| First Author | Choi S | Year | 2007 |
| Journal | J Biol Chem | Volume | 282 |
| Issue | 49 | Pages | 36024-36 |
| PubMed ID | 17925400 | Mgi Jnum | J:129033 |
| Mgi Id | MGI:3768534 | Doi | 10.1074/jbc.M707639200 |
| Citation | Choi S, et al. (2007) The intercalated disc protein, mXinalpha, is capable of interacting with beta-catenin and bundling actin filaments. J Biol Chem 282(49):36024-36 |
| abstractText | Targeted deletion of mXin alpha results in cardiac hypertrophy and cardiomyopathy with conduction defects (Gustafson-Wagner, E., Sinn, H. W., Chen, Y.-L., Wang, D.-Z., Reiter, R. S., Lin, J. L.-C., Yang, B., Williamson, R. A., Chen, J. N., Lin, C.-I., and Lin, J. J.-C. (2007) Am. J. Physiol. 293, H2680-H2692). To understand the underlying mechanisms leading to such cardiac defects, the functional domains of mXin alpha and its interacting proteins were investigated. Interaction studies using co-immunoprecipitation, pull-down, and yeast two-hybrid assays revealed that mXin alpha directly interacts with beta-catenin. The beta-catenin-binding site on mXin alpha was mapped to amino acids 535-636, which overlaps with the known actin-binding domains composed of the Xin repeats. The overlapping nature of these domains provides insight into the molecular mechanism for mXin alpha localization and function. Purified recombinant glutathione S-transferase- or His-tagged mXin alpha proteins are capable of binding and bundling actin filaments, as determined by co-sedimentation and electron microscopic studies. The binding to actin was saturated at an approximate stoichiometry of nine actin monomers to one mXin alpha. A stronger interaction was observed between mXin alpha C-terminal deletion and actin as compared with the interaction between full-length mXin alpha and actin. Furthermore, force expression of green fluorescent protein fused to an mXin alpha C-terminal deletion in cultured cells showed greater stress fiber localization compared with force-expressed GFP-mXin alpha. These results suggest a model whereby the C terminus of mXin alpha may prevent the full-length molecule from binding to actin, until the beta-catenin-binding domain is occupied by beta-catenin. The binding of mXin alpha to beta-catenin at the adherens junction would then facilitate actin binding. In support of this model, we found that the actin binding and bundling activity of mXin alpha was enhanced in the presence of beta-catenin. |
