Loss of Alpha-Hemoglobin-Stabilizing Protein Impairs Erythropoiesis and Exacerbates Beta-Thalassemia

J Clin Invest. 2004 Nov;114(10):1457-66. doi: 10.1172/JCI21982.

Abstract

Hemoglobin (Hb) A production during red blood cell development is coordinated to minimize the deleterious effects of free alpha- and beta-Hb subunits, which are unstable and cytotoxic. The alpha-Hb-stabilizing protein (AHSP) is an erythroid protein that specifically binds alpha-Hb and prevents its precipitation in vitro, which suggests that it may function to limit free alpha-Hb toxicities in vivo. We investigated this possibility through gene ablation and biochemical studies. AHSP(-/-) erythrocytes contained hemoglobin precipitates and were short-lived. In hematopoietic tissues, erythroid precursors were elevated in number but exhibited increased apoptosis. Consistent with unstable alpha-Hb, AHSP(-/-) erythrocytes contained increased ROS and evidence of oxidative damage. Moreover, purified recombinant AHSP inhibited ROS production by alpha-Hb in solution. Finally, loss of AHSP worsened the phenotype of beta-thalassemia, a common inherited anemia characterized by excess free alpha-Hb. Together, the data support a model in which AHSP binds alpha-Hb transiently to stabilize its conformation and render it biochemically inert prior to Hb A assembly. This function is essential for normal erythropoiesis and, to a greater extent, in beta-thalassemia. Our findings raise the possibility that altered AHSP expression levels could modulate the severity of beta-thalassemia in humans.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Apoptosis
  • Erythrocytes / metabolism*
  • Erythrocytes / pathology
  • Erythropoiesis*
  • Heinz Bodies / chemistry
  • Heinz Bodies / metabolism
  • Hemoglobins / chemistry*
  • Hemoglobins / genetics
  • Hemoglobins / physiology*
  • Heterozygote
  • Kinetics
  • Mice
  • Mice, Knockout
  • Models, Biological
  • Protein Conformation
  • Reactive Oxygen Species / metabolism
  • Recombinant Proteins / isolation & purification
  • Recombinant Proteins / metabolism
  • beta-Thalassemia / metabolism*

Substances

  • Hemoglobins
  • Reactive Oxygen Species
  • Recombinant Proteins