Comprehensive Analysis of Murine and Human RBC Ghost Proteomes.

Inherited hemolytic anemia (spherocytosis or elliptocytosis) is one of the most common inherited diseases with an incidence of 1:2500 to 1:5000 in populations of Northern European descent. Mild to severe inherited hemolytic anemias can arise from defects in the red blood cell (RBC) membrane skeleton. Genetic knock-out of various components of this apparatus has led to the creation of mouse models which have contributed significantly to our understanding of these disorders in humans. However, the mouse and human RBC protein complements have not been comprehensively compared.

Using newly developed proteomic methodology, we conducted a peptide level ‘bottom-up’ analysis of the normal mouse and human RBC ghost (i.e., RBC membrane skeleton and associated proteins). RBCs were purified using cellulose acetate chromatography from whole blood taken from three genetically identical mice and two hematologically normal yet genetically diverse humans. The isolated RBCs were lysed to generate RBC ghosts whose protein complements were digested with trypsin and analyzed by shotgun proteomics using microcapillary liquid chromatography coupled with tandem mass spectrometry. In total, 400 and 491 unique proteins were identified in human samples A and B respectively while 469 proteins were found in common across the three mouse samples. All previously identified membrane skeleton proteins were found in the human and mouse samples. Likewise, well-known RBC membrane proteins were represented. Of interest, a surprising number of proteins were found associated with the RBC ghost involved in processes such as protein repair (15–20), protein degradation (30–43), oxidative stress response (4–6), Ras oncogene biology (28–30), and glycolysis (3–6). Collectively, the two human samples represented 544 unique proteins. These results affirm the usefulness of inherited anemia mouse models given the observed conservation of membrane skeleton components and the inherent challenges with doing normal versus diseased RBC analysis in humans due to genetic variation.