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* Department of Anatomy, University of California, San Francisco, CA 94143; and
Department of Pharmacology, University of Illinois, Chicago, IL 60612
The interactions of the selectin family of adhesion molecules with their ligands are essential for the initial rolling stage of leukocyte trafficking. Under inflammatory conditions, the vascular selectins, E- and P-selectin, are expressed on activated vessels and interact with carbohydrate-based ligands on the leukocyte surface. While several ligands have been characterized on human T cells, monocytes and neutrophils, there is limited information concerning ligands on B cells. Endoglycan (EG) together with CD34 and podocalyxin comprise the CD34 family of sialomucins. We found that EG, previously implicated as an L-selectin ligand on endothelial cells, was present on human B cells, T cells and peripheral blood monocytes. Upon activation of B cells, EG increased with a concurrent decrease in PSGL-1. Expression of EG on T cells remained constant under the same conditions. We further found that native EG from several sources (a B cell line, a monocyte line and human tonsils) was reactive with HECA-452, a mAb that recognizes sialyl Lewis X and related structures. Moreover, immunopurified EG from these sources was able to bind to P-selectin and where tested E-selectin. This interaction was divalent cation-dependent and required sialylation of EG. Finally, an EG construct supported slow rolling of E- and P-selectin bearing cells in a sialic acid and fucose dependent manner, and the introduction of intact EG into a B cell line facilitated rolling interactions on a P-selectin substratum. These in vitro findings indicate that EG can function as a ligand for the vascular selectins.
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1 This work was supported by Grants R01-GM57411 and R01-GM23547 to S.D.R. and R01-GM060563 to K.R.S. from the National Institutes of Health. S.C.K. and C.B.F. were supported by Postdoctoral Fellowships from the Arthritis Foundation.
2 Current address: Raven Biotechnologies Inc., One Corporate Drive, South San Francisco, CA 94080.
3 Address correspondence and reprint requests to Dr. Steven D. Rosen, Department of Anatomy, University of California, 513 Parnassus Avenue, San Francisco, CA 94143. E-mail address: sdr{at}itsa.ucsf.edu
4 Abbreviations used in this paper: HEV, high endothelial venule; PNAd, peripheral lymph node addressin; EG, endoglycan; PSGL-1, P-selectin glycoprotein ligand-1; FT, fucosyltransferase; sLex, sialyl lewis(x); pAb, polyclonal Ab; AD-Ig, acidic domain-Fc fusion protein of endoglycan; AD-FT, acidic domain-Fc fusion protein; CHO, chinese hamster ovary.
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