal microscopy showed that tissue plasminogen activator was distributed s imilarly to serglycin, Serglycin may be important for the function of these vesicles and, once secreted, for the modulation of the activity of their c onstituents. (C) 2001 by The American Society of Hematology.