Hemin induces autophagy in a leukemic erythroblast cell line through the LRP1 receptor.

Gustavo Alberto Chiabrando,María Cecilia Sánchez,Ruben Adrian Grosso,Paula Virginia Subirada Caldarone,Claudio Marcelo Fader,María Isabel Colombo

doi:10.1042/bsr20181156

Abstract

Hemin is an erythropoietic inductor capable of inducing autophagy in erythroid-like cell lines. Low-density lipoprotein receptor-related protein 1 (LRP1) is a transmembrane receptor involved in a wide range of cellular processes, such as proliferation, differentiation, and metabolism. Our aim was to evaluate whether LRP1 is responsible for hemin activity in K562 cells, with the results demonstrating a three-fold increase in LRP1 gene expression levels (P-values <0.001) when assessed by quantitative real-time RT-PCR (qRT-PCR). Moreover, a 70% higher protein amount was observed compared with control condition (P-values <0.01) by Western blot (WB). Time kinetic assays demonstrated a peak in light chain 3 (LC3) II (LC3II) levels after 8 h of hemin stimulation and the localization of LRP1 in the autophagosome structures. Silencing LRP1 by siRNA decreased drastically the hemin-induced autophagy activity by almost 80% compared with control cells (P-values <0.01). Confocal localization and biochemical analysis indicated a significant redistribution of LRP1 from early endosomes and recycling compartments to late endosomes and autophagolysosomes, where the receptor is degraded. We conclude that LRP1 is responsible for hemin-induced autophagy activity in the erythroblastic cell line and that hemin–LRP1 complex activation promotes a self-regulation of the receptor. Our results suggest that hemin, via the LRP1 receptor, favors erythroid maturation by inducing an autophagic response, making it a possible therapeutic candidate to help in the treatment of hematological disorders.

Highlights

Erythroid maturation is a highly regulated process where immature cells from bone marrow pass through a series of differentiation stages in order to become mature red blood cells [1,2]
We have previously demonstrated that hemin is able to induce a partial maturation response, which activates autophagy/mitophagy in the K562 cell [14]
As hemin has been described as a lipoprotein receptor-related protein 1 (LRP1) ligand, we analyzed whether hemin was able to modify the LRP1 receptor levels in leukemia cells during erythroid maturation

Summary

Introduction

Erythroid maturation is a highly regulated process where immature cells from bone marrow pass through a series of differentiation stages in order to become mature red blood cells [1,2]. During this process, essential intracellular modifications take place such as nuclear extrusion, hemoglobin synthesis, protein membrane regulation, and the degradation of entire organelles that are unnecessary for erythrocyte functionality [3,4]. An erythropoiesis inductor, is capable of stimulating erythroid cell maturation and promoting hemoglobin synthesis [12,13]

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