| Abstract: | 鳥胺酸去羧化? (ornithine decarboxylase)、抑? (antizyme)與抑?抑制蛋白 (antizyme inhibitor) 在計畫性細胞凋亡中所扮演之角色及其機制之探討與抑癌之應用細胞訊息、轉?因子及蛋白修飾在細胞生長、分化及死亡扮演重要角色；然而細胞中尚有??追蹤、極其動態變化的調控因子，包含其半衰期短、調控?密細緻、機制複雜、捉摸?定而又扮演起重要決定者。?變的蛋白質是重要的，且重要的蛋白質通常也是?變的，鳥胺酸去羧化?（Ornithine decarboxylase；ODC：EC 4.1.1.17）、抑?（Antizyme; AZ）和抑?抑制蛋白（Antizyme inhibitor; AZI）就是一群特殊且?變的蛋白質，所以鳥胺酸去羧化?調控在生命中扮演重要的角色，而它們為多胺生物合成途徑中起始與速?決定步驟之酵素及調控因子，主要功能是催化L-鳥胺酸形成腐胺。鳥胺酸去羧化?和多胺（腐胺、亞?胺和?胺）在胚胎發育、細胞週期與細胞增生之正常生物性功能中扮演重要決定角色。鳥胺酸去羧化?活性的增加與腫瘤的生成具有相關性，而且被認為是癌形成與腫瘤進展的一個指標；在人?的疾病除?癌症外，包括??病、風濕性關節炎、紅斑性?瘡、早期??病引發的腎肥大、心臟肥大、大腦局部缺血和阿茲海默症中皆與鳥胺酸去羧化?活化有密?關?性。先前Ciechanover，Hershko 和Rose（2004 ??貝爾化學獎桂冠）發現泛素（Ubiquitin: ATP-dependent proteolytic factor 1）會?用ATP 共價修飾蛋白質，在被修飾蛋白上”?印一個死亡記號”?調控一般蛋白質?解；然而，在體內的鳥胺酸去羧化?調節相當複雜，鳥胺酸去羧化?與其調控因子抑?和抑?抑制蛋白在哺乳細胞中半衰期極短（小於?十分鐘），鳥胺酸去羧化?藉由抑?而非泛素（Ubiquitin-independent）的方式送至26S 蛋白體?中快速於?十分鐘內被?解，抑??似泛素，但以非共價結合鳥胺酸去羧化?及 cyclin D，將此?蛋白?解，以達調節細胞生長死亡分化之生?功能。另外，抑?在轉譯終止調控（Translational termination regulation）過程中又受核醣核酸?碼框的?動（RNA frameshifting）調節，其有?個開啟密碼（AUG）及?個結束密碼（UGA、UAG），當啟動核醣核酸?碼框的?動，可調節具功能之全長抑?蛋白表現，並且此抑??碼框的?動調控現象在哺乳細胞中目前又屬唯一發現且清楚被研究。細胞死亡可分為計畫性細胞死亡及非計畫性細胞死亡，前者計畫性細胞死亡又可區分細胞凋亡（Apoptosis）、無家可歸的”失巢凋亡”（Anoikis）、細胞自我吞蝕（Autophagy）、壞疽後引發細胞凋亡（Necrapoptosis）、細胞凋亡後壞疽（Aponecrosis）、細胞裁剪死亡（Autoschizis）及?線體凋亡（Mitochondrial suicide: mitoptosis）等。計畫性細胞死亡在胚胎發育、感染病毒細胞、癌細胞之清除及自體免疫?巴細胞剔除上具有重要功能。我們初步研究指出，鳥胺酸去羧化?除引起細胞的增生外，其尚俱阻擾細胞凋亡（Liu et al., 2005; Hung et al., 2005; Hsu et al., 2006; Liao et al., 2008）和干擾血球細胞分化的功能（Liao et al., 2008）；同時地，其回饋抑制蛋白抑?進入?線體造成細胞色素c（Cytochrome c）釋出而誘發細胞凋亡（Liu et al., 2006），且抑?抑制蛋白會干涉細胞週期的運?及對抗細胞凋亡。由先前研究證實鳥胺酸去羧化?、抑?及抑?抑制蛋白在細胞凋亡及分化上的角色扮演，因此我們未?三?研究計畫將深入探究鳥胺酸去羧化?調節（包含核醣核酸?碼框的?動、轉譯終止調控、非泛素蛋白質?解及細胞訊息）在計畫性細胞死亡時之分子及細胞調控機制。另與國家?米中心合作，將抑?片段後修飾（胱胺酸與?米?顆?結合）後，進?抑制腫瘤生成、轉移及血管新生的研究。期待提供人?疾病（癌症）可能致病機轉之?考，進而對?床診斷與治?上的幫助和應用。
A study on the roles of ornithine decarboxylase, antizyme and antizyme inhibitor involved in the programmed cell death, and the applications in tumor suppression Cell signaling apparatus, transcription factor and protein modification (such as phosphorylation, glycosylation, oxidation, deimination, sumoylation and ubiquitination, etc) play a critical role in molecular and cellular function including cell proliferation, differentiation, survival and death. Using labeling technique or molecular monitor methods, they are easily to be chased. Whereas, the dynamic, labile and temporal cell function controllers (including their different concentration, appearance time and place) exist flexible and delicate regulation. ODC regulation has the critical character in life span. They own the character which is difficult to be tracked and short half-life. Labile proteins are important and important proteins are labile. Ornithine decarboxylase (ODC), antizyme (AZ) and antizyme inhibitor (AZI) all are the labile proteins precisely. AZ and AZI proteins rapidly turn over by ubiquitination within a few minutes to one hour in vivo, however binding of AZ promotes the dissociation of ODC homodimers and marks ODC for degradation by the ubiquitin-independent (AZ-dependent) 26S proteasomes within few minutes. Simultaneously AZ gene exists and requires the unique and distinctive RNA frameshifting mechanism in mammalian cells. ODC is the first rate-limiting enzyme of the polyamine biosynthetic pathway, which decarboxylates L-ornithine to form putrescine. ODC and polyamines (putrescine, spermidine and spermine) play a key role in normal biological functions, including embryonic development, cell cycle, proliferation, differentiation and tumorigenesis. AZ delicately regulates ODC enzyme activity, protein degradation and polyamine transportation. Human AZI is capable of acting as a general inhibitor for all members of the AZ family. AZI binds to AZ tightly more than ODC and thus it releases ODC from ODC:AZ complex. ODC regulations include specially and uniquely translational termination regulation (RNA frameshifting) and ubiquitin-independent pathway in mammalian. The traditional studies revealed ODC-provoked cell proliferation; however our preliminary data exposed ODC-prevented apoptotic cell death and -interfered with haematopoietic differentiation. Simultaneously, the feedback inhibition protein, AZ owned the function in the stimulation of cell apoptosis and AZI interfered with anti-apoptosis. Herein, we desire to illuminate the relationships between ODC regulation and programmed cell death (PCD) in this three year scheme that concerns with 1. the molecular mechanisms of ODC-prevented apoptosis in the early events 2. the molecular mechanisms of ODC-resisted anoikis 3. the molecular mechanisms of ODC-interfered in autophagy 4. the role of AZ and AZI in apoptosis, anoikis and autophagy 5. the molecular mechanisms and signaling pathway between ODC regulation (ODC/AZ/AZI interaction and regulation) and PCD relationship 6. the development of AZ peptide-derived Au nano-particle and the valuable application to inhibit tumorigenesis. ODC regulation (ODC/AZ/AZI) is a delicate, complex, evasive and possesses the important biochemical and biophysical function. Elucidation of their molecular and cellular function in PCD will provide a healthy strategy for the manipulation in the interrelated diseases. Our research designs and methods are utilized the conditional and conventional cell or animal (mouse) models to monitor the relationships among ODC, its regulators and programmed cell death. The long-term objectives hope to make the potential drug-selection systems and making reference to the health relatedness of the project contributes the dialogue in the pathogenesis, clinical diagnosis and treatment of human diseases such as various cancers in the future. |
