線蟲dapk-1執行細胞凋亡的功能與遺傳分析及細胞凋亡和自噬間的關係

Functional and genetic analysis of dapk-1 during apoptosis and the construction of connection between apoptosis and autophagy in C. elegans

柯怡如(Yi-Ju Ko)

指導教授 ： 吳益群

國立臺灣大學/生命科學院/分子與細胞生物學研究所/碩士(2006年)

https://doi.org/10.6342/NTU.2006.02808

摘要

根據我們實驗室的研究發現在線蟲計劃性死亡中，dapk-1會促進細胞凋亡。為了了解dapk-1如何作用於計劃性死亡，我們對dapk-1進行結構與功能分析。如同其人類同源蛋白DAPk，DAPK-1也包含kinase domain, ankyrin repeats, and death domain等區域。我們發現DAPK-1的kinase domain以及death domain對於其促進細胞凋亡的功能是必要的。就我們所知這是第一手證據證明在線蟲中death domain會參與計劃性死亡，隱含了外生性死亡途徑可能參與其中的可能性。更進一步地，根據線蟲資料庫的搜尋及遺傳分析，我們發現UNC-5 (the netrin receptor)可能會作用於DAPK-1所調控的外生性死亡途徑並作為死亡接收器。.然而其他區域如cytoskeleton binding region對於DAPK-1促進細胞凋亡的功能則不必要；至於ankyrin repeats對其功能則並非絕對必要。此結果和先前人類的研究發現不同，在人類中發現這些區域為DAPk促進細胞凋亡的活性所必須。更複雜的是，人類DAPk不僅會促進細胞凋亡，也會影響細胞自噬體的形成，隱含了細胞凋亡和細胞自噬死亡途徑間可能的交互作用。我們希望能利用線蟲這種簡單的模式動物來研究細胞自噬基因參與計劃性死亡的情形。我們觀察到細胞自噬基因如bec-1和unc-51會對計劃性死亡產生抑制的影響，而且至少有部分bec-1的突變所造成的細胞死亡不須經由egl-1誘發。更進一步地，根據遺傳分析定位我們發現dapk-1除了可以促進發育所調控的細胞死亡外，也會調控細胞自噬相關的死亡途徑。

關鍵字

細胞凋亡 ； 細胞自噬 ； 計劃性死亡

並列摘要

Recent studies in our lab have revealed the pro-apoptotic function of dapk-1 during programmed cell death. To understand how dapk-1 acts in programmed cell death, we performed structure-function analysis of dapk-1. Like its human homolog DAPk, DAPK-1 contains multiple domains including kinase domain, ankyrin repeats, and death domain. We found that kinase and death domains of DAPK-1 are required for its pro-apoptotic function. To our knowledge, this is the first evidence showing the involvement of death domain in C. elegans programmed cell death, implying the potential role of an extrinsic cell death pathway. Taking a candidate gene approach, we showed that the netrin receptor unc-5 might be the death receptor acting in the DAPK-1 mediated extrinsic cell death pathway. Other regions such as cytoskeleton binding region is dispensable and ankyrin repeats are not absolutely necessary for DAPK-1 pro-apoptotic function. This result is distinct from the previous finding that these regions are required for the apoptosis-promoting activity of human DAPk. More complicatedly, human DAPk is also known as a positive mediator of autophagy, implying the potential interplay of apoptotic and autophagic pathways. Therefore, we tried to include the autophagic genes in C. elegans programmed cell death. In this study we observed that autophagic genes such as bec-1 and unc-51 bring inhibitory effects to C. elegans programmed cell death and at least some bec-1 mediated cell deaths do not require egl-1. Moreover, from double-mutant analysis we found that in addition to developmentally regulated cell death, dapk-1 may also mediate autophagy-dependent cell death.

並列關鍵字

apoptosis ； autophagy ； programmed cell death ； dapk-1 ； bec-1

參考文獻

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