Mutations affecting transmembrane segment interactions impair adhesiveness of E-cadherin.
Lateral clustering of E-cadherin molecules is required for the adhesive properties of this cell-cell adhesion molecule. Both the extracellular domain and the cytoplasmic region of E-cadherin were previously reported to contribute to lateral clustering, but little is known about a role of the transmembrane domain in this respect. Following our previous findings indicating self-assembly of artificial transmembrane segments based on leucine residues, we asked whether the leucine-rich transmembrane segment of E-cadherin participates in lateral clustering. Here, we demonstrate that its transmembrane domain self-assembles as analyzed using the ToxR reporter system. Certain point mutations within the transmembrane domain markedly reduced self-assembly. To study whether the same point mutations also affect E-cadherin-mediated adhesion in vivo, wild-type and mutant E-cadherin cDNAs were transfected into Ltk(-) cells. Indeed, cell aggregation assays revealed significantly reduced adhesiveness when mutations had been introduced which disrupted transmembrane segment interaction. In control experiments, cell-surface expression, interaction with catenins and the cytoskeleton as well as trypsin-resistance of the protein were unaffected. These data suggest that interactions between the transmembrane segments are important for the lateral association of E-cadherin molecules required for cell-cell adhesion.
Huber
O
O
Dept of Clinical Chemistry and Pathobiochemistry, Universitätsklinikum Benjamin Franklin, Hindenburgdamm 30, D-12200 Berlin, Germany. huber@ukbf.fu-berlin.de
Kemler
R
R
Langosch
D
D
D000595:Amino Acid Sequence; D000818:Animals; D001426:Bacterial Proteins; D015820:Cadherins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D002448:Cell Adhesion / Q000502:physiology*; D002449:Cell Aggregation; D004268:DNA-Binding Proteins / Q000235:genetics; D017930:Genes, Reporter; D007739:L Cells; D051379:Mice; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis; D014157:Transcription Factors / Q000235:genetics; D015533:Transcriptional Activation; D014162:Transfection
D001426:Bacterial Proteins; D015820:Cadherins; D004268:DNA-Binding Proteins; D011993:Recombinant Fusion Proteins; D014157:Transcription Factors; C066719:toxR protein, bacteria