Nepmucin, a novel HEV sialomucin, mediates L-selectin–dependent lymphocyte rolling and promotes lymphocyte adhesion under flow

Abstract

Lymphocyte trafficking to lymph nodes (LNs) is initiated by the interaction between lymphocyte L-selectin and certain sialomucins, collectively termed peripheral node addressin (PNAd), carrying specific carbohydrates expressed by LN high endothelial venules (HEVs). Here, we identified a novel HEV-associated sialomucin, nepmucin (mucin not expressed in Peyer's patches [PPs]), that is expressed in LN HEVs but not detectable in PP HEVs at the protein level. Unlike conventional sialomucins, nepmucin contains a single V-type immunoglobulin (Ig) domain and a mucin-like domain. Using materials affinity-purified from LN lysates with soluble L-selectin, we found that two higher molecular weight species of nepmucin (75 and 95 kD) were decorated with oligosaccharides that bind L-selectin as well as an HEV-specific MECA-79 monoclonal antibody. Electron microscopic analysis showed that nepmucin accumulates in the extended luminal microvillus processes of LN HEVs. Upon appropriate glycosylation, nepmucin supported lymphocyte rolling via its mucin-like domain under physiological flow conditions. Furthermore, unlike most other sialomucins, nepmucin bound lymphocytes via its Ig domain, apparently independently of lymphocyte function–associated antigen 1 and very late antigen 4, and promoted shear-resistant lymphocyte binding in combination with intercellular adhesion molecule 1. Collectively, these results suggest that nepmucin may serve as a dual-functioning PNAd in LN HEVs, mediating both lymphocyte rolling and binding via different functional domains.

Transcription Factor Nkx2-3 Controls the Vascular Identity and Lymphocyte Homing in the Spleen

“…According to our qPCR data, these unusual splenic HEVs use predominantly GlyCAM-1 besides some other PNAd core proteins but no or very little MAdCAM-1 as homing receptor (28)(29)(30)(31)(32)(33). Replacement of MAdCAM-1 by PNAd in the spleen of the Nkx2-3 2/2 mouse occurs postnatally, suggesting that early MAdCAM-1 expression may either not be controlled by Nkx2-3 or, alternatively, may be regulated by coexpressed proteins such as Nkx2-5, providing redundant functions.…”

Regulation of Leukocyte Migration Across Endothelial Barriers by ECTO-5′-Nucleotidase-Generated Adenosine

“…The specific adenosine receptor subtype that might be involved has not yet been identified. However, since CD73 has also been reported to function as an adhesion molecule in the interaction between lymphocytes and endothelial cells, [5] this possibility cannot be eliminated by the available data.…”

Constitutive Plasmacytoid Dendritic Cell Migration to the Splenic White Pulp Is Cooperatively Regulated by CCR7- and CXCR4-Mediated Signaling

“…Anti-PV-1 (MECA-32) mAb was from Developmental Studies Hybridoma Bank. Antinepmucin/CD300g (ZAQ5) mAb was prepared in our laboratory, as described previously (28). CCL19-Fc, CXCL12-Fc, and control human IgG Fc were provided by Drs.…”