My objective is to understand the physiologic and medical importance of the posttranslational processing of CAAX proteins (e.g. K-RAS and prelamin A) and to define the suitability of the CAAX protein processing enzymes as therapeutic targets for the treatment of cancer and progeria. CAAX proteins undergo three posttranslational processing steps at a carboxyl-terminal CAAX motif. These processing steps, which are mediated by four different enzymes (FTase, GGTase-I, RCE1, and ICMT), increase the hydrophobicity of the carboxyl terminus of the protein and thereby facilitate interactions with membrane surfaces. Somatic mutations in K-RAS deregulate cell growth and are etiologically involved in the pathogenesis of many forms of cancer. A mutation in prelamin A causes Hutchinson-Gilford progeria syndrome—a pediatric progeroid syndrome associated with misshaped cell nuclei and a host of aging-like disease phenotypes. One strategy to render the mutant K-RAS and prelamin A less harmful is to interfere with their ability to bind to membrane surfaces (e.g. the plasma membrane and the nuclear envelope). This could be accomplished by inhibiting the enzymes that modify the CAAX motif. My Specific Aims are: (1) To define the suitability of the CAAX processing enzymes as therapeutic targets in the treatment of K-RAS-induced lung cancer and leukemia; and (2) To test the hypothesis that inactivation of FTase or ICMT will ameliorate disease phenotypes of progeria. I have developed genetic strategies to produce lung cancer or leukemia in mice by activating an oncogenic K-RAS and simultaneously inactivating different CAAX processing enzymes. I will also inactivate several CAAX processing enzymes in mice with progeria—both before the emergence of phenotypes and after the development of advanced disease phenotypes. These experiments should reveal whether the absence of the different CAAX processing enzymes affects the onset, progression, or regression of cancer and progeria.
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