Formation of membrane ridges and scallops by the F-BAR protein Nervous Wreck

Abstract

Nwk is a neuronal F-BAR/SH3 protein that deforms membranes into positively curved ridges using a novel zigzag assembly of the crescent-shaped F-BAR domain. Membrane between adjacent ridges forms a negatively curved scallop that can be amplified by the cytoskeleton into cellular protrusions.

Coordinated autoinhibition of F-BAR domain membrane binding and WASp activation by Nervous Wreck

“…Nwk 1-731 oligomerized in V-shape dimer pairs and zigzags ( Fig. S5 B and C), similar to the arrangements of Nwk alone (17). Therefore, Nwk 1-731 associates with membranes in a similar fashion to Nwk , consistent with their similar membrane remodeling activities (16,17).…”

“…Compared with the predicted structure of Nwk 1-313 filtered to 20 Å (Fig. 2B, pink) (17), the reconstruction revealed a mass on the inner surface of the curve of the S-shaped dimer (Fig. 2B, red arrows), along with a mass on the outside surface of the curve (Fig.…”

“…For this reconstruction, we excluded class averages (16% of total particles) that were similar to those of the F-BAR domain alone. These are likely to represent the fraction in equilibrium of "open" Nwk , in which the F-BAR is available for membrane binding (16,17) and SH3 domain positions are not constrained (and thus are not defined in class averages). Compared with the isolated F-BAR domain (Nwk 1-428 ), which forms an S-shaped dimer (17), our Nwk 1-731 3D reconstruction exhibited an overall arrangement consistent with an F-BAR domain-shaped mass with additional masses positioned below its concave surface (Fig.…”

“…For this reconstruction, we used 80.7% of the total particles, representing the concave-down or side-down orientations (see above) that we previously showed to be favored for higher-order assembly and for membrane binding (16,17). In contrast to the S-shape of Nwk 1-428 on membranes (17) and the vertical arrangement of the F-BAR domain above the SH3 domains for Nwk 1-731 on carbon film ( Fig. 1 B and D), the membrane-bound Nwk 1-731 dimers displayed a flattened dumbbell shape ( Fig.…”

“…1A). The Nwk F-BAR domain forms a dimer that assembles into higher-order zigzag arrays on negatively charged membranes and promotes the formation of membrane ridges and scallops (17). Nwk is required at the Drosophila larval neuromuscular junction (NMJ) to constrain the traffic and signaling activity of growth factor receptors (18)(19)(20).…”