MOLECULAR BASIS OF CELL AND DEVELOPMENTAL BIOLOGY
Prominent Role of the Ig-like V Domain intrans-Interactions of Nectins: NECTIN3 AND NECTIN4 BIND TO THE PREDICTED C-C′-C“-D β-STRANDS OF THE NECTIN1 V DOMAIN*

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Nectins form a family of integral molecules that belong to the immunoglobulin superfamily. Their ectodomain is made of three Ig-like domains (V, C, C). This family comprises at least five members, namely nectin1, -2, -3, -4, and poliovirus receptor (PVR), that are involved in different physiological and pathological processes. (i) Nectins are adhesion molecules localized at adherens junctions in epithelial cells. (ii) Some nectins act as poliovirus or α-herpesvirus receptors (nectin1). (iii) Nectin1 mutations are involved in orofacial developmental abnormalities in humans. Adhesion properties of nectins are mediated by Ca2+-independent homophilic and heterophilic processes through ectodomaintrans-interactions. We have described a nectintrans-hetero-interaction network: nectin3 binds to nectin1, nectin2, and PVR; nectin1 also binds to nectin4. In the present study we compared the affinities of the differenttrans-interactions mediated by nectin1. We found that theKD of nectin1/nectin3 and nectin1/nectin4 interactions is 1 and 100 nm, respectively, whereas theKD of the nectin1-mediated homophilic interaction is 1 μm. We show that nectin1/nectin3 and nectin1/nectin4trans-hetero-interactions were mediated throughtrans V to V domain interactions, whereas C domains contributed to increase the affinity of the interaction. Nectin3 and nectin4 share a common binding region in the nectin1 V domain: (i) nectin3 strongly competed with nectin4 binding, (ii) nectin3 and nectin4 binding to nectin1 was reduced by a number of monoclonal antibodies directed against the nectin1 V domain, and (iii) the glycoprotein D of herpes simplex virus-1 that binds to the V domain of nectin1 reduced nectin3 and nectin4 binding. Finally, using chimeric nectin1/PVR receptors where PVR V domain β-strands were substituted with the corresponding regions of nectin1, the nectin3 and nectin4 minimal binding region on nectin1 V domain was mapped to the C-C′-C“-D β-strands.

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Published, JBC Papers in Press, May 14, 2002, DOI 10.1074/jbc.M203228200

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This work was supported by INSERM, the Association pour la Recherche Contre le Cancer (ARC), and the Ligue Nationale Française Contre le Cancer (LNFCC). The work done at the University of Bologna was supported by Telethon Grant A141, CNR-Agenzia 2000 grants (to L. M. and G. C. F.), Cofin-MIUR, University of Bologna (60%), and Giovani Ricercatori 2001.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.