Serglycin secreted by leukocytes is efficiently eliminated from the circulation by sinusoidal scavenger endothelial cells in the liver

Abstract

This study was undertaken to determine the fate of the circulating chondroitin sulfate proteoglycan serglycin. The human monocytic cell line THP-1 was cultured under serum-free conditions in the presence of [35S]sulfate. The conditioned medium was harvested and 35S-macromolecules were purified by Q-Sepharose anion-exchange chromatography and Superose 6 gel chromatography. After labeling with 125I, the purified material was treated with chondroitinase ABC and subjected to sodium dodecyl sulfate polyacrylamide gel electrophoresis. A major band with mr of approximately 14 kDa appeared, consistent with the core protein of serglycin. The identity of the proteoglycan was confirmed by amino-terminal amino acid sequencing. Purified serglycin, labeled either with [35S]sulfate or 125I and fluorescein isothiocyanate, was injected intravenously into rats. The blood content of radiolabeled serglycin fell by 50% from 1 to 2.4 min after injection, indicating an initial t1/2 of 1.4 min or shorter. Approximately 90% of the recovered radioactivity was localized in the liver, 5% in the blood, and 5% altogether in urine, kidneys, and spleen about 30 min after injection. Isolation of liver cells at the same time point showed that 70% of the radioactivity was taken up by the sinusoidal scavenger endothelial cells, and 23 and 7% by the hepatocytes and Kupffer cells, respectively. When excess amounts of unlabeled hyaluronan was coinjected with radiolabeled serglycin, the elimination of serglycin was significantly inhibited, indicating that the hyaluronan receptor on the sinusoidal scavenger endothelial cells is responsible for the elimination of serglycin.

Interaction of Pro-matrix Metalloproteinase-9/Proteoglycan Heteromer with Gelatin and Collagen

“…These experiments were repeated several times with almost identical results. In all experiments, the bound fraction contained mainly the 300-kDa pro-MMP-9⅐PG heteromer but in some experiments also a heteromer with an M r Ͼ 10 6 . To summarize, 15-35% of the pro-MMP-9⅐PG heteromers were bound to gelatin-Sepharose.…”

“…However, when monocytes are stimulated and differentiated to macrophages, both the biosynthesis and the secretion of CSPG are increased (4). The human monocyte cell line THP-1 secretes PGs such as versican, perlecan, and serglycin (5,6). The biological role of the secreted PGs such as serglycin from macrophages is not clear, but it has been shown that it binds to other molecules released from the cells through interaction with the GAG chains (7,8), suggesting that this and other PGs may act as a kind of carrier molecule.…”

Serglycin-deficient Cytotoxic T Lymphocytes Display Defective Secretory Granule Maturation and Granzyme B Storage

“…Extracts were prepared from non-stimulated spleen cells (empty symbols) and from ConA-stimulated (3 days) spleen-derived CTLs predominantly highly sulfated GAGs of heparin type ([IdoUA-GlcNAc] n carbohydrate backbone) (36), whereas bone marrow-derived mast cells synthesize GAG chains of equally high charge density albeit of chondroitin sulfate type ([GlcUA-GalNAc] n carbohydrate backbone) (37). In contrast, SG produced by macrophages (38) and NK cells (17) contain chondroitin sulfate chains of much lower charge density.…”

Serglycin: A Structural and Functional Chameleon with Wide Impact on Immune Cells

“…N-terminal sequencing of serglycin isolated from conditioned media of two different monocyte cell lines revealed extensive processing of the core protein N terminus (12,13). However, it is not known whether the N-terminal processing of serglycin has any functional consequence.…”