Synergistic BAR–NPF interactions in actin-driven membrane remodeling

Cell and organelle shape can profoundly influence proper cellular function. In recent years, two machineries have emerged as major regulators of membrane shape: Bin-Amphiphysin-Rvs161/167 (BAR) domain-containing proteins, which induce membrane invaginations or protrusions, and nucleation promoting factors (NPFs), which activate the Arp2/3 complex and are thus responsible for the generation of branched actin networks that push on membranes. Several BAR–NPF interactions have been shown to induce various types of protrusions, such as lamellipodia or filopodia, or invaginations, including trafficking organelles such as caveolae, endosomes and clathrin-coated pits (CCPs). This review focuses on how collaboration between these two interacting machineries, which emerges as a unified mechanism of membrane remodeling, accounts for such a variety of membrane shapes.