Genetic and biochemical dissection of protein linkages in the cadherin-catenin complex.
The cadherin-catenin complex is important for mediating homotypic, calcium-dependent cell-cell interactions in diverse tissue types. Although proteins of this complex have been identified, little is known about their interactions. Using a genetic assay in yeast and an in vitro protein-binding assay, we demonstrate that beta-catenin is the linker protein between E-cadherin and alpha-catenin and that E-cadherin does not bind directly to alpha-catenin. We show that a 25-amino acid sequence in the cytoplasmic domain of E-cadherin and the amino-terminal domain of alpha-catenin are independent binding sites for beta-catenin. In addition to beta-catenin and plakoglobin, another member of the armadillo family, p120 binds to E-cadherin. However, unlike beta-catenin, p120 does not bind alpha-catenin in vitro, although a complex of p120 and endogenous alpha-catenin could be immunoprecipitated from cell extracts. In vitro protein-binding assays using recombinant E-cadherin cytoplasmic domain and alpha-catenin revealed two catenin pools in cell lysates: an approximately 1000- to approximately 2000-kDa complex bound to E-cadherin and an approximately 220-kDa pool that did not contain E-cadherin. Only beta-catenin in the approximately 220-kDa pool bound exogenous E-cadherin. Delineation of these molecular linkages and the demonstration of separate pools of catenins in different cell lines provide a foundation for examining regulatory mechanisms involved in the assembly and function of the cadherin-catenin complex.
Jou
T S
TS
Department of Molecular and Cellular Physiology, Beckman Center for Molecular and Genetic Medicine, Stanford University School of Medicine, CA 94305, USA.
Stewart
D B
DB
Stappert
J
J
Nelson
W J
WJ
Marrs
J A
JA
D000230:Adenocarcinoma; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D015820:Cadherins / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism*; D002460:Cell Line; D003001:Cloning, Molecular; D003110:Colonic Neoplasms; D003598:Cytoskeletal Proteins / Q000302:isolation & purification / Q000378:metabolism*; D017931:DNA Primers; D004285:Dogs; D006801:Humans; D008715:Methionine / Q000378:metabolism; D008969:Molecular Sequence Data; D016133:Polymerase Chain Reaction / Q000379:methods; D011485:Protein Binding; D012441:Saccharomyces cerevisiae / Q000378:metabolism; D015534:Trans-Activators; D014407:Tumor Cells, Cultured; D051178:alpha Catenin; D051176:beta Catenin
C495273:CTNNA1 protein, human; C495270:CTNNB1 protein, human; D015820:Cadherins; D003598:Cytoskeletal Proteins; D017931:DNA Primers; D015534:Trans-Activators; D051178:alpha Catenin; D051176:beta Catenin; D008715:Methionine