The assembly of actin filaments into Arp2/3 complex-branched filament networks powers numerous fundamental eukaryotic cellular processes, including motility, endocytosis, and cytokinesis. Members of the actin depolymerization factor homology (ADF-H)-domain protein family, which includes cofilin and glial maturation factor (GMF), accelerate branched actin filament network reorganization and turnover. Cofilin and GMF accelerate network remodeling by debranching Arp 2/3 complex. Cofilin accelerates network turnover by fragmenting filaments and increasing the concentration of filament ends where subunits add and dissociate. This MIRA proposal integrates biochemical and biophysical approaches, including electron cryo-microscopy, microfluidics, and a recently developed microscopic magnetic cylinders assay, to develop predictive models of actin filament and filament network mechanics, remodeling and fragmentation. General principles regarding the relationship between actin filament elasticity, conformation and regulatory protein occupancy will emerge from this work.
Polymerization of the protein actin into helical filaments and branched filament networks powers the directed motility of eukaryotic cells and some pathogenic bacteria. Cofilin and glial maturation factor (GMF) are two members of the actin depolymerization factor homology (ADF-H)-domain protein family that accelerate actin filament network reorganization and turnover through severing and debranching. The proposed studies will determine the structural basis of filament mechanical properties and severing by cofilin, and evaluate how filaments and branched filament networks respond to physical force.
