The red blood cell proteome and interactome identify a Band 3-BLVRB axis regulating hypoxic metabolic adaptation

Red blood cells (RBCs) are transcriptionally silent yet dynamically remodel metabolism in response to oxygen tension. Using ultra-pure human RBCs, we generated the deepest contamination-free proteome to date (3,775 proteins) and mapped the oxygen-dependent interactome. These datasets reveal an oxygen-responsive metabolon centered on the Band 3 (SLC4A1) N-terminus. We identify biliverdin reductase B (BLVRB) as a previously unrecognized Band 3 interactor that dissociates under hypoxia, coincident with increased Band 3-deoxyhemoglobin contacts. This reversible assembly functions as an oxygen-sensitive switch coordinating redox and glycolytic remodeling. Humanized mice lacking Band 3 N-terminal segments exhibit impaired oxygen-dependent regulation of BLVRB binding to band 3, impaired hypoxic activation of glycolysis, reduced 2,3-bisphosphoglycerate synthesis, and diminished exercise tolerance, demonstrating physiological relevance. Population-scale cis-pQTLs for SLC4A1 and BLVRB suggest functions beyond canonical heme catabolism. Mechanistically, biochemical analyses in vitro suggest that hemoglobin β (HBB), Band 3, and BLVRB can undergo S-nitrosation and may participate in trans-nitrosation reactions with the glycolytic enzyme GAPDH, whose modification at C152 inhibits enzymatic activity in vitro. Collectively, these findings define a Band 3-BLVRB axis that integrates oxygen-dependent protein interactions with thiol-based redox chemistry, providing a framework for understanding how an anucleate cell achieves metabolic adaptability through reversible protein-protein interactions and post-translational modification. These findings suggest that perturbation of the Band 3-BLVRB axis may influence oxygen delivery and metabolic flexibility during hypoxic stress, with potential relevance to high-altitude adaptation, exercise physiology, and cardiopulmonary disease.