Structure-based design of bitopic ligands for the µ-opioid receptor
Abdelfattah Faouzi, Haoqing Wang, Saheem A. Zaidi, Jeffrey F. DiBerto, Tao Che, Qianhui Qu, Michael J. Robertson, Manish K. Madasu, Amal El Daibani, Balazs R. Varga, Tiffany Zhang, Claudia Ruiz, Shan Liu, Jin Xu, Kevin Appourchaux, Samuel T. Slocum, Shainnel O. Eans, Michael D. Cameron, Ream Al-Hasani, Ying Xian Pan, Bryan L. Roth, Jay P. McLaughlin, Georgios Skiniotis, Vsevolod Katritch, Brian K. Kobilka & Susruta Majumdar. Nature. 2023, 613, 767-774.
Mu-opioid receptor agonists such as fentanyl have long been used for pain management, but are considered a major public health concern due to their adverse side effects, including lethal overdose. In a recent effort, scientists have designed novel bitopic ligands that simultaneously engage the orthosteric binding site and a conserved allosteric sodium ion-binding site within the µ-opioid receptor. Cryo-electron microscopy structure of the µ-opioid receptor bound to the bitopic ligand “C6guano” revealed that the positively charged guanidine group of the ligand engages the Asp2.50 residue in the sodium binding site. The bitopic ligand also shows a distinct G-protein signaling profile compared to fentanyl. In mice, C6guano produced potent antinociception with attenuated adverse effects including reduced respiratory depression. These findings reveal that both efficacy and functional selectivity can be modulated by the design of ligands that occupy the orthosteric and sodium binding sites in a bitopic manner, thus providing a novel strategy to develop safer opioid analgesics.
- Insights into distinct signaling profiles of the µOR activated by diverse agonists
Insights into distinct signaling profiles of the µOR activated by diverse agonists
Qianhui Qu, Weijiao Huang, Deniz Aydin, Joseph M. Paggi, Alpay B. Seven, Haoqing Wang, Soumen Chakraborty, Tao Che, Jeffrey F. DiBerto, Michael J. Robertson, Asuka Inoue, Carl-Mikael Suomivuori, Bryan L. Roth, Susruta Majumdar, Ron O. Dror, Brian K. Kobilka & Georgios Skiniotis. Nat Chem Biol. 2022 Nov 21. doi: 10.1038/s41589-022-01208-y. Epub ahead of print. PMID: 36411392.
Using cryoEM, scientists have now determined the structures of the µ-opioid receptor (MOR) in complex with mitragynine pseudoindoxyl (MP) and lofentanil (LFT). The structures show that the ligands occupy distinct sub-pockets in the same overall binding site within MOR. Atomistic simulations show that the ligands can stabilize different receptor conformations, potentially affecting the propensity of MOR to recruit signaling transducers. These results provide insights into the mechanisms that contribute to low propensity of MP in promoting G protein activation and arrestin recruitment compared to higher efficacy of LFT in signaling through both transducers. These findings reveal molecular mechanisms by which diverse ligands differentially engage distinct signaling pathways while binding to the same orthosteric site. The work was supported by NIDA grants R33DA045884 and R37DA036246.
- Synthon-based ligand discovery in virtual libraries of over 11 billion compounds
Synthon-based ligand discovery in virtual libraries of over 11 billion compounds
Structure-based virtual ligand screening is emerging as a key paradigm for early drug discovery owing to the availability of high-resolution target structures and ultra-large libraries of virtual compounds. In a recent study, NIDA-funded scientists have introduced a conceptually new approach, called V-SYNTHES, that enables computational screening of billions of compounds to identify novel ligands to keep pace with the explosive growth of screening libraries. The method utilizes a hierarchical combinatorial approach that first identifies the best synthon-scaffold combinations as seeds suitable for further growth, and then iteratively elaborates these seeds to select complete molecules with the best docking scores. This method allows rapid detection of the best-scoring compounds in the Giga-scale chemical space while performing docking of only a small fraction (<0.1%) of the library compounds. In this study, the investigators applied the V-SYNTHES approach to screen REAL Space library of more than 11 billion compounds to identify new ligands of the cannabinoid receptors CB1 and CB2. Compared with the standard virtual screening, the V-SYNTHES methods demonstrated dramatically improved hit rate. Follow-up synthesis and evaluations led to the identification of several compounds with sub-micromolar potencies including one ligand with CB2 binding Ki of 0.9 nM that displayed 35 to 65-fold CB2/CB1 functional selectivity as an antagonist.
- High-throughput screening and validation of antibodies against synaptic proteins to explore opioid signaling dynamics
High-throughput screening and validation of antibodies against synaptic proteins to explore opioid signaling dynamics
Antibodies are powerful tools to explore signal transduction pathways. In a recent effort, NIDA-funded researchers have developed an integrated approach that combines a strategy of antibody development, a time- and cost-effective method of antibody validation, and a high-throughput microscopy/machine learning pipeline to identify antibodies. Using yeast display antibody libraries from the B cells of immunized rabbits and high-throughput functional screening they identified and validated 137 recombinant high affinity antibodies against understudied synaptic proteins. These antibodies could serve as potential tools to shed light on signaling in the central nervous system.
Using a subset of antibodies targeting the opioid receptors they examined the effect of morphine and fentanyl on mu opioid receptor phosphorylation and signaling. Their studies revealed differences in the rate, extent, and site of opioid receptor phosphorylation induced by morphine and fentanyl, thus highlighting the complexity of opioid signaling and illuminating ligand-dependant differential activation and desensitization of mu opioid receptors. These molecular differences may be relevant to the acceleration in opioid overdose deaths that have been attributed to increased use of fentanyl.
- Structure of a Hallucinogen-Activated Gq-Coupled 5-HT2A Serotonin Receptor
Structure of a Hallucinogen-Activated Gq-Coupled 5-HT2A Serotonin Receptor
Hallucinogens like lysergic acid diethylamide (LSD), psilocybin, and substituted N-benzyl phenylalkylamines are widely used for recreational purposes. In addition to their recreational use, substances such as psilocybin are being considered as therapeutics for many neuropsychiatric disorders including depression, anxiety, and substance abuse. Although the precise mechanisms of action of hallucinogens remain unclear, agonist activity at the 5-HT2A serotonin (5-hydroxytryptamine [5-HT]) receptor is known to play an essential role in their psychedelic effects in humans.
In a landmark study, NIDA-funded scientists have solved active state structure of a prototypical hallucinogen 25-CN-NBOH bound to 5-HT2A receptor in complex with an engineered αq heterotrimer by cryoelectron microscopy (cryo-EM). They also obtained X-ray crystal structures of the arrestin-biased agonist LSD and the inverse agonist methiothepin bound to 5-HT2A receptor. These structures provide insights into the molecular details of both ligand recognition and coupling to the intracellular effectors that are key to gaining a molecular understanding of hallucinogen actions. Moreover, these studies provide a framework for a structure-guided search to identify more selective and efficacious HT2A receptor agonists as potential therapeutic agents for neuropsychiatric disorders.
What We Do:
The Chemistry and Pharmacology Branch (CP) supports research on all aspects of chemistry and pharmacology affected by addictive drugs. The CP Branch maintains, develops, and oversees a portfolio encompassing research, such as:
- Elucidating mechanisms of action, structure-activity relationships, understanding of basic principles involved with biological activity, pharmacology and toxicity,
- Developing new receptor type and subtype specific agents and,
- Supporting research on the pre-clinical development of new pharmacotherapies for the treatment of substance use disorders emphasizing the pre-clinical stages of target identification through hit-to-lead.
This branch supports research programs on
- Elucidate effects of drugs on all the physiological systems including the central nervous system and the other physiological systems such as the cardiovascular, pulmonary, and immune.
- Using synthetic, medicinal, Structure-activity studies (SAR) and pharmacological approaches, develops probes for basic research and potential drug leads to treat addictive disorders; Elucidates the chemical mechanism for drug addiction,
- The discovery of endogenous ligands, and the role of endogenous ligands and systems relevant to drug action, and addiction
- The studies of absorption, metabolism, pharmacokinetics, pharmacodynamics, elimination, transport and delivery
- Investigations on analytical methods development, proteomics, protein folding and related functional genomics and structural biology
- Synthesis, structure-function relationships, conformational studies, structural biology, ligand design of all addictive drugs; synthesis of affinity reagents, chemical probes, drug-receptor interaction model to elucidate drug action
- Pharmacological approaches to understand perinatal drug exposure and the effects of confounding factors, such as, maternal and environmental stress, nutrition etc., on neural systems and other organs utero.
Research Interests and Biographies
Subramaniam Ananthan, Ph.D. - Chief
Dr. Subramaniam (Sam) Ananthan provides leadership, direction, and programmatic oversight to the Chemistry and Pharmacology Branch which manages a diverse portfolio of grants focusing on basic neurochemical mechanisms, signaling pathways, development of pharmacological tools and methods, and identification of druggable targets for addressing addiction and substance use disorders. Prior to joining NIDA, he served as the Principal Investigator on NIDA-funded medicinal chemistry research involving drug design, organic synthesis, and preclinical drug development at Southern Research Institute. He is a co-author on over 90 peer-reviewed publications, co-inventor on 21 U.S. patents, and has been inducted as a Fellow of National Academy of Inventors (NAI). He joined the Division of Neuroscience and Behavior in July 2020. He serves as a member of the trans-NIH working group for the common fund program Illuminating the Druggable Genome (IDG).
Kiran Vemuri, Ph.D. - Program Officer
Dr. Vemuri has a background in organic chemistry and translational science and manages a diverse portfolio that emphasizes the chemistry and biology of addiction and overdose. He also serves as the NIDA representative for the CounterACT Program, a component under the NIH-wide Chemical Countermeasures Research Program and is a member of the Trans-NIH Common Fund Glycoscience Program and Cannabis Science Interest Group. His research interests include multi-step synthesis, route selection and optimization, in vitro and in vivo pharmacology, and the pre-clinical assessment of small-molecules and biologics. Prior to joining NIDA in 2020 as a program officer, he spent sixteen years as an academic researcher while focusing and publishing on the endocannabinoid system. Notably, Dr. Vemuri’s research on pseudo-irreversible ligands led to determining the crystal structures of both the human CB1 and CB2 cannabinoid receptors.
Paul S. Hillery, Ph.D. - Project Officer
Supports research in organic & medicinal chemistry, structural biology.
Paul Hillery has a background in organic and medicinal chemistry, based on NIH intramural research and experience in reviewing drug manufacturing and controls in investigational and new drug applications for the Food and Drug Administration. He currently serves as a project officer for assigned NIDA grants pertaining to opioid, cannabinoid, and nicotinic research topics, involving various GPCRs, channels, and transporters, and the related mechanism of action of small molecules, peptides, and proteins involved in substance use disorders.