Drebrin mediates scar formation and astrocyte reactivity during brain injury by inducing RAB8 tubular endosomes

The brain of mammals lacks a significant ability to regenerate neurons and is thus particularly vulnerable. To protect the brain from injury and disease, damage control by astrocytes through astrogliosis and scar formation is vital. Here, we show that brain injury triggers an upregulation of the actin-binding protein Drebrin (DBN) in astrocytes, which is essential for the formation and maintenance of glial scars . In turn, DBN loss leads to defective glial scar formation and excessive neurodegeneration following mild brain injuries. At the cellular level, DBN switches actin homeostasis from ARP2/3-dependent arrays to microtubule-compatible scaffolds and facilitates the formation of RAB8-positive membrane tubules. This injury-specific RAB8 membrane compartment serves as hub for the trafficking of surface proteins involved in astrogliosis and adhesive responses, such as β1-integrin. Our work identifies DBN as pathology-specific actin regulator, and establishes DBN-dependent membrane trafficking as crucial mechanism in protecting the brain from escalating damage following traumatic injuries.