Dynamic Hand-In-Hand Interaction between Actin and Spectrin during Mammalian Cell Mechanoadaptation

Multicellular organisms have evolved complex mechanisms to sense and adapt to the surrounding environment by dynamically controlling cell shape and exert forces. In this context, spectrin is a particularly overlooked mechano-sensing protein able to self-assemble into a non-polarized elastic meshwork engaged in membrane-cytoskeleton connections. Spectrin has been described to maintain cell shape in erythrocytes and proposed to be involved in the maintenance of axon rigidity; however, its molecular organization and dynamics are unknown in most eukaryotic cell types, while the murine knockout is embryonically lethal. Specifically we investigate spectrin dynamic by different fluorescence microscopy techniques at high spatio-temporal resolution during cell spreading, its role in membrane adaptation during chemical and mechanical perturbations of the cell, and the dominant-negative effect of deletion mutants’ overexpression. Using fibroblasts, we describe how spectrin dynamically interplay with the acto-myosin cytoskeleton and plasma-membrane (PM) with complementary functions, while immunolocalization screening of different mammalian cell lines suggests the existence of highly conserved mechanisms between different systems. By applying external mechanical perturbations such as cell stretch and compression, we identified a fast elastic response by spectrin, while actin reacts with different dynamics. Overall, our results pinpoint a supporting mechanism of the lipid bilayer led by spectrin at regions where the actin cytoskeleton is not established, creating a fencing mechanism for actin remodeling and membrane trafficking; these mechanisms potentially unveil why the spectrin family of protein is evolutionary highly conserved and ubiquitously expressed in eukaryotic cells