Non-erythrocyte spectrin network preferentially stabilizes flat membrane and enhances cell stiffness

Area of Science:

• Cell biology
• Biophysics
• Cytoskeletal dynamics

Background:

• Spectrin (αII and βII) forms non-erythroid cytoskeletal networks crucial for plasma membrane structure.
• The interaction of spectrin networks with membranes of varying curvatures is not well understood.

Purpose of the Study:

• To investigate how spectrin interacts with cell membranes of different curvatures.
• To determine the role of spectrin in regulating cellular mechanical properties, such as stiffness.

Main Methods:

• Microfluidic deformation cytometry was used to measure cell stiffness.
• Fluorescence microscopy was employed to visualize spectrin distribution in cells.
• In vitro reconstitution assays with spherical supported lipid bilayers (SSLBs) assessed spectrin-lipid interactions.

Main Results:

• Spectrin βII overexpression increased the apparent stiffness of MDA-MB-231 breast cancer cells.
• In vivo, spectrin was found to be excluded from highly curved membrane regions and enriched on flatter domains (|κ| < 0.2 µm⁻¹).
• In vitro, purified spectrin heterodimers showed a preference for low-curvature membranes, binding ~15-fold more strongly to larger (1000 nm) SSLBs than smaller (30 nm) ones.

Conclusions:

• Spectrin acts as a curvature-responsive cortical scaffold.
• Spectrin selectively stabilizes flat membrane domains, contributing to overall cellular stiffness.
• Spectrin oligomerization enhances its preference for low-curvature membranes.