WAVE complex self-organization templates lamellipodial formation

Abstract

How local interactions of actin regulators yield large-scale organization of cell shape and movement is not well understood. For example, why does the WAVE complex build lamellipodia, the broad sheet-like protrusions that power cell migration, whereas the homologous actin regulator N-WASP forms spiky finger-like actin networks? N-WASP is known to oligomerize into focal condensates that generate an actin finger. In contrast, the WAVE complex exhibits the linear distribution needed to generate an actin sheet. This linear organization of the WAVE complex could either arise from interactions with the actin cytoskeleton or could represent an ability of the complex to self-organize into a linear template. Using super-resolution microscopy, we find that the WAVE complex forms higher-order linear oligomers that curve into 270 nanometer-wide ring structures in the absence of actin polymer. These rings localize to the necks of membrane invaginations, which display saddle point geometries with positive curvature in one axis and negative curvature in the orthogonal axis. To investigate the molecular mechanism of saddle curvature enrichment, we show that the WAVE complex and IRSp53, a membrane curvature-sensitive protein, collaborate to recognize saddle curvature that IRSp53 cannot sense alone. This saddle preference for the WAVE complex could explain emergent cell behaviors, such as expanding and self-straightening lamellipodia as well as the ability of endothelial cells to recognize and seal transcellular holes. Our work highlights how partnering protein interactions enable complex shape sensing and how feedback between cell shape and actin regulators yields self-organized cell morphogenesis.

Cargo-specific recruitment in clathrin and dynamin-independent endocytosis

“…It also highlights the possibility of unprecedented cargo selectivity functions for the CG pathway in a manner similar to that described for numerous other endocytosed proteins following different endocytosis routes. Moreover, our findings explain the previously reported link between the CG pathway components, IRSp53 and Arf1, and adhesion phenotypes: IRSp53 contributes to cell migration and invasion through multiple mechanisms, including filopodia generation 31,32 , and curvature sensing with WAVE at the neck of membrane invaginations 33 . Arf1 depletion results in defective adhesion and migration in MDA-MB-231 cells 34-36 , and our finding of Arf1 involvement in integrin endocytosis sheds light on the mechanism behind these observations.…”

Structural Basis of CYRI-B Direct Competition with Scar/WAVE Complex for Rac1

“…The resulting structure shows minimal steric clashes between each Scar/WAVE complex suggesting that this dimerization may be a conserved feature of DUF1394 containing proteins. In line with this observation, it has been reported that the Scar/WAVE complex can form higher-order oligomers ( Pipathsouk et al., 2019 ).…”

“…Indeed, if autoinhibitory dimers are a conserved feature of DUF1394 domains, the possibility that Scar/WAVE could also form autoinhibited dimers and that CYRI could disrupt such interactions cannot be excluded. In fact, there have been several reports suggesting that the Scar/WAVE complex could form oligomeric structures ( Pipathsouk et al., 2019 ), making this an attractive question for further investigation.…”

WASP integrates substrate topology and cell polarity to guide neutrophil migration

“…2G). Finally, since WAVE complex exhibits a preference for saddle curvatures (Pipathsouk et al, 2019), we measured its enrichment to bead-induced invaginations. While WAVE complex transiently enriched to some beads, it failed to persistently enrich (Fig.…”

“…The fact that WASP is both curvature-sensitive and essential for HL-60 alignment to nanoridges supports WASP-mediated actin polymerization as a mechanism by which loosely adherent cells can sense and align with their substrate's topology. Membrane curvature has emerged as a key regulator for WASP family proteins; other NPFs from this family such as N-WASP and WAVE also preferentially enrich to sites of membrane curvature (Lou et al, 2019;Pipathsouk et al, 2019). Unique curvature preferences among WASP family NPFs could help differentiate their organization and inform the morphology of the actin networks they generate.…”