Determinants of Arp2/3 recruitment to E-cadherin adhesions

Classical cadherins, like the epithelial E-cadherin participate in dynamic morphogenesis events, such as cell sorting, segregation and intercellular movement. E-cadherins function as membrane proteins to promote cell-cell interactions, where the cadherin ectodomains mediate adhesive recognition between neighbouring cells. The cadherin cytoplasmic tails are involved in binding to a variety of intercellular proteins including molecules that participate in cell signalling as well as cytoskeletal-interacting proteins. Actin filaments are observed in close proximity to cadherins at cell-cell junctions and several observations confirmed that the Arp2/3 complex, which is localized at cadherin contacts, plays an important role in actin assembly. This project builds on significant novel discoveries from the A. Yap group to study the regulation of the actin cytoskeleton in response to E-cadherin signalling. One of the specific aims is to investigate the essential role of the spatio-temporal dynamics of Arp2/3 recruitment at cadherin contacts. This task will involve live cell imaging technology in cultured cell models where subcellular localization of Arp2/3 with E-cadherin and diverse Arp2/3 regulatory proteins will be monitored. The major part of this work will concentrate on the fundamental question how E-cadherin together with the Arp2/3 complex participates in regulation of the actin cytoskeleton. Therefore I intend to characterize the biochemical interaction between E-cadherin and Arp2/3 in detail and will define structural requirements of the cadherin cytoplasmic tail for binding of Arp2/3. Furthermore the contribution of Arp2/3 associated molecules, like the WASP/WAVE proteins will be investigated in their function of Arp2/3 recruitment to E-cadherin adhesions. The results of this study are supposed to contribute to our understanding of the complex molecular mechanisms that take place in E-cadherin dependent organization of cell adhesion and should elucidate the role of E-cadherin and key proteins involved in actin assembly.