title: The homophilic binding of junctional adhesion molecule-C mediates tumor cell-endothelial cell interactions.
abstract: The junctional adhesion molecule C (JAM-C) was recently shown to undergo a heterophilic interaction with the leukocyte beta2 integrin Mac-1, thereby mediating interactions between vascular cells in inflammatory cell recruitment. Here, the homophilic interaction of JAM-C is presented and functionally characterized to mediate tumor cell-endothelial cell interactions. Recombinant soluble JAM-C in fluid phase bound to immobilized JAM-C as assessed in a purified system; moreover, JAM-C-transfected Chinese hamster ovary (CHO) cells adhered to immobilized JAM-C. The homophilic interaction of JAM-C was mediated by the isolated amino-terminal Ig domain (D1), but not the carboxyl-terminal Ig domain (D2), of the molecule. Dimerization of JAM-A is dependent on the sequence RVE in the amino-terminal Ig domain. This motif is conserved in JAM-C (Arg64-Ile65-Glu66), and a single amino acid mutation in this motif (E66R) abolished the homophilic interaction of JAM-C. The lung carcinoma cell line NCI-H522 was found to express JAM-C. NCI-H522 cells adhered to immobilized JAM-C, as well as to JAM-C-transfected CHO cells, but not to mock-transfected CHO cells or to CHO cells transfected with the JAM-C mutant (E66R). Adhesion of NCI-H522 cells to JAM-C protein or JAM-C-transfected CHO cells was abolished in the presence of soluble JAM-C or the isolated D1. Furthermore, the adhesion of NCI-H522 cells to endothelial cells was significantly blocked by soluble JAM-C or the isolated D1. Thus, JAM-C undergoes a homophilic interaction via the Arg64-Ile65-Glu66 motif on the membrane-distal Ig domain of the molecule. The homophilic interaction of JAM-C can mediate tumor cell-endothelial cell interactions and may thereby be involved in the process of tumor cell metastasis.
authors.affiliation: Experimental Immunology Branch, NCI, National Institutes of Health, Bethesda, Maryland 20892, USA.
authors.forename: Sentot
authors.initials: S
authors.lastname: Santoso
authors.forename: Valeria V
authors.initials: VV
authors.lastname: Orlova
authors.forename: Kaimei
authors.initials: K
authors.lastname: Song
authors.forename: Ulrich J
authors.initials: UJ
authors.lastname: Sachs
authors.forename: Cornelia L
authors.initials: CL
authors.lastname: Andrei-Selmer
authors.forename: Triantafyllos
authors.initials: T
authors.lastname: Chavakis
mesh_terms: D020816:Amino Acid Motifs; D000818:Animals; D016466:CHO Cells; D002448:Cell Adhesion; D015815:Cell Adhesion Molecules / Q000737:chemistry / Q000502:physiology*; D045744:Cell Line, Tumor; D002478:Cells, Cultured; D006224:Cricetinae; D019281:Dimerization; D004305:Dose-Response Relationship, Drug; D042783:Endothelial Cells / Q000166:cytology*; D004730:Endothelium, Vascular / Q000166:cytology; D004926:Escherichia coli / Q000378:metabolism; D005434:Flow Cytometry; D006801:Humans; D007074:Immunoglobulin G / Q000737:chemistry; D007136:Immunoglobulins / Q000737:chemistry / Q000502:physiology*; D008565:Membrane Proteins / Q000737:chemistry / Q000502:physiology*; D008856:Microscopy, Fluorescence; D009154:Mutation; D009362:Neoplasm Metastasis; D011485:Protein Binding; D020033:Protein Isoforms; D017434:Protein Structure, Tertiary; D011993:Recombinant Fusion Proteins / Q000737:chemistry; D011994:Recombinant Proteins / Q000737:chemistry; D020349:Surface Plasmon Resonance; D014162:Transfection; D014471:Umbilical Veins / Q000166:cytology
chemical_list: D015815:Cell Adhesion Molecules; D007074:Immunoglobulin G; D007136:Immunoglobulins; C448000:JAM3 protein, human; D008565:Membrane Proteins; D020033:Protein Isoforms; D011993:Recombinant Fusion Proteins; D011994:Recombinant Proteins