HMR Sang Won Kang Role of Reactive Oxygen Species in Cell Death Pathways 서식세포작용을거친다 [6,7] 년에 ROS가이러한세포자멸사를유도하며이를 catalase가저해한다는내용을시작으로 ROS와세포자멸사

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1 세포사멸과정에서활성산소의역할 강상원 pissn X eissn 이화여자대학교생명과학과 Role of Reactive Oxygen Species in Cell Death Pathways Sang Won Kang Department of Life Science, Ewha Womans University, Seoul, Korea Reactive oxygen species (ROS) are the chemical species that includes the superoxide anion, hydrogen peroxide and hydrogen radical. These ROS are simply thought as a group of molecules harmful to cells because they oxidize proteins, lipids and DNA, and they mediate cell death including apoptosis or necrosis. On the other hand, ROS have been shown to act as essential intracellular second messengers for certain cytokines and growth factors. Although the importance of ROS in the execution of cell death is controversial, ROS are likely to be involved in the signal transduction mechanism for cell death as signaling intermediates in death receptor initiated signaling pathways, specifically in the tumor necrosis factor alpha-tumor necrosis factor receptor 1 (TNFα-TNFR1) pathway. In this review, using TNFα-TNFR as the model system, we attempt to address the involvement of intracellular ROS in TNFα induced cell death, including apoptosis, necrosis and an alternative form of programmed cell death, necroptosis. Key Words: Reactive Oxygen Species; Tumor Necrosis Factor-alpha; Apoptosis; Necrosis Correspondence to: Sang Won Kang 우 , 서울시서대문구이화여대길 52 종합과학관 C 동 504 호 Science Bldg. C/ Room 504, 52 Ewhayeodae-gil, Seodaemun-gu, Seoul , Korea Tel: Fax: kangsw@ewha.ac.kr Received 12 March 2013 Revised 23 April 2013 Accepted 26 April 2013 This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License ( which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. 서론활성산소종 (reactive oxygen species, ROS) 은정상적인세포내활성작용과정에서생성되며세포분화, 유전자의발현, 시토카인에대한반응정도를포함한다양한생물학적과정에연관되어있다 [1,2]. 따라서이러한 ROS의항상성을유지하는것은세포성장과생존에매우중요하다. 산화스트레스는 ROS의생성과이를제거하는항산화반응간의불균형으로인해세포내의 ROS가증가하여 DNA나단백질, 지질 (lipid) 과반응하여손상시키는현상이며이는노화나심장과관련된질병들의핵심원인으로알려져있다 [1,3]. 이렇게 ROS는지금까지단순히단백질이나 DNA, 지질등을산화시켜세포괴사를일으키는역할을하는물질로인식되어왔지만또한세포내의필수적인 second messenger 로서특정시토카인이나성장인자의신호전달에중요한역할을수행한다 [4,5]. 비록 ROS와세포사멸과의관계는서로상반된보고가있지만확실한것은 ROS가세포사멸에있어중간신호매개체의역할을하며, 신호를전달하고있다는점이다. 따라서본종설에서는특히종양괴사인자알파-종양괴사인자수용체유형 1 (TNFα-TNFRI) 에의한세포신호전달체계내에서이러한 ROS가실제각각의세포사멸에있어어떤역할을수행하는지알아보기로한다. 본론 1. ROS와세포자멸사 (apoptosis) 세포자멸사는유전적으로보존된관련유전자에의해이루어지며, 조절이가능한능동적세포사멸과정이다. 이과정은형태적으로세포의비중감소, 세포막의파괴, 염색체의응축등과더불어세포내부의물질들이사멸체 (apoptotic body) 라는포낭을형성하면 Hanyang University College of Medicine 77

2 HMR Sang Won Kang Role of Reactive Oxygen Species in Cell Death Pathways 서식세포작용을거친다 [6,7] 년에 ROS가이러한세포자멸사를유도하며이를 catalase가저해한다는내용을시작으로 ROS와세포자멸사와의관계에대한연구가시작되었고이후많은연구자들이호중구나암세포에서이같은연구를진행하였다. 특히 ROS 를 second messenger 로사용하여신호전달체계를구축하여세포자멸사를일으키는것으로잘알려진것이 TNF-R1이다. TNFα는감염에반응하여활성화된대식세포나 T 림프구에의해주로생산되며세포자멸사뿐만아니라전사인자인 nuclear factor kappalight-chain-enhancer of activator B cells (NF-κB) 와 activator protein 1 (AP-1) 을활성화시킴으로써다양한염증반응과면역반응에관여한다. ROS는이러한 TNFα의자극으로인해생성되어다양한신호단백질을산화시킴으로써 caspase를통한세포자멸사신호경로와 NF-κB를통한생존경로를조절한다 [8]. ROS가 TNFα 신호전달에중요하다는사실은 TNFα를처리하였을때세포내 ROS가증가한다는점, butylated hydroxyanisole (BHA) 나 N-acetylcysteine (NAC) 과같은항산화물질을처리하였을때 TNFα에의한세포자멸사가감소한다는점 [9,10], 그리고 TNFα를처리한세포에서이황결합 (disulfide bond) 형성등과같은단백질의산화환원반응변화가일어남으로써신호전달이바뀐다는것을통해서알수있다 [11, 12]. 세포내에서대부분의 thiol기는 GSH/GSSG 비율이 >100:1 이나될정도로환원되어있는상태이고, GSH에의해조절되는단백질의산화환원상태는 glutaredoxin 과 thioredoxin 에의해함께조절된다 [13,14]. ROS에의한이러한 thiol기의산화는 TNFα에의한세포자멸사에있어중요한단백질들의활성여부와밀접한관련이있게되는데그중가장대표적인예가 c-jun N-terminal kinase (JNK) 를포함한 mitogen-activated protein kinase (MAPK) 이다. 1) Mitogen activated protein kinase (MAPK) MAPK는여러가지외부자극에의해세포의성장, 사멸, 분화등에관여하는데 extracellular signal-regulated kinase (ERK), c-jun N-terminal kinase (JNK/SAPK), p38 kinase로구성되어있으며, 전사조절인자들을인산화함으로써다양한유전자들의발현을조절한다. 특히 JNK는 stress-activated protein kinase (SAPK) 라고도불리는데세가지 isoform 이있으며 ROS를포함한물리적, 화학적스트레스또는 TNFα와같은시토카인에대해활성화되어세포자멸사를증가시킨다. 간세포 (hepatocyte) 를포함한다양한세포에서 TNFα 자극에의해 JNK가활성화되는데, 활성화된상태가유지되는기간에따라세포의운명이증식또는세포사멸로결정된다. 즉, NF-kB 또는 MAP kinase phosphatases (MKP) 와같은억제제의작용으로 JNK가단시간 (30-60분) 동안활성화되면세포가증식하나, 활성화가장시간 (120분이상 ) 지속될경우세포자멸사가증가한다. 다른보고에따르면길어진 JNK 활성화는아세트아미노펜 (acetaminophen) 에의한간손상과허혈 / 재관류 (ischemia/reperfusion) 손상에주요물질로작용한다는것이확인되었다 [15,16]. 한편 TNFα 자극이외에도일차배양신경세포나간세포, 그리고이외의다양한세포에서외부적으로 H 2O 2 를처리하게되면 JNK가활성화된다는것이알려져있다 [15,17]. ROS로인해 JNK의활성화가변하는것은크게두가지상황으로나누어설명할수있는데첫번째는 ROS로인한 JNK의불활성화의저해이다. ROS로인해 JNK의억제제인 MKP의시스테인기가산화되어탈인산화효소로서의활성을잃게되고게다가산화된 MKP는즉각적으로 ubiquitin-proteasome 경로에의해분해되기때문에 JNK의감소하지않고유지된다 [11]. ROS에의해 JNK가활성화될수있는두번째방법은 JNK의활성화를촉진시키는방법이다. JNK는신호전달과정에서상위에존재하는단백질인산화효소인 MAP kinase kinase (MAPKK) 와 MAP kinase kinase kinase (MAPKKK) 에의해활성화된다. JNK 를활성화시킬수있는 MAPKK로 mitogen-activated protein kinase 4 (MKK4) 와 MKK7이존재하며그상위로는 apoptosis signal-regulated kinase 1 (ASK1) 이작용한다. ASK1은평소에 thioredoxin (Trx) 과결합함으로인해불활성화되어있지만 Trx 내에있는주요 thiol기가 H 2O 2 나다른 oxidant에의해산화되면 ASK1으로부터분리되어비로소 ASK1이활성화되게된다. 이렇게활성화된 ASK1은하위단계의 MKK를인산화시키고따라서다음단계로 JNK를포함한 MAPK가활성화된다 [18,19]. 그러나 TNFα 신호전달체계와 JNK에의한세포사멸은세포특이적이다. 야행형 (wild type, WT) 보다유전자결손마우스인 JNK1 -/- 과 JNK2 -/- 로부터유래한마우스배아섬유모세포 (mouse embryonic fibroblast, MEF) 에서 TNFα에의한세포자멸사가증가하여 JNK의관련성을시사하나, 최근보고에따르면 concanavalin A (Con A) 에의한간염 (hepatitis) 에서는 JNK의활성화는연관이없다는것이알려졌다 [20,21]. 따라서 TNFα에의한세포자멸사에서 JNK의연관관계는세포에따라다를것이며아직까지도논란의여지가남아있을것이라판단된다. 2) 미토콘드리아미토콘드리아내에존재하는전자전달계 (respiratory chain) 의 complex I (NADH dehydrogenase) 과 complex III (ubiquinone oxdoreductase) 를통해만들어진산소라디칼 (oxygen radical) 은미토콘드리아기질 (matrix) 에서즉시 manganese-dependent superoxide dismutase (Mn-SOD) 에의해 H 2O 2 로변환되고변환된 H 2O 2 는미토콘드리아내에존재하는항산화기전인 peroxiredoxin (Prx) 혹은 glutathione peroxidase (GPx) 에의해물로환원되거나세포질로확산된다 [22]. 미토콘드리아의전자전달계는세포내에서 nicotinamide dinucleotide phosphate (NADPH) oxidase를제외한유일한 ROS의주요생성장소이므로미토콘드리아가 TNFα에 78

3 강상원 세포사멸과정에서활성산소의역할 HMR 의한세포자멸사에관여하는부분을감안하면아마도 TNFα에의한세포자멸사동안생성되는 ROS의주요공급원으로생각된다. 이러한미토콘드리아에서의 ROS의생성과세포질로의방출은 TNFα와같은세포자멸사신호에의해미토콘드리아의막의내구성이약화됨으로써더욱활발히진행되게된다 [23,24]. TNFα 유도세포사멸의신호전달은크게두가지인데, 하나는외인성세포자멸사 (extrinsic apoptosis) 전달체계로세포막에위치한죽음수용체를활성화하여직접 caspase를활성화시켜세포사멸을유도한다 [25]. 다른하나는내재성세포자멸사 (intrinsic apoptosis) 전달체계로서세포내에저장된경로에의해세포자멸사가일어나는기전이다 [26]. 이는주로미토콘드리아를통해이루어지기때문에이때다양한단백질들이여기에관여하게되는데그예로 Bak 와 Bax는평상시에는 monomer 로존재하면서 anti-세포자멸사단백질인 Bcl-2 에의해그작용이저해를받게된다. 세포자멸사신호가들어오면 Bax와 Bak의형태변화가일어나이량체 (dimer) 를형성하여미토콘드리아외막에작용하여구멍을만들고미토콘드리아내부의물질을밖으로유출시킨다. 이때나오는물질은 cytochrome C, apoptotic protease activating factor 1 (Apaf-1), second mitochondria-drived activator of caspase/direct inhibitor of apoptosis binding protein with low pi (Smac/Diablo), apoptosis inducing factor (AIF) 등으로세포질에서 adenosine triphosphate (ATP) 와함께단위체를만들어하위의 caspase를활성화시켜결국세포자멸사를더욱빠르게진행하게된다. 또한 BH3 only protein 으로분류되는 Bid와같은물질은활성화된 caspase에의해잘려서 truncated Bid (tbid) 가되고이는 Bcl-2, Bcl-xL 에결합하여그작용을억제함으로써 Bax와 Bak의작용을활성화시킨다 [26-28]. 간세포에서 tbid가미토콘드리아로이동한결과 ROS의생성이증가되었고, Bid 유전자결핍마우스에서추출한간세포에서도 TNFα와 Actinomycin D 처리시세포자멸사나 ROS의증가가거의보이지않았다 [9]. 한편야생형세포에비해 Bcl-2를과발현한세포는다양한세포자멸사자극원을처리했을때생성된 ROS의양도적고지질과산화 (lipid peroxidation) 가저해되어, Bcl-2가강력한항산화역할을지닌것으로보고되었다 [29]. 이와같이 TNFα로인한세포자멸사가일어날때미토콘드리아와이에관련된단백질들이주요매개체역할을수행하여 ROS 를생성, 또는억제하는기전을일으키는것을종합해볼때, 세포자멸사와 ROS와의연관성이있음을알수있다. 2. ROS와괴사 (necrosis) 1) Caspase와 receptor-interacting protein 1 () 괴사는연구초창기에는명확한진행기전을수반하지않고상처나박테리아등에의한감염뿐만아니라영양의부족, ph, 온도의변화등환경적인요인에의해서도유도되는수동적인세포의 죽음으로인한조직의염증의유발원인이라고알려졌다 [30]. 그러나이후연구자들은괴사역시세포자멸사와마찬가지로 TNFα와같은죽음수용체 (death receptor) 에의해일어날수있다는것을 L929 세포주에서발견하였다 [31]. 그리고여기에 pan-caspase 저해제인 benzyloxycarbonyl-val-ala-asp (OMe)-fluoromethylketone (zvad-fmk) 나 cytokine response modifier (CrmA) 를처리하면 TNFα에의한괴사가더증가하는것을확인하였다. 마찬가지로 T 림프구, 호중구, MEF 등에서강력한세포자멸사리간드인 Fas ligand (FasL) 나 Tumor necrosis factor-related apoptosis-including ligand (TRAIL) 의자극에 zvad-fmk로 caspase에의한세포자멸사를저해하였을때괴사로인한세포사멸이크게일어나는것이보고되었다 [32-34]. 이를통해괴사는세포자멸사와달리다양한분자생물학적과정들이다른단계의세포내상황에서서로간의교차를통해이루어지며 caspase와무관하게일어나는괴사 (necrosis) 와같은세포사멸은정상적으로일어나는 caspase에의존적인세포자멸사가실패했을경우일어나는대체과정이다 [35]. 그리고 TNFα에의한괴사는세포자멸사보다 ROS에더밀접하게관련되어있는데, 예를들어 L929의괴사와같은세포사멸은미토콘드리아로부터유래된 ROS에의한것이라는보고들이있으며 [36,37], 괴사를유도하기위해 caspase를저해하게되면 ROS가증가한다는점을미루어볼때 [31], 죽음수용체에의한괴사와 ROS는서로 positive feedback 을형성한다는것을알수있다. Caspase 외에괴사에관여하는또다른중요한단백질은 receptor-interacting protein 1 () 이다. 은 TNFR1 신호전달콤플렉스의주요단백질이지만이외에도지난몇년간 의세포내스트레스반응에대한역할에대한연구는꾸준히있어왔다 [32,38]. 이전보고에따르면 이 T 림프구에서 FasL나 TNFα, TRAIL에의한괴사에중요하다는것이알려졌으며 [32], virus에감염된 Jurkat 세포주에 TNFα를처리한결과역시마찬가지로 이괴사에주요단백질이라는것을밝혀내었다 [39]. TNFα나 FasL 의자극에의해세포자멸사가일어나이로인해활성화된 caspase 로인해 이잘려서괴사가저해된다는사실도 이 necrosis 에중요하다는사실을시사한다 [40]. 그리고 야생형마우스배아모세포에서는 TNFα에의한괴사에서 ROS가증가하지만 유전자결핍마우스배아모세포에서는 ROS가훨씬감소하였으며 [34] 같은마우스배아모세포에서 TNFα가아닌 H 2O 2 로자극을주었을때 유전자결핍마우스배아모세포의경우에는괴사가일어나지않아괴사가일어날때 과 ROS가함께작용한다는점을제시한다 [41]. 2) NADPH oxidase 이렇게세포자멸사와마찬가지로수용체를통한괴사가일어나기위해서 ROS는밀접하게연관되어있지만괴사에관련된 ROS 공 79

4 HMR Sang Won Kang Role of Reactive Oxygen Species in Cell Death Pathways 급원은미토콘드리아이외에하나더있다고알려져있다. NADPH oxidase는원래는면역계의대식세포에서침입한세균이나이물질을손상시키고죽이는데 ROS를사용하기위해존재하는세포막효소복합체이며그활성체와소단위체의종류에따라 NADPH oxidase 1 (Nox1), Nox2, Nox3, Nox4, Nox5, dual oxidases 1/2 (DUOX1/2) 등으로분류된다. 이는면역계에만국한되는것은아니며암세포나다른일차배양세포에서도조직특이적으로발현되어있고 TNFα를포함한다양한리간드에의해서도활성화된다는것이알려져있다. 몇몇보고에따르면 TNFα가 NADPH oxidase의활성체나소단위체들의발현을증가시키거나활성도를증가시키며또는 Nox2의활성화에기여할수있다고하지만아직그기전은밝혀지지않았다. 오히려 2007년한연구에서는 Nox2가아닌 Nox1 NADPH oxidase가 L929 세포주에서 TNFα에의한괴사에서활성화되어 ROS를생성함으로써괴사를촉진시킨다는내용을발표하였다 [42]. 즉, L929 세포에 TNFα를처리하였을때 30-45분이내에 superoxide 가생성되며이렇게생성된 superoide 가 Nox1에의한결과물이고이로인해 JNK가활성화되어괴사가일어난다는것이다. 지금까지괴사로인해생성된 ROS에대한연구가 TNFα를처리하고몇시간후, 즉단순히세포가이미죽기시작하였을때생성되는비특이적인것이었음을감안하면이연구로인해지금까지 TNFα로인한괴사에서의 ROS의생성기전을좀더특이적이고명확히규명지을수있는계기가될수있을것이라생각한다. 3. ROS와 necroptosis 위에서언급한것처럼최근에는괴사가단순한물리적손상에의한수동적인반응이아닌, 역시세밀하게조절되어있는능동적인세포사멸기전으로밝혀지면서예정괴사 (programmed necrosis) 혹은 necroptosis 로불리게되었다. 괴사와형태적으로는구별되지않지만 necroptosis 는주로 TNFα와같은신호에의해활성화되며바이러스감염등의다양한상황에서 caspase-8의활성이저해되었을때활성화되는것이지만 necroptosis 라는명칭이생긴것은 -RIP3 로구성된 necroptosome complex 가발견되면서부터이다 [43-45]. 1) RIP3와 necroptosome RIP3는 군의일종으로최근 necroptosis 에연관되어있다는사실이보고되면서각광받고있는단백질이다. RIP3는 C-말단부분의 RIP homotypic motif (RHIM) 영역 (domain) 을통해 과결합하며 N-말단부분에는인산화활성을가진영역이있다. 이두영역모두 necroptosis 가일어나는데중요하다. RIP3가발현되지않는세포에 RIP3 유전자를발현시키면 necroptosis 가일어나지만인산화활성돌연변이인 K50A 유전자를발현시키면 necroptosis이일어나지않는것으로미루어 RIP3 인산화활성이 necroptosis 에중요함을알수있다 [43]. 에의한것인지확실히알려지 진않았지만 RIP3 의 199 번째위치인세린잔기의인산화도 [44], 비 록세포밖에서는 이 RIP3 를인산화시키지않는다는실험결 과가있었지만 의인산화활성이 RIP3 의인산화를일으킴을 바탕으로 RIP3 의인산화를통한 necroptosis 의발생에 이간 접적으로역할을수행함을제시할수있었다. 그리고 RHIM 영역 을통한 과 RIP3 와의결합이 necroptosis 를유발하는자극원 이주어졌을때에만일어나는것으로보아둘간의결합이 necroptosis 에중요함을알수있다. 이렇게 necroptosis 가일어나는세포에 서 과 RIP3 가결합한소단위체를 complex IIb 혹은 necroptosome 이라한다 (Fig. 1). 한편, 괴사에중요한인자라는것만알려졌 던 의새로운기전이 necroptosis 의연구과정에서밝혀졌는데 이 cellular inhibitor of apoptosis 1/2 (ciap1/2) 의신속한분해 를유도하는인자인 smac mimetics 인 IAP antagonist 의자극에대 해서는 necroptosis 에관여하지않았기때문이다 [46]. 예를들어 TNFα 와 smac 을처리하였을때는 fas-associated death domain (FADD) 을포함한소단위체에 이포함되면서세포자멸사가 일어났지만 TNFα 와 zvad 를함께처리하였을때에는 과 ROS NF-κB JNK TRADD TRADD TRAF2 clap1 complex l Caspase8 FADD complex lla GSH MnSOD PRx APOPTOSIS TNF-α TNFR1 Deubiquitination of RIP 1 P P RIP3 complex llb or necroptosome NECROPTOSIS NADPH oxidase Fig. 1. TNFα induced formation of apoptotic and necroptotic signaling complexes. TNFR1, tumor necrosis factor receptor 1; TRADD, TNFR type 1-associated death domain protein; TRAF2, TNF receptor-associated factor 2; ciap1, cellular inhibitor of apoptosis 1; JNK, c-jun N- terminal kinase;, receptor-interacting protein 1; FADD, Fas-associated death domain; GSH, glutathione; MnSOD, manganese-dependent superoxide dismutase; PRx, peroxiredoxin-3; NF-κB, nuclear factor kappa-light-chain-enhancer of activator B cells; ROS, reactive oxygen species. ROS 80

5 강상원 세포사멸과정에서활성산소의역할 HMR RIP3를포함한 necrosome 이형성되면서 necroptosis 가일어나는것을 Panc-1 세포에서확인하였다. Smac에의한 ciap1/2 의분해로인해 이어떻게세포자멸사를유도하는소단위체로이동하는지는알수없지만 ciap1/2 가 의유비퀴틴화 (ubiquitination) 를시키는 E3 ligase로작용한다는점을감안할때 의유비퀴틴화여부가세포사멸의운명을결정짓는데중요한역할을한다는점은명확한것같다. ROS의생성은이러한 necroptosis 가일어나는데있어매우강력한결정인자로작용하는데여기에는다양한증거가존재한다. 이는미토콘드리아의에너지대사가괴사가일어나는데중요하게작용하기때문이다. 물론모든종류의 TNFα에의한 necroptosis 에있어서 ROS의생성이필수적인것은아니지만 TNFR1 신호전달에있어서 RIP3의인산화활성도는미토콘드리아의생물학적에너지대사와 ROS의과도한생성여부와밀접한관련이있어보인다. RIP3 는 glucogen phosphorylase (PYGL) 와 glutamate dehydrogenase 1 (GLUD1) 를포함한대사효소들과결합함으로써이들을활성화시킨다. 이는이러한대사효소들의 RNAi를이용한발현저해실험을통해증명하였다 [45]. PYGL 은글리코겐을 glucose-1-phosphate 로분해시켜해당기질인 glucose-6-phosphate 로전환하여결국에는 ROS의발생에기여하는효소이다. 또한 GLUD1 은산화적인산화과정에있어매우중요한효소로알려져있다. 게다가 RIP3는이러한대사에관련된효소들의활성을증진시킴으로써세포사멸을일으키는주요결정요인으로작용하는것으로보인다 [47]. Necroptosis와미토콘드리아 ROS와관련된또다른보고에따르면, necroptosome 이일어날때 이 RIP3의 227번째세린잔기를인산화시켜서미토콘드리아단백질탈인산화효소인 phosphoglycerate mutase 5L (PGAM5L) 과 mixed lineage kinase domainlike protein (MLKL) 을인산화시킨다는것이었다 [48,49]. 이는 RIP3-PGAM5L 을포함한 necroptosome 이미토콘드리아막에존재하는 PGAM5S에결합하여미토콘드리아결합조절인자인 Drp1 을활성화시켜결국활성화된 dynamin-related protein 1 (Drp1) 이미토콘드리아막을손상시켜결국세포내 ROS가증가된다는결과를내놓았다. 그리고미토콘드리아와독립적으로 ROS가 necroptosis와연관된다는또다른연구에서는 TNFα를처리하였을때 riboflavin kinase (RFK) 가 TNFR1과 TNFR type 1-associated death domain protein (TRADD) 와결합한다는보고가있었다. RFK는곧 Nox1과 Nox2, p22 phox 를 TNFR로끌어들여 ROS를생성시켜 necroptosis 를유도하였다 [50]. 결론 TNF 또는같은군에속하는리간드에의한신호전달체계는복잡한생물학적체계내에서결정된다. 수용체하위경로에는매우 중요한기점이되는부분이다양하게존재하며결국이를조절할 수있는부분은관련유전자전사조절, 혹은신호전달경로내에 있는다양한주요단백질들의항산화상태의조절여부가될것이 다. 산화물질 (oxidant) 과항산화물질 (antioxidant) 은죽는지사는 지에국한되는세포의운명을결정짓는것뿐아니라세포사의경로 에도영향을주는신호회로를바꾸어놓을수도있을것이다. 지금 까지살펴본것처럼 ROS 가 TNFα 에의한다양한세포사멸과분화 의자극에있어서그민감도를결정하는만큼좀더세밀하고논리 적으로각각의다양한세포사멸에있어서의 ROS 의역할을규명하 는것이매우중요할것이다. REFERENCES 1. Rhee SG. Cell signaling. H2O2, a necessary evil for cell signaling. Science 2006;312: Rhee SG, Bae YS, Lee SR, Kwon J. Hydrogen peroxide: a key messenger that modulates protein phosphorylation through cysteine oxidation. Sci STKE 2000;2000:pe1. 3. Ozben T. Oxidative stress and apoptosis: impact on cancer therapy. J Pharm Sci 2007;96: Rhee SG, Kang SW, Jeong W, Chang TS, Yang KS, Woo HA. Intracellular messenger function of hydrogen peroxide and its regulation by peroxiredoxins. Curr Opin Cell Biol 2005;17: Rhee SG, Chang TS, Bae YS, Lee SR, Kang SW. Cellular regulation by hydrogen peroxide. J Am Soc Nephrol 2003;14:S Budihardjo I, Oliver H, Lutter M, Luo X, Wang X. Biochemical pathways of caspase activation during apoptosis. Annu Rev Cell Dev Biol 1999;15: Chandra J, Samali A, Orrenius S. Triggering and modulation of apoptosis by oxidative stress. Free Radic Biol Med 2000;29: Wajant H, Pfizenmaier K, Scheurich P. Tumor necrosis factor signaling. Cell Death Differ 2003;10: Ding WX, Ni HM, DiFrancesca D, Stolz DB, Yin XM. Bid-dependent generation of oxygen radicals promotes death receptor activation-induced apoptosis in murine hepatocytes. Hepatology 2004;40: Sakon S, Xue X, Takekawa M, Sasazuki T, Okazaki T, Kojima Y, et al. NFkappaB inhibits TNF-induced accumulation of ROS that mediate prolonged MAPK activation and necrotic cell death. EMBO J 2003;22: Kamata H, Honda S, Maeda S, Chang L, Hirata H, Karin M. Reactive oxygen species promote TNFalpha-induced death and sustained JNK activation by inhibiting MAP kinase phosphatases. Cell 2005;120: Sullivan DM, Wehr NB, Fergusson MM, Levine RL, Finkel T. Identification of oxidant-sensitive proteins: TNF-alpha induces protein glutathiolation. Biochemistry 2000;39: Han D, Hanawa N, Saberi B, Kaplowitz N. Mechanisms of liver injury. III. Role of glutathione redox status in liver injury. Am J Physiol Gastrointest Liver Physiol 2006;291:G Schafer FQ, Buettner GR. Redox environment of the cell as viewed through the redox state of the glutathione disulfide/glutathione couple. Free Radic Biol Med 2001;30: Hanawa N, Shinohara M, Saberi B, Gaarde WA, Han D, Kaplowitz N. Role of JNK translocation to mitochondria leading to inhibition of mitochondria bioenergetics in acetaminophen-induced liver injury. J Biol 81

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2016 학년도약학대학면접문제해설 문제 2 아래의질문에 3-4분이내로답하시오. 표피성장인자수용체 (epidermal growth factor receptor, EGFR) 는수용체티로신인산화효소군 (receptor tyrosine kinases, RTKs) 의일종으로서세

2016 학년도약학대학면접문제해설 문제 2 아래의질문에 3-4분이내로답하시오. 표피성장인자수용체 (epidermal growth factor receptor, EGFR) 는수용체티로신인산화효소군 (receptor tyrosine kinases, RTKs) 의일종으로서세 본문제에대한지적소유권은동국대학교에있습니다. 본교의서면허락없이무단으로출판, 게재, 사용할수없습니다. 문제 2 2016 학년도약학대학면접문제 아래의질문에 3-4 분이내로답하시오. 표피성장인자수용체 (epidermal growth factor receptor, EGFR) 는수용체티로신 인산화효소군 (receptor tyrosine kinases, RTKs) 의일종으로서세포의생존과증식