alpha -Catenin binds directly to spectrin and facilitates spectrin-membrane assembly in vivo.
The anchorage of spectrin to biological membranes is mediated by protein and phosphoinositol phospholipid interactions. In epithelial cells, a nascent spectrin skeleton assembles in regions of cadherin-mediated cell-cell contact, and conversely, cytoskeletal assembly is required to complete the cell-adhesion process. The molecular interactions guiding these processes remain incompletely understood. We have examined the interaction of spectrin with alpha-catenin, a component of the adhesion complex. Spectrin (alphaIIbetaII) and alpha-catenin coprecipitate from extracts of confluent Madin-Darby canine kidney, HT29, and Clone A cells and from solutions of purified spectrin and alpha-catenin in vitro. By surface plasmon resonance and in vitro binding assays, we find that alpha-catenin binds alphaIIbetaII spectrin with an apparent K(d) of approximately 20-100 nm. By gel-overlay assay, alpha-catenin binds recombinant betaII-spectrin peptides that include the first 313 residues of spectrin but not to peptides that lack this region. Similarly, the binding activity of alpha-catenin is fully accounted for in recombinant peptides encompassing the NH(2)-terminal 228 amino acid region of alpha-catenin. An in vivo role for the interaction of spectrin with alpha-catenin is suggested by the impaired membrane assembly of spectrin and its enhanced detergent solubility in Clone A cells that harbor a defective alpha-catenin. Transfection of these cells with wild-type alpha-catenin reestablishes alpha-catenin at the plasma membrane and coincidentally recruits spectrin to the membrane. We propose that ankyrin-independent interactions of modest affinity between alpha-catenin and the amino-terminal domain of beta-spectrin augment the interaction between alpha-catenin and actin, and together they provide a polyvalent linkage directing the topographic assembly of a nascent spectrin-actin skeleton to membrane regions enriched in E-cadherin.
Pradhan
D
D
Department of Pathology, Yale University, New Haven, Connecticut 06510, USA.
Lombardo
C R
CR
Roe
S
S
Rimm
D L
DL
Morrow
J S
JS
D000818:Animals; D001665:Binding Sites; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D003598:Cytoskeletal Proteins / Q000378:metabolism*; D004285:Dogs; D006801:Humans; D011485:Protein Binding; D013049:Spectrin / Q000378:metabolism*; D051178:alpha Catenin
C495273:CTNNA1 protein, human; D003598:Cytoskeletal Proteins; D051178:alpha Catenin; D013049:Spectrin