- 學位論文
Lysosome-responsive Transcription Factor EB Activation upon Mitophagy Degradation Stress
粒線體自噬壓力下溶酶體對轉錄因子 TFEB 的活化調控
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摘要
除了將溶酶體視為降解過程的最後胞器，溶酶體逐漸被認為參與控制細胞功能的上游路徑。因此，溶酶體的動態穩定應該被嚴格的調控，已配合代謝的需求以及維護溶酶體參與的細胞功能調控。這裡我們使用光調控產生粒線體自噬需求，以降解基質影響溶酶體的動態穩定，並定量觀察在不同程度的降解壓力下，溶酶體如何調控其生合成與動態平衡。我們觀察到，在粒線體自噬降解需求下，TFEB轉錄因子調控的溶酶體相關基因有正向活化趨勢，並且基因活化幅度與降解需求有正相關性。細胞藉由調控mTOR的活性抑制，得以產生這種壓力與反應的定量協調。進一步的研究證實粒線體自噬造成的mTOR活性抑制是透過在autolysosome胞器上聚集mTOR活性調節分子，DEPDC5和FLCN。Autolysosome 是一種溶酶體與自噬體融合後的混和胞器。此外，藉由STX17基因靜默進而阻斷自噬體與溶酶體的融合，足以使TFEB基因活化反應與壓力脫鉤。這些結果顯示兩種胞器中，溶酶體和autolysosome在mTOR活性調控和TFEB基因活化的功能上有不同之處。溶酶體透過與自噬體的融合，得以定量上感測降解壓力的幅度並且微調TFEB基因活化以維護自我調節的動態平衡。
關鍵字
粒線體自噬並列摘要
Except of the simplified view of lysosomes as the final compartments of degradation process, lysosomes are increasingly regarded as upstream organelles in the control of cell functions. Therefore, lysosome homeostasis should be tightly regulated to match the catabolic needs as well as to maintain lysosomal pathways. Here we use light-induced mitophagy substrates to disturb lysosome homeostatsis and reveal how lysosome biogenesis responses quantitatively to different levels of degradation stress. We observed that TFEB-mediated lysosomal genes activation is upregulated in dose-dependent manner upon variants mitophagy degradation stresses. This stress-response coordination is quantitatively modulated by mTOR inactivation. We further show that mitophagy-dependent mTOR inactivation is mediated by spatially recruiting mTOR activity regulators, DEPDC5 and FLCN, on autolysosome, a hybrid organelle of autophagosome and lysosome. Also, blocking autophagosome-lysosome fusion, by knocking down STX17, makes TFEB activation response decoupling from stress. These results suggest lysosome and autolysosome are functionally different in respect of mTOR activity and TFEB activation. Through fusing with autophagosomes, lysosomes sense degradation stress and decode into fine-tuning TFEB activation in the maintenance of self-regulated homeostasis.
並列關鍵字
mitophagy參考文獻
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