Aberrant membrane lipid composition and biophysical properties contribute to impair calcium exchanges in elliptocytosis - A severe case study

ABSTRACT: 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

INSTRUMENT(S): Orbitrap Fusion Lumos

ORGANISM(S): Homo Sapiens (human)

TISSUE(S): Erythrocyte, Blood

DISEASE(S): Hereditary Elliptocytosis

SUBMITTER: Didier Vertommen  

LAB HEAD: Donatienne Tyteca

PROVIDER: PXD019059 | Pride | 2020-08-04

REPOSITORIES: Pride