title: The 19-amino acid insertion in the tumor-associated splice isoform Rac1b confers specific binding to p120 catenin.
abstract: The Rac1b splice isoform contains a 19-amino acid insertion not found in Rac1; this insertion leads to decreased GTPase activity and reduced affinity for GDP, resulting in the intracellular predominance of GTP-bound Rac1b. Here, using co-precipitation and proteomic methods, we find that Rac1b does not bind to many common regulators of Rho family GTPases but that it does display enhanced binding to SmgGDS, RACK1, and p120 catenin (p120(ctn)), proteins involved in cell-cell adhesion, motility, and transcriptional regulation. We use molecular modeling and structure analysis approaches to determine that the interaction between Rac1b and p120(ctn) is dependent upon protein regions that are predicted to be unstructured in the absence of molecular complex formation, suggesting that the interaction between these two proteins involves coupled folding and binding. We also find that directed cell movement initiated by Rac1b is dependent upon p120. These results define a distinct binding functionality of Rac1b and provide insight into how the distinct phenotypic program activated by this protein may be implemented through molecular recognition of effectors distinct from those of Rac1.
authors.affiliation: Department of Cancer Biology, Mayo Clinic, Jacksonville, Florida 32224, USA.
authors.forename: Lidiya
authors.initials: L
authors.lastname: Orlichenko
authors.forename: Rory
authors.initials: R
authors.lastname: Geyer
authors.forename: Masahiro
authors.initials: M
authors.lastname: Yanagisawa
authors.forename: Davitte
authors.initials: D
authors.lastname: Khauv
authors.forename: Evette S
authors.initials: ES
authors.lastname: Radisky
authors.forename: Panos Z
authors.initials: PZ
authors.lastname: Anastasiadis
authors.forename: Derek C
authors.initials: DC
authors.lastname: Radisky
mesh_terms: D017398:Alternative Splicing; D000595:Amino Acid Sequence; D000596:Amino Acids / Q000737:chemistry*; D000818:Animals; D051177:Catenins / Q000737:chemistry*; D002448:Cell Adhesion; D002465:Cell Movement; D004847:Epithelial Cells / Q000166:cytology; D051379:Mice; D008969:Molecular Sequence Data; D010641:Phenotype; D011485:Protein Binding; D020033:Protein Isoforms; D014158:Transcription, Genetic; D020830:rac1 GTP-Binding Protein / Q000737:chemistry*; D000095002:Delta Catenin
chemical_list: D000596:Amino Acids; D051177:Catenins; D020033:Protein Isoforms; C107953:RAC1 protein, human; D020830:rac1 GTP-Binding Protein; D000095002:Delta Catenin; C000722349:Ctnnd1 protein, mouse
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