Publications by authors named "Jose A Matta"

20 Publications

  • Page 1 of 1

Functional α6β4 acetylcholine receptor expression enables pharmacological testing of nicotinic agonists with analgesic properties.

J Clin Invest 2020 11;130(11):6158-6170

The α6β4 nicotinic acetylcholine receptor (nAChR) is enriched in dorsal root ganglia neurons and is an attractive non-opioid therapeutic target for pain. However, difficulty expressing human α6β4 receptors in recombinant systems has precluded drug discovery. Here, genome-wide screening identified accessory proteins that enable reconstitution of human α6β4 nAChRs. BARP, an auxiliary subunit of voltage-dependent calcium channels, promoted α6β4 surface expression while IRE1α, an unfolded protein response sensor, enhanced α6β4 receptor assembly. Effects on α6β4 involve BARP's N-terminal region and IRE1α's splicing of XBP1 mRNA. Furthermore, clinical efficacy of nicotinic agents in relieving neuropathic pain best correlated with their activity on α6β4. Finally, BARP-knockout, but not NACHO-knockout mice lacked nicotine-induced antiallodynia, highlighting the functional importance of α6β4 in pain. These results identify roles for IRE1α and BARP in neurotransmitter receptor assembly and unlock drug discovery for the previously elusive α6β4 receptor.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1172/JCI140311DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7598046PMC
November 2020

Hair cell α9α10 nicotinic acetylcholine receptor functional expression regulated by ligand binding and deafness gene products.

Proc Natl Acad Sci U S A 2020 09 14;117(39):24534-24544. Epub 2020 Sep 14.

Neuroscience Discovery, Janssen Pharmaceutical Companies of Johnson & Johnson, San Diego, CA 92121

Auditory hair cells receive olivocochlear efferent innervation, which refines tonotopic mapping, improves sound discrimination, and mitigates acoustic trauma. The olivocochlear synapse involves α9α10 nicotinic acetylcholine receptors (nAChRs), which assemble in hair cells only coincident with cholinergic innervation and do not express in recombinant mammalian cell lines. Here, genome-wide screening determined that assembly and surface expression of α9α10 require ligand binding. Ion channel function additionally demands an auxiliary subunit, which can be transmembrane inner ear (TMIE) or TMEM132e. Both of these single-pass transmembrane proteins are enriched in hair cells and underlie nonsyndromic human deafness. Inner hair cells from TMIE mutant mice show altered postsynaptic α9α10 function and retain α9α10-mediated transmission beyond the second postnatal week associated with abnormally persistent cholinergic innervation. Collectively, this study provides a mechanism to link cholinergic input with α9α10 assembly, identifies unexpected functions for human deafness genes TMIE/TMEM132e, and enables drug discovery for this elusive nAChR implicated in prevalent auditory disorders.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1073/pnas.2013762117DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7533656PMC
September 2020

Hair cell α9α10 nicotinic acetylcholine receptor functional expression regulated by ligand binding and deafness gene products.

Proc Natl Acad Sci U S A 2020 09 14;117(39):24534-24544. Epub 2020 Sep 14.

Neuroscience Discovery, Janssen Pharmaceutical Companies of Johnson & Johnson, San Diego, CA 92121

Auditory hair cells receive olivocochlear efferent innervation, which refines tonotopic mapping, improves sound discrimination, and mitigates acoustic trauma. The olivocochlear synapse involves α9α10 nicotinic acetylcholine receptors (nAChRs), which assemble in hair cells only coincident with cholinergic innervation and do not express in recombinant mammalian cell lines. Here, genome-wide screening determined that assembly and surface expression of α9α10 require ligand binding. Ion channel function additionally demands an auxiliary subunit, which can be transmembrane inner ear (TMIE) or TMEM132e. Both of these single-pass transmembrane proteins are enriched in hair cells and underlie nonsyndromic human deafness. Inner hair cells from TMIE mutant mice show altered postsynaptic α9α10 function and retain α9α10-mediated transmission beyond the second postnatal week associated with abnormally persistent cholinergic innervation. Collectively, this study provides a mechanism to link cholinergic input with α9α10 assembly, identifies unexpected functions for human deafness genes TMIE/TMEM132e, and enables drug discovery for this elusive nAChR implicated in prevalent auditory disorders.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1073/pnas.2013762117DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7533656PMC
September 2020

α7 nicotinic acetylcholine receptor upregulation by anti-apoptotic Bcl-2 proteins.

Nat Commun 2019 06 21;10(1):2746. Epub 2019 Jun 21.

Neuroscience Discovery, Janssen Pharmaceutical Companies of Johnson & Johnson, 3210 Merryfield Row, San Diego, CA, 92121, USA.

Nicotinic acetylcholine receptors (nAChRs) mediate and modulate synaptic transmission throughout the brain, and contribute to learning, memory, and behavior. Dysregulation of α7-type nAChRs in neuropsychiatric as well as immunological and oncological diseases makes them attractive targets for pharmaceutical development. Recently, we identified NACHO as an essential chaperone for α7 nAChRs. Leveraging the robust recombinant expression of α7 nAChRs with NACHO, we utilized genome-wide cDNA library screening and discovered that several anti-apoptotic Bcl-2 family proteins further upregulate receptor assembly and cell surface expression. These effects are mediated by an intracellular motif on α7 that resembles the BH3 binding domain of pro-apoptotic Bcl-2 proteins, and can be blocked by BH3 mimetic Bcl-2 inhibitors. Overexpression of Bcl-2 member Mcl-1 in neurons enhanced surface expression of endogenous α7 nAChRs, while a combination of chemotherapeutic Bcl2-inhibitors suppressed neuronal α7 receptor assembly. These results demonstrate that Bcl-2 proteins link α7 nAChR assembly to cell survival pathways.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/s41467-019-10723-xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6588605PMC
June 2019

α6-Containing Nicotinic Acetylcholine Receptor Reconstitution Involves Mechanistically Distinct Accessory Components.

Cell Rep 2019 01;26(4):866-874.e3

Neuroscience Discovery, Janssen Pharmaceutical Companies of Johnson & Johnson, 3210 Merryfield Row, San Diego, CA 92121, USA. Electronic address:

Acetylcholine gates a large family of nicotinic receptor cation channels that control neuronal excitation and neurotransmitter release. These receptors are key targets for neuropsychiatric disorders; however, difficulties in expressing nicotinic acetylcholine (nACh) receptors hamper elaboration of their pharmacology and obscure elucidation of their biological functions. Particularly intriguing are α6-containing nACh receptors, which mediate nicotine-induced dopamine release in striatum-nucleus accumbens. Using genome-wide cDNA screening, we identify three accessory proteins, β-anchoring and -regulatory protein (BARP), lysosomal-associated membrane protein 5 (LAMP5), and SULT2B1, that complement the nACh receptor chaperone NACHO to reconstitute α6β2β3 channel function. Whereas NACHO mediates α6β2β3 assembly, BARP primarily enhances channel gating and LAMP5 and SULT2B1 promote receptor surface trafficking. BARP knockout mice show perturbations in presynaptic striatal nACh receptors that are consistent with BARP modulation of receptor desensitization. These studies unravel the molecular complexity of α6β2β3 biogenesis and enable physiological studies of this crucial neuropharmacological target.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.celrep.2018.12.103DOI Listing
January 2019

Getting a Handle on Neuropharmacology by Targeting Receptor-Associated Proteins.

Neuron 2017 Dec;96(5):989-1001

Neuroscience Discovery, Janssen Pharmaceutical Companies of Johnson & Johnson, 3210 Merryfield Row, San Diego, CA 92121, USA. Electronic address:

Targeted therapy for neuropsychiatric disorders requires selective modulation of dysfunctional neuronal pathways. Receptors relevant to CNS disorders typically have associated proteins discretely expressed in specific neuronal pathways; these accessory proteins provide a new dimension for drug discovery. Recent studies show that targeting a TARP auxiliary subunit of AMPA receptors selectively modulates neuronal excitability in specific forebrain pathways relevant to epilepsy. Other medicinally important ion channels, gated by glutamate, γ-aminobutyric acid (GABA), and acetylcholine, also have associated proteins, which may be druggable. This emerging pharmacology of receptor-associated proteins provides a new approach for improving drug efficacy while mitigating side effects.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.neuron.2017.10.001DOI Listing
December 2017

NACHO Mediates Nicotinic Acetylcholine Receptor Function throughout the Brain.

Cell Rep 2017 04;19(4):688-696

Neuroscience Discovery, Janssen Pharmaceutical Companies of Johnson & Johnson, 3210 Merryfield Row, San Diego, CA 92121, USA. Electronic address:

Neuronal nicotinic acetylcholine receptors (nAChRs) participate in diverse aspects of brain function and mediate behavioral and addictive properties of nicotine. Neuronal nAChRs derive from combinations of α and β subunits, whose assembly is tightly regulated. NACHO was recently identified as a chaperone for α7-type nAChRs. Here, we find NACHO mediates assembly of all major classes of presynaptic and postsynaptic nAChR tested. NACHO acts at early intracellular stages of nAChR subunit assembly and then synergizes with RIC-3 for receptor surface expression. NACHO knockout mice show profound deficits in binding sites for α-bungarotoxin, epibatidine, and conotoxin MII, illustrating essential roles for NACHO in proper assembly of α7-, α4β2-, and α6-containing nAChRs, respectively. By contrast, GABA receptors are unaffected consistent with NACHO specifically modulating nAChRs. NACHO knockout mice show abnormalities in locomotor and cognitive behaviors compatible with nAChR deficiency and underscore the importance of this chaperone for physiology and disease associated with nAChRs.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.celrep.2017.04.008DOI Listing
April 2017

Discovery and Characterization of AMPA Receptor Modulators Selective for TARP-γ8.

J Pharmacol Exp Ther 2016 May 17;357(2):394-414. Epub 2016 Mar 17.

Janssen Research and Development, LLC, Neuroscience Therapeutic Area, San Diego, California (M.P.M., N.W., S.R., M.K.A., B.M.S., C.L., B.L., R.M.W., J.A.M., C.D., S.Y., A.D.W., N.I.C., T.W.L.); and Janssen Research and Development, a Division of Janssen Pharmaceutica NV, Neuroscience Therapeutic Area, Beerse, Belgium (L.V.D., T.S.).

Members of the α-amino-3-hydroxyl-5-methyl-4-isoxazole-propionic acid (AMPA) subtype of ionotropic glutamate receptors mediate the majority of fast synaptic transmission within the mammalian brain and spinal cord, representing attractive targets for therapeutic intervention. Here, we describe novel AMPA receptor modulators that require the presence of the accessory protein CACNG8, also known as transmembrane AMPA receptor regulatory protein γ8 (TARP-γ8). Using calcium flux, radioligand binding, and electrophysiological assays of wild-type and mutant forms of TARP-γ8, we demonstrate that these compounds possess a novel mechanism of action consistent with a partial disruption of the interaction between the TARP and the pore-forming subunit of the channel. One of the molecules, 5-[2-chloro-6-(trifluoromethoxy)phenyl]-1,3-dihydrobenzimidazol-2-one (JNJ-55511118), had excellent pharmacokinetic properties and achieved high receptor occupancy following oral administration. This molecule showed strong, dose-dependent inhibition of neurotransmission within the hippocampus, and a strong anticonvulsant effect. At high levels of receptor occupancy in rodent in vivo models, JNJ-55511118 showed a strong reduction in certain bands on electroencephalogram, transient hyperlocomotion, no motor impairment on rotarod, and a mild impairment in learning and memory. JNJ-55511118 is a novel tool for reversible AMPA receptor inhibition, particularly within the hippocampus, with potential therapeutic utility as an anticonvulsant or neuroprotectant. The existence of a molecule with this mechanism of action demonstrates the possibility of pharmacological targeting of accessory proteins, increasing the potential number of druggable targets.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1124/jpet.115.231712DOI Listing
May 2016

Brain α7 Nicotinic Acetylcholine Receptor Assembly Requires NACHO.

Neuron 2016 Mar 11;89(5):948-55. Epub 2016 Feb 11.

Neuroscience Discovery, Janssen Pharmaceutical Companies of Johnson & Johnson, 3210 Merryfield Row, San Diego, CA 92121, USA. Electronic address:

Nicotine exerts its behavioral and additive actions through a family of brain nicotinic acetylcholine receptors (nAChRs). Enhancing α7-type nAChR signaling improves symptoms in Alzheimer's disease and schizophrenia. The pharmaceutical study of α7 receptors is hampered because these receptors do not form their functional pentameric structure in cell lines, and mechanisms that underlie α7 receptor assembly in neurons are not understood. Here, a genomic screening strategy solves this long-standing puzzle and identifies NACHO, a transmembrane protein of neuronal endoplasmic reticulum that mediates assembly of α7 receptors. NACHO promotes α7 protein folding, maturation through the Golgi complex, and expression at the cell surface. Knockdown of NACHO in cultured hippocampal neurons or knockout of NACHO in mice selectively and completely disrupts α7 receptor assembly and abolishes α7 channel function. This work identifies NACHO as an essential, client-specific chaperone for nAChRs and has implications for physiology and disease associated with these widely distributed neurotransmitter receptors.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.neuron.2016.01.018DOI Listing
March 2016

Developmental origin dictates interneuron AMPA and NMDA receptor subunit composition and plasticity.

Nat Neurosci 2013 Aug 14;16(8):1032-41. Epub 2013 Jul 14.

Program in Developmental Neurobiology, Eunice Kennedy-Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland, USA.

Disrupted excitatory synapse maturation in GABAergic interneurons may promote neuropsychiatric disorders such as schizophrenia. However, establishing developmental programs for nascent synapses in GABAergic cells is confounded by their sparsity, heterogeneity and late acquisition of subtype-defining characteristics. We investigated synaptic development in mouse interneurons targeting cells by lineage from medial ganglionic eminence (MGE) or caudal ganglionic eminence (CGE) progenitors. MGE-derived interneuron synapses were dominated by GluA2-lacking AMPA-type glutamate receptors (AMPARs), with little contribution from NMDA-type receptors (NMDARs) throughout development. In contrast, CGE-derived cell synapses had large NMDAR components and used GluA2-containing AMPARs. In neonates, both MGE- and CGE-derived interneurons expressed primarily GluN2B subunit-containing NMDARs, which most CGE-derived interneurons retained into adulthood. However, MGE-derived interneuron NMDARs underwent a GluN2B-to-GluN2A switch that could be triggered acutely with repetitive synaptic activity. Our findings establish ganglionic eminence-dependent rules for early synaptic integration programs of distinct interneuron cohorts, including parvalbumin- and cholecystokinin-expressing basket cells.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/nn.3459DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4132661PMC
August 2013

mGluR5 and NMDA receptors drive the experience- and activity-dependent NMDA receptor NR2B to NR2A subunit switch.

Neuron 2011 Apr;70(2):339-51

Developmental Synaptic Plasticity Section, National Institutes of Health, Bethesda, MD 20892, USA.

In cerebral cortex there is a developmental switch from NR2B- to NR2A-containing NMDA receptors (NMDARs) driven by activity and sensory experience. This subunit switch alters NMDAR function, influences synaptic plasticity, and its dysregulation is associated with neurological disorders. However, the mechanisms driving the subunit switch are not known. Here, we show in hippocampal CA1 pyramidal neurons that the NR2B to NR2A switch driven acutely by activity requires activation of NMDARs and mGluR5, involves PLC, Ca(2+) release from IP(3)R-dependent stores, and PKC activity. In mGluR5 knockout mice the developmental NR2B-NR2A switch in CA1 is deficient. Moreover, in visual cortex of mGluR5 knockout mice, the NR2B-NR2A switch evoked in vivo by visual experience is absent. Thus, we establish that mGluR5 and NMDARs are required for the activity-dependent NR2B-NR2A switch and play a critical role in experience-dependent regulation of NMDAR subunit composition in vivo.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.neuron.2011.02.045DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3087383PMC
April 2011

TRPV1 and synaptic transmission.

Curr Pharm Biotechnol 2011 Jan;12(1):95-101

National Institute of General Medical Sciences, Bethesda, MD, 20892, USA.

Transient Receptor Potential Vanilloid Type 1 is a prominent "pain" receptor expressed in sensory afferent neurons. TRPV1 on peripheral nerve terminals detects a variety of noxious stimuli generated at sites of injury and inflammation, and in turn, drives the excitation and sensitization of C-fibers neurons. Significantly, TRPV1 is also located on the central terminals of sensory neurons projecting to the spinal cord and brainstem. These TRPV1 channels appear to stimulate the secretion of glutamate. Further, TRPV1 is expressed diffusely in the brain and there is emerging evidence for TRPV1 modulating transmission at various brain synapses. Here we discuss our current understanding of the potential roles for TRPV1 in synaptic transmission.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.2174/138920111793937925DOI Listing
January 2011

Casein kinase 2 regulates the NR2 subunit composition of synaptic NMDA receptors.

Neuron 2010 Sep;67(6):984-96

Receptor Biology Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892, USA.

N-methyl-D-aspartate (NMDA) receptors (NMDARs) play a central role in development, synaptic plasticity, and neurological disease. NMDAR subunit composition defines their biophysical properties and downstream signaling. Casein kinase 2 (CK2) phosphorylates the NR2B subunit within its PDZ-binding domain; however, the consequences for NMDAR localization and function are unclear. Here we show that CK2 phosphorylation of NR2B regulates synaptic NR2B and NR2A in response to activity. We find that CK2 phosphorylates NR2B, but not NR2A, to drive NR2B-endocytosis and remove NR2B from synapses resulting in an increase in synaptic NR2A expression. During development there is an activity-dependent switch from NR2B to NR2A at cortical synapses. We observe an increase in CK2 expression and NR2B phosphorylation over this same critical period and show that the acute activity-dependent switch in NR2 subunit composition at developing hippocampal synapses requires CK2 activity. Thus, CK2 plays a central role in determining the NR2 subunit content of synaptic NMDARs.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.neuron.2010.08.011DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2947143PMC
September 2010

Plk2 attachment to NSF induces homeostatic removal of GluA2 during chronic overexcitation.

Nat Neurosci 2010 Oct 29;13(10):1199-207. Epub 2010 Aug 29.

Department of Pharmacology, Georgetown University Medical Center, Washington, DC, USA.

Trafficking of AMPA receptors (AMPARs) is important for many forms of synaptic plasticity. However, the link between activity and resulting synaptic alterations is not fully understood. We identified a direct interaction between N-ethylmaleimide-sensitive fusion protein (NSF), an ATPase involved in membrane fusion events and stabilization of surface AMPARs, and Polo-like kinase- 2 (Plk2), an activity-inducible kinase that homeostatically decreases excitatory synapse number and strength. Plk2 disrupted the interaction of NSF with the GluA2 subunit of AMPARs, promoting extensive loss of surface GluA2 in rat hippocampal neurons, greater association of GluA2 with adaptor proteins PICK1 and GRIP1, and decreased synaptic AMPAR current. Plk2 engagement of NSF, but not Plk2 kinase activity, was required for this mechanism and occurred through a motif in the Plk2 protein that was independent of the canonical polo box interaction sites. These data reveal that heightened synaptic activity, acting through Plk2, leads to homeostatic decreases in surface AMPAR expression via the direct dissociation of NSF from GluA2.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/nn.2624DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2947592PMC
October 2010

A novel Conus snail polypeptide causes excitotoxicity by blocking desensitization of AMPA receptors.

Curr Biol 2009 Jun 28;19(11):900-8. Epub 2009 May 28.

Department of Biology, University of Utah, Salt Lake City, UT 84112-0840, USA.

Background: Ionotropic glutamate receptors (iGluRs) are glutamate-gated ion channels that mediate excitatory neurotransmission in the central nervous system. Based on both molecular and pharmacological criteria, iGluRs have been divided into two major classes, the non-NMDA class, which includes both AMPA and kainate subtypes of receptors, and the NMDA class. One evolutionarily conserved feature of iGluRs is their desensitization in the continued presence of glutamate. Thus, when in a desensitized state, iGluRs can be bound to glutamate, yet the channel remains closed. However, the relevance of desensitization to nervous system function has remained enigmatic.

Results: Here, we report the identification and characterization of a novel polypeptide (con-ikot-ikot) from the venom of a predatory marine snail Conus striatus that specifically disrupts the desensitization of AMPA receptors (AMPARs). The stoichiometry of con-ikot-ikot appears reminiscent of the proposed subunit organization of AMPARs, i.e., a dimer of dimers, suggesting that it acts as a molecular four-legged clamp that holds the AMPAR channel open. Application of con-ikot-ikot to hippocampal slices caused a large and rapid increase in resting AMPAR-mediated current leading to neuronal death.

Conclusions: Our findings provide insight into the mechanisms that regulate receptor desensitization and demonstrate that in the arms race between prey and predators, evolution has selected for a toxin that blocks AMPAR desensitization, thus revealing the fundamental importance of desensitization for regulating neural function.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.cub.2009.05.017DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2722447PMC
June 2009

General anesthetics sensitize the capsaicin receptor transient receptor potential V1.

Mol Pharmacol 2008 Nov 8;74(5):1261-8. Epub 2008 Aug 8.

Department of Pharmacology, Georgetown University, 3900 Reservoir Rd., NW, Washington DC 20007, USA.

General anesthetics (GAs) are central nervous system depressants that render patients unresponsive to external stimuli. In contrast, many of these agents are also known to stimulate peripheral sensory nerves, raising the possibility that they may exacerbate tissue inflammation. We have found that pungent GAs excite sensory neurons by directly activating the transient receptor potential (TRP) A1 ion channel. Here, we show that GAs also sensitize the capsaicin receptor TRPV1, a key ion channel expressed in nociceptive neurons. Clinically relevant concentrations of isoflurane, sevoflurane, enflurane, and desflurane sensitize TRPV1 to capsaicin and protons and reduce the threshold for heat activation. Furthermore, isoflurane directly activates TRPV1 after stimulation of protein kinase C. Likewise, isoflurane excites TRPV1 and sensory neurons during concomitant application of bradykinin, a key inflammatory mediator formed during tissue injury. Thus, GAs can enhance the activation of TRPV1 that occurs during surgically induced tissue damage. These results support the hypothesis that some GAs, through direct actions at TRP channels, increase postsurgical pain and inflammation.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1124/mol.108.049684DOI Listing
November 2008

General anesthetics activate a nociceptive ion channel to enhance pain and inflammation.

Proc Natl Acad Sci U S A 2008 Jun 23;105(25):8784-9. Epub 2008 Jun 23.

Departments of Pharmacology and Physiology and Biophysics, Georgetown University, 3900 Reservoir Road, NW, Washington, DC 20007, USA.

General anesthetics (GAs) have transformed surgery through their actions to depress the central nervous system and blunt the perception of surgical insults. Counterintuitively, many of these agents activate peripheral nociceptive neurons. However, the underlying mechanisms and significance of these effects have not been explored. Here, we show that clinical concentrations of noxious i.v. and inhalation GAs excite sensory neurons by selectively activating TRPA1, a key ion channel in the pain pathway. Further, these GAs induce pain-related responses in mice that are abolished in TRPA1-null animals. Significantly, TRPA1-dependent neurogenic inflammation is greater in mice anesthetized with pungent compared with nonpungent anesthetics. Thus, our results show that TRPA1 is essential for sensing noxious GAs. The pronociceptive effects of GAs combined with surgical tissue damage could lead to a paradoxical increase in postoperative pain and inflammation.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1073/pnas.0711038105DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2438393PMC
June 2008

Voltage is a partial activator of rat thermosensitive TRP channels.

J Physiol 2007 Dec 11;585(Pt 2):469-82. Epub 2007 Oct 11.

Department of Pharmacology, Georgetown University, MedDent SW401, 3900 Reservoir Rd Washington, DC 20007, USA.

TRPV1 and TRPM8 are sensory nerve ion channels activated by heating and cooling, respectively. A variety of physical and chemical stimuli activate these receptors in a synergistic manner but the underlying mechanisms are unclear. Both channels are voltage sensitive, and temperature and ligands modulate this voltage dependence. Thus, a voltage-sensing mechanism has become an attractive model to explain the generalized gating of these and other thermo-sensitive TRP channels. We show here using whole-cell and single channel measurements that voltage produces only a partial activation of TRPV1 and TRPM8. At room temperature (20-25 degrees C) membrane depolarization evokes responses that saturate at approximately 50-60% of the maximum open probability. Furthermore, high concentrations of capsaicin (10 microm), resiniferatoxin (5 microm) and menthol (6 mm) reveal voltage-independent gating. Similarly, other modes of TRPV1 regulation including heat, protein kinase C-dependent phosphorylation, and protons enhance both the efficacy and sensitivity of voltage activation. In contrast, the TRPV1 antagonist capsazepine produces the opposite effects. These data can be explained by an allosteric model in which voltage, temperature, agonists and inverse agonists are independently coupled, either positively or negatively, to channel gating. Thus, voltage acts separately but in concert with other stimuli to regulate channel activation, and, therefore, a voltage-sensitive mechanism is unlikely to represent a final, gating mechanism for these channels.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1113/jphysiol.2007.144287DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2375500PMC
December 2007

Long-lasting NMDA receptor-mediated EPSCs in mouse striatal medium spiny neurons.

J Neurophysiol 2007 Nov 5;98(5):2693-704. Epub 2007 Sep 5.

Department of Physiology and Biophysics, Georgetown University School of Medicine, Washington, DC 20007, USA.

Excitatory postsynaptic currents (EPSCs) from dorsolateral medium spiny neurons (MSNs) were recorded in cortico-striatal slice preparations from postnatal day 6-8 (P6-8) and >P12 wild-type mice and mice that were lacking either the NR2A or the NR2C subunit of the N-methyl-D-aspartate (NMDA) receptor. EPSCs were elicited by stimulation of the excitatory afferents and the NMDA and non-NMDA receptor-mediated components were pharmacologically isolated. The ratio of these components decreased with development and was significantly reduced only between age-matched +/+ and NR2A -/- neurons. In many MSNs, the NMDA-EPSC decay was characterized by the presence of a slow exponential component with a time constant lasting >1 s regardless of genotype or age. In the NR2A -/-, no developmental increase in the decay time (Tw) of the NMDA-EPSCs was observed although it was almost twofold longer than in +/+ MSNs. NR1/NR2B antagonists were ineffective in reducing the slow NMDA-EPSCs at all ages. Input-output studies revealed differences in stimulation threshold sensitivity of MSNs based on stimulus location. High-threshold responders were preferentially identified with stimulation from intracortical locations that produced considerably faster NMDA-EPSCs, whereas low-threshold responders were mainly elicited with stimulation more proximal to the striatum and exhibited slower NMDA-EPSCs. A low-affinity competitive antagonist of NMDA receptors failed to alter the decay of NMDA-EPSCs elicited from either location, suggesting that glutamate spillover is not responsible for the long-lasting NMDA-EPSCs. Our data are consistent with the expression of a unique NMDA receptor complex in MSNs with very slow deactivation kinetics.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1152/jn.00462.2007DOI Listing
November 2007

TRPV1 is a novel target for omega-3 polyunsaturated fatty acids.

J Physiol 2007 Jan 12;578(Pt 2):397-411. Epub 2006 Oct 12.

Department of Pharmacology, Georgetown University, Washington, DC 20007, USA.

Omega-3 (n-3) fatty acids are essential for proper neuronal function, and they possess prominent analgesic properties, yet their underlying signalling mechanisms are unclear. Here we show that n-3 fatty acids interact directly with TRPV1, an ion channel expressed in nociceptive neurones and brain. These fatty acids activate TRPV1 in a phosphorylation-dependent manner, enhance responses to extracellular protons, and displace binding of the ultrapotent TRPV1 ligand [3H]resiniferatoxin. In contrast to their agonistic properties, n-3 fatty acids competitively inhibit the responses of vanilloid agonists. These actions occur in mammalian cells in the physiological concentration range of 1-10 mum. Significantly, docosahexaenoic acid exhibits the greatest efficacy as an agonist, whereas eicosapentaenoic acid and linolenic acid are markedly more effective inhibitors. Similarly, eicosapentaenoic acid but not docosahexaenoic acid profoundly reduces capsaicin-evoked pain-related behaviour in mice. These effects are independent of alterations in membrane elasticity because the micelle-forming detergent Triton X-100 only minimally affects TRPV1 properties. Thus, n-3 fatty acids differentially regulate TRPV1 and this form of signalling may contribute to their biological effects. Further, these results suggest that dietary supplementation with selective n-3 fatty acids would be most beneficial for the treatment of pain.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1113/jphysiol.2006.121988DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2075157PMC
January 2007