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（例如 Ras 和 Rho 蛋白）和一些核纤层蛋白以羧基末端 CAAX 基序终止。 CAAX 蛋白经历三个连续的翻译后修饰。首先，半胱氨酸（即 CAAX 基序的 C）被一对胞质酶——法尼基转移酶 (FTase) 和香叶基香叶基转移酶 I (GGTase I) 法尼基化或香叶基香叶基化。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) 的一种整合膜蛋白酶）裂解。第三，新暴露的羧基末端异戊二烯半胱氨酸被另一种ER蛋白异戊二烯半胱氨酸羧基甲基转移酶（Icmt）甲基化。这些翻译后修饰使 CAAX 蛋白的 C 末端更具疏水性，增强蛋白质与膜表面的附着并促进某些蛋白质-蛋白质相互作用。 已在 30% 的人类癌症中检测到激活 Ras 突变，并且在白血病和骨髓增殖性疾病中很常见。 FTase 抑制剂已被用于治疗含有突变激活 Ras 蛋白的癌症。不幸的是，K-Ras 和 N-Ras（最常与人类癌症相关的 Ras 亚型）在 FTase 抑制的情况下很容易被 GGTase I 香叶基香叶基化。这种替代异戊二烯化途径引起了对该途径中其他酶的关注，例如 GGTase I、Rcel 和 Icmt。令人惊讶的是，没有关于抑制这些其他酶对小鼠癌症发展的影响的数据。在这个项目中，这个空白将得到解决。 在初步研究中，已经产生了同时携带 Cre 诱导型潜在致癌 Kras2 等位基因 (KrasLsL) 和诱导型 Mx1-Cre 转基因的小鼠。在这些小鼠中诱导 Cre 会激活潜在的 Ras 等位基因，并导致一种成熟的致命性骨髓增殖性疾病，类似于人类的慢性粒细胞白血病或幼年粒单核细胞白血病。最近，翻译后加工酶（FTase、GGTase I、Rcel 和 Icmt）的条件“floxed”等位基因已经产生。因此，现在可以培育出可以使用 Cre 表达来同时激活潜在致癌 K-Ras 等位基因并灭活 CAAX 加工酶的小鼠。使用这些小鼠，我们将确定 CAAX 处理缺陷对 Ras 诱导的骨髓增殖性疾病的发生、进展和致死率的影响。