Homophilic adhesion and CEACAM1-S regulate dimerization of CEACAM1-L and recruitment of SHP-2 and c-Src.
Carcinoembryonic antigen (CEA)-related cell adhesion molecule 1 (CAM1 [CEACAM1]) mediates homophilic cell adhesion and regulates signaling. Although there is evidence that CEACAM1 binds and activates SHP-1, SHP-2, and c-Src, knowledge about the mechanism of transmembrane signaling is lacking. To analyze the regulation of SHP-1/SHP-2/c-Src binding, we expressed various CFP/YFP-tagged CEACAM1 isoforms in epithelial cells. The supramolecular organization of CEACAM1 was examined by cross-linking, coclustering, coimmunoprecipitation, and fluorescence resonance energy transfer. SHP-1/SHP-2/c-Src binding was monitored by coimmunoprecipitation and phosphotyrosine-induced recruitment to CEACAM1-L in cellular monolayers. We find that trans-homophilic CEACAM1 binding induces cis-dimerization by an allosteric mechanism transmitted by the N-terminal immunoglobulin-like domain. The balance of SHP-2 and c-Src binding is dependent on the monomer/dimer equilibrium of CEACAM1-L and is regulated by trans-binding, whereas SHP-1 does not bind under physiological conditions. CEACAM1-L homodimer formation is reduced by coexpression of CEACAM1-S and modulated by antibody ligation. These data suggest that transmembrane signaling by CEACAM1 operates by alteration of the monomer/dimer equilibrium, which leads to changes in the SHP-2/c-Src-binding ratio.
Müller
Mario M
MM
Department of Cell and Molecular Biology, Karolinska Institutet, 171 77 Stockholm, Sweden.
Klaile
Esther
E
Vorontsova
Olga
O
Singer
Bernhard B
BB
Obrink
Björn
B
D000818:Animals; D015703:Antigens, CD / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D002448:Cell Adhesion / Q000235:genetics; D015815:Cell Adhesion Molecules / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D045744:Cell Line, Tumor; D002462:Cell Membrane / Q000737:chemistry / Q000235:genetics / Q000502:physiology; D019281:Dimerization; D020868:Gene Silencing; D010446:Peptide Fragments / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D011485:Protein Binding / Q000235:genetics; D020033:Protein Isoforms / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D021381:Protein Transport / Q000235:genetics; D054592:Protein Tyrosine Phosphatase, Non-Receptor Type 11 / Q000378:metabolism*; D051381:Rats; D015398:Signal Transduction / Q000235:genetics; D019061:src-Family Kinases / Q000378:metabolism*
D015703:Antigens, CD; C069847:CD66 antigens; D015815:Cell Adhesion Molecules; D010446:Peptide Fragments; D020033:Protein Isoforms; D019061:src-Family Kinases; D054592:Protein Tyrosine Phosphatase, Non-Receptor Type 11