35 Oral - Physiology, Aging, and Metabolism I
Thursday April 07, 5:15 PM - 5:30 PM

Authors:
Nader Mahmoudzadeh ¹; Yasaman Heidarian ¹; Katherine Beebe ²; Alexander Fitt ¹; Aylin Rodan ²; Jason Tennessen ¹

Affiliations:
1) Indiana University; 2) University of Utah

Keywords:
g. oxidative damage; h. mitochondria

The oncometabolite L-2-hydroxyglutarate (L-2HG) is considered a waste-product of central carbon metabolism that is capable of disrupting chromatin architecture, mitochondrial metabolism, and cellular differentiation. As a result, ectopic L-2HG accumulation in humans is toxic and promotes the growth of renal cell carcinomas, however, few studies have examined how this molecule functions in vivo. The fruit fly Drosophila melanogaster has emerged as a powerful model to study L-2HG. Not only are the metabolic mechanisms that regulate L-2HG accumulation conserved between flies and humans but L-2HG levels undergo predictable fluctuations during the fly lifecycle that allow for mechanistic studies. Here we exploit this system to understand how inappropriate L-2HG accumulation affects the metabolism and physiology of adult flies. Using CRISPR/Cas9, we generated mutations in the sole Drosophila L-2-hydroxyglutarate dehydrogenase (L2HGDH) ortholog, which is required to degrade L-2HG. Although L2hgdh mutant adults accumulate L-2HG levels that are 50-times higher than controls, these mutants are viable and fertile under normal conditions and exhibit no apparent phenotypes. However, L2hgdh mutant adults are extremely sensitive to hypoxic stress and die following exposure to 1% O₂. Subsequent metabolomic studies indicate that hypoxia exposed L2hgdh mutants become locked in a glycolytic state and are unable to restart mitochondrial metabolism upon reoxygenation. Finally, we find that the hypoxia-sensitive phenotype of L2hgdh mutants stem, in part, from defects in the Malpighian tubules (MTs). Not only do L2hgdh mutant MTs display mitochondrial defects, but L2hgdh mutants that express a rescuing transgene in only the principal cells of MTs exhibit normal viability following hypoxia exposure. Considering that renal cell carcinomas are the only cancer where L2hgdh is known to function as a tumor suppressor, our findings suggest that L-2HG is capable of uniquely disrupting renal cell function and establish the fly as a powerful disease model for studying this oncometabolite.