EMR4, a novel epidermal growth factor (EGF)-TM7 molecule up-regulated in activated mouse macrophages, binds to a putative cellular ligand on B lymphoma cell line A20.
A novel member of the EGF-TM7 family, mEMR4, was identified and characterized. The full-length mouse EMR4 cDNA encodes a predicted 689-amino acid protein containing two epidermal growth factor (EGF)-like modules, a mucin-like spacer domain, and a seven-transmembrane domain with a cytoplasmic tail. Genetic mapping established that mEMR4 is localized in the distal region of mouse chromosome 17 in close proximity to another EGF-TM7 gene, F4/80 (Emr1). Similar to F4/80, mEMR4 is predominantly expressed on resident macrophages. However, a much lower expression level was also detected in thioglycollate-elicited peritoneal neutrophils and bone marrow-derived dendritic cells. The expression of mEMR4 is up-regulated following macrophage activation in Biogel and thioglycollate-elicited peritoneal macrophages. Similarly, mEMR4 is over-expressed in TNF-alpha-treated resident peritoneal macrophages, whereas interleukin-4 and -10 dramatically reduce the expression. mEMR4 was found to undergo proteolytic processing within the extracellular stalk region resulting in two protein subunits associated noncovalently as a heterodimer. The proteolytic cleavage site was identified by N-terminal amino acid sequencing and located at the conserved GPCR (G protein-coupled receptor) proteolytic site in the extracellular region. Using multivalent biotinylated mEMR4-mFc fusion proteins as a probe, a putative cell surface ligand was identified on a B lymphoma cell line, A20, in a cell-binding assay. The mEMR4-ligand interaction is Ca2+-independent and is mediated predominantly by the second EGF-like module. mEMR4 is the first EGF-TM7 receptor known to mediate the cellular interaction between myeloid cells and B cells.
Stacey
Martin
M
Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford, OX1 3RE, United Kingdom.
Chang
Gin-Wen
GW
Sanos
Stephanie L
SL
Chittenden
Laura R
LR
Stubbs
Lisa
L
Gordon
Siamon
S
Lin
Hsi-Hsien
HH
D000595:Amino Acid Sequence; D000596:Amino Acids / Q000737:chemistry; D000818:Animals; D001665:Binding Sites; D019921:Biotinylation; D015153:Blotting, Western; D002478:Cells, Cultured; D002874:Chromosome Mapping; D003001:Cloning, Molecular; D003593:Cytoplasm / Q000378:metabolism; D018076:DNA, Complementary / Q000378:metabolism; D003713:Dendritic Cells / Q000378:metabolism; D004815:Epidermal Growth Factor / Q000737:chemistry* / Q000378:metabolism*; D005434:Flow Cytometry; D008040:Genetic Linkage; D005822:Genetic Vectors; D008024:Ligands; D016393:Lymphoma, B-Cell / Q000737:chemistry*; D008262:Macrophage Activation; D008264:Macrophages / Q000378:metabolism*; D051379:Mice; D008954:Models, Biological; D008969:Molecular Sequence Data; D022423:Myeloid Cells / Q000378:metabolism; D009504:Neutrophils / Q000378:metabolism; D017434:Protein Structure, Tertiary; D012313:RNA / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction; D014018:Tissue Distribution; D015854:Up-Regulation
D000596:Amino Acids; D018076:DNA, Complementary; C464944:Emr4 protein, mouse; D008024:Ligands; D004815:Epidermal Growth Factor; D012313:RNA