A new molecular link between defective autophagy and erythroid abnormalities in chorea-acanthocytosis

Blood. 2016 Dec 22;128(25):2976-2987. doi: 10.1182/blood-2016-07-727321. Epub 2016 Oct 14.

Abstract

Chorea-acanthocytosis is one of the hereditary neurodegenerative disorders known as the neuroacanthocytoses. Chorea-acanthocytosis is characterized by circulating acanthocytes deficient in chorein, a protein of unknown function. We report here for the first time that chorea-acanthocytosis red cells are characterized by impaired autophagy, with cytoplasmic accumulation of active Lyn and of autophagy-related proteins Ulk1 and Atg7. In chorea-acanthocytosis erythrocytes, active Lyn is sequestered by HSP90-70 to form high-molecular-weight complexes that stabilize and protect Lyn from its proteasomal degradation, contributing to toxic Lyn accumulation. An interplay between accumulation of active Lyn and autophagy was found in chorea-acanthocytosis based on Lyn coimmunoprecipitation with Ulk1 and Atg7 and on the presence of Ulk1 in Lyn-containing high-molecular-weight complexes. In addition, chorein associated with Atg7 in healthy but not in chorea-acanthocytosis erythrocytes. Electron microscopy detected multivesicular bodies and membrane remnants only in circulating chorea-acanthocytosis red cells. In addition, reticulocyte-enriched chorea-acanthocytosis red cell fractions exhibited delayed clearance of mitochondria and lysosomes, further supporting the impairment of authophagic flux. Because autophagy is also important in erythropoiesis, we studied in vitro CD34+-derived erythroid precursors. In chorea-acanthocytosis, we found (1) dyserythropoiesis; (2) increased active Lyn; (3) accumulation of a marker of autophagic flux and autolysososme degradation; (4) accumlation of Lamp1, a lysosmal membrane protein, and LAMP1-positive aggregates; and (5) reduced clearance of lysosomes and mitochondria. Our results uncover in chorea-acanthocytosis erythroid cells an association between accumulation of active Lyn and impaired autophagy, suggesting a link between chorein and autophagic vesicle trafficking in erythroid maturation.

MeSH terms

  • Adult
  • Anion Exchange Protein 1, Erythrocyte / metabolism
  • Autophagy* / drug effects
  • Autophagy-Related Protein 7 / metabolism
  • Autophagy-Related Protein-1 Homolog / metabolism
  • Benzoquinones / pharmacology
  • Bortezomib / pharmacology
  • Cell Differentiation / drug effects
  • Cytosol / drug effects
  • Cytosol / metabolism
  • Demography
  • Erythrocytes / drug effects
  • Erythrocytes / metabolism
  • Erythrocytes / pathology
  • Erythrocytes / ultrastructure
  • Erythroid Cells / drug effects
  • Erythroid Cells / pathology*
  • Erythroid Cells / ultrastructure
  • Erythropoiesis / drug effects
  • Female
  • Heat-Shock Proteins / metabolism
  • Humans
  • Intracellular Signaling Peptides and Proteins / metabolism
  • Lactams, Macrocyclic / pharmacology
  • Lysosomes / drug effects
  • Lysosomes / metabolism
  • Male
  • Middle Aged
  • Mitochondria / drug effects
  • Mitochondria / metabolism
  • Molecular Weight
  • Multivesicular Bodies / drug effects
  • Multivesicular Bodies / metabolism
  • Neuroacanthocytosis / pathology*
  • Phosphorylation / drug effects
  • Proteasome Endopeptidase Complex / metabolism
  • Proteolysis / drug effects
  • src-Family Kinases / metabolism

Substances

  • Anion Exchange Protein 1, Erythrocyte
  • Benzoquinones
  • Heat-Shock Proteins
  • Intracellular Signaling Peptides and Proteins
  • Lactams, Macrocyclic
  • Bortezomib
  • lyn protein-tyrosine kinase
  • src-Family Kinases
  • Autophagy-Related Protein-1 Homolog
  • ULK1 protein, human
  • Proteasome Endopeptidase Complex
  • ATG7 protein, human
  • Autophagy-Related Protein 7
  • geldanamycin