title: Increased internalization of p120-uncoupled E-cadherin and a requirement for a dileucine motif in the cytoplasmic domain for endocytosis of the protein.
abstract: E-cadherin is a member of the cadherin family of Ca2+-dependent cell-cell adhesion molecules. E-cadherin associates with beta-catenin at the membrane-distal region of its cytosolic domain and with p120 at the membrane-proximal region of its cytoplasmic domain. It has been shown that a pool of cell surface E-cadherin is constitutively internalized and recycled back to the surface. Further, p120 knockdown by small interference RNA resulted in dose-dependent elimination of cell surface E-cadherin. Consistent with these observations, we found that selective uncoupling of p120 from E-cadherin by introduction of amino acid substitutions in the p120-binding site increased the level of E-cadherin endocytosis. The increased endocytosis was clathrin-dependent, because it was blocked by expression of a dominant-negative form of dynamin or by hypertonic shock. A dileucine motif in the juxtamembrane cytoplasmic domain is required for E-cadherin endocytosis, because substitution of these residues to alanine resulted in impaired internalization of the protein. The alanine substitutions in the p120-uncoupled construct reduced endocytosis of the protein, indicating that this motif was dominant to p120 binding in the control of E-cadherin endocytosis. Therefore, these results are consistent with the idea that p120 regulates E-cadherin endocytosis by masking the dileucine motif and preventing interactions with adaptor proteins required for internalization.
authors.affiliation: Department of Biochemistry and Molecular Biology, Graduate School of Medical and Dental Sciences, Kagoshima University, Kagoshima 890-8544, Japan.
authors.forename: Yayoi
authors.initials: Y
authors.lastname: Miyashita
authors.forename: Masayuki
authors.initials: M
authors.lastname: Ozawa
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000818:Animals; D000941:Antigens / Q000378:metabolism; D015820:Cadherins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D051177:Catenins; D015815:Cell Adhesion Molecules / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D002966:Clathrin / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism*; D004285:Dogs; D004705:Endocytosis; D011992:Endosomes / Q000378:metabolism; D007930:Leucine / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D010750:Phosphoproteins / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D034622:RNA Interference; D013997:Time Factors; D000095002:Delta Catenin
chemical_list: D000941:Antigens; D015820:Cadherins; D051177:Catenins; D015815:Cell Adhesion Molecules; D002966:Clathrin; D010750:Phosphoproteins; D007930:Leucine; D000095002:Delta Catenin