Ventral stress fibers induce plasma membrane deformation in human fibroblasts

Interactions between the actin cytoskeleton and the plasma membrane are important in many eukaryotic cellular processes. During these processes, actin structures deform the cell membrane outward by applying forces parallel to the fiber's major axis (as in migration) or they deform the membrane...

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Bibliographic Details
Published in:Molecular biology of the cell 2021-08, Vol.32 (18), p.1707-1723
Main Authors: Ghilardi, Samuel J, Aronson, Mark S, Sgro, Allyson E
Format: Article
Language:English
Subjects:
Actins - metabolism
Cell Membrane - drug effects
Cell Membrane - pathology
Cell Membrane - ultrastructure
Cells, Cultured
Cytochalasin D - pharmacology
Cytosol - metabolism
Fibroblasts - cytology
Fluorescent Dyes - metabolism
Humans
Infant
Myosin Type II - metabolism
Ouabain - pharmacology
Skin - cytology
Stress Fibers - drug effects
Stress Fibers - physiology
Transforming Growth Factor beta1 - pharmacology
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Summary:Interactions between the actin cytoskeleton and the plasma membrane are important in many eukaryotic cellular processes. During these processes, actin structures deform the cell membrane outward by applying forces parallel to the fiber's major axis (as in migration) or they deform the membrane inward by applying forces perpendicular to the fiber's major axis (as in the contractile ring during cytokinesis). Here we describe a novel actin-membrane interaction in human dermal myofibroblasts. When labeled with a cytosolic fluorophore, the myofibroblasts displayed prominent fluorescent structures on the ventral side of the cell. These structures are present in the cell membrane and colocalize with ventral actin stress fibers, suggesting that the stress fibers bend the membrane to form a "cytosolic pocket" that the fluorophores diffuse into, creating the observed structures. The existence of this pocket was confirmed by transmission electron microscopy. While dissolving the stress fibers, inhibiting fiber protein binding, or inhibiting myosin II binding of actin removed the observed pockets, modulating cellular contractility did not remove them. Taken together, our results illustrate a novel actin-membrane bending topology where the membrane is deformed outward rather than being pinched inward, resembling the topological inverse of the contractile ring found in cytokinesis.
ISSN:1059-1524
1939-4586
1939-4586
DOI:10.1091/mbc.E21-03-0096