CAPS1 RNA Editing Promotes Dense Core Vesicle Exocytosis

Kotaro Miyake,Toshio Ohta,Hisako Nakayama,Nobutaka Doe,Yuri Terao,Eiji Oiki,Izumi Nagatomo,Yui Yamashita,Takaya Abe,Kazuko Nishikura,Atsushi Kumanogoh,Kouichi Hashimoto,Yukio Kawahara

doi:10.1016/j.celrep.2016.10.073

Abstract

Calcium-dependent activator protein for secretion 1 (CAPS1) plays a distinct role in the priming step of dense core vesicle (DCV) exocytosis. CAPS1 pre-mRNA is known to undergo adenosine-to-inosine RNA editing in its coding region, which results in a glutamate-to-glycine conversion at a site in its C-terminal region. However, the physiological significance of CAPS1 RNA editing remains elusive. Here, we created mutant mice in which edited CAPS1 was solely expressed. These mice were lean due to increased energy expenditure caused by physical hyperactivity. Electrophysiological and biochemical analyses demonstrated that the exocytosis of DCVs was upregulated in the chromaffin cells and neurons of these mice. Furthermore, we showed that edited CAPS1 bound preferentially to the activated form of syntaxin-1A, a component of the exocytotic fusion complex. These findings suggest that RNA editing regulates DCV exocytosis invivo, affecting physical activity.

Highlights

Post-transcriptional modification is a mechanism by which vast repertoires of mature RNAs and their proteins are generated from a single gene
Calcium-dependent activator protein for secretion 1 (CAPS1) pre-mRNA is known to undergo adenosineto-inosine RNA editing in its coding region, which results in a glutamate-to-glycine conversion at a site in its C-terminal region
Electrophysiological and biochemical analyses demonstrated that the exocytosis of dense core vesicle (DCV) was upregulated in the chromaffin cells and neurons of these mice

Summary

Introduction

Post-transcriptional modification is a mechanism by which vast repertoires of mature RNAs and their proteins are generated from a single gene. One type of post-transcriptional modification is adenosine-to-inosine RNA editing, which is catalyzed by ADAR1 (adenosine deaminase acting on RNA type1) and ADAR2 in mammals. These enzymes recognize double-stranded RNAs (dsRNAs) as targets (Behm and Öhman, 2016; Tomaselli et al, 2014). Editing in coding regions is quite rare (55 sites [Li et al, 2009]), this modification can generate proteins that are not encoded directly by the genome, given that the translational machinery interprets inosine as if it were guanosine. Only a few mouse models exist in which either edited or unedited proteins are expressed exclusively; these include the glutamate receptor

Results

Discussion

Conclusion