Large-scale deorphanization of G-protein coupled receptors from Platynereis dumerilii

G-protein coupled receptors (GPCRs) are an important receptor class that can have various types of ligands, including neuropeptides and biogenic amines. Many GPCR families are conserved throughout animals, highlighting their importance in neuronal and hormonal signaling. While the ligands of many human GPCRs and GPCRs from popular model organisms are known, most of the GPCRs of other animals remain without a known ligand (“orphan GPCRs”) or their ligands have only been predicted based on sequence similarity to known GPCRs. Especially within the understudied phylum of the lophotrochozoa, few GPCRs have been biochemically characterized. In this thesis, I present an approach for the large-scale deorphanization of G-protein coupled receptors and a large dataset of deorphanized receptors from the lophotrochozoan Platynereis dumerilii and other marine invertebrates. Among these are neuropeptide receptors and biogenic amine receptors. By testing 87 GPCRs against 126 neuropeptides, I could deorphanize 19 neuropeptide GPCRs. Among them are GPCRs that belong to hitherto undescribed families. Some of these, namely the FMRFamide receptors, achatin receptors, and elevenin receptors, are conserved across bilateria. Others are restricted to the lophotrochozoa. I also identified a ligand for the Platynereis thyrotropin-releasing hormone receptor. In a second study, I concentrated on biogenic amine receptors. I deorphanized adrenergic, octopaminergic and tyraminergic receptors from Platynereis as well as the ecdysozoan Priapulus caudatus and the deuterostome Saccoglossus kovalewskii, a hemichordate. This way I could show that all three receptor families are conserved across bilaterians. They are therefore much older than was previously appreciated. Also, this is proof that octopamine is clearly not an equivalent of norepinephrine, as was often suggested by scientists in the field. Taken together, my dataset sheds light on the evolution of GPCRs in bilateral animals. Important aspects of GPCR evolution that had been overlooked because of limited taxon sampling were cleared up. Also, the dataset presented here will be an important resource for future GPCR deorphanizations.G-Protein-gekoppelte Rezeptoren (GPCRs) sind ein wichtiger Rezeptor-Typ mit vielen unterschiedlichen Arten von Liganden, zu denen unter anderem Neuropeptide und biogene Amine gehören. Viele GPCR-Familien sind in allen Tieren konserviert, was ihre Bedeutung in der neuronalen und hormonellen Signalweiterleitung unterstreicht. Während die Liganden vieler GPCRs des Menschen und populärer Modellorganismen bekannt sind, ist für die meisten GPCRs anderer Tiere kein Ligand bekannt (“orphan GPCRs”) oder der Ligand wurde nur aufgrund von Sequenzähnlichkeit zu bekannten GPCRs vorhergesagt. Besonders innerhalb des wenig erforschten Phylums der Lophotrochozoa wurden bisher nur wenige GPCRs biochemisch untersucht. In dieser Dissertation stelle ich eine Herangehensweise zur Deorphanisierung von GPCRs im großen Maßstab vor, sowie einen großen Datensatz an deorphanisierten Rezeptoren aus dem Lophotrochohzoen Platynereis dumerilii und weiteren marinen Invertebraten. Darunter befinden sich Rezeptoren für Neuropeptide und biogene Amine. Ich habe 87 GPCRs gegen 126 Neuropeptide getestet und konnte dadurch 19 neuropeptiderge GPCRs deorphanisieren. Darunter befinden sich GPCRs aus bisher noch nicht beschriebenen Familien. Einige davon, nämlich die FMRFamid-Rezeptoren, Achatin-Rezeptoren und Elevenin-Rezeptoren, sind in Bilateriern konserviert. Andere kommen nur in Lophotrochozoen vor. Ich habe außerdem einen Liganden für den Thyreotropin Releasing Hormon-Rezeptor identifiziert. In einer zweiten Studie habe ich mich auf Rezeptoren von biogenen Aminen konzentriert. Ich habe adrenerge, octopaminerge und tyraminerge Rezeptoren aus Platynereis sowie dem Ecdysozoen Priapulus caudatus und dem Deuterostomier Saccoglossus kovalewskii, einem Hemichordaten, deorphanisiert. Dadurch konnte ich zeigen, dass alle drei Rezeptorfamilien in Bilateriern konserviert sind. Sie sind also viel älter als bisher angenommen wurde. Außerdem beweist dies, dass Octopamin eindeutig nicht das Äquivalent zu Noradrenalin ist, wie dies von Forschern in diesem Feld häufig behauptet worden war. Zusammenfassend beleuchtet mein Datensatz die Evolution der GPCRs in Bilateriern. Wichtige Aspekte der Evolution von GPCRs, die bisher übersehen worden waren, da nur Stichproben aus wenigen Taxa untersucht wurden, sind nun aufgeklärt. Außerdem wird dieser Datensatz eine wichtige Ressource für die Deorphanisierung von weiteren GPCRs darstellen

An ancient FMRFamide-related peptide-receptor pair induces defense behavior in a brachiopod larva

Animals show different behaviors that can consist of various spatially or temporally separated sub-reactions. Even less complex organisms, like ciliated larvae that display important behaviors (e.g. metamorphosis, defense, feeding), need to coordinate coherent sub-reactions with their simple nervous system. These behaviors can be triggered by neuropeptides, which are short signaling peptides. Despite the high diversity of neuropeptides in animals, and although their immunoreactivity is widely used in morphological studies of animal nervous systems (e.g. FMRFamide), their function and role in trochozoan larval behavior has so far only been tested in a few cases. When mechanically disturbed, the planktonic larvae of the brachiopod Terebratalia transversa protrude their stiff and pointy chaetae in a defensive manner and sink down slowly: a startle reaction that is known from different chaetous trochozoan larvae. We found that both of these reactions can be induced simultaneously by the FMRFamide-related neuropeptide FLRFamide. We deorphanized the Terebratalia FLRFamide receptor and found its expression spatially separated in the apical lobe at the prototroch of the larvae and in the trunk musculature, which correlates with the tissues that are responsible to perform the two sub-reactions. A behavioral assay showed a decreasing efficiency of modified peptides in triggering this behavior, which correlates with the decreasing efficiency of activating the FLRFamide receptor in transfected CHO-K1 cells. Immunohistochemistry and in situ hybridization show FLRFamidergic neurons in the apical lobe as well as next to the trunk musculature. Our results show that the single neuropeptide FLRFamide can specifically induce the two coherent sub-reactions of the T. transversa startle behavior.draf

Switching antipsychotics to partial dopamine D2-agonists in individuals affected by schizophrenia: a narrative review

Objective: The aim of this review is to analyse the literature regarding studies centred on the clinical outcome of individuals affected by schizophrenia and treated with various antipsychotics, and then switched to orally administered partial D2-dopamine agonists (PD2A): Aripiprazole (ARI), brexpiprazole (BREX) or cariprazine (CARI). Method: A PubMed literature search was performed on 16 February 2021, and updated on Jan 26, 2022 for literature on antipsychotic switching in individuals affected by schizophrenia. Literature was included from 2002 onward. Six strategies were defined: Abrupt, gradual and cross-taper switch, and 3 hybrid strategies. The primary outcome was all-cause discontinuation rate per switch strategy per goal medication. Results: In 10 reports on switching to ARI, 21 studies with different strategies were described, but there were only 4 reports and 5 strategies on switching to BREX. Only one study about CARI was included, but it was not designed as a switch study. The studies are difficult to compare due to differences in methodology, previous antipsychotic medication, doses of the introduced P2DA and study duration. Conclusion: This analysis did not reveal evidence for a preferable switching strategy. A protocol should be developed which defines optimal duration, instruments to be used, and the timing of the exams.KEY MESSAGESMost switch studies on partial D2-agonists focus on ARI, with only a few on BREX, while little is known about the clinical outcome of switching individuals to CARIThere is a wide variation of possible switch methods: Abrupt switch - gradual switch - cross-tapering switch - hybrid strategies including plateau switchThe protocols used differ considerably between the studies. A strict comparison between the studies is difficult, for which reason the present evidence does not support an unambiguous preference for a particular switch strategy.From a methodological point of view, a standardised clinical protocol should be developed to allow comparisons between studies regarding the clinical outcome of individuals switched from one antipsychotic drug to another

Large-Scale Combinatorial Deorphanization of Platynereis Neuropeptide GPCRs

Neuropeptides, representing the largest class of neuromodulators, commonly signal by G-protein-coupled receptors (GPCRs). While the neuropeptide repertoire of several metazoans has been characterized, many GPCRs are orphans. Here, we develop a strategy to identify GPCR-peptide pairs using combinatorial screening with complex peptide mixtures. We screened 126 neuropeptides against 87 GPCRs of the annelid Platynereis and identified ligands for 19 receptors. We assigned many GPCRs to known families and identified conserved families of achatin, FMRFamide, RGWamide, FLamide, and elevenin receptors. We also identified a ligand for the Platynereis ortholog of vertebrate thyrotropin-releasing hormone (TRH) receptors, revealing the ancient origin of TRH-receptor signaling. We predicted ligands for several metazoan GPCRs and tested predicted achatin receptors. These receptors were specifically activated by an achatin D-peptide, revealing a conserved mode of activation. Our work establishes an important resource and provides information about the complexity of peptidergic signaling in the urbilaterian

Additional file 1: of Ancient coexistence of norepinephrine, tyramine, and octopamine signaling in bilaterians

Maximum likelihood tree of adrenergic, octopamine, and tyramine receptors. Bootstrap support values are shown. This tree contains all investigated GPCRs. The tree was rooted on 5HT receptor sequences. Sub-trees are shown in Additional files 2, 3, 4, 5, 6, 7, and 8. (PDF 118 kb

Additional file 8: of Ancient coexistence of norepinephrine, tyramine, and octopamine signaling in bilaterians

Maximum likelihood tree of octopamine-β receptors. Bootstrap support values are shown for selected nodes. This tree is part of a larger tree containing all investigated GPCRs. The identifiers of deorphanized octopamine receptors were tagged with _Ob. (PDF 16730 kb

An ancient FMRFamide-related peptide-receptor pair induces defense behavior in a brachiopod larva

Animals show different behaviors that can consist of various spatially or temporally separated sub-reactions. Even less complex organisms, like ciliated larvae that display important behaviors (e.g. metamorphosis, defense, feeding), need to coordinate coherent sub-reactions with their simple nervous system. These behaviors can be triggered by neuropeptides, which are short signaling peptides. Despite the high diversity of neuropeptides in animals, and although their immunoreactivity is widely used in morphological studies of animal nervous systems (e.g. FMRFamide), their function and role in trochozoan larval behavior has so far only been tested in a few cases. When mechanically disturbed, the planktonic larvae of the brachiopod Terebratalia transversa protrude their stiff and pointy chaetae in a defensive manner and sink down slowly: a startle reaction that is known from different chaetous trochozoan larvae. We found that both of these reactions can be induced simultaneously by the FMRFamide-related neuropeptide FLRFamide. We deorphanized the Terebratalia FLRFamide receptor and found its expression spatially separated in the apical lobe at the prototroch of the larvae and in the trunk musculature, which correlates with the tissues that are responsible to perform the two sub-reactions. A behavioral assay showed a decreasing efficiency of modified peptides in triggering this behavior, which correlates with the decreasing efficiency of activating the FLRFamide receptor in transfected CHO-K1 cells. Immunohistochemistry and in situ hybridization show FLRFamidergic neurons in the apical lobe as well as next to the trunk musculature. Our results show that the single neuropeptide FLRFamide can specifically induce the two coherent sub-reactions of the T. transversa startle behavior