Non-muscle myosin II drives vesicle loss during human reticulocyte maturation

Abstract

The process of maturation of reticulocytes into fully mature erythrocytes that occurs in the circulation is known to be characterized by a complex interplay between loss of cell surface area and volume, removal of remnant cell organelles and redundant proteins, and highly selective membrane and cytoskeletal remodeling. However, the mechanisms that underlie and drive these maturational processes in vivo are currently poorly understood and, at present, reticulocytes derived through in vitro culture fail to undergo the final transition to erythrocytes. Here, we used high-throughput proteomic methods to highlight differences between erythrocytes, cultured reticulocytes and endogenous reticulocytes. We identify a cytoskeletal protein, non-muscle myosin IIA (NMIIA) whose abundance and phosphorylation status differs between reticulocytes and erythrocytes and localized it in the proximity of autophagosomal vesicles. An ex vivo circulation system was developed to simulate the mechanical shear component of circulation and demonstrated that mechanical stimulus is necessary, but insufficient for reticulocyte maturation. Using this system in concurrence with non-muscle myosin II inhibition, we demonstrate the involvement of non-muscle myosin IIA in reticulocyte remodeling and propose a previously undescribed mechanism of shear stress-responsive vesicle clearance that is crucial for reticulocyte maturation.

Proteome of Stored RBC Membrane and Vesicles from Heterozygous Beta Thalassemia Donors

“…Upregulation of myosin levels may account for these phenomenally paradoxical findings. As a probable result of different reticulocyte maturation in beta thalassemia [ 21 ], it has been considered a cellular volume regulator in the microcytic βThal + RBCs [ 22 ]. βThal + membrane enrichment in several non-muscle myosin proteoforms might contribute to structural integrity, deformability, and resistance to stress [ 23 ], including storage-induced stress, since the expression of structural proteins did not reduce with storage time, as opposed to control RBCs.…”

Myotonic dystrophy kinase‐related CDC42‐binding kinase α, a new transferrin receptor type 2‐binding partner, is a regulator of erythropoiesis

“…Cytoskeleton reorganization is primordial for erythroid differentiation, prompting major morphological changes such as cell shrinking and nuclear extrusion. During reticulocyte maturation, myosin‐II‐mediated cytoskeleton reorganization leads to a 20% loss of membrane and a decreased cell volume required to obtain a mature and functional red blood cell 47,48 . Additionally, it has recently been described that red blood cells' curvature is maintained through the contractility of myosin‐II 49 .…”

MYH9‐related disease mutations cause abnormal red blood cell morphology through increased myosin‐actin binding at the membrane

“…MYH9 ‐RD may affect low numbers of RBCs because changes in NMIIA contractility may have different effects on RBC membrane properties at different stages in RBC lifetimes. Previous studies suggest a role for NMII in erythroblast cell division prior to enucleation and in reticulocyte maturation . Future studies using mouse models of MYH9 ‐RD could test whether MYH9 ‐RD affects erythroblast terminal differentiation.…”