Our studies address a critical problem in hemoglobin (Hb) biology: how inherently unstable globin protein subunits are folded and maintained during normal and pathological erythropoiesis. We discovered alpha hemoglobin stabilizing protein (AHSP), an erythroid protein that specifically binds free alpha globin subunit, stabilizes its structure and limits its pro-oxidant activities. Our preliminary studies suggest two distinct functions for AHSP. First, to detoxify excess alpha globin that accumulates during normal erythropoiesis and in various anemias, particularly beta thalassemia. Second, to fold and stabilize newly formed alpha globin subunits en route to HbA (alpha beta) synthesis. Of potential importance to both functions, we discovered that degradation of AHSP mRNA is accelerated by iron, an essential component of HbA and determinant of nascent globin protein stability. Our overall view is that AHSP facilitates normal HbA synthesis and also buffers against imbalances that arise from genetic or environmental stresses, such as thalassemias and iron deficiency. Now we seek to better understand AHSP activities and their relevance to human health.
Aim 1 uses mouse genetics to investigate AHSP functions in vivo. We will examine the consequences of manipulated AHSP expression in thalassemias and create Ahsp gene missense mutations in mice to probe mechanisms of AHSP protein function.
Aim 2 studies the biochemical properties of AHSP. We will test in vitro if AHSP promotes reconstitution of HbA from its purified apo-globin and heme components and search for new erythroid proteins that interact with alpha globin-AHSP complexes.
Aim 3 examines the mechanisms by which iron regulates AHSP expression and the physiological implications of this pathway during altered iron homeostasis. If successful, our work will establish new basic principles of Hb biology and erythropoiesis. In addition, there are potential practical long-term benefits. For example, understanding how AHSP detoxifies excess alpha Hb should illustrate novel therapeutic approaches for human beta thalassemias. Elucidating the role of AHSP in HbA synthesis may provide tools to optimize the manufacture of recombinant Hb-based blood substitutes. Finally, defining functional interactions between iron and AHSP could provide insights into the pathophysiology and management of iron overload and deficiency states.

National Institute of Health (NIH)
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Research Project (R01)
Project #
Application #
Study Section
Erythrocyte and Leukocyte Biology Study Section (ELB)
Program Officer
Bishop, Terry Rogers
Project Start
Project End
Budget Start
Budget End
Support Year
Fiscal Year
Total Cost
Indirect Cost
Children's Hospital of Philadelphia
United States
Zip Code
Thom, Christopher S; Traxler, Elizabeth A; Khandros, Eugene et al. (2014) Trim58 degrades Dynein and regulates terminal erythropoiesis. Dev Cell 30:688-700
Strader, Michael Brad; Hicks, Wayne A; Kassa, Tigist et al. (2014) Post-translational transformation of methionine to aspartate is catalyzed by heme iron and driven by peroxide: a novel subunit-specific mechanism in hemoglobin. J Biol Chem 289:22342-57
Crowley, Moira A; Mollan, Todd L; Abdulmalik, Osheisa Y et al. (2011) A hemoglobin variant associated with neonatal cyanosis and anemia. N Engl J Med 364:1837-43
Mollan, Todd L; Yu, Xiang; Weiss, Mitchell J et al. (2010) The role of alpha-hemoglobin stabilizing protein in redox chemistry, denaturation, and hemoglobin assembly. Antioxid Redox Signal 12:219-31
Khandros, Eugene; Weiss, Mitchell J (2010) Protein quality control during erythropoiesis and hemoglobin synthesis. Hematol Oncol Clin North Am 24:1071-88
Krishna Kumar, Kaavya; Dickson, Claire F; Weiss, Mitchell J et al. (2010) AHSP (?-haemoglobin-stabilizing protein) stabilizes apo-?-haemoglobin in a partially folded state. Biochem J 432:275-82
Gell, David A; Feng, Liang; Zhou, Suiping et al. (2009) A cis-proline in alpha-hemoglobin stabilizing protein directs the structural reorganization of alpha-hemoglobin. J Biol Chem 284:29462-9
Weiss, Mitchell J; dos Santos, Camila O (2009) Chaperoning erythropoiesis. Blood 113:2136-44
Yu, Xiang; Mollan, Todd L; Butler, Andrew et al. (2009) Analysis of human alpha globin gene mutations that impair binding to the alpha hemoglobin stabilizing protein. Blood 113:5961-9
dos Santos, Camila O; Zhou, Suiping; Secolin, Rodrigo et al. (2008) Population analysis of the alpha hemoglobin stabilizing protein (AHSP) gene identifies sequence variants that alter expression and function. Am J Hematol 83:103-8

Showing the most recent 10 out of 18 publications