自噬体形成过程中Atg4B和LC3与自噬膜的动态作用及调控

细胞自噬是真核细胞中依赖溶酶体的降解途径，双层膜自噬体的形成是自噬完成的基础。自噬蛋白LC3与自噬膜的结合为自噬体形成所必需，其中涉及半胱氨酸蛋白酶Atg4B对胞质和自噬膜上LC3的特异切割作用。但是，自噬发生时Atg4B何时和如何上膜与LC3相互作用尚不明确。前期研究中我们发现，Atg4B能结合于早期自噬结构；自噬体形成过程中，Atg4B和LC3均能动态地发生与膜的结合和解离；高浓度Brefeldin A能阻止LC3与自噬膜的动态结合，但不影响Atg4B的上下膜。这些结果提示Atg4B和LC3与自噬膜动态结合的不同特性和Atg4B与自噬膜结合对LC3的非依赖性。本项目将在前期结果的基础上，深入开展Atg4B和LC3与自噬膜作用的动力学研究，通过鉴定自噬膜上Atg4B和LC3的新的作用蛋白，弄清Atg4B和LC3与膜结合和解离的分子机制，明确它们在膜上的动态相互作用调控自噬体形成的机理。

Autophagy is a lysosome-dependent intracellular degradation pathway in eukaryotic cells. The formation of the double-membraned autophagosomes in the cytoplasm is a fundamental basis for autophagic degradation. The membrane-binding of the autophagy-related protein LC3 is essential for autophagosome formation which invloves the specific cleavage of cytosolic and membrane-associated LC3 by the cystein proteinase Atg4B. However, when and how Atg4B associates with autophagic membranes and interacts with LC3 on the membranes are not clear. In our preliminary work, we have found that, Atg4B is localized to the early autophagic membrane structures; Atg4B and LC3 undergo dynamicly on-and-off the membranes; when high concentration of brefeldin A blocks the dynamic membrane-binding of LC3, it shows no effect on the cycle of Atg4B. These results suggest a different characteristic of Atg4B membrane-binding from that of LC3, and a independence of the membrane association of Atg4B from membrane LC3. In this study, we will further investigate the dynamics of the membrane-binding of Atg4B and LC3. By identifying new interaction proteins of Atg4B and LC3 on the membrane, we aim to clarify the regulation of their membrane association and dissociation, and the underlying mechanism of autophagosme formation controled by the dynamic Atg4B-LC3 interaction on the membranes.