Study Of The Binding Between Tumor Suppressor Protein APC And Asef, DLG

Cancer is one of the major diseases affecting human health, and tumorigenesis is widely studied. APC plays an important cancer-involved protein in Wnt pathway by controlling the cellular expression level ofβ-catenin to regulate target gene transcription, which influences cell development, cell division and cell differentiation. APC is also involved in cell adhesion and cell migration independent of Wnt signaling pathway, partly through recognition and activation of Asef. By binding to the ABR region of Asef through its Arm domain, APC can activate auto-inhibited Asef. In human hereditary and sporadic colorectal cancers, human tumor suppressor APC is always observed as a mutant or truncated form and thus continuously activates Asef and promotes cell migration and angiogenesis. Besides, it is reported that the combination between the very C terminal of APC and PDZ region of DLG negatively regulates the cell cycle precession from G0/G1 phase to S phase. Additionally, by interaction with DLG, APC links the microtubule to plasma membrane so that epithelial cell migration and morphogenesis can be properly regulated.In this study, ABR domain of Asef, PDZ repeats of DLG and the two truncations of APC were respectively constructed previously. By over-expression, purification and crystallization, the Asef/APC complexes structures were resolved, and their key binding sites were discovered. And through point mutation, we examined these binding sites weather are key ones or not by manipulating non degeneration gel and isothermal titration calorimetry. This work provides the structural basis for the recognition and combination of APC to Asef and DLG, as well as the potential targets for pharmaceutical development.