REGγ Contributes to Regulation of Hemoglobin and Hemoglobin δ Subunit.

Qiuhong Zuo,Xiaotao Li,Bianhong Zhang,Yuanyuan Zhang,Junjiang Fu,Shanshan Cheng,Yanyan Xue,Jiwu Chen,Muhammad Zeeshan Bhatti,Lin Wu,Lei Li,Wenxiang Huang

doi:10.1155/2017/7295319

Abstract

Hemoglobin (Hb) is a family of proteins in red blood cells responsible for oxygen transport and vulnerable for oxidative damage. Hemoglobin δ subunit (HBD), a member of Hb family, is normally expressed by cells of erythroid lineage. Expression of Hb genes has been previously reported in nonerythroid and hematopoietic stem cells. Here, we report that Hb and HBD can be degraded via REGγ proteasome in hemopoietic tissues and nonerythroid cells. For this purpose, bone marrow, liver, and spleen hemopoietic tissues from REGγ+/+ and REGγ−/− mice and stable REGγ knockdown cells were evaluated for the degradation of Hb and HBD via REGγ. Western blot and immunohistochemical analyses exhibited downregulation of Hb in REGγ wild-type mouse tissues. This was validated by dynamic analysis following blockade of de novo synthesis of proteins with CHX. Degradation of HBD only occurred in REGγ WT cells but not in REGγN151Y, a dominant-negative REGγ mutant cell. Notably, downregulation of HBD was found in HeLa shN cells with stimulation of phenylhydrazine, an oxidation inducer, suggesting that the REGγ proteasome may target oxidatively damaged Hbs. In conclusion, our findings provide important implications for the degradation of Hb and HBD in hemopoietic tissues and nonerythroid cells via the REGγ proteasome.

Highlights

Hemoglobin (Hb) is one of the most abundant proteins in the human body and the major component of erythrocytes
We investigated the roles of REGγmediated regulation of Hb degradation in REGγ+/+ and REGγ−/− mice tissues (1-2-week-old mice), including the bone marrow, liver, and spleen, since these tissues are associated with removal of aged erythrocytes and clearance of oxidized Hb
Hemoglobin is a major protein of erythrocytes (RBCs) responsible for the transport of oxygen (O2)

Summary

Introduction

Hemoglobin (Hb) is one of the most abundant proteins in the human body and the major component of erythrocytes. Eryptosis is characterized by cell shrinkage, cell membrane bleeding, and cell membrane phospholipids scrambling with phosphatidylserine exposure at the cell surface In this regard, eryptosis is stimulated by an increase in cytosolic Ca2+ activity, ceramide, hyperosmotic shock, oxidative stress, energy depletion, hyperthermia, and a wide verity of xenobiotics and endogenous substances [1, 2]. Eryptosis is stimulated by an increase in cytosolic Ca2+ activity, ceramide, hyperosmotic shock, oxidative stress, energy depletion, hyperthermia, and a wide verity of xenobiotics and endogenous substances [1, 2] These eryptosis factors participate in the Hb damage of RBCs as well as in various hemoglobinopathies, which have been observed in Hb damage.

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Conclusion