{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,4,23]],"date-time":"2026-04-23T04:48:32Z","timestamp":1776919712563,"version":"3.51.2"},"reference-count":38,"publisher":"Frontiers Media SA","license":[{"start":{"date-parts":[[2023,5,12]],"date-time":"2023-05-12T00:00:00Z","timestamp":1683849600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100001659","name":"Deutsche Forschungsgemeinschaft","doi-asserted-by":"publisher","id":[{"id":"10.13039\/501100001659","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100001659","name":"Deutsche Forschungsgemeinschaft","doi-asserted-by":"publisher","id":[{"id":"10.13039\/501100001659","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100001659","name":"Deutsche Forschungsgemeinschaft","doi-asserted-by":"publisher","id":[{"id":"10.13039\/501100001659","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100001659","name":"Deutsche Forschungsgemeinschaft","doi-asserted-by":"publisher","id":[{"id":"10.13039\/501100001659","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100001659","name":"Deutsche Forschungsgemeinschaft","doi-asserted-by":"publisher","id":[{"id":"10.13039\/501100001659","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100002347","name":"Bundesministerium f\u00fcr Bildung und Forschung","doi-asserted-by":"publisher","id":[{"id":"10.13039\/501100002347","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":["frontiersin.org"],"crossmark-restriction":true},"short-container-title":["Front. Mol. Neurosci."],"abstract":"<jats:p>N-(3-fluoro-1-phenethylpiperidine-4-yl)-N-phenyl propionamide is a newly-designed pain killer selectively activating G-protein-coupled mu-opioid receptors (MOR) in acidic injured tissues, and therefore devoid of central side effects which are typically elicited at normal pH values in healthy tissues. However, the neuronal mechanisms underlying NFEPP\u2019s antinociceptive effects were not examined in detail so far. Voltage-dependent Ca<jats:sup>2+<\/jats:sup> channels (VDCCs) in nociceptive neurons play a major role in the generation and inhibition of pain. In this study, we focused on the effects of NFEPP on calcium currents in rat dorsal root ganglion (DRG) neurons. The inhibitory role of the G-protein subunits G<jats:sub><jats:italic>i\/o<\/jats:italic><\/jats:sub> and G\u03b2\u03b3 on VDCCs was investigated using the blockers pertussis toxin and gallein, respectively. GTP\u03b3S binding, calcium signals and MOR phosphorylation were also investigated. All experiments were performed at acidic and normal pH values using NFEPP in comparison to the conventional opioid agonist fentanyl. At low pH, NFEPP produced more efficient G-protein activation in transfected HEK293 cells and significantly reduced VDCCs in depolarized DRG neurons. The latter effect was mediated by G\u03b2\u03b3 subunits, and NFEPP-mediated MOR phosphorylation was pH-dependent. Fentanyl\u2019s responses were not affected by pH changes. Our data indicate that NFEPP-induced MOR signaling is more effective at low pH and that the inhibition of calcium channels in DRG neurons underlies NFEPP\u2019s antinociceptive actions.<\/jats:p>","DOI":"10.3389\/fnmol.2023.1171855","type":"journal-article","created":{"date-parts":[[2023,5,12]],"date-time":"2023-05-12T05:51:55Z","timestamp":1683870715000},"update-policy":"https:\/\/doi.org\/10.3389\/crossmark-policy","source":"Crossref","is-referenced-by-count":6,"title":["Modulation of G-protein activation, calcium currents and opioid receptor phosphorylation by the pH-dependent antinociceptive agonist NFEPP"],"prefix":"10.3389","volume":"16","author":[{"given":"Melih \u00d6zg\u00fcr","family":"Celik","sequence":"first","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Viola","family":"Seitz","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Fatih","family":"Yerg\u00f6z","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Sandeep","family":"Dembla","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Nina Kathleen","family":"Blum","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Stefan","family":"Schulz","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Christoph","family":"Stein","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1965","published-online":{"date-parts":[[2023,5,12]]},"reference":[{"key":"B1","doi-asserted-by":"publisher","first-page":"907","DOI":"10.1136\/rapm-2020-101779","article-title":"Role of peripheral sensory neur. on mu-opioid receptors in nociceptive, inflammatory, and neuropathic pain.","volume":"45","author":"Barpujari","year":"2020","journal-title":"Reg. Anesth. Pain Med."},{"key":"B2","doi-asserted-by":"crossref","first-page":"695","DOI":"10.1080\/14728222.2017.1328057","article-title":"Targeting dorsal root ganglia and primary sensory neurons for the treatment of chronic pain.","volume":"21","author":"Berta","year":"2017","journal-title":"Expert Opin. Ther. Targets"},{"key":"B3","doi-asserted-by":"crossref","first-page":"248","DOI":"10.1016\/0003-2697(76)90527-3","article-title":"A rapid and sensitive method for the quantitation of microgram quantities of protein utilizing the principle of protein-dye binding.","volume":"72","author":"Bradford","year":"1976","journal-title":"Anal. Biochem."},{"key":"B4","author":"Castro-Junior","year":"2018","journal-title":"Role of Calcium Permeable Channels in Pain Processing."},{"key":"B5","doi-asserted-by":"crossref","DOI":"10.1038\/s41598-019-55886-1","article-title":"pKa of opioid ligands as a discriminating factor for side effects.","volume":"9","author":"Del Vecchio","year":"2019","journal-title":"Sci. Rep."},{"key":"B6","doi-asserted-by":"publisher","DOI":"10.7554\/eLife.26280","article-title":"Anti-nociceptive action of peripheral mu-opioid receptors by G-beta-gamma protein-mediated inhibition of TRPM3 channels.","volume":"6","author":"Dembla","year":"2017","journal-title":"eLife"},{"key":"B7","doi-asserted-by":"publisher","first-page":"1238","DOI":"10.1016\/j.pain.2010.12.031","article-title":"Genetic ablation of delta opioid receptors in nociceptive sensory neurons increases chronic pain and abolishes opioid analgesia.","volume":"152","author":"Gaveriaux-Ruff","year":"2011","journal-title":"Pain"},{"key":"B8","doi-asserted-by":"publisher","first-page":"231","DOI":"10.1016\/0006-8993(95)00883-r","article-title":"Effect of extracellular K+ on the intracellular free Ca2+ concentration in leech glial cells and Retzius neurones.","volume":"696","author":"Hochstrate","year":"1995","journal-title":"Brain Res."},{"key":"B9","doi-asserted-by":"publisher","first-page":"107","DOI":"10.1080\/09540261.2018.1514295","article-title":"Systematic review of sex-based differences in opioid-based effects.","volume":"30","author":"Huhn","year":"2018","journal-title":"Int. Rev. Psychiatry"},{"key":"B10","doi-asserted-by":"publisher","first-page":"238","DOI":"10.1016\/j.neuropharm.2017.12.032","article-title":"Progress in understanding mechanisms of opioid-induced gastrointestinal adverse effects and respiratory depression.","volume":"131","author":"Imam","year":"2018","journal-title":"Neuropharmacology"},{"key":"B11","doi-asserted-by":"publisher","first-page":"2056","DOI":"10.1016\/j.pain.2014.07.011","article-title":"Peripheral opioid receptor blockade increases postoperative morphine demands\u2013a randomized, double-blind, placebo-controlled trial.","volume":"155","author":"Jagla","year":"2014","journal-title":"Pain"},{"key":"B12","doi-asserted-by":"crossref","first-page":"463","DOI":"10.1124\/mol.118.114637","article-title":"Dynamic opioid receptor regulation in the periphery.","volume":"95","author":"Jeske","year":"2019","journal-title":"Mol. Pharmacol."},{"key":"B13","doi-asserted-by":"publisher","first-page":"695","DOI":"10.1136\/gutjnl-2021-324070","article-title":"Agonist that activates the \u03bc-opioid receptor in acidified microenvironments inhibits colitis pain without side effects.","volume":"71","author":"Jim\u00e9nez-Vargas","year":"2022","journal-title":"Gut"},{"key":"B14","doi-asserted-by":"publisher","DOI":"10.1016\/j.neuropharm.2022.109202","article-title":"\u03b4-Opioid receptors in primary sensory neurons tonically restrain nociceptive input in chronic pain but do not enhance morphine analgesic tolerance.","volume":"217","author":"Jin","year":"2022","journal-title":"Neuropharmacology"},{"key":"B15","doi-asserted-by":"publisher","DOI":"10.1371\/journal.pbio.1000412","article-title":"Improving bioscience research reporting: the ARRIVE guidelines for reporting animal research.","volume":"8","author":"Kilkenny","year":"2010","journal-title":"PLoS Biol."},{"key":"B16","doi-asserted-by":"publisher","first-page":"3566","DOI":"10.1021\/acs.jcim.0c00185","article-title":"Potential energy function for fentanyl-based opioid pain killers.","volume":"60","author":"Le\u0161nik","year":"2020","journal-title":"J. Chem. Inf. Model"},{"key":"B17","first-page":"426","article-title":"Strategies for investigating G-protein modulation of voltage-gated Ca2+ channels.","volume":"5","author":"Lu","year":"2016","journal-title":"Cold Spring Harb. Protoc."},{"key":"B18","doi-asserted-by":"crossref","first-page":"93","DOI":"10.1038\/nature01905","article-title":"Proton-sensing G-protein-coupled receptors.","volume":"425","author":"Ludwig","year":"2003","journal-title":"Nature"},{"key":"B19","doi-asserted-by":"publisher","DOI":"10.3389\/fphar.2018.01388","article-title":"Advances in achieving opioid analgesia without side effects.","volume":"9","author":"Machelska","year":"2018","journal-title":"Front. Pharmacol."},{"key":"B20","doi-asserted-by":"publisher","first-page":"311","DOI":"10.1111\/bph.12627","article-title":"Different mechanisms of homologous and heterologous \u03bc-opioid receptor phosphorylation.","volume":"172","author":"Mann","year":"2015","journal-title":"Br. J. Pharmacol."},{"key":"B21","doi-asserted-by":"publisher","first-page":"136","DOI":"10.1097\/FBP.0000000000000558","article-title":"Peripherally acting opioid analgesics and peripherally-induced analgesia.","volume":"31","author":"Mart\u00ednez","year":"2020","journal-title":"Behav. Pharmacol."},{"key":"B22","doi-asserted-by":"crossref","first-page":"4510","DOI":"10.1111\/bph.14810","article-title":"Modulation of \u03bc-opioid receptor activation by acidic pH is dependent on ligand structure and an ionizable amino acid residue","volume":"176","author":"Meyer","year":"2019","journal-title":"Br. J. Pharmacol"},{"key":"B23","doi-asserted-by":"publisher","first-page":"1263","DOI":"10.1002\/emmm.201201980","article-title":"The K(+) channel GIRK2 is both necessary and sufficient for peripheral opioid-mediated analgesia.","volume":"5","author":"Nockemann","year":"2013","journal-title":"EMBO Mol. Med."},{"key":"B24","doi-asserted-by":"publisher","first-page":"890","DOI":"10.1124\/mol.114.096008","article-title":"G protein regulation of neuronal calcium channels: back to the future.","volume":"87","author":"Proft","year":"2015","journal-title":"Mol. Pharmacol."},{"key":"B25","doi-asserted-by":"crossref","first-page":"1443","DOI":"10.1080\/08927022.2020.1839660","article-title":"How to calculate pH-dependent binding rates for receptor\u2013ligand systems based on thermodynamic simulations with different binding motifs.","volume":"46","author":"Ray","year":"2020","journal-title":"Mol. Simulat."},{"key":"B26","doi-asserted-by":"publisher","first-page":"2277","DOI":"10.1097\/j.pain.0000000000001328","article-title":"Analgesic effects of a novel pH-dependent \u03bc-opioid receptor agonist in models of neuropathic and abdominal pain.","volume":"159","author":"Rodriguez-Gaztelumendi","year":"2018","journal-title":"Pain"},{"key":"B27","doi-asserted-by":"crossref","first-page":"1353","DOI":"10.1021\/acsmedchemlett.9b00335","article-title":"\u03b2-Fluorofentanyls Are pH-sensitive Mu opioid receptor agonists.","volume":"10","author":"Rosas","year":"2019","journal-title":"ACS Med. Chem. Lett."},{"key":"B28","doi-asserted-by":"publisher","first-page":"2349","DOI":"10.1093\/emboj\/20.10.2349","article-title":"Suppression of inflammatory and neuropathic pain symptoms in mice lacking the N-type Ca2+ channel.","volume":"20","author":"Saegusa","year":"2001","journal-title":"EMBO J."},{"key":"B29","doi-asserted-by":"crossref","first-page":"123","DOI":"10.1146\/annurev-pharmtox-010617-052554","article-title":"The genetics of pain: implications for therapeutics.","volume":"58","author":"Sexton","year":"2018","journal-title":"Annu. Rev. Pharmacol. Toxicol."},{"key":"B30","doi-asserted-by":"crossref","first-page":"966","DOI":"10.1126\/science.aai8636","article-title":"A nontoxic pain killer designed by modeling of pathological receptor conformations.","volume":"355","author":"Spahn","year":"2017","journal-title":"Science"},{"key":"B31","doi-asserted-by":"publisher","DOI":"10.1038\/s41598-018-27313-4","article-title":"Opioid receptor signaling, analgesic and side effects induced by a computationally designed pH-dependent agonist.","volume":"8","author":"Spahn","year":"2018","journal-title":"Sci. Rep."},{"key":"B32","doi-asserted-by":"crossref","first-page":"765","DOI":"10.1080\/13543784.2018.1516204","article-title":"New concepts in opioid analgesia.","volume":"27","author":"Stein","year":"2018","journal-title":"Expert Opin Investig. Drugs"},{"key":"B33","doi-asserted-by":"publisher","first-page":"1661","DOI":"10.1113\/JP277428","article-title":"\u03bc-Opioid receptors in primary sensory neurons are essential for opioid analgesic effect on acute and inflammatory pain and opioid-induced hyperalgesia.","volume":"597","author":"Sun","year":"2019","journal-title":"J. Physiol."},{"key":"B34","doi-asserted-by":"crossref","first-page":"5092","DOI":"10.1523\/JNEUROSCI.1157-07.2007","article-title":"\u03b2-Arrestin2 and c-Src regulate the constitutive activity and recycling of \u03bc opioid receptors in dorsal root ganglion neurons.","volume":"27","author":"Walwyn","year":"2007","journal-title":"J. Neurosci."},{"key":"B35","doi-asserted-by":"crossref","first-page":"630","DOI":"10.1097\/AJP.0000000000000012","article-title":"Single-dose intra-articular bupivacaine versus morphine after arthroscopic knee surgery: a meta-analysis of randomized-controlled studies.","volume":"30","author":"Wei","year":"2014","journal-title":"Clin. J. Pain"},{"key":"B36","doi-asserted-by":"publisher","DOI":"10.1371\/journal.pone.0074706","article-title":"Mu opioid receptors on primary afferent Nav1.8 neurons contribute to opiate-induced analgesia: insight from conditional knockout mice.","volume":"8","author":"Weibel","year":"2013","journal-title":"PLoS One"},{"key":"B37","doi-asserted-by":"crossref","first-page":"839","DOI":"10.1007\/s10571-020-00894-3","article-title":"Opioid receptor regulation of neuronal voltage-gated calcium channels.","volume":"41","author":"Weiss","year":"2021","journal-title":"Cell Mol. Neurobiol."},{"key":"B38","doi-asserted-by":"publisher","first-page":"202","DOI":"10.1124\/mol.64.2.202","article-title":"Painful inflammation-induced increase in mu-opioid receptor binding and G-protein coupling in primary afferent neurons.","volume":"64","author":"Z\u00f6llner","year":"2003","journal-title":"Mol. Pharmacol."}],"container-title":["Frontiers in Molecular Neuroscience"],"original-title":[],"link":[{"URL":"https:\/\/www.frontiersin.org\/articles\/10.3389\/fnmol.2023.1171855\/full","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2023,5,12]],"date-time":"2023-05-12T05:52:13Z","timestamp":1683870733000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.frontiersin.org\/articles\/10.3389\/fnmol.2023.1171855\/full"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2023,5,12]]},"references-count":38,"alternative-id":["10.3389\/fnmol.2023.1171855"],"URL":"https:\/\/doi.org\/10.3389\/fnmol.2023.1171855","relation":{},"ISSN":["1662-5099"],"issn-type":[{"value":"1662-5099","type":"electronic"}],"subject":[],"published":{"date-parts":[[2023,5,12]]},"article-number":"1171855"}}