Competitive regulation of E-cadherin juxtamembrane domain degradation by p120-catenin binding and Hakai-mediated ubiquitination.
p120-Catenin binding to, and Hakai-mediated ubiquitination of the E-cadherin juxtamembrane domain (JMD) are thought to be involved in regulating E-cadherin internalization and degradation. However, the relationship between these two pathways is not understood. We targeted the E-cadherin JMD to mitochondria (WT-JMD) to isolate this domain from the plasma membrane and internalization, and to examine protein modifications and degradation. WT-JMD localized to mitochondria, but did not accumulate there except when proteasome activity was inhibited. We found WT-JMD was ubiquitinated, and arginine substitution of lysines at position 5 (K5R) and 83 (K83R) resulted in the stable accumulation of mutant JMD at mitochondria. p120-Catenin did not localize, or bind to WT-JMD even upon proteasome inhibition, whereas the K5,83R-JMD mutant bound and localized p120-catenin to mitochondria. Mutation of the p120-catenin binding site in combination with these lysine mutations inhibited p120-catenin binding, but did not decrease JMD stability or its accumulation at mitochondria. Thus, increased stability of JMD lysine mutants was due to inhibition of ubiquitination and not to p120-catenin binding. Finally, mutation of these critical lysines in full length E-cadherin had similar effects on protein stability as WT-JMD. Our results indicate that ubiquitination of the JMD inhibits p120-catenin binding, and targets E-cadherin for degradation.
Department of Molecular and Cellular Physiology, Stanford University, Stanford, California, United States of America.
Andrea
A
Hartsock
W James
WJ
Nelson
D000595:Amino Acid Sequence; D000818:Animals; D001667:Binding, Competitive; D015820:Cadherins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D051177:Catenins / Q000378:metabolism*; D002448:Cell Adhesion; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D002465:Cell Movement; D004285:Dogs; D008239:Lysine; D051379:Mice; D008928:Mitochondria / Q000378:metabolism; D008969:Molecular Sequence Data; D009154:Mutation; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D011485:Protein Binding; D055550:Protein Stability; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D059748:Proteolysis; D044767:Ubiquitin-Protein Ligases / Q000378:metabolism*; D054875:Ubiquitination; D019061:src-Family Kinases / Q000378:metabolism; D000095002:Delta Catenin
D015820:Cadherins; D051177:Catenins; D044767:Ubiquitin-Protein Ligases; D019061:src-Family Kinases; D046988:Proteasome Endopeptidase Complex; D008239:Lysine; D000095002:Delta Catenin