Smad2/3-pathway ligand trap luspatercept enhances erythroid differentiation in murine ?-thalassaemia by increasing GATA-1 availability.

ABSTRACT: In ?-thalassaemia, anaemia results from ineffective erythropoiesis characterized by inhibition of late-stage erythroid differentiation. We earlier used luspatercept and RAP-536 protein traps for certain Smad2/3-pathway ligands to implicate Smad2/3-pathway overactivation in dysregulated erythroid differentiation associated with murine ?-thalassaemia and myelodysplasia. Importantly, luspatercept alleviates anaemia and has been shown to reduce transfusion burden in patients with ?-thalassaemia or myelodysplasia. Here, we investigated the molecular mechanisms underlying luspatercept action and pSmad2/3-mediated inhibition of erythroid differentiation. In murine erythroleukemic (MEL) cells in vitro, ligand-mediated overactivation of the Smad2/3 pathway reduced nuclear levels of GATA-1 (GATA-binding factor-1) and its transcriptional activator TIF1? (transcription intermediary factor 1?), increased levels of reactive oxygen species, reduced cell viability and haemoglobin levels, and inhibited erythroid differentiation. Co-treatment with luspatercept in MEL cells partially or completely restored each of these. In ?-thalassaemic mice, RAP-536 up-regulated Gata1 and its target gene signature in erythroid precursors determined by transcriptional profiling and gene set enrichment analysis, restored nuclear levels of GATA-1 in erythroid precursors, and nuclear distribution of TIF1? in erythroblasts. Bone marrow cells from ?-thalassaemic mice treated with luspatercept also exhibited restored nuclear availability of GATA-1 ex vivo. Our results implicate GATA-1, and likely TIF1?, as key mediators of luspatercept/RAP-536 action in alleviating ineffective erythropoiesis.

SUBMITTER: Martinez PA 

PROVIDER: S-EPMC7294138 | biostudies-literature | 2020 Jun

REPOSITORIES: biostudies-literature