Required to coordinate membrane tubulation with reorganization of the actin cytoskeleton during endocytosis. Also acts as a link between CDC42 signaling and regulation of the actin cytoskeleton. Binds to lipids such as phosphatidylinositol 4,5-bisphosphate and phosphatidylserine and promotes membrane invagination and the formation of tubules. Also enhances actin polymerization in the vicinity of membrane tubules by recruiting WASL/N-WASP which in turn activates the Arp2/3 complex. Actin polymerization and dynamin may promote the fission of membrane tubules to form endocytic vesicles. Required for the formation of podosomes, actin-rich adhesion structures specific to monocyte-derived cells. Required for translocation of GLUT4 to the plasma membrane in response to insulin signaling. May be required for the lysosomal retention of FASLG/FASL (By similarity). Homodimerizes, the dimers can polymerize end-to-end to form filamentous structures. Interacts specifically with GTP-bound CDC42 and RHOQ. Interacts with AKAP9, ARHGAP17, DAAM1, DIAPH1, DIAPH2, DNM1, DNM2, FASLG/FASL, GAPVD1, LYN, microtubules, SRC, WAS/WASP and WASL/N-WASP. Interacts with the ligand binding domain of the thyroid receptor (TR) in the presence of thyroid hormone. May interact with CTNNB1 and HD/HTT (By similarity). Interacts with PDE6G. Localizes to cortical regions coincident with F-actin, to lysosomes and to sites of phagocytosis in macrophages. Also localizes to the Golgi, and this requires AKAP9. Translocates to the plasma membrane in response to insulin stimulation, and this may require active RHOQ (By similarity). Expressed in adrenal gland, aorta, brain, heart, kidney, liver, skeletal muscle and spleen. The F-BAR domain binds the phospholipid membrane with its concave surface. The end-to-end polymerization of dimers of these domains provides a curved surface that fits best membranes with around 600 A diameter, and may drive tubulation (By similarity). Belongs to the FNBP1 family.