Interaction of α9α10 Nicotinic Receptors With Peptides and Proteins From Animal Venoms

Unlike most neuronal nicotinic acetylcholine receptor (nAChR) subunits, α7, α9, and α10 subunits are able to form functional homo- or heteromeric receptors without any β subunits. While the α7 subtype is widely distributed in the mammalian brain and several peripheral tissues, α9 and α9α10 nAChRs are mainly found in the cochlea and immune cells. α-Conotoxins that specifically block the α9α10 receptor showed anti-nociceptive and anti-hyperalgesic effects in animal models. Hence, this subtype is considered a drug target for analgesics. In contrast to the α9α10-selective α-conotoxins, the three-finger toxin α-bungarotoxin inhibits muscle-type and α7 nAChRs in addition to α9α10 nAChRs. However, the selectivity of α-neurotoxins at the α9α10 subtype was less intensively investigated. Here, we compared the potencies of α-conotoxins and α-neurotoxins at the human α9α10 nAChR by two-electrode voltage clamp analysis upon expression in Xenopus oocytes. In addition, we analyzed effects of several α9α10-selective α-conotoxins on mouse granulocytes from bone marrow to identify possible physiological functions of the α9α10 nAChR subtype in these cells. The α-conotoxin-induced IL-10 release was measured upon LPS-stimulation. We found that α-conotoxins RgIA, PeIA, and Vc1.1 enhance the IL-10 expression in granulocytes which might explain the known anti-inflammatory and associated analgesic activities of α9α10-selective α-conotoxins. Furthermore, we show that two long-chain α-neurotoxins from the cobra Naja melanoleuca venom that were earlier shown to bind to muscle-type and α7 nAChRs, also inhibit the α9α10 subtype at nanomolar concentrations with one of them showing a significantly slower dissociation from this receptor than α-bungarotoxin.

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αD-Conotoxins in Species of the Eastern Pacific: The Case of Conus princeps from Mexico

Toxins ◽

10.3390/toxins11070405 ◽

2019 ◽

Vol 11 (7) ◽

pp. 405 ◽

Cited By ~ 1

Author(s):

Arisaí C. Hernández-Sámano ◽

Andrés Falcón ◽

Fernando Zamudio ◽

César V.F. Batista ◽

Jesús Emilio Michel-Morfín ◽

...

Keyword(s):

Disulfide Bonds ◽

Biological Activities ◽

Induced Response ◽

Xenopus Laevis Oocytes ◽

Average Mass ◽

Rp Hplc ◽

C Terminus ◽

Nachr Subtype ◽

Electrode Voltage ◽

Α7 Nachrs

Conus snails produce venoms containing numerous peptides such as the α-conotoxins (α-CTXs), which are well-known nicotinic acetylcholine receptor (nAChR) antagonists. Thirty-eight chromatographic fractions from Conus princeps venom extract were isolated by RP-HPLC. The biological activities of 37 fractions (0.07 µg/µL) were assayed by two-electrode voltage clamp on human α7 nAChRs expressed in Xenopus laevis oocytes. Fractions F7 and F16 notably inhibited the response elicited by acetylcholine by 52.7 ± 15.2% and 59.6 ± 2.5%, respectively. Fraction F7 was purified, and an active peptide (F7-3) was isolated. Using a combination of Edman degradation, mass spectrometry, and RNASeq, we determined the sequence of peptide F7-3: AVKKTCIRSTOGSNWGRCCLTKMCHTLCCARSDCTCVYRSGKGHGCSCTS, with one hydroxyproline (O) and a free C-terminus. The average mass of this peptide, 10,735.54 Da, indicates that it is a homodimer of identical subunits, with 10 disulfide bonds in total. This peptide is clearly similar to αD-CTXs from species of the Indo-Pacific. Therefore, we called it αD-PiXXA. This toxin slowly and reversibly inhibited the ACh-induced response of the hα7 nAChR subtype, with an IC50 of 6.2 μM, and it does not affect the hα3β2 subtype at 6.5 μM.

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Modeling temperature- and Cav3 subtype-dependent alterations in T-type calcium channel mediated burst firing

Molecular Brain ◽

10.1186/s13041-021-00813-7 ◽

2021 ◽

Vol 14 (1) ◽

Author(s):

Fernando R. Fernandez ◽

Mircea C. Iftinca ◽

Gerald W. Zamponi ◽

Ray W. Turner

Keyword(s):

Calcium Channel ◽

Neuronal Excitability ◽

Neuronal Firing ◽

Mammalian Brain ◽

Peripheral Tissues ◽

Window Current ◽

Modeling Data ◽

The Brain ◽

Firing Neuron ◽

Cav3 Channel

AbstractT-type calcium channels are important regulators of neuronal excitability. The mammalian brain expresses three T-type channel isoforms (Cav3.1, Cav3.2 and Cav3.3) with distinct biophysical properties that are critically regulated by temperature. Here, we test the effects of how temperature affects spike output in a reduced firing neuron model expressing specific Cav3 channel isoforms. The modeling data revealed only a minimal effect on baseline spontaneous firing near rest, but a dramatic increase in rebound burst discharge frequency for Cav3.1 compared to Cav3.2 or Cav3.3 due to differences in window current or activation/recovery time constants. The reduced response by Cav3.2 could optimize its activity where it is expressed in peripheral tissues more subject to temperature variations than Cav3.1 or Cav3.3 channels expressed prominently in the brain. These tests thus reveal that aspects of neuronal firing behavior are critically dependent on both temperature and T-type calcium channel subtype.

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Functional Characterization of the Oxantel-Sensitive Acetylcholine Receptor from Trichuris muris

Pharmaceuticals ◽

10.3390/ph14070698 ◽

2021 ◽

Vol 14 (7) ◽

pp. 698

Author(s):

Tina V. A. Hansen ◽

Richard K. Grencis ◽

Mohamed Issouf ◽

Cédric Neveu ◽

Claude L. Charvet

Keyword(s):

Single Dose ◽

Mouse Model ◽

Xenopus Laevis ◽

Acetylcholine Receptor ◽

Drug Target ◽

Functional Characterization ◽

Xenopus Laevis Oocytes ◽

Trichuris Muris ◽

Electrode Voltage

The human whipworm, Trichuris trichiura, is estimated to infect 289.6 million people globally. Control of human trichuriasis is a particular challenge, as most anthelmintics have a limited single-dose efficacy, with the striking exception of the narrow-spectrum anthelmintic, oxantel. We recently identified a novel ACR-16-like subunit from the pig whipworm, T. suis which gave rise to a functional acetylcholine receptor (nAChR) preferentially activated by oxantel. However, there is no ion channel described in the mouse model parasite T. muris so far. Here, we have identified the ACR-16-like and ACR-19 subunits from T. muris, and performed the functional characterization of the receptors in Xenopus laevis oocytes using two-electrode voltage-clamp electrophysiology. We found that the ACR-16-like subunit from T. muris formed a homomeric receptor gated by acetylcholine whereas the ACR-19 failed to create a functional channel. The subsequent pharmacological analysis of the Tmu-ACR-16-like receptor revealed that acetylcholine and oxantel were equally potent. The Tmu-ACR-16-like was more responsive to the toxic agonist epibatidine, but insensitive to pyrantel, in contrast to the Tsu-ACR-16-like receptor. These findings confirm that the ACR-16-like nAChR from Trichuris spp. is a preferential drug target for oxantel, and highlights the pharmacological difference between Trichuris species.

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Nicotinic Receptors and the Treatment of Attentional and Cognitive Deficits in Neuropsychiatric Disorders: Focus on the α7 Nicotinic Acetylcholine Receptor as a Promising Drug Target for Schizophrenia

Central Nervous System Agents in Medicinal Chemistry ◽

10.2174/187152407783220797 ◽

2007 ◽

Vol 7 (4) ◽

pp. 269-288 ◽

Cited By ~ 6

Author(s):

Christian Chiamulera ◽

Guido Fumagalli

Keyword(s):

Acetylcholine Receptor ◽

Nicotinic Acetylcholine Receptor ◽

Cognitive Deficits ◽

Drug Target ◽

Nicotinic Receptors ◽

Neuropsychiatric Disorders ◽

Nicotinic Acetylcholine

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Determining the Bioenergetic Capacity for Fatty Acid Oxidation in the Mammalian Nervous System

Molecular and Cellular Biology ◽

10.1128/mcb.00037-20 ◽

2020 ◽

Vol 40 (10) ◽

Cited By ~ 2

Author(s):

Cory J. White ◽

Jieun Lee ◽

Joseph Choi ◽

Tiffany Chu ◽

Susanna Scafidi ◽

...

Keyword(s):

Fatty Acids ◽

Nervous System ◽

Fatty Acid ◽

Conditional Knockout ◽

Mammalian Brain ◽

Metabolic State ◽

Peripheral Tissues ◽

Mitochondrial Fatty Acid ◽

The Brain ◽

Long Chain

ABSTRACT The metabolic state of the brain can greatly impact neurologic function. Evidence of this includes the therapeutic benefit of a ketogenic diet in neurologic diseases, including epilepsy. However, brain lipid bioenergetics remain largely uncharacterized. The existence, capacity, and relevance of mitochondrial fatty acid β-oxidation (FAO) in the brain are highly controversial, with few genetic tools available to evaluate the question. We have provided evidence for the capacity of brain FAO using a pan-brain-specific conditional knockout (KO) mouse incapable of FAO due to the loss of carnitine palmitoyltransferase 2, the product of an obligate gene for FAO (CPT2B−/−). Loss of central nervous system (CNS) FAO did not result in gross neuroanatomical changes or systemic differences in metabolism. Loss of CPT2 in the brain did not result in robustly impaired behavior. We demonstrate by unbiased and targeted metabolomics that the mammalian brain oxidizes a substantial quantity of long-chain fatty acids in vitro and in vivo. Loss of CNS FAO results in robust accumulation of long-chain acylcarnitines in the brain, suggesting that the mammalian brain mobilizes fatty acids for their oxidation, irrespective of diet or metabolic state. Together, these data demonstrate that the mammalian brain oxidizes fatty acids under normal circumstances with little influence from or on peripheral tissues.

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Chapter 7: Nicotinic receptors in mammalian brain: localization and relation to cholinergic innervation

Cholinergic Function and Dysfunction - Progress in Brain Research ◽

10.1016/s0079-6123(08)62383-3 ◽

1993 ◽

pp. 77-83 ◽

Cited By ~ 52

Author(s):

Paul B.S. Clarke

Keyword(s):

Nicotinic Receptors ◽

Cholinergic Innervation ◽

Mammalian Brain ◽

Brain Localization

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Receptor binding interactions of the angiotensin II antagonist, 125I-[sarcosine1,leucine8]angiotensin II, with mammalian brain and peripheral tissues

European Journal of Pharmacology ◽

10.1016/0014-2999(80)90003-5 ◽

1980 ◽

Vol 67 (1) ◽

pp. 11-25 ◽

Cited By ~ 39

Author(s):

James P. Bennett ◽

Solomon H. Snyder

Keyword(s):

Angiotensin Ii ◽

Receptor Binding ◽

Mammalian Brain ◽

Binding Interactions ◽

Peripheral Tissues ◽

Angiotensin Ii Antagonist

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The binding of [3H]mepyramine to histamine H1 receptors in monkey brain

Canadian Journal of Physiology and Pharmacology ◽

10.1139/y85-125 ◽

1985 ◽

Vol 63 (6) ◽

pp. 756-759 ◽

Cited By ~ 7

Author(s):

B. Bielkiewicz ◽

D. A. Cook

Keyword(s):

Binding Sites ◽

Specific Binding ◽

Histamine Receptor ◽

Detailed Examination ◽

Mammalian Brain ◽

Binding Studies ◽

Peripheral Tissues ◽

Monkey Brain ◽

Specific Binding Sites ◽

Histamine H1 Receptors

Several laboratories have reported ligand binding studies using radioactive histamine H1 antagonists to label the H1 receptors in mammalian brain. We have extended these studies to a detailed examination of the binding of [3H]mepyramine to monkey brain and have shown that the distribution is similar to that in man, with specific binding sites being concentrated in the frontal cortex with relatively low binding to the pons and basal ganglia. The binding shows a single saturable component with a KD of about 1 nM and a Hill plot slope close to unity. These observations are the same for all structures tested. Comparison with data from other laboratories suggests that in this species, the histamine receptor is the same as that in peripheral tissues. From Ki values for various ligands and comparison of KD estimates in other species, the receptor seems to be essentially identical to the H1 receptor in central and peripheral tissues of the guinea pig and also to that in human brain. The rat and possibly the dog have minor differences from the monkey in terms of KD values for [3H]mepyramine binding.

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