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Heparanase enhances shedding of syndecan-1 (CD138), and high levels of heparanase and shed syndecan-1 in the tumor microenvironment are associated with elevated angiogenesis and poor prognosis in myeloma and other cancers. To explore how the heparanase/ syndecan-1 axis regulates angiogenesis, we used myeloma cells expressing either high or low levels of heparanase and examined their impact on endothelial cell invasion and angiogenesis. Medium conditioned by heparanase-high cells significantly stimulated endothelial invasion in vitro compared with medium from heparanase-low cells. The stimulatory activity was traced to elevated levels of vascular endothelial growth factor (VEGF) and syndecan-1 in the medium. We discovered that the heparan sulfate chains of syndecan-1 captured VEGF and also attached the syndecan-1/VEGF complex to the extracellular matrix where it then stimulated endothelial invasion. In addition to its heparan sulfate chains, the core protein of syndecan-1 was also required because endothelial invasion was blocked IntroductionEnzymatic remodeling of heparan sulfate proteoglycans has emerged as a key mechanism for controlling tumor cell behavior. 1 For example, cell membrane bound heparan sulfate proteoglycans can be shed via proteases into the extracellular matrix. 2,3 Shed syndecan-1 remains biologically active and can promote tumor growth and metastasis. 4 In addition to protease-mediated shedding of proteoglycans, the heparan sulfate chains of proteoglycans can be modified by extracellular endosulfatases that specifically remove 6-O sulfate groups. 5 This structural change in heparan sulfate alters their capacity to regulate growth factor activities in a manner that can either promote or inhibit tumor growth. 6 Heparan sulfate chains can also be altered by heparanase, an enzyme that cleaves heparan sulfate chains. This activity reduces the heparan sulfate content of the proteoglycan being attacked by the enzyme and also releases biologically active fragments of heparan sulfate that are 5 to 7 kDa in molecular size. 7 Substantial data support the conclusion that heparanase promotes an aggressive phenotype in many tumor types. Much of this activity can be attributed to the fact that heparanase acts as a potent stimulator of tumor angiogenesis. 7 This effect on angiogenesis probably occurs via several mechanisms. Heparanase enzyme activity has been associated with destruction of the basement membrane before cell invasion, an event that may enhance endothelial cell migration. Heparanase can also liberate growth factors that may be "stored" on the heparan sulfate chains present both at the cell surface and within the extracellular matrix. There is also evidence that the fragments of heparan sulfate generated by heparanase can bind to and facilitate growth factor activities that enhance angiogenesis. 8 In addition, via nonenzymatic activity, heparanase can stimulate up-regulation of Akt signaling and vascular endothelial growth factor (VEGF) expression in tumor cells. 9 Although there are data suppo...

Glycosaminoglycans such as heparan sulphate and chondroitin sulphate are extracellular sugar chains involved in intercellular signalling. Disruptions of genes encoding enzymes that mediate glycosaminoglycan biosynthesis have severe consequences in Drosophila and mice. Mutations in the Drosophila gene sugarless, which encodes a UDP-glucose dehydrogenase, impairs developmental signalling through the Wnt family member Wingless, and signalling by the fibroblast growth factor and Hedgehog pathways. Heparan sulphate is involved in these pathways, but little is known about the involvement of chondroitin. Undersulphated and oversulphated chondroitin sulphate chains have been implicated in other biological processes, however, including adhesion of erythrocytes infected with malaria parasite to human placenta and regulation of neural development. To investigate chondroitin functions, we cloned a chondroitin synthase homologue of Caenorhabditis elegans and depleted expression of its product by RNA-mediated interference and deletion mutagenesis. Here we report that blocking chondroitin synthesis results in cytokinesis defects in early embryogenesis. Reversion of cytokinesis is often observed in chondroitin-depleted embryos, and cell division eventually stops, resulting in early embryonic death. Our findings show that chondroitin is required for embryonic cytokinesis and cell division.

Endocannabinoids are endogenous ligands of the cannabinoid receptors CB1 and CB2. Two arachidonic acid derivatives, arachidonoylethanolamide (anandamide) and 2-arachidonoylglycerol, are considered to be physiologically important endocannabinoids. In the known metabolic pathway in mammals, anandamide and other bioactive N-acylethanolamines, such as palmitoylethanolamide and oleoylethanolamide, are biosynthesized from glycerophospholipids by a combination of Ca 2+ -dependent N-acyltransferase and N-acyl-phosphatidylethanolamine-hydrolyzing phospholipase D, and are degraded by fatty acid amide hydrolase. However, recent studies have shown the involvement of other enzymes and pathways, which include the members of the tumor suppressor HRASLS family (the phospholipase A/acyltransferase family) functioning as Ca 2+ -independent N-acyltransferases, N-acyl-phosphatidylethanolamine-hydrolyzing phospholipaseDindependent multistep pathways via N-acylated lysophospholipid, and N-acylethanolamine-hydrolyzing acid amidase, a lysosomal enzyme that preferentially hydrolyzes palmitoylethanolamide. Although their physiological significance is poorly understood, these new enzymes/pathways may serve as novel targets for the development of therapeutic drugs. For example, selective N-acylethanolamine-hydrolyzing acid amidase inhibitors are expected to be new anti-inflammatory and analgesic drugs. In this minireview, we focus on advances in the understanding of these enzymes/pathways. In addition, recent findings on 2-arachidonoylglycerol metabolism are described.

We have identified a human chondroitin synthase from the HUGE (human unidentified gene-encoded large proteins) protein data base by screening with two keywords: "one transmembrane domain" and "galactosyltransferase family." The identified protein consists of 802 amino acids with a type II transmembrane protein topology. The protein showed weak homology to the ␤1,3-galactosyltransferase family on the amino-terminal side and to the ␤1,4-galactosyltransferase family on the carboxyl-terminal side. The expression of a soluble recombinant form of the protein in COS-1 cells produced an active enzyme, which transferred not only the glucuronic acid (GlcUA) from UDP-[ 14 C]GlcUA but also Nacetylgalactosamine (GalNAc) from UDP-[ 3 H]GalNAc to the polymer chondroitin. Identification of the reaction products demonstrated that the enzyme was chondroitin synthase, with both ␤1,3-GlcUA transferase and ␤1,4-GalNAc transferase activities. The coding region of the chondroitin synthase was divided into three discrete exons and localized to chromosome 15. Northern blot analysis revealed that the chondroitin synthase gene exhibited ubiquitous but markedly differential expression in the human tissues examined. Thus, we demonstrated that analogous to human heparan sulfate polymerases, the single polypeptide chondroitin synthase possesses two glycosyltransferase activities required for chain polymerization.