Dissecting metabolic functions of mitochondrial electron transport in kidney epithelium

About This Grant

The kidney transports ions, solutes, and water through energy-intensive processes that depend on the efficient synthesis of ATP via oxidative phosphorylation (OxPhos). Central to OxPhos is the mitochondrial (mt) electron transport chain (ETC), which generates ATP through chemiosmosis by driving ATP synthase activity. However, ATP production is not the only ETC-associated function essential for kidney health. The ETC also regulates intermediary metabolism and maintains cellular redox balance by oxidizing NADH and FADH2 to regenerate NAD+ and FAD. Furthermore, through its regulation of intermediary metabolism, the ETC intersects with hypoxia-inducible factor (HIF)- dependent oxygen sensing, underscoring its pivotal role in linking cellular metabolism to cellular adaptation to hypoxia. Despite its central importance in kidney physiology and disease, in vivo studies dissecting these diverse ETC functions have been limited by the lack of suitable genetic models. The interconnections between mt electron transport, redox balance, and intermediary metabolism in kidney homeostasis and pathogenesis therefore remain incompletely understood. To address these knowledge gaps, we take advantage of novel mouse models with targeted disruption of mt complexes I and III using pan-epithelial and nephron segment-specific gene targeting. Aim 1 examines the metabolic and biochemical consequences of complex I and complex III deficiency in the kidney through comprehensive in vivo and in vitro analyses. Using state-of-the-art approaches, including metabolic flux analysis, mass spectrometry-based metabolite imaging, and 3D super- resolution structured illumination microscopy, we delineate nephron segment-specific effects of ETC disruption on epithelial homeostasis and function. Aim 2 tests the hypothesis that aberrant intermediary metabolism, rather than ATP deficiency per se, drives epithelial dysfunction and tubulointerstitial injury in kidneys with ETC dysfunction. Through genetic restoration of redox balance and metabolite flux without reestablishing OxPhos, we will distinguish the molecular and pathological consequences of dysregulated intermediary metabolism from those of impaired ATP synthesis. Aim 3 investigates how aberrant intermediary metabolism and altered redox potential regulate HIF oxygen sensing and contribute to epithelial injury.