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Splenectomy of patients with hereditary spherocytosis improves erythrocyte functionality in a septin-dependent manner

ABSTRACT: Splenectomy improves clinical parameters of patients with hereditary spherocytosis but its potential benefit to red blood cell (RBC) morphology and deformability and the mechanism behind remain unknown. We here compared 7 non-splenectomized and 12 splenectomized patients with mutations in the β-spectrin (SPTB) or the ankyrin (ANK1) gene. We showed that hematological parameters, spherocyte abundance, osmotic fragility, intracellular calcium and extracellular vesicle release were largely restored by splenectomy, but cryohemolysis was not. To elucidate the only partial improvement of RBC morphology and deformability by splenectomy, we performed a quantative proteomic analysis and cytoskeleton characterization. Patients exhibited decreased ankyrin and/or β-spectrin contents but the extent of RBC alteration only slightly and negatively correlated with the ankyrin and not with β-spectrin content nor membrane association. In contrast, patients exhibited increased abundance of septins, small GTP-binding cytoskeletal proteins involved in cytokinesis. Among the four septins detected, septins-2,7 and 8 but not 11 were less abundant upon splenectomy and correlated with the disease severity. The septin increase was accompanied by exacerbated oxidative stress especially in the non splenectomized patients. Except cryohemolysis, all the RBC morphology and deformability alterations and oxidative stress correlated with septin content. Impairments can result from RBC maturation defects since endoplasmic reticulum remnants were found in RBCs from non-splenectomized patients and lysosomal and mitochondrial remnants in splenectomised patients. The correlation between septin abundance and disease severity opens the way towards using septins as disease biomarkers. Moreover, the absence of restoration of septin-independent cryohemolysis by splenectomy could question its systematic recommendation

INSTRUMENT(S): Orbitrap Fusion Lumos

ORGANISM(S): Homo Sapiens (human)

TISSUE(S): Erythrocyte, Blood Cell, Blood

DISEASE(S): Hereditary Spherocytosis

SUBMITTER: Didier Vertommen

LAB HEAD: Donatienne Tyteca

PROVIDER: PXD034588 | Pride | 2023-02-13

REPOSITORIES: Pride

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Project description:Hereditary elliptocytosis is a red blood cell (RBC) disease mainly caused by mutations in spectrin, leading to cytoskeletal destabilization. Although patients with heterozygous mutation in α-spectrin (SPTA1) are asymptomatic, morphological changes and hemolysis are observed upon reduced functional α-spectrin production. The molecular mechanism is unknown. We analyzed the consequences of a α-spectrin mutation in a patient almost exclusively expressing the Pro260 variant of SPTA1 (pEl). pEl RBCs showed decreased size and circularity and increased fragility. The pEl RBC proteome was globally preserved but spectrin density at the cell edges rised and the two membrane anchorage complexes were less segregated. Hence, the pEl membrane was strongly impaired. First, the lipidome was modified, showing decreased phosphatidylserine vs increased lysophosphatidylserine species. Second, although membrane transversal asymmetry was preserved, curvature at the RBC edges and rigidity were increased. Third, sphingomyelin-enriched domains were altered in abundance, membrane:cytoskeleton anchorage and cholesterol content were targeted by the plasmatic acid sphingomyelinase (aSMase). Fourth, membrane calcium exchanges through the mechanosensitive channel PIEZO1 and the efflux pump PMCA were impaired, leading to increased intracellular calcium and ROS, lipid peroxidation and methemoglobin. Mecanistically, increased curvature through lysophosphatidylserine membrane insertion in healthy RBCs abrogated calcium influx. Cholesterol depletion of sphingomyelin-enriched domains by methyl-beta-cyclodextrin in pEl RBCs worsened calcium accumulation whereas aSMase inhibition by amitriptyline did the opposite. Those data indicated that α-spectrin tetramerization defect, lysophosphatidylserine, cholesterol domain depletion and aSMase cooperate to alter membrane properties and calcium exchanges, leading to calcium accumulation and oxidative stress. It could help develop novel therapies

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Splenectomy of patients with hereditary spherocytosis improves erythrocyte functionality in a septin-dependent manner

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