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.

Transgenic overexpression of Cu ؉2 ͞Zn ؉2 superoxide dismutase 1 (SOD1) harboring an amyotrophic lateral sclerosis (ALS)-linked familial genetic mutation (SOD1 G93A ) in a Sprague-Dawley rat results in ALS-like motor neuron disease. Motor neuron disease in these rats depended on high levels of mutant SOD1 expression, increasing from 8-fold over endogenous SOD1 in the spinal cord of young presymptomatic rats to 16-fold in end-stage animals. Disease onset in these rats was early, Ϸ115 days, and disease progression was very rapid thereafter with affected rats reaching end stage on average within 11 days. Pathological abnormalities included vacuoles initially in the lumbar spinal cord and subsequently in more cervical areas, along with inclusion bodies that stained for SOD1, Hsp70, neurofilaments, and ubiquitin. Vacuolization and gliosis were evident before clinical onset of disease and before motor neuron death in the spinal cord and brainstem. Focal loss of the EAAT2 glutamate transporter in the ventral horn of the spinal cord coincided with gliosis, but appeared before motor neuron͞axon degeneration. At end-stage disease, gliosis increased and EAAT2 loss in the ventral horn exceeded 90%, suggesting a role for this protein in the events leading to cell death in ALS. These transgenic rats provide a valuable resource to pursue experimentation and therapeutic development, currently difficult or impossible to perform with existing ALS transgenic mice.A myotrophic lateral sclerosis (ALS) is a late-onset neuromuscular disorder characterized by progressive motor dysfunction that leads to paralysis and eventually death. The pathology of the disease results from the death of large motor neurons in the spinal cord and brainstem (1, 2). ALS occurs in both sporadic and familial forms (3). Familial ALS accounts for Ϸ5-10% of all reported cases. Approximately 15-20% of familial ALS cases has been linked to inheritance in an autosomal dominant fashion of a mutant form of Cu ϩ2 ͞Zn ϩ2 superoxide dismutase 1 (SOD1) (4, 5). SOD1 normally functions in the regulation of oxidative stress by conversion of free radical superoxide anions to hydrogen peroxide and molecular oxygen. Over 90 distinct familial SOD1 mutations have been found to date. SOD1 mutations that have been tested in transgenic mice result in ALS-like motor neuron disease (6-8), but SOD1-null mice do not develop motor neuron disease (9). Furthermore, crossing SOD1-null mice with transgenic ALS mice does not alter disease onset or progression (10). Taken together, these results indicate that familial ALS does not result from loss of SOD1 function but rather an unidentified gain of function. There is no consensus as to the mechanism, and theories include alterations in SOD1 folding, oxidative stress from aberrant catalysis (11), or cytoplasmic aggregates (12). New studies also suggest that the disease is not cell autonomous-that nonneuronal cells are necessary for motor neuron degeneration (13, 14, ¶).Transgenic mouse models expressing mutant forms of SOD1 (15-21) develop...

The Ras-related GTP-binding protein Cdc42 is implicated in a variety of biological activities including the establishment of cell polarity in yeast, the regulation of cell morphology, motility and cell-cycle progression in mammalian cells and the induction of malignant transformation. We identified a Cdc42 mutant (Cdc42F28L) which binds GTP in the absence of a guanine nucleotide exchange factor, but still hydrolyses GTP with a turnover number identical to that for wild-type Cdc42. Expression of this mutant in NIH 3T3 fibroblasts causes cellular transformation, mimicking many of the characteristics of cells transformed by the Dbl oncoprotein, a known guanine nucleotide exchange factor for Cdc42. Here we searched for new Cdc42 targets in an effort to understand how Cdc42 mediates cellular transformation. We identified the gamma-subunit of the coatomer complex (gammaCOP) as a specific binding partner for activated Cdc42. The binding of Cdc42 to gammaCOP is essential for a transforming signal distinct from those elicited by Ras.

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