Targeting the PAC1 Receptor for Neurological and Metabolic Disorders

The pituitary adenylate cyclase-activating polypeptide (PACAP)-selective PAC1 receptor (PAC1R, ADCYAP1R1) is a member of the vasoactive intestinal peptide (VIP)/secretin/glucagon family of G protein-coupled receptors (GPCRs). PAC1R has been shown to play crucial roles in the central and peripheral nervous systems. The activation of PAC1R initiates diverse downstream signal transduction pathways, including adenylyl cyclase, phospholipase C, MEK/ERK, and Akt pathways that regulate a number of physiological systems to maintain functional homeostasis. Accordingly, at times of tissue injury or insult, PACAP/PAC1R activation of these pathways can be trophic to blunt or delay apoptotic events and enhance cell survival. Enhancing PAC1R signaling under these conditions has the potential to mitigate cellular damages associated with cerebrovascular trauma (including stroke), neurodegeneration (such as Parkinson’s and Alzheimer's disease), or peripheral organ insults. Conversely, maladaptive PACAP/PAC1R signaling has been implicated in a number of disorders, including stressrelated psychopathologies (i.e., depression, posttraumatic stress disorder, and related abnormalities), chronic pain and migraine, and metabolic diseases; abrogating PAC1R signaling under these pathological conditions represent opportunities for therapeutic intervention. Given the diverse PAC1R-mediated biological activities, the receptor has emerged as a relevant pharmaceutical target. In this review, we first describe the current knowledge regarding the molecular structure, dynamics, and function of PAC1R. Then, we discuss the roles of PACAP and PAC1R in the activation of a variety of signaling cascades related to the physiology and diseases of the nervous system. Lastly, we examine current drug design and development of peptides and small molecules targeting PAC1R based on a number of structure- activity relationship studies and key pharmacophore elements. At present, the rational design of PAC1R-selective peptide or small-molecule therapeutics is largely hindered by the lack of structural information regarding PAC1R activation mechanisms, the PACAP-PAC1R interface, and the core segments involved in receptor activation. Understanding the molecular basis governing the PACAP interactions with its different cognate receptors will undoubtedly provide a basis for the development and/or refinement of receptor-selective therapeutics.

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Molecular Basis of Class B GPCR Selectivity for the Neuropeptides PACAP and VIP

Frontiers in Molecular Biosciences ◽

10.3389/fmolb.2021.644644 ◽

2021 ◽

Vol 8 ◽

Author(s):

Chenyi Liao ◽

Jacob M. Remington ◽

Victor May ◽

Jianing Li

Keyword(s):

Rational Design ◽

Structural Information ◽

Receptor Activation ◽

Binding Selectivity ◽

Pac1 Receptor ◽

Ligand Selectivity ◽

Receptor Interactions ◽

Class B ◽

State Models ◽

Class B Gpcr

The related neuropeptides PACAP and VIP, and their shared PAC1, VPAC1 and VPAC2 receptors, regulate a large array of physiological activities in the central and peripheral nervous systems. However, the lack of comparative and molecular mechanistic investigations hinder further understanding of their preferred binding selectivity and function. PACAP and VIP have comparable affinity at the VPAC1 and VPAC2 receptor, but PACAP is 400–1,000 fold more potent than VIP at the PAC1 receptor. A molecular understanding of the differing neuropeptide-receptor interactions and the details underlying the receptor transitions leading to receptor activation are much needed for the rational design of selective ligands. To these ends, we have combined structural information and advanced simulation techniques to study PACAP/VIP binding selectivity, full-length receptor conformation ensembles and transitions of the PACAP/VIP receptor variants and subtypes, and a few key interactions in the orthosteric-binding pocket. Our results reveal differential peptide-receptor interactions (at the atomistic detail) important for PAC1, VPAC1 and VPAC2 receptor ligand selectivity. Using microsecond-long molecular dynamics simulations and the Markov State Models, we have also identified diverse receptor conformational ensembles and microstate transition paths for each receptor, the potential mechanisms underlying receptor open and closed states, and the interactions and dynamics at the transmembrane orthosteric pocket for receptor activation. These analyses reveal important features in class B GPCR structure-dynamics-function relationships, which provide novel insights for structure-based drug discovery.

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Ligand recognition, unconventional activation, and G protein coupling of the prostaglandin E2 receptor EP2 subtype

Science Advances ◽

10.1126/sciadv.abf1268 ◽

2021 ◽

Vol 7 (14) ◽

pp. eabf1268

Author(s):

Changxiu Qu ◽

Chunyou Mao ◽

Peng Xiao ◽

Qingya Shen ◽

Ya-Ni Zhong ◽

...

Keyword(s):

G Protein ◽

Rational Design ◽

Receptor Activation ◽

Prostaglandin E ◽

Toggle Switch ◽

G Protein Coupling ◽

Protein Coupling ◽

Ligand Selectivity ◽

Activation Mechanisms ◽

Prostaglandin E2 Receptor

Selective modulation of the heterotrimeric G protein α S subunit–coupled prostaglandin E2 (PGE2) receptor EP2 subtype is a promising therapeutic strategy for osteoporosis, ocular hypertension, neurodegenerative diseases, and cardiovascular disorders. Here, we report the cryo–electron microscopy structure of the EP2-Gs complex with its endogenous agonist PGE2 and two synthesized agonists, taprenepag and evatanepag (CP-533536). These structures revealed distinct features of EP2 within the EP receptor family in terms of its unconventional receptor activation and G protein coupling mechanisms, including activation in the absence of a typical W6.48 “toggle switch” and coupling to Gs via helix 8. Moreover, inspection of the agonist-bound EP2 structures uncovered key motifs governing ligand selectivity. Our study provides important knowledge for agonist recognition and activation mechanisms of EP2 and will facilitate the rational design of drugs targeting the PGE2 signaling system.

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Neutrophils in acute inflammation - current concepts and translational implications

Blood ◽

10.1182/blood.2021012295 ◽

2021 ◽

Author(s):

Andreas Margraf ◽

Clifford A. Lowell ◽

Alexander Zarbock

Keyword(s):

Acute Inflammation ◽

Tissue Injury ◽

Inflammatory Cells ◽

Organ Damage ◽

Receptor Activation ◽

Immune Defense ◽

Neutrophil Recruitment ◽

Underlying Mechanisms ◽

And Function ◽

And Control

Modulation of neutrophil recruitment and function is crucial for targeting inflammatory cells to sites of infection to combat invading pathogens while at the same time limiting host tissue injury or autoimmunity. The underlying mechanisms regulating recruitment of neutrophils, one of the most abundant inflammatory cells, have gained increasing interest over the years. The previously described classical recruitment cascade of leukocytes has been extended to include not only capturing, rolling, adhesion, crawling and transmigration but furthermore a reverse-transmigration step that is crucial for balancing immune defense and control of remote organ endothelial leakage. Current developments in the field emphasize the importance of cellular interplay, tissue-environmental cues, circadian rhythmicity, detection of neutrophil phenotypes, differential chemokine sensing, and contribution of distinct signaling components to receptor activation and integrin conformations. Use of therapeutics modulating neutrophil activation responses as well as mutations causing dysfunctional neutrophil receptors and impaired signaling cascades have been defined in translational animal models. Human correlates of such mutations result in increased susceptibility to infections or organ damage. This review focuses on current advances in the understanding of the regulation of neutrophil recruitment and functionality and translational implications of current discoveries in the field with a focus on acute inflammation and sepsis.

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Ferroptosis: molecular mechanisms and health implications

Cell Research ◽

10.1038/s41422-020-00441-1 ◽

2020 ◽

Cited By ~ 3

Author(s):

Daolin Tang ◽

Xin Chen ◽

Rui Kang ◽

Guido Kroemer

Keyword(s):

Cell Death ◽

Molecular Mechanisms ◽

Tissue Injury ◽

Current Knowledge ◽

Apoptotic Cell ◽

Oxidation Products ◽

Redox Active ◽

Lipid Oxidation Products ◽

Dependent Form ◽

And Function

AbstractCell death can be executed through different subroutines. Since the description of ferroptosis as an iron-dependent form of non-apoptotic cell death in 2012, there has been mounting interest in the process and function of ferroptosis. Ferroptosis can occur through two major pathways, the extrinsic or transporter-dependent pathway and the intrinsic or enzyme-regulated pathway. Ferroptosis is caused by a redox imbalance between the production of oxidants and antioxidants, which is driven by the abnormal expression and activity of multiple redox-active enzymes that produce or detoxify free radicals and lipid oxidation products. Accordingly, ferroptosis is precisely regulated at multiple levels, including epigenetic, transcriptional, posttranscriptional and posttranslational layers. The transcription factor NFE2L2 plays a central role in upregulating anti-ferroptotic defense, whereas selective autophagy may promote ferroptotic death. Here, we review current knowledge on the integrated molecular machinery of ferroptosis and describe how dysregulated ferroptosis is involved in cancer, neurodegeneration, tissue injury, inflammation, and infection.

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PROTAC-DB: an online database of PROTACs

Nucleic Acids Research ◽

10.1093/nar/gkaa807 ◽

2020 ◽

Vol 49 (D1) ◽

pp. D1381-D1387 ◽

Cited By ~ 2

Author(s):

Gaoqi Weng ◽

Chao Shen ◽

Dongsheng Cao ◽

Junbo Gao ◽

Xiaowu Dong ◽

...

Keyword(s):

Physicochemical Properties ◽

Small Molecules ◽

Rational Design ◽

Structural Information ◽

Biological Activities ◽

Ubiquitin Proteasome System ◽

Phase I Clinical Trials ◽

E3 Ligases ◽

Chemical Structures ◽

Substantial Progress

Abstract Proteolysis-targeting chimeras (PROTACs), which selectively degrade targeted proteins by the ubiquitin-proteasome system, have emerged as a novel therapeutic technology with potential advantages over traditional inhibition strategies. In the past few years, this technology has achieved substantial progress and two PROTACs have been advanced into phase I clinical trials. However, this technology is still maturing and the design of PROTACs remains a great challenge. In order to promote the rational design of PROTACs, we present PROTAC-DB, a web-based open-access database that integrates structural information and experimental data of PROTACs. Currently, PROTAC-DB consists of 1662 PROTACs, 202 warheads (small molecules that target the proteins of interest), 65 E3 ligands (small molecules capable of recruiting E3 ligases) and 806 linkers, as well as their chemical structures, biological activities, and physicochemical properties. Except the biological activities of warheads and E3 ligands, PROTAC-DB also provides the degradation capacities, binding affinities and cellular activities for PROTACs. PROTAC-DB can be queried with two general searching approaches: text-based (target name, compound name or ID) and structure-based. In addition, for the convenience of users, a filtering tool for the searching results based on the physicochemical properties of compounds is also offered. PROTAC-DB is freely accessible at http://cadd.zju.edu.cn/protacdb/.

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Cryo-EM structure of the human PAC1 receptor coupled to an engineered heterotrimeric G protein

10.1101/2019.12.23.887737 ◽

2019 ◽

Author(s):

Kazuhiro Kobayashi ◽

Wataru Shihoya ◽

Tomohiro Nishizawa ◽

Francois Marie Ngako Kadji ◽

Junken Aoki ◽

...

Keyword(s):

G Protein ◽

Structural Information ◽

Receptor Activation ◽

Peptide Ligand ◽

Pac1 Receptor ◽

Peripheral Tissues ◽

Class B ◽

Neuropeptide Hormone ◽

The Central Nervous System ◽

Glucagon Like Peptide 1

AbstractPituitary adenylate cyclase-activating polypeptide (PACAP) is a pleiotropic neuropeptide hormone functioning in the central nervous system and peripheral tissues. The PACAP receptor PAC1R, which belongs to the class B G-protein-coupled receptors (GPCRs), is a drug target for mental disorders and dry eye syndrome. Here we present a cryo-electron microscopy structure of human PAC1R bound to PACAP and an engineered Gs heterotrimer. The structure revealed that TM1 plays an essential role in PACAP recognition. The ECD (extracellular domain) of PAC1R tilts by ~40° as compared to that of the glucagon-like peptide-1 receptor (GLP1R), and thus does not cover the peptide ligand. A functional analysis demonstrated that the PAC1R-ECD functions as an affinity trap and is not required for receptor activation, whereas the GLP1R-ECD plays an indispensable role in receptor activation, illuminating the functional diversity of the ECDs in the class B GPCRs. Our structural information will facilitate the design and improvement of better PAC1R agonists for clinical applications.This article is a preprint version and has not been certified by peer review.

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Effects of Maternal Obesity and Gestational Diabetes Mellitus on the Placenta: Current Knowledge and Targets for Therapeutic Interventions

Current Vascular Pharmacology ◽

10.2174/1570161118666200616144512 ◽

2020 ◽

Vol 19 (2) ◽

pp. 176-192

Author(s):

Samantha Bedell ◽

Janine Hutson ◽

Barbra de Vrijer ◽

Genevieve Eastabrook

Keyword(s):

Diabetes Mellitus ◽

Gestational Diabetes ◽

Gestational Diabetes Mellitus ◽

Maternal Obesity ◽

Environmental Changes ◽

Current Knowledge ◽

Therapeutic Interventions ◽

Placental Development ◽

Exchange Site ◽

And Function

: Obesity and gestational diabetes mellitus (GDM) are becoming more common among pregnant women worldwide and are individually associated with a number of placenta-mediated obstetric complications, including preeclampsia, macrosomia, intrauterine growth restriction and stillbirth. The placenta serves several functions throughout pregnancy and is the main exchange site for the transfer of nutrients and gas from mother to fetus. In pregnancies complicated by maternal obesity or GDM, the placenta is exposed to environmental changes, such as increased inflammation and oxidative stress, dyslipidemia, and altered hormone levels. These changes can affect placental development and function and lead to abnormal fetal growth and development as well as metabolic and cardiovascular abnormalities in the offspring. This review aims to summarize current knowledge on the effects of obesity and GDM on placental development and function. Understanding these processes is key in developing therapeutic interventions with the goal of mitigating these effects and preventing future cardiovascular and metabolic pathology in subsequent generations.

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The Oxford Handbook of the Auditory Brainstem

10.1093/oxfordhb/9780190849061.001.0001 ◽

2018 ◽

Cited By ~ 1

Keyword(s):

Current Knowledge ◽

Auditory Pathway ◽

Auditory Brainstem ◽

Auditory Midbrain ◽

Current State ◽

Neuronal Mechanisms ◽

Maladaptive Plasticity ◽

And Function ◽

Auditory Field

The Oxford Handbook of the Auditory Brainstem provides an in-depth reference to the organization and function of ascending and descending auditory pathways in the mammalian brainstem. Individual chapters are organized along the auditory pathway, beginning with the cochlea and ending with the auditory midbrain. Each chapter provides an introduction to the respective area and summarizes our current knowledge before discussing the disputes and challenges that the field currently faces.The handbook emphasizes the numerous forms of plasticity that are increasingly observed in many areas of the auditory brainstem. Several chapters focus on neuronal modulation of function and plasticity on the synaptic, neuronal, and circuit level, especially during development, aging, and following peripheral hearing loss. In addition, the book addresses the role of trauma-induced maladaptive plasticity with respect to its contribution in generating central hearing dysfunction, such as hyperacusis and tinnitus.The book is intended for students and postdoctoral fellows starting in the auditory field and for researchers of related fields who wish to get an authoritative and up-to-date summary of the current state of auditory brainstem research. For clinical practitioners in audiology, otolaryngology, and neurology, the book is a valuable resource of information about the neuronal mechanisms that are currently discussed as major candidates for the generation of central hearing dysfunction.

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The relevance of adhesion G protein-coupled receptors in metabolic functions

Biological Chemistry ◽

10.1515/hsz-2021-0146 ◽

2021 ◽

Vol 0 (0) ◽

Author(s):

Isabell Kaczmarek ◽

Tomáš Suchý ◽

Simone Prömel ◽

Torsten Schöneberg ◽

Ines Liebscher ◽

...

Keyword(s):

G Protein ◽

Drug Targets ◽

Metabolic Diseases ◽

Current Knowledge ◽

G Protein Coupled Receptors ◽

Specific Expression ◽

Physiological Functions ◽

Metabolic Functions ◽

Central Nervous Systems ◽

G Protein Coupled

Abstract G protein-coupled receptors (GPCRs) modulate a variety of physiological functions and have been proven to be outstanding drug targets. However, approximately one-third of all non-olfactory GPCRs are still orphans in respect to their signal transduction and physiological functions. Receptors of the class of Adhesion GPCRs (aGPCRs) are among these orphan receptors. They are characterized by unique features in their structure and tissue-specific expression, which yields them interesting candidates for deorphanization and testing as potential therapeutic targets. Capable of G-protein coupling and non-G protein-mediated function, aGPCRs may extend our repertoire of influencing physiological function. Besides their described significance in the immune and central nervous systems, growing evidence indicates a high importance of these receptors in metabolic tissue. RNAseq analyses revealed high expression of several aGPCRs in pancreatic islets, adipose tissue, liver, and intestine but also in neurons governing food intake. In this review, we focus on aGPCRs and their function in regulating metabolic pathways. Based on current knowledge, this receptor class represents high potential for future pharmacological approaches addressing obesity and other metabolic diseases.

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In Vitro Chemopreventive Potential of Phlorotannins-Rich Extract from Brown Algae by Inhibition of Benzo[a]pyrene-Induced P2X7 Activation and Toxic Effects

Marine Drugs ◽

10.3390/md19010034 ◽

2021 ◽

Vol 19 (1) ◽

pp. 34

Author(s):

Mélody Dutot ◽

Elodie Olivier ◽

Sophie Fouyet ◽

Romain Magny ◽

Karim Hammad ◽

...

Keyword(s):

Brown Algae ◽

P2x7 Receptor ◽

Biological Activities ◽

Receptor Activation ◽

Cytotoxic Effects ◽

Human Lung Cells ◽

Cytochrome P450 Activity ◽

Species Production ◽

E Cadherin

Phlorotannins are polyphenols occurring exclusively in some species of brown algae, known for numerous biological activities, e.g., antioxidant, antiproliferative, antidiabetic, and antiallergic properties. Their effects on the response of human lung cells to benzo[a]pyrene (B[a]P) has not been characterized. Our objective was to in vitro evaluate the effects of a phlorotannin-rich extract obtained from the brown algae Ascophyllum nodosum and Fucus vesiculosus on B[a]P cytotoxic effects. The A549 cell line was incubated with B[a]P for 48 and 72 h in the presence or absence of the brown algae extract. Cytochrome P450 activity, activation of P2X7 receptor, F-actin disorganization, and loss of E-cadherin expression were assessed using microplate cytometry and fluorescence microscopy. Relative to control, incubation with the brown algae extract was associated with lower B[a]P-induced CYP1 activity, lower P2X7 receptor activation, and lower reactive oxygen species production. The brown algae extract inhibited the alterations of F-actin arrangement and the downregulation of E-cadherin expression. We identified a phlorotannins-rich extract that could be deeper investigated as a cancer chemopreventive agent to block B[a]P-mediated carcinogenesis.

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