2013-11-012024-05-13https://scholars.lib.ntu.edu.tw/handle/123456789/652748摘要：Retinoic-acid inducible gene I（RIG-I）是一種細胞內可識別RNA 病毒的識別受體，其啟動可以引發體細胞抗病毒免疫反應。以往的研究發現，其N 端 Caspaserecruitment domains（CARDs）和C 端的阻遏結構域（repressor domain, RD）皆在RIG-I 激活過程中扮演重要的控制角色。RIG-I 必須以CARDs 和其他蛋白交互作用，如14-3-3 epsilon 和TRIM25 RD，而RD 會自體抑制在靜息細胞中的RIG-I。當RNA ligand 結合後，RIG-I 產上立體結構上的變化，形成一個構象的同型二聚體，這個步驟為RIG-I 誘導下游先天免疫信號之先決條件。RIG-I 的RD 控制了RIG-I 的立體結構變化和RIG-I 二聚體，然而， RIG-I 的二聚化如何調節這些過程，目前還不清楚。本計畫將會評估，RIG-I RD 部份的的lysine 之可逆乙醯化（acetyltaion）修飾反應是否控制了RIG-I 激活。我們的初步的實驗結果顯示，乙醯基-模擬突變的RIG-I 無法回應急性Sendai 病毒（SenV）感染致使其無法激活下游IRF-3 之訊息傳遞；然而，RIG-I 對於病毒RNA 的識別和結合是完整的。此外，細胞質中之脫乙醯基酶的可能參與RIG-I脫乙醯反應以對在急性病毒感染。我們的研究結果將進一步定義脫乙醯在於RIG-I 激活先天抗病毒免疫反應為一必須的關鍵步驟。這些結果可以作為抗病毒治療藥物發展之參考。我們預計看到在病毒感染下，乙醯基-模擬突變的RIG-I 不能形成二聚體，而在靜息細胞中，acetyl-lysine 可能會阻止RIG-I 二聚體。在急性感染時，當RNAligand 結合後，RIG-I RD 脫乙醯化的發生將促進RIG-I 形成二聚體。當SenV感染之細胞只能表現極少量細胞質中HDACs 時，RIG-I 下游之IFN-β啟動子的活性將會下降，而當細胞質中之HDACs 表現量增加時將加快病毒感染後RIG-I 激活下游之干擾素反應。此研究成果將可用以提供抗病毒藥物研發之參考。<br> Abstract: Retinoic-acid inducible gene I (RIG-I) is a cytosolic pathogen recognition receptorthat initiates the immune response against RNA viruses. Previous studies showed thatRIG-I activation is regulated by both of its N-terminus Caspase recruitment domains(CARDs) and C-terminus repressor domain (RD). The CARDs are required for thebindings of accessory proteins, such as 14-3-3 epsilon and TRIM25, where as the RDgoverns auto-repression of RIG-I in the resting cells. Upon ligand binding, RIG-Iundergoes a conformational for homodimerization, and this RNA ligand-induceddimerization is a prerequisite of its induction of downstream innate immune signalling.The RD of RIG-I governs RIG-I conformational change and RIG-I dimerization;however, how RIG-I dimerization is regulated beyond these processes is unclear. Wewill assess that if reversible acetylation modifications of lysine residues in the RDcontrols RIG-I activation. Our preliminary data indicated that Acetyl-mimetic mutantsof RIG-I failed to signal downstream to activate IRF-3 in response to acute Sendai virus(SenV) infection, while HCV RNA recognition and binding activities of RIG-I werefully intact, and also, the cytoplasmic deacetylases may be involved in deacetylation ofRIG-I during acute infection. Our results will further define deacetylation as a key stepin controlling RIG-I activation required for innate immunity. These results may beinsightful in drug development for anti-viral treatments.We expect to see that the acetylmimetic mutants of RIG-I fail to form virus-inducedhomodimers, suggesting that acetyl-lysine residues in the resting cells may preventRIG-I from homodimerization. During acute infection, deacetylation of RIG-I RDoccurs and promotes RIG-I dimerization upon ligand binding. Knock-down cells ofcytoplasmic HDACs will be impaired in RIG-I-dependent IFN-beta promoter activityduring SenV infection, and overexpression of cytoplasmic HDACs will accelerate thekinetics of RIG-I activation in response to viral infections. These results will provideinsightful information for future developments of antiviral therapies.