Cytoskeleton Remodeling Induces Membrane Stiffness and Stability Changes of Maturing Reticulocytes

Abstract

Reticulocytes, the precursors of erythrocytes, undergo drastic alterations in cell size, shape, and deformability during maturation. Experimental evidence suggests that young reticulocytes are stiffer and less stable than their mature counterparts; however, the underlying mechanism is yet to be fully understood. Here, we develop a coarse-grained molecular-dynamics reticulocyte membrane model to elucidate how the membrane structure of reticulocytes contributes to their particular biomechanical properties and pathogenesis in blood diseases. First, we show that the extended cytoskeleton in the reticulocyte membrane is responsible for its increased shear modulus. Subsequently, we quantify the effect of weakened cytoskeleton on the stiffness and stability of reticulocytes, via which we demonstrate that the extended cytoskeleton along with reduced cytoskeleton connectivity leads to the seeming paradox that reticulocytes are stiffer and less stable than the mature erythrocytes. Our simulation results also suggest that membrane budding and the consequent vesiculation of reticulocytes can occur independently of the endocytosis-exocytosis pathway, and thus, it may serve as an additional means of removing unwanted membrane proteins from reticulocytes. Finally, we find that membrane budding is exacerbated when the cohesion between the lipid bilayer and the cytoskeleton is compromised, which is in accord with the clinical observations that erythrocytes start shedding membrane surface at the reticulocyte stage in hereditary spherocytosis. Taken together, our results quantify the stiffness and stability change of reticulocytes during their maturation and provide, to our knowledge, new insights into the pathogenesis of hereditary spherocytosis and malaria.

Reticulocyte Infection Leads to Altered Behaviour, Drug Sensitivity and Host Cell Remodelling byPlasmodium falciparum

“…To elucidate possible correlations, we measured membrane deformability properties of P. falciparum infected CD71 + and CD71 - cells. Membrane of the healthy CD71 + reticulocytes were significantly rigid with an estimated membrane shear modulus of 19 pN/μm compared to normocytes (average smear modulus of 6.5 pN/μm), as reported 22-37 . P. falciparum- infected CD71 + cells remained rigid during the progression of parasites ( Fig.…”

“…Reticulocytes possess complex membranous composition 37 and architecture rendering increased rigidity thereby influencing membrane permeability and molecular transport 38 . Previous studies show that reticulocytes have increased cation permeability for calcium (43-fold) and sodium (6-fold) 39 .…”

Mechanical characterization of vesicles and cells: A review

“…This controls the extent of deformation that the cell can undergo. Cells, however, at different stages of their differentiation, expel unwanted membrane proteins by releasing small vesicles in the form of exosomes . These exosomes share striking structural similarities with bioengineered liposomes.…”

Structural and functional studies of erythrocyte membrane-skeleton by single-cell and single-molecule techniques

“…When a small hemispherical portion of the erythrocyte was aspired into the micropipette, the erythrocyte deformability was assessed by the surface elastic moduli, which could be calculated through the size of the aspired portion and the applied pressure. 45,46 When erythrocyte was aspirated into a micropipette with a long tongue, the shear modulus of membrane-skeleton could be determined by the tongue length. 47 The actin¯laments of the membraneskeleton were found to be obviously modi¯ed when erythrocyte was aspirated with a long tongue inside the micropipette.…”