REGγContributes to Regulation of Hemoglobin and HemoglobinδSubunit

Abstract

Hemoglobin (Hb) is a family of proteins in red blood cells responsible for oxygen transport and vulnerable for oxidative damage. Hemoglobinδsubunit (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 REGγproteasome in hemopoietic tissues and nonerythroid cells. For this purpose, bone marrow, liver, and spleen hemopoietic tissues fromREGγ+/+andREGγ−/−mice and stable REGγknockdown cells were evaluated for the degradation of Hb and HBD via REGγ. Western blot and immunohistochemical analyses exhibited downregulation of Hb in REGγwild-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 REGγWT cells but not in REGγN151Y, a dominant-negative REGγmutant cell. Notably, downregulation of HBD was found in HeLa shN cells with stimulation of phenylhydrazine, an oxidation inducer, suggesting that the REGγproteasome 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 REGγproteasome.