Developmental change in the electrophysiological and pharmacological properties of acid-sensing ion channels in CNS neurons

Article (PDF Available)inThe Journal of Physiology 588(Pt 20):3883-900 · October 2010with31 Reads
DOI: 10.1113/jphysiol.2010.192922 · Source: PubMed
Abstract
Acid-sensing ion channels (ASICs) are proton-gated cation channels that play important roles in the CNS including synaptic plasticity and acidosis-mediated neuronal injury. ASIC1a and ASIC2a subunits are predominant in CNS neurons, where homomultimeric and heteromultimeric channel configurations co-exist. Since ASIC1a and ASIC2a have dramatic differences in pH sensitivity, Ca(2+) permeability and channel kinetics, any change in the level of individual subunits may have significant effects on the properties and functions of ASICs. Using patch-clamp recording, fluorescent Ca(2+) imaging and molecular biological techniques, we show dramatic developmental changes in the properties of ASICs in mouse cortical neurons. For example, the amplitude of ASIC currents increases whereas desensitization decreases with neuronal maturation. Decreased H(+) affinity and acid-evoked [Ca(2+)](i) but increased Zn(2+) potentiation were also recorded in mature neurons. RT-PCR revealed significant increases in the ratio of ASIC2/ASIC1 mRNA with neuronal maturation. Thus, contributions of ASIC1a and ASIC2a to overall ASIC-mediated responses undergo distinct developmental changes. These findings may help in understanding the precise role of ASICs in physiological and pathological conditions at different developmental stages.

Figures

Figure
Figure
Figure
Figure
Figure
    • "Accordingly, our ratiometric and regional data are consistent with previous electrophysiological recordings and provide a molecular and semi-quantitative explanation for the observed current properties. In addition, the developmental increase in ASIC2:1 ratio in brain (Fig. 3) constitutes the same trend as that observed during the maturation of cultured neu- rons [41]. The difference in 1a/2a/2b ratio in the brain suggests changes in current properties. "
    [Show abstract] [Hide abstract] ABSTRACT: Background: Acid-sensing ion channels (ASICs) are key mediators of acidosis-induced responses in neurons. However, little is known about the relative abundance of different ASIC subunits in the brain. Such data are fundamental for interpreting the relative contribution of ASIC1a homomers and 1a/2 heteromers to acid signaling, and essential for designing therapeutic interventions to target these channels. We used a simple biochemical approach and semi-quantitatively determined the molar ratio of ASIC1a and 2 subunits in mouse brain. Further, we investigated differential surface trafficking of ASIC1a, ASIC2a, and ASIC2b. Results and conclusions: ASIC1a subunits outnumber the sum of ASIC2a and ASIC2b. There is a region-specific variation in ASIC2a and 2b expression, with cerebellum and striatum expressing predominantly 2b and 2a, respectively. Further, we performed surface biotinylation and found that surface ASIC1a and ASIC2a ratio correlates with their total expression. In contrast, ASIC2b exhibits little surface presence in the brain. This result is consistent with increased co-localization of ASIC2b with an ER marker in 3T3 cells. Our data are the first semi-quantitative determination of relative subunit ratio of various ASICs in the brain. The differential surface trafficking of ASICs suggests that the main functional ASICs in the brain are ASIC1a homomers and 1a/2a heteromers. This finding provides important insights into the relative contribution of various ASIC complexes to acid signaling in neurons.
    Full-text · Article · Dec 2016
    • "The whole cell patch-clamp recording shows that treatment with 1 mM cpt-cAMP significantly increases the density of ASIC current (p < 0.05, n = 12, Fig. 5c, d). These findings are consistent with other reports showing that ASIC expression increases with neuronal maturation [1]. "
    [Show abstract] [Hide abstract] ABSTRACT: Cultured neuronal cell lines can express properties of mature neurons if properly differentiated. Although the precise mechanisms underlying neuronal differentiation are not fully understood, the expression and activation of ion channels, particularly those of Ca2+-permeable channels, have been suggested to play a role. In this study, we explored the presence and characterized the properties of acid-sensing ion channels (ASICs) in NS20Y cells, a neuronal cell line previously used for the study of neuronal differentiation. In addition, the potential role of ASICs in cell differentiation was explored. Reverse Transcription Polymerase Chain Reaction and Western blot revealed the presence of ASIC1 subunits in these cells. Fast drops of extracellular pH activated transient inward currents which were blocked, in a dose dependent manner, by amiloride, a non-selective ASIC blocker, and by Psalmotoxin-1 (PcTX1), a specific inhibitor for homomeric ASIC1a and heteromeric ASIC1a/2b channels. Incubation of cells with PcTX1 significantly reduced the differentiation of NS20Y cells induced by cpt-cAMP, as evidenced by decreased neurite length, dendritic complexity, decreased expression of functional voltage gated Na+ channels. Consistent with ASIC1a inhibition, ASIC1a knockdown with small interference RNA significantly attenuates cpt-cAMP-induced increase of neurite outgrowth. In summary, we described the presence of functional ASICs in NS20Y cells and demonstrate that ASIC1a plays a role in the differentiation of these cells.
    Full-text · Article · Jun 2016
    • "Price et al. (2000) demonstrated the expression of ASIC2a/b in the DRG of the PNS by IF; Peng et al. (2004) reported the expression of ASIC2a in the spiral ganglion by IHC (Peng et al., 2004). The expression of Asic2 mRNA in the brain, spinal cord and DRG was further confirmed by NB (Price et al., 2000; Chen et al., 2002; Wemmie et al., 2002), RT-PCR (Price et al., 2001; Askwith et al., 2004; Page et al., 2005; Baron et al., 2008; Hattori et al., 2009; Lu et al., 2009; Li et al., 2010; Walder et al., 2010; Rahman et al., 2011; Cheng et al., 2014) and ISH (Price et al., 2000; Hughes et al., 2007 ). ASIC2-containing DRG neurons may be involved in mechanosensory function because ASIC2 immunoreactivity was observed in lanceolate fibers of hair follicles, the Meissner corpuscle (GarciaAnoveros et al., 2001), and Pacinian corpuscles (Montano et al., 2009). "
    [Show abstract] [Hide abstract] ABSTRACT: Advanced gene targeting technology and related tools in mice have been incorporated into studies of acid-sensing ion channels (ASICs). A single ASIC subtype can be knocked out specifically and screened thoroughly for expression in the nervous system at the cellular level. Mapping studies have further shed light on the initiation and identification of related behavioral phenotypes. Here we review studies involving genetically engineered mouse models used to investigate the physiological function of individual ASIC subtypes: ASIC1 (and ASIC1a), ASIC2, ASIC3 and ASIC4. We discuss the detailed expression studies and significant phenotypes revealed with gene knockout for most known Asic subtypes. Each strategy designed to manipulate mouse genetics has advantages and disadvantages. We discuss the limitations of these Asic-knockout models and propose future directions to solve the genetic issues. Copyright © 2014. Published by Elsevier Ltd.
    Full-text · Article · Jan 2015
Show more