Nepmucin, a novel HEV sialomucin, mediates L-selectin-dependent lymphocyte rolling and promotes lymphocyte adhesion under flow.
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.
Umemoto
Eiji
E
Laboratory of Immunodynamics, Department of Microbiology and Immunology, Graduate School of Medicine, Osaka University, Osaka 565-0871, Japan.
Tanaka
Toshiyuki
T
Kanda
Hidenobu
H
Jin
Soojung
S
Tohya
Kazuo
K
Otani
Kazuhiro
K
Matsutani
Takahiro
T
Matsumoto
Masanori
M
Ebisuno
Yukihiko
Y
Jang
Myoung Ho
MH
Fukuda
Minoru
M
Hirata
Takako
T
Miyasaka
Masayuki
M
D000595:Amino Acid Sequence; D000818:Animals; D002448:Cell Adhesion; D018076:DNA, Complementary / Q000235:genetics; D004730:Endothelium, Vascular / Q000502:physiology; D006801:Humans; D019041:L-Selectin / Q000502:physiology*; D008214:Lymphocytes / Q000382:microbiology / Q000502:physiology*; D051379:Mice; D008969:Molecular Sequence Data; D010581:Peyer's Patches / Q000276:immunology / Q000502:physiology; D012333:RNA, Messenger / Q000235:genetics; D052116:Sialomucins / Q000235:genetics / Q000502:physiology*; D014699:Venules / Q000502:physiology
D018076:DNA, Complementary; D012333:RNA, Messenger; D052116:Sialomucins; C512481:nepmucin, mouse; D019041:L-Selectin