Isolation of the SO4-4-GalNAcβ1,4GlcNAcβ1,2Manα-specific Receptor from Rat Liver

We previously reported that CR-Fc, an Fc chimeric protein containing the cysteine-rich (CR) domain of the mannose receptor, binds to marginal zone metallophilic macrophages (Mø) and B cell areas in the spleen and to subcapsular sinus Mø in lymph nodes of naive mice (CRFc ؉ cells). Several CR-Fc ligands were found in spleen and lymph node tissue lysates using ligand blots. In this paper we report the identification of two of these ligands as sialoadhesin (Sn), an Mø-specific membrane molecule, and the leukocyte common antigen, CD45. CR-Fc bound selectively to Sn purified from spleen and lymph nodes and to two low molecular weight isoforms of CD45 in a sugar-dependent manner. CR-Fc binding and non-binding forms of Sn, probably derived from CR-Fc؉ and CR-Fc ؊ cells respectively, were selected from spleen lysates. Analysis of the glycan pool associated with the CR-Fc-binding form revealed the presence of charged structures resistant to sialidase, absent in the non-binding form, that could correspond to sulfated structures. These results confirm the identification of the CR region of the mannose receptor as a lectin. We also demonstrate that the same glycoprotein expressed in different cells of the same organ can display distinct sugar epitopes that determine its binding properties.

Section: Discussionmentioning

confidence: 99%

Cell-specific Glycoforms of Sialoadhesin and CD45 Are Counter-receptors for the Cysteine-rich Domain of the Mannose Receptor

Martı́nez-Pomares¹,

Crocker²,

Silva³

et al. 1999

“…with ␤1,4-linked GalNAc-4-SO 4 are recognized by a receptor located in hepatic endothelial cells, the Man/GalNAc-4-SO 4 receptor, and are rapidly removed from the circulation (1)(2)(3)(4). Rapid clearance in conjunction with stimulated release from dense core storage granules in LH-producing cells located in the anterior lobe of the pituitary produce the episodic rise and fall in serum LH levels that is important for the expression of LH bioactivity in vivo.…”

mentioning

confidence: 99%

The Mannose/N-Acetylgalactosamine-4-SO4Receptor Displays Greater Specificity for Multivalent than Monovalent Ligands

Roseman

Baenziger²

2001

Self Cite

Recognition of carbohydrates on glycosylated molecules typically requires multivalent interactions with receptors. Monovalent forms of terminal saccharides engaged by the receptor binding sites typically display weak affinities in the mM range and poor specificity. In contrast, multivalent forms of the same saccharides are bound with strong affinity (10 ؊7 -10 ؊9 M) and significantly greater specificity. Although multivalency can readily account for increased affinity, the molecular basis for enhanced specificity is not well understood. We have examined the specificity of the cysteine-rich domain of the mannose/GalNAc-4-SO 4 receptor using monovalent and multivalent forms of the trisaccharide GalNAc␤1,4GlcNAc␤1,2Man␣ (GGnM) sulfated at either the C4 (S4GGnM) or C3 ( We previously demonstrated that glycoproteins such as LH 1 and thyrotropin bearing N-linked oligosaccharides terminating with ␤1,4-linked GalNAc-4-SO 4 are recognized by a receptor located in hepatic endothelial cells, the Man/GalNAc-4-SO 4 receptor, and are rapidly removed from the circulation (1-4). Rapid clearance in conjunction with stimulated release from dense core storage granules in LH-producing cells located in the anterior lobe of the pituitary produce the episodic rise and fall in serum LH levels that is important for the expression of LH bioactivity in vivo. A novel feature of the Man/GalNAc-4-SO 4 receptor is its capacity to bind carbohydrate moieties terminating with Man and GalNAc-4-SO 4 at physically distinct domains that are not structurally related. The binding site for GalNAc-4-SO 4 is located in the cysteine-rich domain found at the N terminus of the Man/GalNAc-4-SO 4 receptor (5). The Cys-rich domain is a member of the ␤-trefoil family of proteins that includes proteins such as acidic fibroblast growth factor. The binding site is a neutral pocket that accommodates the sulfate group, which accounts for the major interactions with the protein (6). Inhibition and modeling studies with monovalent ligands have indicated that the binding site in the Cys-rich domain can also accommodate saccharides with terminal Gal or GalNAc when the sulfate is located at C3 rather than C4 (6, 7).The latter observations were unexpected because we had reported that bovine serum albumin substituted with 6 -8 molecules of SO 4 -4-GalNAc␤1,4GlcNAc␤1,2Man␣ (S4GGnM-BSA) is removed from the circulation at a rate that is at least 12-fold greater than that seen for bovine serum albumin substituted with 6 -8 molecules of SO 4 -3-GalNAc␤1,4GlcNAc␤1,2Man␣ (S3GGnM-BSA). Furthermore, isolated hepatic endothelial cells do not bind and internalize S3GGnM-BSA, and the purified Man/GalNAc-4-SO 4 receptor does not display significant binding of S3GGnM-BSA in precipitation assays (2, 3). We have recently determined that the Man/GalNAc-4-SO 4 receptor must be dimeric and engage at least two terminal GalNAc-4-SO 4 moieties on separate oligosaccharides to mediate uptake by hepatic endothelial cells with a K d of 1.63 ϫ 10 Ϫ7 M (8). These observations raise the possibility th...

“…In the case of LH, the structural features of the LacdiNAc determine the circulatory half-life of the hormone following its release into the circulation, and as a result, its potency in vivo (22,23,36). SO 4 -4-GalNAc␤1, 4GlcNAc␤ is recognized by the N-terminal Cys-rich domain of the mannose receptor in its dimeric form (18,19,21,23), whereas NeuNAc␣2,6GalNAc␤1,4GlcNAc␤ is recognized by the asialoglycoprotein receptor (24). The mannose receptor and the asialoglycoprotein receptor are highly abundant endocytic receptors that reside in endothelial cells and parenchymal cells of the liver, respectively.…”

Section: Discussionmentioning

confidence: 99%

Peptide-specific Transfer of N-Acetylgalactosamine to O-Linked Glycans by the Glycosyltransferases β1,4-N-Acetylgalactosaminyl Transferase 3 (β4GalNAc-T3) and β4GalNAc-T4

Fiete

Beranek

Baenziger

2012

Self Cite

Background: LacdiNAc (GalNAc␤1,4GlcNAc) is present on O-and N-linked carbohydrate moieties of pro-opiomelanocortin. Results: ␤1,4-N-acetylgalactosaminyltransferases ␤4GalNAc-T3 and ␤4GalNAc-T4 mediate peptide-specific transfer of GalNAc to O-linked structures in vivo and in vitro. Conclusion: ␤4GalNAc-T3 and ␤4GalNAc-T4 can account for LacdiNAc sequences on O-linked structures on specific glycoproteins. Significance: The protein-specific addition of LacdiNAc to O-linked carbohydrates generates a family of unique structures recognized by carbohydrate-specific receptors.