Glutaminase 1 Promotes the Proliferation of Endothelial Cells via the Induction of Cyclin A

Abstract

Glutaminase (GLS) is a phosphate‐dependent enzyme that converts glutamine to glutamate and ammonia. There are two distinct isoforms of GLS, GLS1 and GLS2, which possess discrete tissue distribution, structural properties, enzyme kinetics, and molecular regulation. Although endothelial cells possess substantial GLS activity, its functional role in these cells remains largely unknown. In the present study, we characterized the expression of GLS in endothelial cells and investigated the effect of GLS on the proliferation of endothelial cells. Human umbilical vein endothelial cells (HUVEC) expressed high levels of GLS1, but GLS2 was not detected in these cells. Treatment of HUVEC with the non‐selective GLS inhibitor 6‐diazo‐5‐oxo‐L‐ornithine or the selective GLS1 inhibitors bis‐2‐(5‐phenylacetamido‐1,3,4‐thiadiazol‐2‐yl)ethyl sulfide or CB‐839 resulted in a concentration‐dependent inhibition of endothelial cell growth. All three GLS1 inhibitors also blocked DNA synthesis in both HUVEC and mouse aortic endothelial cells. Similarly, knockdown of GLS1 expression using a siRNA approach blocked the mitogenic response of endothelial cells. Flow cytometry experiments demonstrated that GLS1 inhibitors or GLS1 silencing arrested endothelial cells in the G0/G1 phase of the cell cycle, as reflected by increases in the percentage of cells in G0/G1 with corresponding decreases in the fraction of cells in S and G2/M phases. Cell cycle arrest by these GLS1 inhibitors was associated with a significant decrease in the expression of cyclin A protein that was paralleled by a reduction in cyclin A mRNA and promoter activity. Finally, adenoviral‐mediated gene transfer of cyclin A largely restored the proliferative response of GLS1‐inhibited endothelial cells. In conclusion, this study demonstrates that endothelial cells selectively express GLS1, and that GLS1 plays a central role in stimulating endothelial cell proliferation and cell cycle progression via the induction of cyclin A. In addition, it identifies GLS1 as an attractive therapeutic target in treating diseases associated with aberrant endothelial cell growth.Support or Funding InformationThis work was supported by the American Heart Association Grant 15GRNT25250015.