Effect of sialylation on leukocyte transmigration through endothelial cells

我们想知道唾液酸化缺陷如何影响内皮细胞的表型。为此，我们从野生型和ST 6 Gal I缺陷小鼠制备肝窦状内皮细胞（LSEC）。胶原酶灌注后，分离肝脏并切成小块。然后通过磁珠分离LSEC。我们发现，特定细胞粘附分子的细胞表面水平在来自ST 6 Ga 1 I缺陷小鼠的LSEC中显著降低。我们做了细胞表面生物素化实验，发现细胞表面粘附分子的半衰期缩短。有趣的是，sislylateion缺陷的细胞更敏感的细胞凋亡stimulations.We阐明的生物学意义的ST 6 Gal I裂解BACE 1。通过BACE 1过表达，可溶性糖蛋白（例如转铁蛋白）的唾液酸化显著增加（J. Biol. Chem. 282，34896-34903）。在肝脏急性反应时，肝脏产生大量的血浆糖蛋白，其中大部分是唾液酸化的。非唾液酸化糖蛋白被肝脏中的去唾液酸糖蛋白受体捕获以降解。我们目前的假设是血浆糖蛋白通过BACE 1过表达被可溶性唾液酸转移酶有效地唾液酸化。我们的发现揭示了糖基转移酶裂解分泌的功能意义。

We wanted to know how sialylation deficiency would affect on the phenotype of endothelial cells. To do so, we prepared liver sinudoidal endothelial cells (LSECs) from wild type and ST6Ga1 I defieicnt mice. After collagenase perfusion, liver was isolated and cut into small pieces. LSECs were then separated by magnetic beads. We found that cell surface level of particular cell adhesion molecule was significantly decreased in LSECs from ST6Ga1 I deficient mice. We did cell surface biotinylation experiment and showed that half life of cell surface adhesion molecule was decreased. Interestingly, sislylateion deficient cells were more sensitive to mitochondrial-dependent apoptotic stimuli.We elucidate the biological significance of ST6Gal I cleavage by BACE1. By BACE1 over-expression, sialylation of soluble glycoproteins (e.g. transferrin) were significantly increased (J. Biol. Chem. 282, 34896-34903). During hepatic acute reaction, liver produces a large amount of plasma glycoproteins, most of which are sialylated. Non-sialylated glycoproteins are trapped by asialoglycoprotein receptor in livers for degradation. Our current hypotheis is that plasma glycoproteins are effectively sialylated by soluble sialyltransferases by BACE1 over-expression. Our finding shed light on the functional siginificance of the cleavage-secretion of glycosyltransferase.