Membrane potentials regulating GPCRs: insights from experiments and molecular dynamics simulations

Vickery, Owen N.; Machtens, Jan‐Philipp; Zachariae, Ulrich

doi:10.1016/j.coph.2016.06.011

Cited by 35 publications

(41 citation statements)

References 51 publications

(91 reference statements)

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“…In any case, since Kir are K+ channels, their participation would be indirect, unless flux-independent actions of these receptors could be involved. Alternatively, some reports have demonstrated that without ligand, GPCR can be activated by membrane depolarization, thus opening the possibility that this mechanism is involved in iCa2+ rise (53).…”

Section: Discussionmentioning

confidence: 99%

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Dual NMDAR signaling in astrocytes: flux-independent pH sensor & flux-dependent mitochondrial regulator through membrane-mitochondria communication

Balderas

Hernández‐Cruz

2019

Preprint

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Glutamate N-methyl-D-aspartate (NMDA) receptor (NMDAR) is critical for neurotransmission as a Ca2+ channel. Nonetheless, several reports have also demonstrated fluxindependent signaling. Astrocytes express NMDAR distinct from its neuronal counterpart, but cultured astrocytes have no electrophysiological response and controversial findings have questioned NMDAR function. We recently demonstrated that in cultured astrocytes NMDA at pH6 (NMDA/pH&) elicits flux-independent Ca2+ release from the Endoplasmic Reticulum (ER) and depletes mitochondrial membrane potential (m). Here we show that flux-independent Ca2+ release is mainly due to pH6, whereas m depletion requires both pH6 and flux-dependent NMDAR signaling. Immunofluorescence exhibited that plasma membrane (PM) NMDAR is apposed to ER and mitochondria or surrounds these organelles. Moreover, NMDA/pH6 treatment generated ER stress, increased endocytosis, mitochondria-ER and -nuclear contacts and strikingly, PM invaginations near mitochondria along with electrodense structures referred here as PMmitochondrial bridges (PM-m-br). These data and earlier observations strongly suggest PMmitochondria communication. As a proof of concept of this notion, NMDA/pH6 provoked mitochondria labeling by the PM dye FM-4-64FX. Finally, we analyzed by WB NMDAR subunit GluN1 to explore putative causes of NMDAR dual function, we found fragments with M.W. consistent with previously identified cleavage sites. Accordingly, GluN1 intracellular and extracellular domains presented little colocalization. Our findings demonstrate that NMDAR plays a dual function: a flux-independent pH sensor and a flux-dependent regulator of m. More importantly, m depletion seems to be mediated by PM-mitochondria communication. Finally, we found different GluN1 fragments that could be involved in NMDAR dual signaling, although causality awaits demonstration. NMDAR described so far, as it plays a central role for NMDAR assembly at the Endoplasmic Reticulum (ER) and its intracellular (IC) trafficking (1-3). However, NMDAR signaling is more complex, because Ca2+ inflow can switch on or off IC pathways with pro-survival or pro-death effects, suggested to be the result of synaptic or extra-synaptic NMDAR function, respectively (4). Moreover, several reports have also demonstrated flux-independent actions of this receptor (also termed metabotropic-like or non-canonical functions), that mediate long term depression (LTD) and other cellular events, through molecular mechanisms that have been only slightly investigated (5).In astrocytes, NMDAR expression and function were matter of debate for several years. However, nowadays it is clear that astrocytes in situ express functional NMDAR, although it displays several singularities, given in part by its subunit composition (6, 7). Nevertheless, classical electrophysiological experiments found no ionic flux in cultured astrocytes, and controversial findings have questioned NMDAR function (6,8). Nonetheless, we and others have recently demonstrated that the NMDAR ca...

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Section: Discussionmentioning

confidence: 99%

“…Alternatively, some reports have demonstrated that without ligand, GPCR can be activated by membrane depolarization, thus opening the possibility that this mechanism is involved in iCa2+ rise [53].…”

Section: Discussionmentioning

confidence: 99%

Dual NMDAR signaling in astrocytes: flux-independent pH sensor & flux-dependent mitochondrial regulator through membrane-mitochondria communication

Balderas

Hernández‐Cruz

2019

Preprint

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“…Indeed, every transmembrane protein that binds a charged ligand, undergoes conformational shifts, or transports charged moieties across the membrane is, in principle, susceptible to changes in membrane voltage [58]. Electrogenic transporters are sensitive to membrane voltage, as are some GPCRs[59, 60]. Voltage affects the activity of the multidrug resistance proteins MRP4 and MRP5 [61], though there has been controversy over whether voltage also affects the multi-drug efflux transporter P-gp (also known as MDR1) [62, 63].…”

Section: Figurementioning

confidence: 99%

Optogenetic Approaches to Drug Discovery in Neuroscience and Beyond

Zhang

Cohen

2017

Trends in Biotechnology

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Recent advances in optogenetics have opened new routes to drug discovery, particularly in neuroscience. Physiological cellular assays probe functional phenotypes that connect genomic data to patient health. Optogenetic tools, and in particular tools for all-optical electrophysiology, now provide means to probe cellular disease models with unprecedented throughput and information content. These techniques promise to identify functional phenotypes associated with disease states and to identify compounds that improve cellular function regardless of whether the compound acts directly on a target or through a bypass mechanism. This review discusses opportunities and unresolved challenges in applying optogenetic techniques throughout the discovery pipeline, from target identification and validation, to target-based and phenotypic screens, to clinical trials.

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“…The M2 muscarinic receptor is the one of the most intensively studied GPCRs in its voltage-dependent behaviors and molecular mechanisms 1–4, 6–12 . For example, membrane hyperpolarization increases the affinity of the M2 muscarinic receptor for its native full agonist, acetylcholine (ACh), and decreases affinity for its partial agonist pilocarpine 3, 9, 10 .…”

Section: Introductionmentioning

confidence: 99%

Structural determinants at the M2 muscarinic receptor modulate the RGS4-GIRK response to pilocarpine by impairment of the receptor voltage sensitivity

Chen

Furutani

Kurachi

2017

Sci Rep

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Membrane potential controls the response of the M2 muscarinic receptor to its ligands. Membrane hyperpolarization increases response to the full agonist acetylcholine (ACh) while decreasing response to the partial agonist pilocarpine. We previously have demonstrated that the regulator of G-protein signaling (RGS) 4 protein discriminates between the voltage-dependent responses of ACh and pilocarpine; however, the underlying mechanism remains unclear. Here we show that RGS4 is involved in the voltage-dependent behavior of the M2 muscarinic receptor-mediated signaling in response to pilocarpine. Additionally we revealed structural determinants on the M2 muscarinic receptor underlying the voltage-dependent response. By electrophysiological recording in Xenopus oocytes expressing M2 muscarinic receptor and G-protein-gated inwardly rectifying K+ channels, we quantified voltage-dependent desensitization of pilocarpine-induced current in the presence or absence of RGS4. Hyperpolarization-induced desensitization of the current required for RGS4, also depended on pilocarpine concentration. Mutations of charged residues in the aspartic acid-arginine-tyrosine motif of the M2 muscarinic receptor, but not intracellular loop 3, significantly impaired the voltage-dependence of RGS4 function. Thus, our results demonstrated that voltage-dependence of RGS4 modulation is derived from the M2 muscarinic receptor. These results provide novel insights into how membrane potential impacts G-protein signaling by modulating GPCR communication with downstream effectors.

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Membrane potentials regulating GPCRs: insights from experiments and molecular dynamics simulations

Cited by 35 publications

References 51 publications

Dual NMDAR signaling in astrocytes: flux-independent pH sensor & flux-dependent mitochondrial regulator through membrane-mitochondria communication

Dual NMDAR signaling in astrocytes: flux-independent pH sensor & flux-dependent mitochondrial regulator through membrane-mitochondria communication

Optogenetic Approaches to Drug Discovery in Neuroscience and Beyond

Structural determinants at the M2 muscarinic receptor modulate the RGS4-GIRK response to pilocarpine by impairment of the receptor voltage sensitivity

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