Distant coupling between RNA editing and alternative splicing of the osmosensitive cation channel Tmem63b.

Post-transcriptional modifications of pre-mRNAs expand the diversity of proteomes in higher eukaryotes. In the brain, these modifications diversify the functional output of many critical neuronal signal molecules. In this study, we identified a brain-specific A-to-I RNA editing that changed glutamine to arginine (Q/R) at exon 20 and an alternative splicing of exon 4 in Tmem63b, which encodes a ubiquitously expressed osmosensitive cation channel. The channel isoforms lacking exon 4 occurred in ∼80% of Tmem63b mRNAs in the brain but were not detected in other tissues, suggesting a brain-specific splicing. We found that the Q/R editing was catalyzed by Adar2 (Adarb1) and required an editing site complementary sequence located in the proximal 5' end of intron 20. Moreover, the Q/R editing was almost exclusively identified in the splicing isoform lacking exon 4, indicating a coupling between the editing and the splicing. Elimination of the Q/R editing in brain-specific Adar2 knockout mice did not affect the splicing efficiency of exon 4. Furthermore, transfection with the splicing isoform containing exon 4 suppressed the Q/R editing in primary cultured cerebellar granule neurons. Thus, our study revealed a coupling between an RNA editing and a distant alternative splicing in the Tmem63b pre-mRNA, in which the splicing plays a dominant role. Finally, physiological analysis showed that the splicing and the editing coordinately regulate Ca2+ permeability and osmosensitivity of channel proteins, which may contribute to their functions in the brain. Copyright © 2020 © 2020 Wu et al. Published by Elsevier Inc. All rights reserved.

Citation

Dan Wu, Yan-Yu Zang, Yong-Yun Shi, Chang Ye, Wen-Min Cai, Xiao-Hui Tang, Liyun Zhao, Yong Liu, Zhenji Gan, Gui-Quan Chen, Yun Xu, Jian-Jun Yang, Yun Stone Shi. Distant coupling between RNA editing and alternative splicing of the osmosensitive cation channel Tmem63b. The Journal of biological chemistry. 2020 Dec 25;295(52):18199-18212

PMID: 33453827

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