Abstract
Podocytes are highly differentiated cells and critical elements for the filtration barrier of the kidney. Loss of their foot process (FP) architecture (FP effacement) results in urinary protein loss. Here we show a novel role for the neutral amino acid glutamine in structural and functional regulation of the kidney filtration barrier. Metabolic flux analysis of cultured podocytes using genetic, toxic, and immunologic injury models identified increased glutamine utilization pathways. We show that glutamine uptake is increased in diseased podocytes to couple nutrient support to increased demand during the disease state of FP effacement. This feature can be utilized to transport increased amounts of glutamine into damaged podocytes. The availability of glutamine determines the regulation of podocyte intracellular pH (pHi). Podocyte alkalinization reduces cytosolic cathepsin L protease activity and protects the podocyte cytoskeleton. Podocyte glutamine supplementation reduces proteinuria in LPS-treated mice, whereas acidification increases glomerular injury. In summary, our data provide a metabolic opportunity to combat urinary protein loss through modulation of podocyte amino acid utilization and pHi.
Background: Podocyte injury can be caused by cytosolic cathepsin L activity, leading to foot process effacement and proteinuria.
Results: Glutamine blunts the damaging activity of induced cytosolic cathepsin L in podocytes by modulating intracellular pH.
Conclusion: Podocyte pH modulation is a novel way to tackle proteinuric kidney disease.
Significance: The optimization of amino acid metabolism fluxes and associated pHi of podocytes may form a basis for novel therapeutic approaches.
