Alpha-2-Macroglobulin/LRP1 signaling promotes mitochondrial clearance and autophagic extracellular vesicle release in erythroid cells

Abstract

Despite advances in the understanding of the cellular and molecular mechanisms involved in erythropoiesis, there are still unanswered questions regarding the coordination between autophagy, vesicular trafficking, and endocytic signaling during this process. The complexity of these events suggests the existence of regulatory mechanisms capable of integrating these pathways. In this context, low-density lipoprotein receptor-related protein 1 (LRP1) emerges as a potential modulator given its function as a multifunctional endocytic receptor and its involvement in the regulation of degradation and signaling processes in various cellular models. However, its role in modulating mitophagy, a particular type of autophagy, and its link to vesicular trafficking associated with multivesicular bodies (MVBs) and the release of exosomes during erythroid maturation has been poorly explored. In this regard, alpha-2-Macroglobulin (2M), the main physiological ligand of LRP1, has been identified in extracellular vesicles (EVs) in various pathophysiological contexts, suggesting that it may be involved in vesicular dynamics and cellular clearance. In this study, we demonstrate that activated 2M (2M*), induces autophagy and particularly mitophagy, in K562 cells, and that LRP1 is directly responsible for this activation. Furthermore, we observed that 2M* stimulates the interaction of autophagosomes with MVBs/amphisomes and that EVs from K562 cells are positive for LC3, supporting a close relationship between the endocytic pathway and the autophagic pathway mediated by the 2M-LRP1 interaction. Taken together, these findings expand our understanding of erythroid biology and provide a conceptual foundation for exploring altered mechanisms in erythropoietic diseases and for the development of diagnostic and therapeutic strategies.