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Ferrata Storti Foundation
Haematologica 2021 Volume 106(10):2726-2739
Protein-L-isoaspartate O-methyltransferase is required for in vivo control of oxidative damage in red blood cells
Angelo D’Alessandro,1 Ariel Hay,2 Monika Dzieciatkowska,1 Benjamin C. Brown,1 Evan J Morrison,1 Kirk C. Hansen1 and James C Zimring2
1Department of Biochemistry and Molecular Genetics, University of Colorado Denver – Anschutz Medical Campus, Aurora, CO and 2University of Virginia, Charlotesville, VA, USA
ABSTRACT
Red blood cells (RBC) have the special challenge of a large amount of reactive oxygen species (from their substantial iron load and Fenton reactions) combined with the inability to synthesize new gene prod- ucts. Considerable progress has been made in elucidating the multiple pathways by which RBC neutralize reactive oxygen species via NADPH driven redox reactions. However, far less is known about how RBC repair the inevitable damage that does occur when reactive oxygen species break through anti-oxidant defenses. When structural and functional proteins become oxidized, the only remedy available to RBC is direct repair of the damaged molecules, as RBC cannot synthesize new proteins. Amongst the most common amino acid targets of oxidative damage is the conversion of asparagine and aspartate side chains into a succinimidyl group through deamidation or dehydration, respectively. RBC express an L-isoaspartyl methyltransferase (PIMT, gene name PCMT1) that can convert succin- imidyl groups back to an aspartate. Herein, we report that deletion of PCMT1 significantly alters RBC metabolism in a healthy state, but does not impair the circulatory lifespan of RBC. Through a combination of genetic ablation, bone marrow transplantation and oxidant stimulation with phenylhydrazine in vivo or blood storage ex vivo, we use omics approaches to show that, when animals are exposed to oxidative stress, RBC from PCMT1 knockout undergo significant metabolic reprogram- ming and increased hemolysis. This is the first report of an essential role of PCMT1 for normal RBC circulation during oxidative stress.
Introduction
Dysfunction of red blood cells (RBC) is a component of numerous diseases and oxidant stress is a key component to both normal RBC aging and also pathological dysfunction.1 In addition, approximately one of every 70 Americans is transfused with packed RBC each year.2 RBC are stored for up to 42 days prior to transfusion out of logistical necessity, resulting in oxidative damage that affects their ability to function upon transfusion,3 thus impacting a wide variety of diseases for which transfusion is essential, including trauma, issues of chronic hemostasis, cancer, and chronic bone marrow disorders.2 Thus, damaged or dysfunctional RBC are a wide- spread factor in human disease and therapy.4
RBC face particular metabolic challenges regarding generation and mitigation of oxidative damage. First, RBC have a unique source of oxidative stress because of the high load of iron associated with hemoglobin (RBC account for appriximately 66% of bodily iron),4 which drives radical-generating Fenton reactions. Second, unlike most other tissues, repair of oxidant stress in RBC cannot involve new protein syn- thesis owing to the lack of nuclei or ribosomes. As such, elucidating and understand- ing the nonsynthetic pathways by which RBC manage oxidative stress can provide unique clues on cellular responses to oxidant injury. Although reactive oxygen species (ROS) are highly reactive, they preferentially attack particular chemical groups. When damaging proteins, the side chains of asparagine and aspartate are par- ticularly susceptible to oxidative conversion into a succinimidyl group through deamidation or dehydration, respectively.5 The succinimidyl group is unstable, and
Red Cell Biology & its Disorders
Correspondence:
ANGELO D’ALESSANDRO
angelo.dalessandro@ucdenver.edu
JAMES C ZIMRING
jcz2k@virginia.edu
Received: July 13, 2020.
Accepted: September 2, 2020. Pre-published: September 10, 2020.
https://doi.org/10.3324/haematol.2020.266676 ©2021 Ferrata Storti Foundation
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