CAAX Processing Enzymes as Anticancer Targets

CAAX 加工酶作为抗癌靶标

• 批准号: 6872463
• 负责人: Stephen G. Young
• 金额: $ 13.88万
• 依托单位: UNIVERSITY OF CALIFORNIA LOS ANGELES
• 依托单位国家: 美国
• 财政年份: 2004
• 资助国家: 美国
• 起止时间: 2004-04-01 至 2006-03-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6872463
• 关键词: SDS polyacrylamide gel electrophoresis; alkyltransferase; antineoplastics; biological signal transduction; endoplasmic reticulum; enzyme activity; enzyme inhibitors; farnesyl compound; flow cytometry; gene expression; genetically modified animals; geranyl compound; guanine nucleotide binding protein; hematopoietic stem cells; intracellular; laboratory mouse; myeloproliferative neoplasm; polymerase chain reaction; posttranslational modifications; protein protein interaction; technology /technique development

DESCRIPTION (provided by applicant): Many intracellular signaling proteins (e.g., the Ras and Rho proteins) and several nuclear lamins terminate with a carboxyl-terminal CAAX motif. CAAX proteins undergo three sequential posttranslational modifications. First, the cysteine (i.e., the C of the CAAX motif) is farnesylated or geranylgeranylated by a pair of cytosolic enzymes--farnesyltransferase (FTase) and geranylgeranyltransferase I (GGTase I). Second, the last three amino acids (i.e., the -AAX) are cleaved off by Ras and a-factor converting enzyme (Rcel), an integral membrane protease of the endoplasmic reticulum (ER). Third, the newly exposed carboxyl-terminal isoprenylcysteine is methylated by another ER protein, isoprenylcysteine carboxyl methyltransferase (Icmt). These posttranslational modifications render the C-terminus of CAAX proteins more hydrophobic, enhancing the attachment of the proteins to membrane surfaces and facilitating certain protein-protein interactions. Activating Ras mutations have been detected in 30% of all human cancers, and are common in leukemia and myeloproliferative diseases. Inhibitors of FTase have been used to treat cancers that harbor mutationally activated Ras proteins. Unfortunately, K-Ras and N-Ras--the Ras isoforms most often implicated in human cancers--are readily geranylgeranylated by GGTase I in the setting FTase inhibition. This alternate isoprenylation pathway has focused attention on other enzymes in the pathway, such as GGTase I, Rcel, and Icmt. Surprisingly, there are no data on the impact of inhibiting these other enzymes on the development of cancer in mice. In this project, this void will be addressed. In preliminary studies, mice harboring both a Cre-inducible latent oncogenic Kras2 allele (KrasLsL) and the inducible Mx1-Cre transgene have been generated. Induction of Cre in those mice activates the latent Ras allele and results in a full-fledged, lethal, myeloproliferative disease that is reminiscent of chronic myelogenous leukemia or juvenile myelomonocytic leukemia in humans. Recently, conditional "floxed" alleles for the posttranslational processing enzymes (FTase, GGTase I, Rcel, and Icmt) have been generated. Thus, it is now possible to breed mice in which Cre expression can be used to simultaneously activate the latent oncogenic K-Ras allele and inactivate the CAAX processing enzymes. Using these mice, we will define the impact of defective CAAX processing on the development, progression, and lethality of Ras-induced myeloproliferative disease.

描述（由申请人提供）：许多细胞内信号蛋白（如Ras和Rho蛋白）和一些核层蛋白以羧基端CAAX基序终止。CAAX蛋白经过三个顺序的翻译后修饰。首先，半胱氨酸（即CAAX基序的C）被一对细胞质酶——法尼基转移酶（FTase）和香叶基转移酶I （GGTase I）法尼基化或香叶基化。其次，最后三个氨基酸（即-AAX）被Ras和a因子转换酶（Rcel）（内质网（ER）的一种完整膜蛋白酶）切割掉。第三，新暴露的羧基端异戊酰半胱氨酸被另一种内质网蛋白异戊酰半胱氨酸羧甲基转移酶（Icmt）甲基化。这些翻译后修饰使CAAX蛋白的c端更具疏水性，增强了蛋白与膜表面的附着，促进了某些蛋白-蛋白相互作用。