The Formin Daam1 Binding Fascin Promotes Actin Filaments Formation And Breast Cancer Cell Migration

Distant metastasis of tumor cells is still the biggest challenge in clinical cancer treatment,and it is also the main cause of death of cancer patients.Cell motility is the most basic cell behavior causing metastasis,which depends on actin dynamics.Actin is the main component of actin filament,and interacts with actin-binding proteins to promote the assembly and deassembly of actin filament.Our laboratory has proved that Daam1(dishevelled-associated activator of morphogenesis 1)can regulate the extension of invadopodia and the chemotaxis of breast cancer cells.However,how Daam1 participates in actin filament assembly and pseudopodia formation remains little known.Fascin is an important actin filament bundling protein.Through a series of preliminary experiments,we found that the morphology of actin filament was destroyed and the number of that was decreasing after knocking down the expression level of Fascin in MCF-7 cells.Also,co-immunoprecipitation assay showed that Daam1 interacted with Fascin.The aim of this study is to further explore the molecular mechanism of Daam1 and Fascin on actin filament formation.For further experimental study,we collected 100 samples of breast cancer patients to detect the expression levels of Daam1 and Fascin by immunohistochemistry.In addition,wound healing and Boyden chamber assays were used to examine the migration and pseudopodia extension of breast cancer cells.Immunofluorescence assay was explored to observe whether Daam1 and Fascin co-localized and commonly regulate actin filament assembly.A series of study results exhibited that: 1)compared with paracancerous tissues,the expression level of Fascin was up-regulated in breast cancer tissues;2)knockdown of Fascin leaded to decreasing pseudopodia formation and inhibiting cell motility;3)Daam1interacted with Fascin through FH domain,especially FH2 domain;4)immunofluorescence presented that Daam1 and Fascin could partially co-localize to actin filament,and whether downregulated Daam1 or Fascin,they both fail to co-localize with the short and curly actin filament.Therefore,the study results show that Daam1 can specifically combine with Fascin by FH domain to promote actin filament assembly and cancer cells migration,which provides a new insight into the functional mechanism of Daam1 on actin filament formation.