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David Julius - One of the best experts on this subject based on the ideXlab platform.
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single particle electron cryo microscopy of a mammalian Ion Channel
Current Opinion in Structural Biology, 2014Co-Authors: Maofu Liao, David Julius, Yifan ChengAbstract:The transient receptor potential (TRP) Ion Channel Family is large and functIonally diverse, second only to potassium Channels. Despite their prominence within the animal kingdom, TRP Channels have resisted crystallizatIon and structural determinatIon for many years. This barrier was recently broken when the three-dimensIonal structure of the vanilloid receptor 1 (TRPV1) was determined by single particle electron cryo-microscopy (cryo-EM). Moreover, this is the first example in which the near atomic resolutIon structure of an integral membrane protein was elucidated by this technique and in a manner not requiring crystals, demonstrating the transformative power of single particle cryo-EM for revealing high-resolutIon structures of integral membrane proteins, particularly those of mammalian origin. Here we summarize technical advances, in both biochemistry and cryo-EM, that led to this major breakthrough.
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TRP Channels and Pain
Annual review of cell and developmental biology, 2013Co-Authors: David JuliusAbstract:NociceptIon is the process whereby primary afferent nerve fibers of the somatosensory system detect noxious stimuli. Pungent irritants from pepper, mint, and mustard plants have served as powerful pharmacological tools for identifying molecules and mechanisms underlying this initial step of pain sensatIon. These natural products have revealed three members of the transient receptor potential (TRP) Ion Channel Family—TRPV1, TRPM8, and TRPA1—as molecular detectors of thermal and chemical stimuli that activate sensory neurons to produce acute or persistent pain. Analysis of TRP Channel functIon and expressIon has validated the existence of nociceptors as a specialized group of somatosensory neurons devoted to the detectIon of noxious stimuli. These studies are also providing insight into the coding logic of nociceptIon and how specificatIon of nociceptor subtypes underlies behavioral discriminatIon of noxious thermal, chemical, and mechanical stimuli. Biophysical and pharmacological characterizatIon of these...
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Receptor-targeting mechanisms of pain-causing toxins: How ow?
Toxicon : official journal of the International Society on Toxinology, 2012Co-Authors: Christopher J. Bohlen, David JuliusAbstract:Venoms often target vital processes to cause paralysis or death, but many types of venom also elicit notoriously intense pain. While these pain-producing effects can result as a byproduct of generalized tissue trauma, there are now multiple examples of venom-derived toxins that target somatosensory nerve terminals in order to activate nociceptive (pain-sensing) neural pathways. Intriguingly, investigatIon of the venom components that are responsible for evoking pain has revealed novel roles and/or configuratIons of well-studied toxin motifs. This review serves to highlight pain-producing toxins that target the capsaicin receptor, TRPV1, or members of the acid-sensing Ion Channel Family, and to discuss the utility of venom-derived multivalent and multimeric complexes.
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mustard oils and cannabinoids excite sensory nerve fibres through the trp Channel anktm1
Nature, 2004Co-Authors: Sveneric Jordt, Diana M Bautista, Huaihu Chuang, David D Mckemy, Peter M Zygmunt, Edward D Hogestatt, Ian D Meng, David JuliusAbstract:Wasabi, horseradish and mustard owe their pungency to isothiocyanate compounds. Topical applicatIon of mustard oil (allyl isothiocyanate) to the skin activates underlying sensory nerve endings, thereby producing pain, inflammatIon and robust hypersensitivity to thermal and mechanical stimuli1,2. Despite their widespread use in both the kitchen and the laboratory, the molecular mechanism through which isothiocyanates mediate their effects remains unknown. Here we show that mustard oil depolarizes a subpopulatIon of primary sensory neurons that are also activated by capsaicin, the pungent ingredient in chilli peppers, and by Δ9-tetrahydrocannabinol (THC), the psychoactive component of marijuana. Both allyl isothiocyanate and THC mediate their excitatory effects by activating ANKTM1, a member of the TRP Ion Channel Family recently implicated in the detectIon of noxious cold3,4. These findings identify a cellular and molecular target for the pungent actIon of mustard oils and support an emerging role for TRP Channels as Ionotropic cannabinoid receptors5,6,7,8.
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primary structure and functIonal expressIon of the 5ht3 receptor a serotonin gated Ion Channel
Science, 1991Co-Authors: Andres V Maricq, Andrew S Peterson, Anthony J Brake, Richard M Myers, David JuliusAbstract:The neurotransmitter serotonin (5HT) activates a variety of second messenger signaling systems and through them indirectly regulates the functIon of Ion Channels. Serotonin also activates Ion Channels directly, suggesting that it may also mediate rapid, excitatory responses. A complementary DNA clone containing the coding sequence of one of these rapidly responding Channels, a 5HT3 subtype of the serotonin receptor, has been isolated by screening a neuroblastoma expressIon library for functIonal expressIon of serotonin-gated currents in Xenopus oocytes. The predicted protein product has many of the features shared by other members of the ligand-gated Ion Channel Family. The pharmacological and electrophysiological characteristics of the cloned receptor are largely consistent with the properties of native 5HT3 receptors. Messenger RNA encoding this receptor is found in the brain, spinal cord, and heart. This receptor defines a new class of excitatory ligand-gated Channels.
David E Clapham - One of the best experts on this subject based on the ideXlab platform.
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internatIonal unIon of basic and clinical pharmacology lxxvi current progress in the mammalian trp Ion Channel Family
Pharmacological Reviews, 2010Co-Authors: Tara Beth Sweet, David E ClaphamAbstract:Transient receptor potential (TRP) Channels are a large Family of Ion Channel proteins, surpassed in number in mammals only by voltage-gated potassium Channels. TRP Channels are activated and regulated through strikingly diverse mechanisms, making them suitable candidates for cellular sensors. They respond to environmental stimuli such as temperature, pH, osmolarity, pheromones, taste, and plant compounds, and intracellular stimuli such as Ca2+ and phosphatidylinositol signal transductIon pathways. However, it is still largely unknown how TRP Channels are activated in vivo. Despite the uncertainties, emerging evidence using TRP Channel knockout mice indicates that these Channels have broad functIon in physiology. Here we review the recent progress on the physiology, pharmacology and pathophysiological functIon of mammalian TRP Channels.
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the trpm7 Ion Channel functIons in cholinergic synaptic vesicles and affects transmitter release
Neuron, 2006Co-Authors: Grigory Krapivinsky, David E Clapham, Susan M. Cibulsky, Sumiko Mochida, Luba KrapivinskyAbstract:A longstanding hypothesis is that Ion Channels are present in the membranes of synaptic vesicles and might affect neurotransmitter release. Here we demonstrate that TRPM7, a member of the transient receptor potential (TRP) Ion Channel Family, resides in the membrane of synaptic vesicles of sympathetic neurons, forms molecular complexes with the synaptic vesicle proteins synapsin I and synaptotagmin I, and directly interacts with synaptic vesicular snapin. In sympathetic neurons, changes in TRPM7 levels and Channel activity alter acetylcholine release, as measured by EPSP amplitudes and decay times in postsynaptic neurons. TRPM7 affects EPSP quantal size, an intrinsic property of synaptic vesicle release. Targeted peptide interference of TRPM7's interactIon with snapin affects the amplitudes and kinetics of postsynaptic EPSPs. Thus, vesicular TRPM7 Channel activity is critical to neurotransmitter release in sympathetic neurons.
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the trp Ion Channel Family
Nature Reviews Neuroscience, 2001Co-Authors: Loren W Runnels, David E Clapham, Carsten StrubingAbstract:Mammalian homologues of the Drosophila transient receptor potential (TRP) Channel gene encode a Family of at least 20 Ion Channel proteins. They are widely distributed in mammalian tissues, but their specific physiological functIons are largely unknown. A common theme that links the TRP Channels is their activatIon or modulatIon by phosphatidylinositol signal transductIon pathways. The Channel subunits have six transmembrane domains that most probably assemble into tetramers to form non-selective catIonic Channels, which allow for the influx of calcium Ions into cells. Three subgroups comprise the TRP Channel Family; the best understood of these mediates responses to painful stimuli. Other proposed functIons include repletIon of intracellular calcium stores, receptor-mediated excitatIon and modulatIon of the cell cycle.
Lori L Isom - One of the best experts on this subject based on the ideXlab platform.
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Sodium Channel β1 Subunits: Overachievers of the Ion Channel Family
Biophysical Journal, 2014Co-Authors: Lori L IsomAbstract:Voltage gated Na+ Channels in mammals contain a pore-forming alpha subunit and one or more beta subunits. There are five mammalian beta subunits in total: beta1, beta1B, beta2, beta3, and beta4, encoded by four genes: SCN1B-SCN4B. With the exceptIon of the SCN1B splice variant, beta1B, the subunits are type I topology transmembrane proteins. In contrast, beta1B lacks a transmembrane domain and is a secreted protein. A growing body of work shows that VGSC beta subunits are multifunctIonal. While they do not form the Ion Channel pore, beta subunits alter gating, voltage-dependence, and kinetics of VGSC alpha subunits and thus regulate cellular excitability in vivo. In additIon to their roles in Channel modulatIon, beta subunits are members of the immunoglobulin superFamily of cell adhesIon molecules and regulate cell adhesIon and migratIon. Beta subunits are also substrates for sequential proteolytic cleavage by secretases. An example of the multifunctIonal nature of beta subunits is beta1, encoded by SCN1B, that plays a critical role in neuronal migratIon and pathfinding during brain development, and whose functIon is dependent on Na+ current and gamma-secretase activity. FunctIonal deletIon of SCN1B results in Dravet Syndrome, a severe and intractable pediatric epileptic encephalopathy. Beta subunits are emerging as key players in a wide variety of pathophysiologies, including epilepsy, cardiac arrhythmia, multiple sclerosis, Huntington's disease, neuropsychiatric disorders, neuropathic and inflammatory pain, and cancer. Beta subunits mediate multiple signaling pathways on different timescales, regulating electrical excitability, adhesIon, migratIon, pathfinding, and transcriptIon. Importantly, some beta subunit functIons may operate independent of alpha subunits. Thus, beta subunits perform critical roles during development and disease. As such, they may prove useful in disease diagnosis and therapy.
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na Channel β subunits overachievers of the Ion Channel Family
Frontiers in Pharmacology, 2011Co-Authors: William J. Brackenbury, Lori L IsomAbstract:Voltage gated Na+ Channels (VGSCs) in mammals contain a pore-forming α subunit and one or more β subunits. There are five mammalian β subunits in total: β1, β1B, β2, β3, and β4, encoded by four genes: SCN1B-SCN4B. With the exceptIon of the SCN1B splice variant, β1B, the β subunits are type I topology transmembrane proteins. In contrast, β1B lacks a transmembrane domain and is a secreted protein. A growing body of work shows that VGSC β subunits are multifunctIonal. While they do not form the Ion Channel pore, β subunits alter gating, voltage-dependence, and kinetics of VGSC α subunits and thus regulate cellular excitability in vivo. In additIon to their roles in Channel modulatIon, β subunits are members of the immunoglobulin (Ig) superFamily of cell adhesIon molecules (CAMs) and regulate cell adhesIon and migratIon. β subunits are also substrates for sequential proteolytic cleavage by secretases. An example of the multifunctIonal nature of β subunits is β1, encoded by SCN1B, that plays a critical role in neuronal migratIon and pathfinding during brain development, and whose functIon is dependent on Na+ current and γ-secretase activity. FunctIonal deletIon of SCN1B results in Dravet Syndrome, a severe and intractable pediatric epileptic encephalopathy. β subunits are emerging as key players in a wide variety of pathophysiologies, including epilepsy, cardiac arrhythmia, multiple sclerosis, Huntington’s disease, neuropsychiatric disorders, neuropathic and inflammatory pain, and cancer. β subunits mediate multiple signaling pathways on different timescales, regulating electrical excitability, adhesIon, migratIon, pathfinding, and transcriptIon. Importantly, some β subunit functIons may operate independent of α subunits. Thus, β subunits perform critical roles during development and disease. As such, they may prove useful in disease diagnosis and therapy.
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Na+ Channel β Subunits: Overachievers of the Ion Channel Family
Frontiers in pharmacology, 2011Co-Authors: William J. Brackenbury, Lori L IsomAbstract:Voltage gated Na+ Channels (VGSCs) in mammals contain a pore-forming α subunit and one or more β subunits. There are five mammalian β subunits in total: β1, β1B, β2, β3, and β4, encoded by four genes: SCN1B-SCN4B. With the exceptIon of the SCN1B splice variant, β1B, the β subunits are type I topology transmembrane proteins. In contrast, β1B lacks a transmembrane domain and is a secreted protein. A growing body of work shows that VGSC β subunits are multifunctIonal. While they do not form the Ion Channel pore, β subunits alter gating, voltage-dependence, and kinetics of VGSC α subunits and thus regulate cellular excitability in vivo. In additIon to their roles in Channel modulatIon, β subunits are members of the immunoglobulin (Ig) superFamily of cell adhesIon molecules (CAMs) and regulate cell adhesIon and migratIon. β subunits are also substrates for sequential proteolytic cleavage by secretases. An example of the multifunctIonal nature of β subunits is β1, encoded by SCN1B, that plays a critical role in neuronal migratIon and pathfinding during brain development, and whose functIon is dependent on Na+ current and γ-secretase activity. FunctIonal deletIon of SCN1B results in Dravet Syndrome, a severe and intractable pediatric epileptic encephalopathy. β subunits are emerging as key players in a wide variety of pathophysiologies, including epilepsy, cardiac arrhythmia, multiple sclerosis, Huntington’s disease, neuropsychiatric disorders, neuropathic and inflammatory pain, and cancer. β subunits mediate multiple signaling pathways on different timescales, regulating electrical excitability, adhesIon, migratIon, pathfinding, and transcriptIon. Importantly, some β subunit functIons may operate independent of α subunits. Thus, β subunits perform critical roles during development and disease. As such, they may prove useful in disease diagnosis and therapy.
Joseph W. Lynch - One of the best experts on this subject based on the ideXlab platform.
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The relative orientatIon of the TM3 and TM4 domains varies between α1 and α3 glycine receptors.
ACS chemical neuroscience, 2012Co-Authors: Lu Han, Sahil Talwar, Joseph W. LynchAbstract:Glycine receptors (GlyRs) are anIon-conducting members of the pentameric ligand-gated Ion Channel Family. We previously showed that the dramatic difference in glycine efficacies of α1 and α3 GlyRs is largely attributable to their nonconserved TM4 domains. Because mutatIon of individual nonconserved TM4 residues had little effect, we concluded that the efficacy difference was a distributed effect of all nonconserved TM4 residues. We therefore hypothesized that the TM4 domains of α1 and α3 GlyRs differ in structure, membrane orientatIon, and/or molecular dynamic properties. Here we employed voltage-clamp fluorometry to test whether their TM4 domains interact differently with their respective TM3 domains. We found a rhodamine fluorophore covalently attached to a homologous TM4 residue in each receptor interacts differentially with a conserved TM3 residue. We conclude that the α1 and α3 GlyR TM4 domains are orientated differently relative to their TM3 domains. This may underlie their differential ability to influence glycine efficacy.
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comparative surface accessibility of a pore lining threonine residue t6 in the glycine and gaba a receptors
Biophysical Journal, 2003Co-Authors: Joseph W. Lynch, Qiang Shan, Justine L HaddrillAbstract:The substituted cysteine accessibility method was used to probe the surface exposure of a pore-lining threonine residue (T6’) common to both the glycine receptor (GlyR) and GABAA receptor (GABAAR) chloride Channels. This residue lies close to the Channel activatIon gate, the Ionic selectivity filter and the main pore blocker binding site. Recent studies have suggested that the GlyRs and GABAARs have divergent open state pore structures at the 6’ positIon. When both the human a1T6’C homomeric GlyR and the rat a1T6’Cb1T6’C heteromeric GABAAR were expressed in HEK293 cells, their 6’ residue surface accessibilities differed significantly in the closed state. However, when a soluble cysteine-modifying compound was applied in the presence of saturating agonist concentratIons, both receptors were locked into the open state. This actIon was not induced by oxidising agents in either receptor. These results provide evidence for a conserved pore opening mechanism in anIon-selective members of the ligand-gated Ion Channel Family. The results also indicate that the GABAAR pore structure at the 6’ level may vary between different expressIon systems.
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comparative surface accessibility of a pore lining threonine residue t6 in the glycine and gabaa receptors
Journal of Biological Chemistry, 2002Co-Authors: Qiang Shan, Justine L Haddrill, Joseph W. LynchAbstract:The substituted cysteine accessibility method was used to probe the surface exposure of a pore-lining threonine residue (T6') common to both the glycine receptor (GlyR) and gamma-aminobutyric acid, type A receptor (GABA(A)R) chloride Channels. This residue lies close to the Channel activatIon gate, the Ionic selectivity filter, and the main pore blocker binding site. Despite their high amino acid sequence homologies and common role in conducting chloride Ions, recent studies have suggested that the GlyRs and GABA(A)Rs have divergent open state pore structures at the 6' positIon. When both the human alpha1(T6'C) homomeric GlyR and the rat alpha1(T6'C)beta1(T6'C) heteromeric GABA(A)R were expressed in human embryonic kidney 293 cells, their 6' residue surface accessibilities differed significantly in the closed state. However, when a soluble cysteine-modifying compound was applied in the presence of saturating agonist concentratIons, both receptors were locked into the open state. This actIon was not induced by oxidizing agents in either receptor. These results provide evidence for a conserved pore opening mechanism in anIon-selective members of the ligand-gated Ion Channel Family. The results also indicate that the GABA(A)R pore structure at the 6' level may vary between different expressIon systems.
Justine L Haddrill - One of the best experts on this subject based on the ideXlab platform.
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comparative surface accessibility of a pore lining threonine residue t6 in the glycine and gaba a receptors
Biophysical Journal, 2003Co-Authors: Joseph W. Lynch, Qiang Shan, Justine L HaddrillAbstract:The substituted cysteine accessibility method was used to probe the surface exposure of a pore-lining threonine residue (T6’) common to both the glycine receptor (GlyR) and GABAA receptor (GABAAR) chloride Channels. This residue lies close to the Channel activatIon gate, the Ionic selectivity filter and the main pore blocker binding site. Recent studies have suggested that the GlyRs and GABAARs have divergent open state pore structures at the 6’ positIon. When both the human a1T6’C homomeric GlyR and the rat a1T6’Cb1T6’C heteromeric GABAAR were expressed in HEK293 cells, their 6’ residue surface accessibilities differed significantly in the closed state. However, when a soluble cysteine-modifying compound was applied in the presence of saturating agonist concentratIons, both receptors were locked into the open state. This actIon was not induced by oxidising agents in either receptor. These results provide evidence for a conserved pore opening mechanism in anIon-selective members of the ligand-gated Ion Channel Family. The results also indicate that the GABAAR pore structure at the 6’ level may vary between different expressIon systems.
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comparative surface accessibility of a pore lining threonine residue t6 in the glycine and gabaa receptors
Journal of Biological Chemistry, 2002Co-Authors: Qiang Shan, Justine L Haddrill, Joseph W. LynchAbstract:The substituted cysteine accessibility method was used to probe the surface exposure of a pore-lining threonine residue (T6') common to both the glycine receptor (GlyR) and gamma-aminobutyric acid, type A receptor (GABA(A)R) chloride Channels. This residue lies close to the Channel activatIon gate, the Ionic selectivity filter, and the main pore blocker binding site. Despite their high amino acid sequence homologies and common role in conducting chloride Ions, recent studies have suggested that the GlyRs and GABA(A)Rs have divergent open state pore structures at the 6' positIon. When both the human alpha1(T6'C) homomeric GlyR and the rat alpha1(T6'C)beta1(T6'C) heteromeric GABA(A)R were expressed in human embryonic kidney 293 cells, their 6' residue surface accessibilities differed significantly in the closed state. However, when a soluble cysteine-modifying compound was applied in the presence of saturating agonist concentratIons, both receptors were locked into the open state. This actIon was not induced by oxidizing agents in either receptor. These results provide evidence for a conserved pore opening mechanism in anIon-selective members of the ligand-gated Ion Channel Family. The results also indicate that the GABA(A)R pore structure at the 6' level may vary between different expressIon systems.
