title: Deficiency in RNA editing enzyme ADAR2 impairs regulated exocytosis.
abstract: 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 Ca(2+)-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.
authors.affiliation: Institute for Nutritional Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China. liuy@sibs.ac.cn
authors.forename: Liu
authors.initials: L
authors.lastname: Yang
authors.forename: Liyun
authors.initials: L
authors.lastname: Zhao
authors.forename: Zhenji
authors.initials: Z
authors.lastname: Gan
authors.forename: Zixuan
authors.initials: Z
authors.lastname: He
authors.forename: Jingyue
authors.initials: J
authors.lastname: Xu
authors.forename: Xiang
authors.initials: X
authors.lastname: Gao
authors.forename: Xiaorui
authors.initials: X
authors.lastname: Wang
authors.forename: Weiping
authors.initials: W
authors.lastname: Han
authors.forename: Liangyi
authors.initials: L
authors.lastname: Chen
authors.forename: Tao
authors.initials: T
authors.lastname: Xu
authors.forename: Wenjun
authors.initials: W
authors.lastname: Li
authors.forename: Yong
authors.initials: Y
authors.lastname: Liu
mesh_terms: D000243:Adenosine Deaminase / Q000235:genetics / Q000502:physiology*; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D001483:Base Sequence; D055162:Biocatalysis; D015153:Blotting, Western; D002118:Calcium / Q000378:metabolism; D002478:Cells, Cultured; D017931:DNA Primers; D005089:Exocytosis / Q000502:physiology*; D055785:Gene Knockdown Techniques; D008564:Membrane Potentials; D046529:Microscopy, Electron, Transmission; D017393:RNA Editing; D034622:RNA Interference; D016601:RNA-Binding Proteins; D051381:Rats; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D017931:DNA Primers; D016601:RNA-Binding Proteins; D000255:Adenosine Triphosphate; C567955:ADARB1 protein, human; D000243:Adenosine Deaminase; D002118:Calcium