最近美國《實(shí)驗(yàn)生物學(xué)聯(lián)合會會刊》 (The FASEB Journal)發(fā)表了中科院上海生科院營養(yǎng)所劉勇研究組在RNA編輯與細(xì)胞分泌功能研究方面所取得的最新進(jìn)展—“Deficiency in RNA editing enzyme ADAR2 impairs regulated exocytosis”,。
RNA編輯(RNA editing)泛指真核細(xì)胞中對RNA分子在轉(zhuǎn)錄后進(jìn)行再加工和修飾的過程，能夠使基因編碼的遺傳信息在RNA水平上進(jìn)一步產(chǎn)生多樣性與可塑性,。RNA腺苷脫氨酶ADAR (Adenosine Deaminase Acting on RNA) 家族的RNA編輯酶ADAR1和ADAR2,，能識別特定RNA底物分子中的腺苷（A）并催化其水解脫氨成為肌苷（I），因此RNA編輯可以改變mRNA所編碼蛋白質(zhì)分子的功能活性,，影響mRNA的穩(wěn)定性,，或參與microRNA的加工成熟以及改變microRNA對其底物RNA分子的識別等一系列重要的生物學(xué)過程。在中樞神經(jīng)系統(tǒng)中,，A－to－I編輯通過選擇性調(diào)節(jié)關(guān)鍵離子通道和神經(jīng)遞質(zhì)受體的功能特性,，從而發(fā)揮及其重要的生理學(xué)功能。劉勇研究組此前發(fā)表的研究工作顯示,，在胰島β細(xì)胞中ADAR2介導(dǎo)的RNA編輯過程受機(jī)體營養(yǎng)與能量代謝狀況的調(diào)控（Gan et al. JBC 281:33386-94,，2006），但ADAR2在專職分泌的細(xì)胞中行使怎樣的細(xì)胞生物學(xué)功能卻依然不明了,。
為進(jìn)一步探尋ADAR介導(dǎo)的RNA編輯在代謝平衡相關(guān)調(diào)節(jié)過程中的功能,，劉勇研究組博士研究生楊柳、趙麗韻等通過研究發(fā)現(xiàn),，特異性地抑制ADAR2編輯酶的表達(dá),，能夠顯著削弱葡萄糖刺激下β細(xì)胞或胰島中的胰島素分泌,，也同樣導(dǎo)致PC12細(xì)胞分泌能力的缺損，而且ADAR2對細(xì)胞分泌過程的影響依賴于其編輯酶的催化活性,。在β細(xì)胞中,，ADAR2的缺失雖然不影響胞內(nèi)鈣離子的動員激活，卻顯著削弱由鈣離子激發(fā)的細(xì)胞膜電容變化,，還導(dǎo)致錨定于細(xì)胞膜上胰島素分泌囊泡數(shù)量的降低,，并伴隨著參與細(xì)胞胞吐過程的重要調(diào)節(jié)因子Munc18-1和 Synaptotagmin-7其表達(dá)水平的下調(diào)。這些結(jié)果表明,，ADAR2編輯酶介導(dǎo)的RNA編輯作為一種基因轉(zhuǎn)錄后的調(diào)控機(jī)制參與了細(xì)胞胞吐這一過程的調(diào)節(jié),。這為深入了解RNA編輯在中樞神經(jīng)或外周組織的細(xì)胞分泌、代謝平衡等方面所發(fā)揮的作用提供了機(jī)制上的新線索,。
此項(xiàng)工作得到國家973研究計(jì)劃,、國家自然科學(xué)基金委重點(diǎn)項(xiàng)目、上海市科委和中科院知識創(chuàng)新工程的經(jīng)費(fèi)資助,。（生物谷Bioon.com）
生物谷推薦英文摘要：
The FASEB Journal. 2010;24:3720-3732. doi：10.1096/fj.09-152363.
Deficiency in RNA editing enzyme ADAR2 impairs regulated exocytosis
Liu Yang*,1, Liyun Zhao*,1, Zhenji Gan*,2, Zixuan He,3, Jingyue Xu, Xiang Gao, Xiaorui Wang, Weiping Han, Liangyi Chen, Tao Xu, Wenjun Li*,4 and Yong Liu*,4
* Key Laboratory of Nutrition and Metabolism, Institute for Nutritional Sciences, Shanghai Institutes for Biological Sciences (SIBS), Shanghai, China;
Institute of Biophysics, Chinese Academy of Sciences (CAS), Beijing, China;
Model Animal Research Center, Nanjing University, Nanjing, China; and
Singapore Bioimaging Consortium, Agency for Science, Technology, and Research (A*STAR), Singapore
Mammalian RNA editing catalyzed by adenosine deaminases acting on RNA (ADARs) ADAR1 and ADAR2 plays pivotal roles in the brain through functional modifications of neurotransmitter receptors and ion channels. We have demonstrated previously that RNA editing by ADAR2 is regulated metabolically in pancreatic β cells. To investigate the cellular functions of ADAR2 in professional secretory cells, we studied the effects of ADAR2 knockdown on regulated exocytosis. Selective knockdown of ADAR2 expression markedly impaired glucose-stimulated insulin secretion in the rat insulinoma INS-1 cells and primary pancreatic islets and significantly diminished KCl-stimulated secretion of exogenous human growth hormone or endogenous chromogranin B protein in the rat adrenal pheochromocytoma PC12 cells. Notably, restored overexpression of catalytically active but not editing-deficient mutant ADAR2 could rescue the impairment in stimulated secretion from ADAR2 knockdown cells. Moreover, ADAR2 suppression significantly attenuated Ca2+-evoked membrane capacitance increases and appreciably reduced the number of membrane-docked insulin granules in INS-1 cells. Interestingly, the secretory defects resulting from ADAR2 deficiency were coupled to decreased expression of Munc18-1 and synaptotagmin-7, two key molecules in the regulation of vesicle exocytosis. Thus, these findings reveal an important aspect of ADAR2 actions in regulated exocytosis, implicating RNA editing in the control of cellular secretory machinery.—Yang, L., Zhao, L., Gan, Z., He, Z., Xu, J., Gao, X., Wang, X., Han, W., Chen, L., Xu, T., Li, W., Liu, Y. Deficiency in RNA editing enzyme ADAR2 impairs regulated exocytosis.
