Lateral dimerization of the E-cadherin extracellular domain is necessary but not sufficient for adhesive activity.
Cadherins are transmembrane glycoproteins involved in Ca(2+)-dependent cell-cell adhesion. Using L cells coexpressing E-cadherin constructs with different epitope tags, we examined the lateral dimerization of E-cadherin and its adhesive activity by co-immunoprecipitation and aggregation assays, respectively. Although the transmembrane domain is required for dimerization, tail-less constructs possessing the transmembrane domain of either N-cadherin or CD45 show dimerization and are active in aggregation assays. Two mutant constructs having either of two amino acid substitutions, W2A or substitutions that disrupt the recognition sequence for endoproteolytic enzymes involved in removal of the precursor segment, cannot form dimers and are inactive in aggregation. These monomeric proteins, like their wild-type dimerizing counterparts, retain their Ca(2+)-dependent resistance to trypsin digestion, suggesting that dimerization per se does not induce a large conformational change. Two other constructs, having either an amino acid substitution, D134A, or a C-terminal deletion of 70 amino acid residues, retain the ability to associate laterally but are inactive in aggregation assays. Staurosporine treatment of cells expressing the latter construct increases aggregation but does not increase the extent of lateral dimerization. Thus, lateral dimerization is necessary, but not sufficient for adhesive activity.
Ozawa
Masayuki
M
Department of Biochemistry, Faculty of Medicine, Kagoshima University, Kagoshima 890-8520, Japan. mozawa@m.kufm.kagoshima-u.ac.jp
D000595:Amino Acid Sequence; D000818:Animals; D015820:Cadherins / Q000737:chemistry* / Q000378:metabolism; D002118:Calcium / Q000378:metabolism; D002448:Cell Adhesion; D003593:Cytoplasm / Q000378:metabolism; D018076:DNA, Complementary / Q000378:metabolism; D019281:Dimerization; D004791:Enzyme Inhibitors / Q000494:pharmacology; D000939:Epitopes; D005347:Fibroblasts / Q000378:metabolism; D006801:Humans; D015151:Immunoblotting; D017493:Leukocyte Common Antigens / Q000378:metabolism; D051379:Mice; D008969:Molecular Sequence Data; D011233:Precipitin Tests; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D051381:Rats; D017386:Sequence Homology, Amino Acid; D019311:Staurosporine / Q000494:pharmacology; D014162:Transfection; D014357:Trypsin / Q000494:pharmacology
D015820:Cadherins; D018076:DNA, Complementary; D004791:Enzyme Inhibitors; D000939:Epitopes; D017493:Leukocyte Common Antigens; D014357:Trypsin; D019311:Staurosporine; D002118:Calcium