α-synuclein aggregates inhibit reticulocyte maturation

Abstract Anemia is highly associated with Parkinson's disease (PD), yet the underlying mechanisms linking PD to erythropoiesis remain poorly defined. α-synuclein (α-syn, encoded by SNCA), a core pathogenic protein in PD, forms aggregates that accumulate in the brain and drive neuronal degeneration. Notably, red blood cells (RBCs) from PD patients exhibit abnormal morphology and highly enrich α-syn aggregates. However, the impact of α-syn aggregates on erythropoiesis is unknown. To investigate the role of α-syn aggregates in erythropoiesis, we utilized B6; C3-Tg(Prnp-SNCA*A53T)83Vle/J mice (PD mice), which develop motor symptoms of PD by 10 months. PD mice displayed mild anemia at both 3 and 10 months old. Flow cytometry revealed comparable percentages of hematopoietic stem cells, common myeloid progenitors, granulocyte-macrophage progenitors, and megakaryocyte-erythroid progenitors in PD versus wild-type (WT) mice. Critically, PD mice exhibited increased reticulocytes and decreased RBCs in the bone marrow (BM), suggesting impaired reticulocyte maturation. Reticulocytes from PD mice showed higher mean fluorescence intensity for CD71 and forward scatter (FSC). Consistently, umbilical cord blood-derived reticulocytes overexpressing SNCA-WT and SNCA-A53T, and peripheral blood mononuclear cell-derived reticulocytes from PD patients (vs. healthy controls), displayed similar immaturity phenotypes, indicating that α-syn aggregates disrupts reticulocyte maturation. Membrane proteomics and SDS-PAGE analysis indicated unchanged skeleton composition in PD RBCs. However, higher expression of exosome-targeted membrane proteins, including CD49d and amino acid transporters (SLC15A4, SLC38A5), suggested defective membrane remodeling in PD mice. Subsequently, co-immunoprecipitation confirmed that α-syn interacted with membrane skeleton proteins (band3, p55, ankyrin, actin, α-spectrin, and β-spectrin), and proteins related to the extracellular exosome, implicating that α-syn is associated with the exosome pathway during maturation. Together, our findings demonstrated that α-syn aggregates impair reticulocyte maturation in PD by exosome-mediated membrane protein clearance. Keywords: α-syn aggregates; reticulocyte maturation; exosome pathway.