Dynamic actin filaments control the mechanical behavior of the human red blood cell membrane

Short, uniform-length actin filaments function as structural nodes in the spectrin-actin membrane skeleton to optimize the biomechanical properties of red blood cells (RBCs). Despite the widespread assumption that RBC actin filaments are not dynamic (i.e., do not exchange subunits with G-actin in th...

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Bibliographic Details
Published in:Molecular biology of the cell 2015-05, Vol.26 (9), p.1699-1710
Main Authors: Gokhin, David S, Nowak, Roberta B, Khoory, Joseph A, Piedra, Alfonso de la, Ghiran, Ionita C, Fowler, Velia M
Format: Article
Language:English
Subjects:
Actin Cytoskeleton - metabolism
Actins - metabolism
Biomechanical Phenomena
Cell Membrane - physiology
Erythrocytes - metabolism
Humans
Osmotic Fragility
Protein Multimerization
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Summary:Short, uniform-length actin filaments function as structural nodes in the spectrin-actin membrane skeleton to optimize the biomechanical properties of red blood cells (RBCs). Despite the widespread assumption that RBC actin filaments are not dynamic (i.e., do not exchange subunits with G-actin in the cytosol), this assumption has never been rigorously tested. Here we show that a subpopulation of human RBC actin filaments is indeed dynamic, based on rhodamine-actin incorporation into filaments in resealed ghosts and fluorescence recovery after photobleaching (FRAP) analysis of actin filament mobility in intact RBCs (~25-30% of total filaments). Cytochalasin-D inhibition of barbed-end exchange reduces rhodamine-actin incorporation and partially attenuates FRAP recovery, indicating functional interaction between actin subunit turnover at the single-filament level and mobility at the membrane-skeleton level. Moreover, perturbation of RBC actin filament assembly/disassembly with latrunculin-A or jasplakinolide induces an approximately twofold increase or ~60% decrease, respectively, in soluble actin, resulting in altered membrane deformability, as determined by alterations in RBC transit time in a microfluidic channel assay, as well as by abnormalities in spontaneous membrane oscillations (flickering). These experiments identify a heretofore-unrecognized but functionally important subpopulation of RBC actin filaments, whose properties and architecture directly control the biomechanical properties of the RBC membrane.
ISSN:1059-1524
1939-4586
DOI:10.1091/mbc.e14-12-1583