Recovering from hypoxia-induced metabolic suppression: Role of N-myc Downstream Regulated Gene 1a in Na+/K+/ATPase restoration from the cytosol to the plasma membrane

Abstract

Oxygen plays a life-critical role in oxidative phosphorylation. Zebrafish embryos, however, can survive nearly fifty hours in a zero-oxygen (anoxic) environment by entering a state of metabolic suppression characterized by metabolic arrest of ATP-demanding processes, such as ion pumping driven by the sodium potassium pump (NKA). The Brewster Lab has previously shown that the N-myc Downstream Regulated Gene 1 (NDRG1) mediates NKA downregulation in the embryonic kidney and ionocytes, allowing for embryonic energy conservation. Here, I explore the question of whether Ndrg1a promotes the return of membrane NKA levels upon re-oxygenation after sustained anoxia, using the proximity ligation assay (PLA) to detect whether these proteins interact in situ. I focus on ionocyte morphology because qualitative analysis of these structures allows for direct assessment of protein subcellular localization. I hypothesize that if Ndrg1 is required for NKA recycling or exocytosis post- anoxia, then these proteins should remain associated throughout re-oxygenation, transitioning from the cytosol to the plasma membrane over time; this is consistent with known protein trafficking roles of NDRGs. My preliminary data(n=2) reveal a significant shift in NKA localization. In contrast, PLA signal remained relatively consistent over time, suggesting an NKANdrg1a interaction confined to the cytosol. These findings suggest that NDRG1, acting as a versatile adapter protein and environmental oxygen-lactate sensor, may play a role in intracellular trafficking of NKA to mediate post-metabolic-arrest survival. Identification of the subcellular compartments where these proteins interact will further our understanding of the role of Ndrg1a in hypoxia adaptation.