The role of intracellular material transport dynamics in the regulation of apoptosis and autophagy

• Main Authors: Janaki Narasimha Sudhakar, 蘇塔克
• Other Authors: Kuan-Chih Chow
• Format: Others
• Language: en_US
• Published: 2014
• Online Access: http://ndltd.ncl.edu.tw/handle/13417286255725102135

博士 === 國立中興大學 === 生物醫學研究所 === 103 === This dissertation includes two topics: (1) The mechanism of apoptosis-inducing factor (AIF) transportation from mitochondria into the nucleus during the initiation of apoptosis, and (2) A model for autophagosome membrane source upon interrupting ceramide trafficking at mitochondria-associated membrane (MAM)?mitochondria contact sites. AIF is a 67-kDa FAD-dependent NADH oxidase located in the intermembranous space (IMS) of mitochondria and plays an important role in the oxidative phosphorylation of mitochondrial complex I and III. Upon apoptosis induction, AIF translocates from the mitochondrial IMS to the cytosol and into the nucleus to induce caspase-independent stage I peripheral chromatin condensation and large-scale DNA fragmentation. However, the AIF-interacting proteins in the cytosol and the nuclear AIF targets have not yet been identified. Therefore, we identify hHR23A as a key candidate with which AIF interacts for its translocation from the mitochondria-cytosol to the nucleus. Our results suggest that, hHR23A affects the nuclear transportation of AIF and drug sensitivity. The three proteins DRP1, ATAD3A, and MFN2 are involved in an alternative transport of proteins and lipids from the MAM to the mitochondria by a vesicular passage. Silencing these 3 proteins would rapidly induce autophagy. However, the mechanism of autophagosome formation is not well understood. In this study we showed that DRP1 and ATAD3A are essential for ceramide transport from the MAM to mitochondria. Disruption of ceramide flow between MAM-mitochondria contact sites would result in the accumulation of ceramide in the MAM and causes MAM to enlarge. This induces the MAM membrane to invaginate and create a concave curvature in the ceramide-enriched area of the MAM, which eventually forms the membrane for autophagosome. Thus we proposed a model for autophagosome membrane formation.