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Domains 1 and 4 of vascular cell adhesion molecule-1 (CD106) both support very late activation antigen-4
H E Chuluyan1, L Osborn, R Lobb
1Department of Pediatrics, Dalhousie University, Halifax, Nova Scotia, Canada.
Insights
Investigating vascular cell adhesion molecule-1 (VCAM-1) domains, this study shows VLA-4 interaction with VCAM-1 domains 1 or 4 mediates monocyte migration. VCAM-1 variants on endothelium depend on activation duration.
Area of Science:
- Immunology
- Cell Biology
- Molecular Biology
Background:
- Vascular cell adhesion molecule-1 (VCAM-1) is crucial for immune cell trafficking.
- Alpha 4 beta 1 integrin (VLA-4) on monocytes interacts with VCAM-1.
- Monocyte migration is a key process in inflammatory responses.
Purpose of the Study:
- To investigate the specific domains of human VCAM-1 (6-domain and 7-domain forms) involved in VLA-4-mediated monocyte migration.
- To determine the role of VCAM-1 domains 1 and 4 in C5a-induced monocyte transendothelial migration.
- To assess the influence of IL-1 activation duration on VCAM-1 expression and function.
Main Methods:
- Transfection of Chinese hamster ovary (CHO) cells with VCAM-1 6D and 7D variants.
- Monocyte migration assays across CHO cell monolayers and IL-1-treated human umbilical vein endothelium (HUVE).
- Inhibition studies using monoclonal antibodies (mAbs) against CD18, VLA-4 (alpha 4), VCAM-1 domain 1 (4B9), and VCAM-1 domain 4 (GH12).
Main Results:
- Monocyte migration across CHO cells expressing VCAM-1 variants was significantly inhibited by anti-alpha 4 mAbs.
- mAbs targeting VCAM-1 domain 1 or domain 4 partially inhibited migration across CHO VCAM-7D cells.
- Combined mAbs to VCAM-1 domains 1 and 4 completely inhibited VLA-4-mediated migration across both CHO and HUVE cells.
- CD18-independent migration across IL-1-activated HUVE was significantly inhibited by anti-VCAM-1 domain 1 mAb, with complete inhibition upon combining domain 1 and 4 mAbs.
- The efficacy of anti-VCAM-1 domain 1 mAb varied with the duration of IL-1 treatment on HUVE.
Conclusions:
- VCAM-1 domains 1 and 4 are critical mediators of VLA-4-dependent monocyte transendothelial migration.
- Interaction with either VCAM-1 domain 1 or domain 4 is sufficient to mediate VLA-4-dependent migration.
- The expression and functional contribution of VCAM-1 variants on activated endothelium are modulated by the duration of inflammatory stimulus.
Abstract:
We investigated the role of the 6 domain (6D) and 7 domain (7D) forms of human VCAM-1 as counter-receptors for the alpha 4 beta 1 integrin (VLA-4) in monocyte migration induced by C5a. Across Chinese hamster ovary (CHO) cell monolayers transfected with VCAM-6D or VCAM-7D, monocyte migration was not inhibited by treatment of monocytes with mAb to CD18. Addition of mAb to alpha 4 to the CD18 mAb inhibited monocyte migration by 90% across CHO VCAM-6D and CHO VCAM-7D. mAbs to domain 1 (4B9) or domain 4 (GH12) of VCAM-1 each inhibited migration across CHO VCAM-7D partially, when monocytes were also treated with anti-CD18 mAb. When the VCAM-1 mAbs were combined, migration of these monocytes across CHO VCAM-7D was further inhibited to the same degree as with mAbs to alpha 4 plus CD18. IL-1-treated human umbilical vein endothelium (HUVE) supported CD18-independent, VLA-4-mediated monocyte migration to C5a. A mAb to domain 1 of VCAM-1 almost completely inhibited the CD18-independent migration across HUVE activated with IL-1 for 2 h or 20 h, but was less inhibitory when HUVE was treated with IL-1 for 5 h. However, when mAbs to domain 1 and domain 4 were combined, CD18-independent migration was inhibited completely under all conditions tested. These results suggest that either domain 1 or domain 4 of VCAM-1 can mediate VLA-4-dependent monocyte transendothelial migration, that VLA-4 interaction with these two domains can account for all of the VLA-4-mediated migration, and that the expression of VCAM-1 variants on HUVE depends partly on the duration of IL-1 activation.