Fyn is Involved in Erythropoietin Signaling Pathway and Interfaces Oxidation to Regulate Erythropoiesis

ABSTRACT Erythropoiesis is a complex multistep process responsible of the production of circulating mature erythrocytes and involved the production of reactive oxygen species (ROS) during erythroid differentiation. Here, we document that Fyn, a Src-family-kinase, participates in erythropoietin (EPO) signaling pathway, by the reducing extent of Tyr-phosphorylation of EPO-R and by decreasing STAT5 activity. The importance of Fyn in EPO cascade is also supported by the increased sensitivity of Fyn −/− mice to stress erythropoiesis. Fyn −/− mouse erythroblasts adapt to the induced stress by the activation of the redox-related-transcription-factor Nrf2. However, the absence of the Nrf2 physiologic repressor Fyn resulted in the persistent activation of Nrf2 and accumulation of non-functional proteins. This is paralleled by ROS induced over-activation of Jak2-Akt-mTOR pathway and repression of autophagy and perturbation of lysosomal-clearance during Fyn −/− reticulocyte maturation. Treatment with Rapamycin, a mTOR inhibitor and autophagy activator, ameliorates Fyn −/− mouse baseline erythropoiesis and restored the erythropoietic response to phenylhydrazine. Taken together these findings have enabled to identify the novel multimodal action of Fyn in the developmental program of erythropoiesis.