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© The Rockefeller University Press,
0021-9525/2000//189 $5.00
The Journal of Cell Biology, Volume 148, Number 1,
, 2000 189-202
Original Article |
Selective Uncoupling of P120ctn from E-Cadherin Disrupts Strong Adhesion
al.reynolds{at}mcmail.vanderbilt.edu
p120ctn is a catenin whose direct binding to the juxtamembrane domain of classical cadherins suggests a role in regulating cell–cell adhesion. The juxtamembrane domain has been implicated in a variety of roles including cadherin clustering, cell motility, and neuronal outgrowth, raising the possibility that p120 mediates these activities. We have generated minimal mutations in this region that uncouple the E-cadherin–p120 interaction, but do not affect interactions with other catenins. By stable transfection into E-cadherin–deficient cell lines, we show that cadherins are both necessary and sufficient for recruitment of p120 to junctions. Detergent-free subcellular fractionation studies indicated that, in contrast to previous reports, the stoichiometry of the interaction is extremely high. Unlike
- and β-catenins, p120 was metabolically stable in cadherin-deficient cells, and was present at high levels in the cytoplasm. Analysis of cells expressing E-cadherin mutant constructs indicated that p120 is required for the E-cadherin–mediated transition from weak to strong adhesion. In aggregation assays, cells expressing p120-uncoupled E-cadherin formed only weak cell aggregates, which immediately dispersed into single cells upon pipetting. As an apparent consequence, the actin cytoskeleton failed to insert properly into peripheral E-cadherin plaques, resulting in the inability to form a continuous circumferential ring around cell colonies. Our data suggest that p120 directly or indirectly regulates the E-cadherin–mediated transition to tight cell–cell adhesion, possibly blocking subsequent events necessary for reorganization of the actin cytoskeleton and compaction.
Key Words: metastasis • catenin • compaction • clustering • adherens junction
© 2000 The Rockefeller University Press
Abbreviations used in this paper: APC, adenomatous polyposis coli; Dex, dexamethasone; JMD, juxtamembrane domain; MDA231, MDA-MB-231; p120, p120 catenin; RT, room temperature; wt, wild-type.
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