The WAVE complex associates with sites of saddle membrane curvature

Abstract

How local interactions of actin regulators yield large-scale organization of cell shape and movement is not well understood. Here we investigate how the WAVE complex organizes sheet-like lamellipodia. Using super-resolution microscopy, we find that the WAVE complex forms actin-independent 230-nm-wide rings that localize to regions of saddle membrane curvature. This pattern of enrichment could explain several emergent cell behaviors, such as expanding and self-straightening lamellipodia and the ability of endothelial cells to recognize and seal transcellular holes. The WAVE complex recruits IRSp53 to sites of saddle curvature but does not depend on IRSp53 for its own localization. Although the WAVE complex stimulates actin nucleation via the Arp2/3 complex, sheet-like protrusions are still observed in ARP2-null, but not WAVE complex-null, cells. Therefore, the WAVE complex has additional roles in cell morphogenesis beyond Arp2/3 complex activation. Our work defines organizing principles of the WAVE complex lamellipodial template and suggests how feedback between cell shape and actin regulators instructs cell morphogenesis.

WASP integrates substrate topology and cell polarity to guide neutrophil migration

“…We also investigated the effect of bead-induced membrane deformation on the recruitment of other proteins that are known to sense membrane curvature–clathrin LCa ( Elkhatib et al, 2017 ; Zhao et al, 2017 ) and the WAVE complex ( Pipathsouk et al, 2021 ). Although components of CME enrich to bead-induced membrane invaginations in MDA-MB-231 cells ( Elkhatib et al, 2017 ), clathrin LCa exhibited less robust recruitment to beads than WASP in neutrophils ( Fig.…”

“…2 G ). We previously found that the WAVE complex exhibits a preference for saddle curvatures and enriches to the necks of membrane invaginations and transepithelial holes ( Pipathsouk et al, 2021 ). While the WAVE complex transiently enriched to some bead-induced invaginations, it failed to persistently enrich ( Fig.…”

“…Membrane curvature has emerged as a key regulator for WASP family proteins; other NPFs from this family, such as N-WASP ( Lou et al, 2019 ) and WAVE ( Pipathsouk et al, 2021 ), also preferentially enrich to sites of membrane curvature. Unique curvature preferences among WASP family NPFs could help to differentiate their organization and inform the morphology of the actin networks they generate.…”

“…For N-WASP, enrichment to membrane invaginations could facilitate scission of endocytic vesicles from the plasma membrane ( Kaksonen et al, 2005 ; Akamatsu et al, 2020 ). For WAVE, saddle preference could help to organize a coherently advancing flat lamellipod ( Pipathsouk et al, 2021 ), and for WASP, enrichment to stable inward curvature (in particular the saddle-shaped necks of invaginations) could help the cell to integrate substrate topologies with motility. Interestingly, these proteins also appear to have different rules for reading curvature; for instance, WASP is much better than WAVE at persistently enriching to saddles at bead-induced membrane invaginations ( Fig.…”

Revisiting I-BAR Proteins at Central Synapses

“…Interestingly the nucleation-promoting factor WASP co-localized with MIM at spine initiation sites to form filopodia in vitro . Recent results suggest that WAVE1 induces sheet-type actin polymerization, whereas N-WASP creates more focal point polymerization (Pipathsouk et al, 2021 ). Differential interactions of I-BAR domains with WASP may facilitate actin polymerization in dendritic filopodia whereas interactions with WASP might be needed for more organized actin structures such as spine heads.…”