Biophysical approaches to protein-induced membrane deformations in trafficking

To control their shape and movement, cells leverage nucleation promoting factors (NPFs) to regulate when and where they polymerize actin. Here we investigate the role of the immune-specific NPF WASP during neutrophil migration. Endogenously-tagged WASP localizes to substrate-induced plasma membrane deformations. Super-resolution imaging of live cells reveals that WASP preferentially enriches to the necks of these substrate-induced membrane invaginations, a distribution that could support substrate pinching. Unlike other curvature-sensitive proteins, WASP only enriches to membrane deformations at the cell front, where it controls Arp2/3 complex recruitment and actin polymerization. Despite relatively normal migration on flat substrates, WASP depletion causes defects in topology sensing and directed migration on textured substrates. WASP therefore both responds to and reinforces cell polarity during migration. Surprisingly, front-biased WASP puncta continue to form in the absence of Cdc42. We propose that WASP integrates substrate topology with cell polarity for 3D guidance by selectively polymerizing actin around substrate-induced membrane deformations at the leading edge. A misregulation of WASP-mediated contact guidance could provide insight into the immune disorder Wiskott-Aldrich syndrome.

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WASP integrates substrate topology and cell polarity to guide neutrophil migration

The Journal of Cell Biology ◽

10.1083/jcb.202104046 ◽

2021 ◽

Vol 221 (2) ◽

Author(s):

Rachel M. Brunetti ◽

Gabriele Kockelkoren ◽

Preethi Raghavan ◽

George R.R. Bell ◽

Derek Britain ◽

...

Keyword(s):

Cell Polarity ◽

Neutrophil Migration ◽

Geometric Features ◽

Actin Assembly ◽

Membrane Deformation ◽

Induced Membrane ◽

Superresolution Imaging ◽

Directed Migration ◽

Membrane Deformations

To control their movement, cells need to coordinate actin assembly with the geometric features of their substrate. Here, we uncover a role for the actin regulator WASP in the 3D migration of neutrophils. We show that WASP responds to substrate topology by enriching to sites of inward, substrate-induced membrane deformation. Superresolution imaging reveals that WASP preferentially enriches to the necks of these substrate-induced invaginations, a distribution that could support substrate pinching. WASP facilitates recruitment of the Arp2/3 complex to these sites, stimulating local actin assembly that couples substrate features with the cytoskeleton. Surprisingly, WASP only enriches to membrane deformations in the front half of the cell, within a permissive zone set by WASP’s front-biased regulator Cdc42. While WASP KO cells exhibit relatively normal migration on flat substrates, they are defective at topology-directed migration. Our data suggest that WASP integrates substrate topology with cell polarity by selectively polymerizing actin around substrate-induced membrane deformations in the front half of the cell.

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