Dataset Information

RNA editing of the IQ domain in Ca(v)1.3 channels modulates their Ca²?-dependent inactivation.

ABSTRACT: Adenosine-to-inosine RNA editing is crucial for generating molecular diversity, and serves to regulate protein function through recoding of genomic information. Here, we discover editing within Ca(v)1.3 Ca²? channels, renown for low-voltage Ca²?-influx and neuronal pacemaking. Significantly, editing occurs within the channel's IQ domain, a calmodulin-binding site mediating inhibitory Ca²?-feedback (CDI) on channels. The editing turns out to require RNA adenosine deaminase ADAR2, whose variable activity could underlie a spatially diverse pattern of Ca(v)1.3 editing seen across the brain. Edited Ca(v)1.3 protein is detected both in brain tissue and within the surface membrane of primary neurons. Functionally, edited Ca(v)1.3 channels exhibit strong reduction of CDI; in particular, neurons within the suprachiasmatic nucleus show diminished CDI, with higher frequencies of repetitive action-potential and calcium-spike activity, in wild-type versus ADAR2 knockout mice. Our study reveals a mechanism for fine-tuning Ca(v)1.3 channel properties in CNS, which likely impacts a broad spectrum of neurobiological functions.

SUBMITTER: Huang H

PROVIDER: S-EPMC3271027 | biostudies-literature | 2012 Jan

REPOSITORIES: biostudies-literature

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RNA editing of the IQ domain in Ca(v)1.3 channels modulates their Ca²⁺-dependent inactivation.

Huang Hua H Tan Bao Zhen BZ Shen Yiru Y Tao Jin J Jiang Fengli F Sung Ying Ying YY Ng Choon Keow CK Raida Manfred M Köhr Georg G Higuchi Miyoko M Fatemi-Shariatpanahi Hadi H Harden Bradley B Yue David T DT Soong Tuck Wah TW

Neuron 20120101 2

Adenosine-to-inosine RNA editing is crucial for generating molecular diversity, and serves to regulate protein function through recoding of genomic information. Here, we discover editing within Ca(v)1.3 Ca²⁺ channels, renown for low-voltage Ca²⁺-influx and neuronal pacemaking. Significantly, editing occurs within the channel's IQ domain, a calmodulin-binding site mediating inhibitory Ca²⁺-feedback (CDI) on channels. The editing turns out to require RNA adenosine deaminase ADAR2, whose variable a ...[more]

PMID: 22284185

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Project description:Stac protein (named for its SH3- and cysteine-rich domains) was first identified in brain 20 years ago and is currently known to have three isoforms. Stac2, Stac1, and Stac3 transcripts are found at high, modest, and very low levels, respectively, in the cerebellum and forebrain, but their neuronal functions have been little investigated. Here, we tested the effects of Stac proteins on neuronal, high-voltage-activated Ca2+ channels. Overexpression of the three Stac isoforms eliminated Ca2+-dependent inactivation (CDI) of l-type current in rat neonatal hippocampal neurons (sex unknown), but not CDI of non-l-type current. Using heterologous expression in tsA201 cells (together with β and α2-δ1 auxiliary subunits), we found that CDI for CaV1.2 and CaV1.3 (the predominant, neuronal l-type Ca2+ channels) was suppressed by all three Stac isoforms, whereas CDI for the P/Q channel, CaV2.1, was not. For CaV1.2, the inhibition of CDI by the Stac proteins appeared to involve their direct interaction with the channel's C terminus. Within the Stac proteins, a weakly conserved segment containing ∼100 residues and linking the structurally conserved PKC C1 and SH3_1 domains was sufficient to fully suppress CDI. The presence of CDI for l-type current in control neonatal neurons raised the possibility that endogenous Stac levels are low in these neurons and Western blotting indicated that the expression of Stac2 was substantially increased in adult forebrain and cerebellum compared with neonate. Together, our results indicate that one likely function of neuronal Stac proteins is to tune Ca2+ entry via neuronal l-type channels.SIGNIFICANCE STATEMENT Stac protein, first identified 20 years ago in brain, has recently been found to be essential for proper trafficking and function of the skeletal muscle l-type Ca2+ channel and is the site of mutations causing a severe, inherited human myopathy. In neurons, however, functions for Stac protein have remained unexplored. Here, we report that one likely function of neuronal Stac proteins is tuning Ca2+ entry via l-type, but not that via non-l-type, Ca2+ channels. Moreover, there is a large postnatal increase in protein levels of the major neuronal isoform (Stac2) in forebrain and cerebellum, which could provide developmental regulation of l-type channel Ca2+ signaling in these brain regions.

Dataset Information

RNA editing of the IQ domain in Ca(v)1.3 channels modulates their Ca²?-dependent inactivation.

Publications

RNA editing of the IQ domain in Ca(v)1.3 channels modulates their Ca²⁺-dependent inactivation.

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