SUMMARY Rho GTPases impact a number of activities important for oncogenesis. Here we describe a small molecule inhibitor which blocks oncogenic transformation induced by various Rho GTPases in fibroblasts, and the growth of human breast cancer and B lymphoma cells, without affecting normal cells. We identify the target of this inhibitor to be the metabolic enzyme glutaminase, which catalyzes the hydrolysis of glutamine to glutamate. We show that transformed fibroblasts and breast cancer cells exhibit elevated glutaminase activity that is dependent on Rho GTPases and NFκB activity, and is blocked by the small molecule inhibitor. These findings highlight a previously unappreciated connection between Rho GTPase activation and cellular metabolism, and demonstrate that targeting glutaminase activity can inhibit oncogenic transformation.

integration ͉ structure ͉ retrovirus ͉ transcription ͉ host factor L ike all retroviruses, HIV-1 must integrate a reversetranscribed copy of its viral RNA genome into a host cell chromosome to establish a productive infection. Integration is mediated by the viral integrase (IN) protein acting on the DNA attachment sites at the ends of the linear reverse transcript. IN acts within the context of a higher-order preintegration complex (PIC) that is derived from the core of the infecting virion. IN catalyzes two sequential reactions, initially removing 3Ј terminal GT nucleotides from both ends of HIV-1 cDNA. After nuclear entry, IN inserts the processed 3Ј termini into opposing strands of chromosomal DNA. Repair of single-strand gaps by host cell enzymes completes the integration process (for a review, see ref.

Glutamine is an essential nutrient for cancer cell proliferation, especially in the context of citric acid cycle anaplerosis. In this manuscript we present results that collectively demonstrate that, of the three major mammalian glutaminases identified to date, the lesser studied splice variant of the gene gls, known as Glutaminase C (GAC), is important for tumor metabolism. We show that, although levels of both the kidney-type isoforms are elevated in tumor vs. normal tissues, GAC is distinctly mitochondrial. GAC is also most responsive to the activator inorganic phosphate, the content of which is supposedly higher in mitochondria subject to hypoxia. Analysis of X-ray crystal structures of GAC in different bound states suggests a mechanism that introduces the tetramerization-induced lifting of a "gating loop" as essential for the phosphate-dependent activation process. Surprisingly, phosphate binds inside the catalytic pocket rather than at the oligomerization interface. Phosphate also mediates substrate entry by competing with glutamate. A greater tendency to oligomerize differentiates GAC from its alternatively spliced isoform and the cycling of phosphate in and out of the active site distinguishes it from the liver-type isozyme, which is known to be less dependent on this ion.glutamine metabolism | Warburg effect