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

doi:10.1074/jbc.274.49.35211

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

From the ^‡Sir William Dunn School of Pathology, Oxford University, Oxford OX1 3RE, the ^¶Department of Biochemistry, Wellcome Trust Building, University of Dundee, Dundee DD1 4HN, Scotland, the ^‖Division of Immunology, Department of Pathology, Cambridge University, Cambridge CB2 1QP, and the ^**Glycobiology Institute, Department of Biochemistry, Oxford University, Oxford OX1 3QU, United Kingdom

Abstract

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 (CR-Fc⁺ 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.

Footnotes

↵* This work has been funded by the Arthritis Research Campaign, the Medical Research Council, and the Biotechnology and Biological Sciences Research Council, UK.The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
↵§ To whom correspondence should be addressed: Sir William Dunn School of Pathology, University of Oxford, South Parks Rd., Oxford OX1 3RE, UK. Tel.: 44-(0)1865 275531; Fax: 44-(0)1865 275515; E-mail: pomares@worf.molbiol.ox.ac.uk.
↵2 L. Martı́nez-Pomares, unpublished observations.
Abbreviations:

MR

mannose receptor

CR-Fc

cysteine-rich domain Fc chimera

Mø

macrophage

Sn

sialoadhesin

MZMMø

marginal zone metallophilic macrophages

HPLC

high performance liquid chromatography

NP-HPLC

normal phase high performance liquid chromatography

WAX

weak anionic exchange chromatography

2-AB

2-aminobenzamide

PNGase F

peptideN-glycosidase F

PAGE

polyacrylamide gel electrophoresis

mAb

monoclonal antibody

Ab

antibody

LN

lymph nodes

DTT

dithiothreitol

NMS

normal mouse serum

thio-Mø

thioglycollate-elicited Mø

CHO

Chinese hamster ovary
- Received July 26, 1999.
- Revision received September 22, 1999.
The American Society for Biochemistry and Molecular Biology, Inc.