Band 4.1 proteins regulate integrin-dependent cell spreading

Integrins link the extracellular matrix (ECM) to the cytoskeleton to control cell behaviors including adhesion, spreading and migration. Band 4.1 proteins contain 4.1, ezrin, radixin, moesin (FERM) domains that likely mediate signaling events and cytoskeletal reorganization via integrins. However, the mechanisms by which Band 4.1 proteins and integrins are functionally interconnected remain enigmatic. Here we have investigated roles for Band 4.1 proteins in integrin-mediated cell spreading using primary astrocytes as a model system. We demonstrate that Proteins 4.1B and 4.1G show dynamic patterns of sub-cellular localization in astrocytes spreading on fibronectin. During early stages of cell spreading Proteins 4.1B and 4.1G are enriched in ECM adhesion sites but become more diffusely localized at later stages of spreading. Combinatorial inactivation of Protein 4.1B and 4.1G expression leads to impaired astrocyte spreading. Furthermore, in exogenous expression systems we show that the isolated Protein 4.1 FERM domain significantly enhances integrin-mediated cell spreading. Protein 4.1B is dispensable for reactive astrogliosis in experimental models of cortical injury, likely due to functional compensation by related Protein 4.1 family members. Collectively, these findings reveal that Band 4.1 proteins are important intracellular components for integrin-mediated cell spreading.

► Band 4.1 proteins contain N-terminal FERM domains but their roles in cell adhesion and spreading remain enigmatic. ► In primary astrocytes Band 4.1B and 4.1G proteins co-localize with β1 integrins in ECM adhesion sites. ► Combined inactivation of Band 4.1B and 4.1G lead to impaired astrocyte spreading in vitro. ► Band 4.1B is dispensable for reactive astrogliosis in vivo likely due to compensation by related family members.