Abstract
The spectrin-based membrane skeleton is a major component of the cell cortex. While expressed by all metazoans, its dynamic interactions with the other cortex components, including the plasma membrane or the acto-myosin cytoskeleton, are poorly understood. Here, we investigate how spectrin re-organizes spatially and dynamically under the membrane during changes in cell mechanics. We find spectrin and acto-myosin to be spatially distinct but cooperating during mechanical challenges, such as cell adhesion and contraction, or compression, stretch and osmolarity fluctuations, creating a cohesive cortex supporting the plasma membrane. Actin territories control protrusions and contractile structures while spectrin territories concentrate in retractile zones and low-actin density/inter-contractile regions, acting as a fence that organize membrane trafficking events. We unveil here the existence of a dynamic interplay between acto-myosin and spectrin necessary to support a mesoscale organization of the lipid bilayer into spatially-confined cortical territories during cell mechanoresponse.
Highlights
The spectrin-based membrane skeleton is a major component of the cell cortex
Endogenous βII-spectrin and actin displayed a remarkable complementary pattern, which was prominent along the actin stress fibers that were devoid of βII-spectrin (Fig. 1a–c)
It is worth noticing that in cortical regions prominently enriched in spectrin-based membrane skeleton, a faint actin staining could still be observed in highly overcontrasted images (Supplementary Fig. 1A)
Summary
The spectrin-based membrane skeleton is a major component of the cell cortex. While expressed by all metazoans, its dynamic interactions with the other cortex components, including the plasma membrane or the acto-myosin cytoskeleton, are poorly understood. While a lot of efforts have been devoted to the study of the actomyosin and microtubule cytoskeletons, our understanding of cytoskeletal scaffolds directly connected to the plasma membrane (PM) lags behind These systems are expected to play crucial roles in many cellular mechanoadaptive processes by shaping PM topology in association with the underlying cell cortex. In accordance with its broad range of physiological functions, αII- and βII-spectrin genes have been found to be essential in embryonic development[10], and are involved in many pathological conditions[11] Despite this wealth of knowledge, our understanding of spectrin macromolecular organization is limited to the study of ex vivo erythrocytes and neurons, where it forms a triangle-like lattice and a repetitive barrel-like array interspaced by actin nodes, respectively[12,13,14,15,16,17]. The elasticity of the meshwork is ensured by the intrinsic flexibility of the so-called spectrin repeats[22,23]
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