|Budget Amount *help
¥3,000,000 (Direct Cost : ¥3,000,000)
Fiscal Year 1998 : ¥1,100,000 (Direct Cost : ¥1,100,000)
Fiscal Year 1997 : ¥1,900,000 (Direct Cost : ¥1,900,000)
alpha-Catenin is an important molecule for the adhesive function of cadherins, which mainly function at adherence junction through the homophilic mechanism. We have reported that alpha-catenin binds with beta-catenin or plakoglobin by its the amino-terminal region. In this study we examined firstly whether alpha-catenin can directly bind to the cytoskeleton, actin filament. Various regions of alpha-catenin were expressed as the fusion protein with glutathione-S-transferase (GST). GST/alpha-catenin fusion proteins were incubated with actin filaments. The binding ability of GST/alpha-catenin fusion proteins to actin filament was assessed by co-sedimentation assay. The assay revealed that the carboxyl-terminal region bound most strongly to actin filament. This carboxyl-terminal region was also found to be able to interact with the central region of alpha-catenin. As the affinity of alpha-catenin for the cytoskeleton is weaker than that of the carboxyl-terminal region of alpha-catenin, the interaction between central and carboxyl regions might interfere the access of the carboxyl-terminal region to actin filament. Phosphatidyl-inositol 4,5-bisphosphate (PIP2) is known to regulate functions of many actin binding proteins, for example, alpha-actinin, vinculin, gelsolin and profilin. As the next project, we checked the interaction between PIP2 and alpha-catenin. The binding assay revealed that alpha-catenin bound most strongly to PIP2 in tested five lipids, and that the carboxyl-terminal region was important for this interaction. The binding ability of alpha-catenin to actin filament might be modulated by PlP2 associated with conformational change of alpha-catenin. These results mentioned above suggest that the carboxyl-terminal region of alpha-catenin may have multi-function, actin-binding, PIP2-binding and inter-domains interaction. These functions possibly regulate the link between cadherin molecules and cytoskeleton.