Novel chondroitin sulfate-modified ligands for L-selectin on lymph node high endothelial venules

Chondroitin 6-sulfotransferase (C6ST) catalyzes the transfer of sulfate to position 6 of the N-acetylgalactosamine residue of chondroitin. To obtain direct evidence regarding the function of C6ST and its product, chondroitin 6-sulfate, in vivo, we isolated the mouse C6ST gene (C6st) and generated mice deficient in this gene (C6st ؊/؊ ) by embryonic stem cell technology. C6st؊/؊ mice were born at approximately the expected frequency and were viable through adulthood. In the spleen of C6st ؊/؊ mice, the level of chondroitin 6-sulfate became almost undetectable. Analyses of these knockout mice provided insights into the biosynthesis of oversulfated chondroitin sulfates in mice; chondroitin sulfate D in the brain of null mice and the cartilage and telencephalon of null embryos disappeared, whereas the chondroitin sulfate E level in the spleen and brain of the null mice was unchanged. Despite the disappearance of chondroitin sulfate D structure, brain development was normal in the C6st ؊/؊ mice. Further analysis revealed that the number of CD62L ؉ CD44 low T lymphocytes corresponding to naive T lymphocytes in the spleen of 5-6-week-old C6st ؊/؊ mice was significantly decreased, whereas those in other secondary lymphoid organs were unchanged. This finding suggested that chondroitin 6-sulfate plays a role in the maintenance of naive T lymphocytes in the spleen of young mice.

mentioning

confidence: 60%

Functional Analysis of the Chondroitin 6-Sulfotransferase Gene in Relation to Lymphocyte Subpopulations, Brain Development, and Oversulfated Chondroitin Sulfates

Uchimura¹,

Kadomatsu²,

Nishimura³

et al. 2002

“…In addition, several CS proteoglycans, i.e. L-selectin-reactive CS proteoglycans of 150 and Ͼ200 kDa (38) and endoglycan (39), have been reported to be expressed in lymph node high endothelial venules where SLC is produced (36). It would be interesting to examine whether these CS proteoglycans can interact with SLC to regulate the function of SLC in situ.…”

Section: Discussionmentioning

confidence: 99%

Versican Interacts with Chemokines and Modulates Cellular Responses

Hirose¹,

Kawashima²,

Yoshie³

et al. 2001

193

140

We previously reported that versican, a large chondroitin sulfate proteoglycan, isolated from a renal adenocarcinoma cell line, ACHN, binds L-selectin. Here we report that versican also binds certain chemokines and regulates chemokine function. This binding was strongly inhibited by the chondroitinase digestion of versican or by the addition of soluble chondroitin sulfate (CS) B, CS E, or heparan sulfate. Furthermore, these glycosaminoglycans (GAGs) could bind directly to the chemokines that bind versican. Thus, versican appears to interact with chemokines via its GAGs. We next examined if versican or GAGs affect secondary lymphoid tissue chemokine (SLC)-induced integrin activation and Ca 2؉ mobilization in lymphoid cells expressing a receptor for SLC, CC chemokine receptor 7. Interestingly, whereas heparan sulfate supported both ␣ 4 ␤ 7 integrindependent binding to mucosal addressin cell adhesion molecule-1 (MAdCAM-1)-IgG and Ca 2؉ mobilization induced by SLC, versican or CS B inhibited these cellular responses, and the extent of inhibition was dependent on the dose of versican or CS B added. These findings suggest that different proteoglycans have different functions in the regulation of chemokine activities and that versican may negatively regulate the function of SLC via its GAG chains.

“…Specifically, capping groups including galactose-6-O-SO 3 Ϫ and N-acetylglucosamine-6-O-SO 3 Ϫ in the context of sialyl-Lewis x have been implicated in L-selectin ligand activity (57)(58)(59). Interestingly, a chondroitin sulfate-modified sialomucin with L-selectin binding activity has been isolated from cultures of rat high endothelial cells (60). This material was resolved into 150-and Ͼ200-kDa species by SDS-PAGE, which is reminiscent of the 165-and Ͼ200-kDa species observed for HUVEC endoglycan.…”

Section: Discussionmentioning

confidence: 99%

Identification of Endoglycan, a Member of the CD34/Podocalyxin Family of Sialomucins

Sassetti

Zante

Rosen

2000

100

125

CD34 and podocalyxin are structurally related sialomucins, which are expressed in multiple tissues including vascular endothelium and hematopoietic progenitors. These glycoproteins have been proposed to be involved in processes as diverse as glomerular filtration, inhibition of stem cell differentiation, and leukocyteendothelial adhesion. Using homologies present in the cytoplasmic tails of these proteins, we have identified a novel member of this family, which we designate endoglycan. This protein shares a similar overall domain structure with the other family members including a sialomucin domain, but also possesses an extremely acidic amino-terminal region. In addition, endoglycan contains several potential glycosaminoglycan attachment sites and is modified with chondroitin sulfate. Endoglycan mRNA and protein were detected in both endothelial cells and CD34؉ bone marrow cells. Thus, CD34, podocalyxin, and endoglycan comprise a family of sialomucins sharing both structural similarity and sequence homology, which are expressed by both endothelium and multipotent hematopoietic progenitors. While the members of this family may perform overlapping functions at these sites, the unique structural features of endoglycan suggest distinct functions for this molecule.CD34 and podocalyxin are evolutionarily related glycoproteins, which share a similar overall domain structure as well as significant sequence homology. Structurally, the extracellular region of each of these molecules is dominated by an aminoterminal mucin-like domain, which is densely substituted with sialylated O-linked carbohydrates. This extensive glycosylation causes mucin domains to adopt an extended, rodlike structure (1, 2). The mucin-like region is followed by a cysteine-containing and presumably globular domain. This domain may fold into an immunoglobulin-like structure as the positions of 2 of the cysteines are conserved in the C2 set of the immunoglobulin superfamily (3). The cytoplasmic domains of these proteins are 73-76 amino acids in length and highly conserved between species orthologs. It is also in this region that the highest homology between CD34 and podocalyxin is found (4).