National Institute of General Medical Sciences 5F32GM156029-02

The role of cortactin-mediated actin branch stabilization in force-producing actin networks

This award funds research to understand the role of cortactin in stabilizing actin branches that produce cellular forces, investigating how it prevents premature branch removal and affects actin network force production and recycling.

Description

Networks of branched actin filaments produce forces necessary for cellular processes ranging from cell migration to endocytosis. These branches are formed by proteins actin-related protein 2/3 (Arp2/3) complex, along with proteins that promote Arp2/3 activation. Cortactin is a multifunctional protein that can activate Arp2/3 complex on its own at high concentrations, synergize with certain nucleation promoting factors, or stabilize branches after they are formed. This multifunctionality has made isolating the role of cortactin as a branch stabilizer difficult. Actin branches are intrinsically stable, so why cortactin-mediated branch stabilization is important for regulating force-producing actin networks is unknown. One possibility is that cortactin protects branches from being removed by a class of debranching proteins, such as coronin 1B or glia maturation factor-γ. Additionally, actin networks are age-segregated, with newer branches near the surface being thought to be more important in the ability of the network to provide pushing forces, so the importance of cortactin may be related to whether debranchers target the younger or older regions of the network. In this project, the researchers will utilize a reconstituted assay to isolate cortactin's role as a branch stabilizer, and determine whether it is important for force production by preventing branches from being removed prematurely. They will use bead motility assays to observe force production by age-segregated actin networks that push against beads in the presence of cortactin alone and with differentially targeted debranching proteins. The study will also assess how these proteins affect the recycling of monomeric actin from branched actin networks, incorporating proteins like cofilin into the assay. Additionally, the activity of the debrancher coronin 7 will be characterized through assays and fluorescence microscopy to observe debranching frequency and binding/dissociation to actin filaments.

View original record