Principal Investigator: Richard Cerione
Contact Information: E-mail: rac1@cornell.edu
Sponsor: NIH - NIGMS
Grant Number: 3 R01 GM047458-18S1
Title: ARRA: Roles of Cdc42 and its Signaling Partners in Cell Growth and Differentiation
Annual Direct Cost: $75,000
Project Period: 08/14/09 – 07/31/10
DESCRIPTION (provided by applicant): Studies supported by GM47458 have been directed toward understanding the roles played by the small GTPase Cdc42 in cell growth and differentiation. We have begun to examine the importance of Cdc42 in these cellular processes and in developmental events by using conditional Cdc42-knock-out mice. These studies have shown that the tight regulation of Cdc42 expression and activation is necessary to enable pluripotent cells to transition to progenitor cells that ultimately differentiate into specific cell lineages. Excessive signaling by Cdc42 appears to block this transition through its ability to influence cellular metabolism. Recently, we discovered that Cdc42, when over-expressed and/or hyper-activated, triggers the activation of a particular form of the mitochondrial enzyme glutaminase, which has a key role in glutamine metabolism by converting glutamine to glutamate. Rapidly proliferating cells and cells undergoing malignant transformation rely on the activation of glutaminase to stimulate the citric acid cycle to generate biosynthetic intermediates necessary for sustaining enhanced cell growth and for making cells immortal. These changes in metabolic activity are an important requirement for transformed/cancer cells. However, there are good reasons to suspect that metabolic re-programming also plays an important role in the induction of pluripotent stem cells (iPS cells), given that embryonic cells have metabolic requirements that are similar to cancer cells. Indeed, it has recently been shown that c-Myc, which stimulates the re-programming of metabolism required for malignant transformation, when introduced together with Oct4, Sox2, and Klf4 into fibroblasts, can generate iPS cells. Thus, in the coming year, we will examine the intriguing possibility that by manipulating the expression of Cdc42 and glutaminase, we can achieve metabolic re-programming and increase the efficiency of generating iPS cells from adult mouse fibroblasts. We plan to perform the following lines of study: 1) Examine the role of glutaminase activation in the generation of iPS cells by assaying the effects of a small molecule that we have identified as a specific inhibitor of the enzyme when activated downstream from Cdc42 and c-Myc, and 2) Examine the effects on iPS cell production of introducing Cdc42 and glutaminase (in place of c-Myc) into adult fibroblasts together with Oct4, Sox2, and Klf4. In the long run, we will set out to take advantage of this information, together with our mouse model systems, to transduce differentiated cells (i.e. mouse mammary epithelial cells) into pluripotent stem cells. Our hope is that these studies will ultimately set the stage for using small molecules, that we are in the processing of designing to direct metabolic re-programming, as a means of generating iPS cells.