FUNCTION OF THE PCPH ONCOGENE IN MAMM;CARCINOGENESIS

描述（由申请方提供）：基于在化学引发的致瘤叙利亚仓鼠胚胎细胞中频繁检测到PCPH作为活化癌基因（mt-PCPH），在PI实验室中最初将其鉴定为原癌基因。后来证明PCPH在脊椎动物中高度保守，并且mt-PCPH癌基因在鼠NIH 3 T3成纤维细胞的转化中与人H-ras癌基因协同作用。本延续申请的中心目的是研究正常PCPH功能，并确定PCPH改变促进肿瘤发展的机制。在当前资助期间获得的结果表明：i）PCPH和mt-PCPH都具有主要的细胞内定位; ii）存在于mt-PCPH癌蛋白中的疏水C末端尾是其转化活性的关键决定因素; iii）mt-PCPH的表达激活ERK 1激酶，但PCPH的表达不激活ERK 1激酶; v）mt-PCPH表达通过将内源性ATP库部分消耗至低于对于应激诱导的信号传导和细胞凋亡最佳的水平而提供细胞存活功能，和vi）PCPH多肽的表达在肿瘤动物和人细胞中经常失调。我们假设PCPH是细胞ATP敏感机制的一个组成部分，并通过与负责平衡内源性ATP池和外部供应的信号通路相互作用来发挥作用。通过突变激活PCPH成为癌蛋白（mt-PCPH）或通过PCPH表达的失调来改变这些相互作用有助于肿瘤的发展。这一假设将通过几种方法进行检验：1）分析mt-PCPH或PCPH表达失调的转化机制; 2）研究PCPH参与调节细胞ATP库; 3）分析酵母细胞中PCPH/mTOR功能相互作用; 4）研究PCPH参与人类癌症。这些研究将提供野生型和致癌PCPH在正常和恶性细胞中的功能和调节的基本理解，并可能对人类肿瘤的诊断和管理具有重要意义。

DESCRIPTION (provided by applicant): PCPH was initially identified as a proto-oncogene in the PI's laboratory on the basis of its frequent detection as an activated oncogene (mt-PCPH) in chemically initiated, tumorigenic Syrian hamster embryo cells. It was later shown that PCPH is highly conserved in vertebrates, and that the mt-PCPH oncogene synergized with the human H-ras oncogene in the transformation of murine NIH3T3 fibroblasts. The central objective of this continuation application is to investigate the normal PCPH function and to establish the mechanism(s) by which PCPH alterations contribute to tumor development. Results obtained during the current funding period have shown that: i) Both PCPH and mt-PCPH have a predominant intracellular location; ii) the hydrophobic C-terminal tail present in the mt-PCPH oncoprotein is a key determinant of its transforming activity; iii) expression of mt-PCPH, but not of PCPH, activates the ERK1 kinase; iv) both PCPH and mt-PCPH have intrinsic ATP diphosphohydrolase (apyrase) activity, v) mt- PCPH expression provides cell survival functions by partially depleting endogenous ATP pools to levels below those optimal for stress-induced signaling and apoptosis, and vi) expression of PCPH polypeptides is frequently deregulated in neoplastic animal and human cells. We hypothesize that PCPH is a component of the cellular ATP-sensing machinery and functions by interacting with signaling circuits in charge of balancing endogenous ATP pools and external supplies, Alterations of these interactions by either mutational activation of PCPH into an oncoprotein (mt-PCPH) or by deregulation of PCPH expression contribute to tumor development. This hypothesis will be tested by several approaches: 1) Analysis of mechanisms of transformation by mt-PCPH or deregulated expression of PCPH; 2) Study of the involvement of PCPH in regulating cellular ATP pools; 3) Analysis of PCPH/mTOR functional interactions in yeast cells; and 4) Study of the participation of PCPH in human cancer. These studies will provide a fundamental understanding of the function and regulation of wild type and oncogenic PCPH in normal and malignant cells, and may have important implications for the diagnosis and management of human tumors.