Red blood cell (RBC) deformability is altered in inherited RBC disorders but the mechanism behind this is poorly understood. Here, we explored the molecular, biophysical, morphological, and functional consequences of α-spectrin mutations in a patient with hereditary elliptocytosis (pEl) almost exclusively expressing the Pro260 variant of SPTA1 and her mother (pElm), heterozygous for this mutation. At the molecular level, the pEI RBC proteome was globally preserved but spectrin density at cell edges was increased. Decreased phosphatidylserine vs. increased lysophosphatidylserine species, and enhanced lipid peroxidation, methemoglobin, and plasma acid sphingomyelinase (aSMase) activity were observed. At the biophysical level, although membrane transversal asymmetry was preserved, curvature at RBC edges and rigidity were increased. Lipid domains were altered for membrane:cytoskeleton anchorage, cholesterol content and response to Ca²⁺ exchange stimulation. At the morphological and functional levels, pEl RBCs exhibited reduced size and circularity, increased fragility and impaired membrane Ca²⁺ exchanges. The contribution of increased membrane curvature to the pEl phenotype was shown by mechanistic experiments in healthy RBCs upon lysophosphatidylserine membrane insertion. The role of lipid domain defects was proved by cholesterol depletion and aSMase inhibition in pEl. The data indicate that aberrant membrane content and biophysical properties alter pEl RBC morphology and functionality.

Piezo1 is a mechanosensitive ion channel required for various biological processes, but its regulation remains poorly understood. Here, we used erythrocytes to address this question since they display Piezo1 clusters, a strong and dynamic cytoskeleton and three types of submicrometric lipid domains, respectively enriched in cholesterol, GM1 ganglioside/cholesterol and sphingomyelin/cholesterol. We revealed that Piezo1 clusters were present in both the rim and the dimple erythrocyte regions. Upon Piezo1 chemical activation by Yoda1, the Piezo1 cluster proportion mainly increased in the dimple area. This increase was accompanied by Ca²⁺ influx and a rise in echinocytes, in GM1/cholesterol-enriched domains in the dimple and in cholesterol-enriched domains in the rim. Conversely, the effects of Piezo1 activation were abrogated upon membrane cholesterol depletion. Furthermore, upon Piezo1-independent Ca²⁺ influx, the above changes were not observed. In healthy donors with a high echinocyte proportion, Ca²⁺ influx, lipid domains and Piezo1 fluorescence were high even at resting state, whereas the cytoskeleton membrane occupancy was lower. Accordingly, upon decreases in cytoskeleton membrane occupancy and stiffness in erythrocytes from patients with hereditary spherocytosis, Piezo1 fluorescence was increased. Altogether, we showed that Piezo1 was differentially controlled by lipid domains and the cytoskeleton and was favored by the stomatocyte–discocyte–echinocyte transformation.

Tyrosine kinase inhibitors (TKI), such as imatinib, have revolutionized chronic myeloid leukemia (CML) treatment. Despite this success, TKI intolerance and resistance remain significant clinical challenges. A promising therapeutic approach is to simultaneously target the BCR::ABL1 oncogene and other oncogenic drivers. The polycistronic miR-17-92 cluster is known to contribute to CML development and progression, but the specific roles of miR-92a-1-5p within this cluster remain unclear. In this study, we assess the roles of this microRNA and evaluate the therapeutic potential of combining microRNA inhibition with imatinib to improve treatment outcome. Our results show that miR-92a-1-5p is downregulated by imatinib in myeloid cell lines harboring BCR::ABL1 and in CML patient samples. Inhibition of miR-92a-1-5p reduces proliferation and enhances imatinib-induced cell death, while its overexpression increases proliferation and counteracts the effects of imatinib on cell death. This decrease in proliferation caused by miR-92a-1-5p inhibition is rescued after simultaneous inhibition of two newly identified target genes: BNIP3L (NIX) and TP53INP1. We confirm that miR-92a-1-5p regulates proliferation and cell cycle by targeting TP53INP1 and decreases autophagy by targeting BNIP3L. Our data suggest that miR-92a-1-5p plays a role in CML progression, and its inhibition enhances imatinib anti-leukemic efficacy, making it a potential therapeutic target.