Rapid optical control of nociception with an ion channel photoswitch

Department of Molecular and Cell Biology, University of California Berkeley, Berkeley, California, USA.
Nature Methods (Impact Factor: 32.07). 02/2012; 9(4):396-402. DOI: 10.1038/nmeth.1897
Source: PubMed


Local anesthetics effectively suppress pain sensation, but most of these compounds act nonselectively, inhibiting activity of all neurons. Moreover, their actions abate slowly, preventing precise spatial and temporal control of nociception. We developed a photoisomerizable molecule, quaternary ammonium-azobenzene-quaternary ammonium (QAQ), that enables rapid and selective optical control of nociception. QAQ is membrane-impermeant and has no effect on most cells, but it infiltrates pain-sensing neurons through endogenous ion channels that are activated by noxious stimuli, primarily TRPV1. After QAQ accumulates intracellularly, it blocks voltage-gated ion channels in the trans form but not the cis form. QAQ enables reversible optical silencing of mouse nociceptive neuron firing without exogenous gene expression and can serve as a light-sensitive analgesic in rats in vivo. Because intracellular QAQ accumulation is a consequence of nociceptive ion-channel activity, QAQ-mediated photosensitization is a platform for understanding signaling mechanisms in acute and chronic pain.

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Available from: Alexandre Mourot, Oct 09, 2015
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    • "Optopharmacological agents have been enthusiastically received in neuroscience for in vitro applications (Banghart and Sabatini, 2012; Callaway and Katz, 1993; Carter and Sabatini, 2004; Matsuzaki et al., 2001), but their use in vivo has been limited. Although compelling findings exist addressing the external visual nervous system and the surface of the cortex (Mourot et al., 2012; Noguchi et al., 2011; Polosukhina et al., 2012; Tochitsky et al., 2014), optopharmacological application in the deep brain remains a significant challenge. Optofluidic devices that provide access to the UV spectrum with advanced m-ILEDs could target these highly selective photosensitive tools to spatially isolated regions of the central nervous system in nongenetically altered mammals. "
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    ABSTRACT: In vivo pharmacology and optogenetics hold tremendous promise for dissection of neural circuits, cellular signaling, and manipulating neurophysiological systems in awake, behaving animals. Existing neural interface technologies, such as metal cannulas connected to external drug supplies for pharmacological infusions and tethered fiber optics for optogenetics, are not ideal for minimally invasive, untethered studies on freely behaving animals. Here, we introduce wireless optofluidic neural probes that combine ultrathin, soft microfluidic drug delivery with cellular-scale inorganic light-emitting diode (μ-ILED) arrays. These probes are orders of magnitude smaller than cannulas and allow wireless, programmed spatiotemporal control of fluid delivery and photostimulation. We demonstrate these devices in freely moving animals to modify gene expression, deliver peptide ligands, and provide concurrent photostimulation with antagonist drug delivery to manipulate mesoaccumbens reward-related behavior. The minimally invasive operation of these probes forecasts utility in other organ systems and species, with potential for broad application in biomedical science, engineering, and medicine. Copyright © 2015 Elsevier Inc. All rights reserved.
    Cell 07/2015; 162(3). DOI:10.1016/j.cell.2015.06.058 · 32.24 Impact Factor
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    • "However, subsequent work indicated that PCLs enter the cell and photosensitize a wide range of voltage-gated channels via the internal TEA site (Banghart et al., 2009; Fehrentz et al., 2012). Most notably, such compounds have been used for photocontrol of ion channels in the retina for vision restoration in blind mice (Tochitsky et al., 2012) and for optically controlled analgesia via a PCL called quaternary ammonium-azobenzene-quaternary ammonium (QAQ) that specifically enters nociceptive ion channel-expressing cells (Mourot et al., 2012). However, despite their power for control of membrane potential, in most cases PCLs lack target specificity which makes it difficult to determine a particular channel’s contribution. "
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    ABSTRACT: Optogenetic tools were originally designed to target specific neurons for remote control of their activity by light and have largely been built around opsin-based channels and pumps. These naturally photosensitive opsins are microbial in origin and are unable to mimic the properties of native neuronal receptors and channels. Over the last 8 years, photoswitchable tethered ligands (PTLs) have enabled fast and reversible control of mammalian ion channels, allowing optical control of neuronal activity. One such PTL, maleimide-azobenzene-quaternary ammonium (MAQ), contains a maleimide (M) to tether the molecule to a genetically engineered cysteine, a photoisomerizable azobenzene (A) linker and a pore-blocking quaternary ammonium group (Q). MAQ was originally used to photocontrol SPARK, an engineered light-gated potassium channel derived from Shaker. Potassium channel photoblock by MAQ has recently been extended to a diverse set of mammalian potassium channels including channels in the voltage-gated and K2P families. Photoswitchable potassium channels, which maintain native properties, pave the way for the optical control of specific aspects of neuronal function and for high precision probing of a specific channel's physiological functions. To extend optical control to natively expressed channels, without overexpression, one possibility is to develop a knock-in mouse in which the wild-type channel gene is replaced by its light-gated version. Alternatively, the recently developed photoswitchable conditional subunit technique provides photocontrol of the channel of interest by molecular replacement of wild-type complexes. Finally, photochromic ligands also allow photocontrol of potassium channels without genetic manipulation using soluble compounds. In this review we discuss different techniques for optical control of native potassium channels and their associated advantages and disadvantages.
    Frontiers in Molecular Neuroscience 04/2013; 6:6. DOI:10.3389/fnmol.2013.00006 · 4.08 Impact Factor
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    • "Shaker a K b v Na b, c v L-type Ca c v 367 4 min f, j 20–30 Banghart, 2009; Banghart et al., 2009 PrAQ Shaker a 338 13 min f, j 40 Banghart, 2009; Banghart et al., 2009 DENAQ K v 3.1 a K v 2.1 a, f K v 4.2 a, f K b, f v Shaker a K ir 2.1 a, f Ca v 2.2 a, f Na f v 470 300 ms k 100 Mourot et al., 2011 PhENAQ Shaker a K v 3.1 a, f K b v 456 160 ms to 2.6 s k 20–50 Mourot et al., 2011 QAQ Shaker a K v 2.1 a K v 3.1 a K v 4.2 a K b, i v Na b, g, h, i v Na v 1.5 a, f Ca v 2.2 a L-type Ca c v K ir 2.1 a HCN g iGluR b 362 7 min j 100–300 l Banghart et al., 2009; Mourot et al., 2012 "
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    ABSTRACT: Ion channels are transmembrane proteins that control the movement of ions across the cell membrane. They are the molecular machines that make neurons excitable by enabling the initiation and propagation of action potentials (APs). Rapid signaling within and between neurons requires complex molecular processes that couple the sensing of membrane voltage or neurotransmitter release to the fast opening and closing of the ion channel gate. Malfunction of an ion channel's sensing or gating module can have disastrous pathological consequences. However, linking molecular changes to the modulation of neural circuits and ultimately to a physiological or pathological state is not a straightforward task. It requires precise and sophisticated methods of controlling the function of ion channels in their native environment. To address this issue we have developed new photochemical tools that enable the remote control of neuronal ion channels with light. Due to its optical nature, our approach permits the manipulation of the nervous system with high spatial, temporal and molecular precision that will help us understand the link between ion channel function and physiology. In addition, this strategy may also be used in the clinic for the direct treatment of some neuronal disorders.
    Frontiers in Molecular Neuroscience 03/2013; 6:5. DOI:10.3389/fnmol.2013.00005 · 4.08 Impact Factor
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