Papers by Burcin Duan Sahbaz
Free Radical Biology and Medicine
Expert Reviews in Molecular Medicine, Nov 15, 2022
ACS Omega, 2020
G protein-coupled receptors (GPCRs) play a pivotal role in regulating key physiological events in... more G protein-coupled receptors (GPCRs) play a pivotal role in regulating key physiological events in all animal species. Recent advances in collective analysis of genes and proteins revealed numerous potential neuropeptides and GPCRs from insect species, allowing for the characterization of peptide−receptor pairs. In this work, we used fluorescence resonance energy transfer (FRET)-based genetically encoded biosensors in intact mammalian cells to study the pharmacological features of the cognate GPCR of the type-C allatostatin (AST-C) peptide from the stick insect, Carausius morosus. Analysis of multiple downstream pathways revealed that AST-C can activate the human Gi 2 protein, and not Gs or Gq, through AST-C receptor (AlstRC). Activated AlstRC recruits β-arrestin2 independent of the Gi protein but stimulates ERK phosphorylation in a Gi protein-dependent manner. Identification of Gαi-, arrestin-, and GRK-like transcripts from C. morosus revealed high evolutionary conservation at the G protein level, while β-arrestins and GRKs displayed less conservation. In conclusion, our study provides experimental and homology-based evidence on the functionality of vertebrate G proteins and downstream signaling biosensors to characterize early signaling steps of an insect GPCR. These results may serve as a scaffold for developing assays to characterize pharmacological and structural aspects of other insect GPCRs and can be used in deorphanization and pesticide studies.
Journal of Molecular Graphics and Modelling, 2020
Adipokinetic hormone (AKH) is an insect neuropeptide that plays crucial roles in a variety of phy... more Adipokinetic hormone (AKH) is an insect neuropeptide that plays crucial roles in a variety of physiological functions such as regulation of heartbeat frequency, blood hemolymph trehalose levels, and protein synthesis. It exerts its functions through binding to its cognate G protein-coupled receptor (GPCR), named adipokinetic hormone receptor (AKHR). The aim of this study is to characterize AKHR of stick insect, Carausius morosus, which becomes an agricultural and forest pest during its outbreaks, and to screen pesticide candidates that would act through inhibition of AKHR. To this aim, the sequence of the receptor and its ligand were obtained from previously published transcriptome data and homology modeling, molecular docking, and molecular dynamics (MD) simulations were combined to find the ligand-binding pocket of AKHR. As a result, crucial residues in ligand binding were identified. These residues were located at the 6th and 7th transmembrane (TM) domains and the 2nd extracellular loop (ECL) of AKHR model. In order to propose pesticide candidates, virtual screening was performed, and candidate ligands were obtained. Considering the binding energies and the stability of the interaction between the ligand and the receptor, four hit compounds were selected. In conclusion, this study revealed a possible ligand-binding pocket of AKHR and proposed some high-affinity small-molecules to block its function, which would further facilitate pesticide design studies against the same receptor of various pests.
Ligand, 2018
Neuropeptides constitute an important part of the nervous system, since the simple nerve nets (i.... more Neuropeptides constitute an important part of the nervous system, since the simple nerve nets (i.e. of Hydra). The assigned functions of these peptides vary enormously. For instance, besides inhibiting or stimulating the release of some hormones, they can be responsible for tentacle contraction of the Hydra, dropping the tail of the lizard, postnatal care of the beetles and also aggressiveness of humans. They perform these tasks via activating their cognate GPCRs, which are hypothesized to be coevolved with their ligand neuropeptides. In this chapter, we will introduce the concept of neuropeptide, its intracellular maturation process, characteristics of some typical neuropeptide families and the common properties of their cognate GPCRs. At last, we will try to give information about the widely used methods for studying GPCR-neuropeptide interactions.
TURKISH JOURNAL OF BIOLOGY, 2019
Introduction G protein-coupled receptors (GPCRs) constitute the major targets of small regulatory... more Introduction G protein-coupled receptors (GPCRs) constitute the major targets of small regulatory peptides or peptide hormones. They transduce these extracellular stimuli to intracellular molecular responses and become the key regulators of endocrine signaling. They contain conserved 7-transmembrane (7TM) helices, a variable extracellular N-terminus, and an intracellular C-terminus. They interact with the trimeric G-proteins from the intracellular site. GPCRs are the largest group of proteins in eukaryotes and are clustered in separate classes, namely rhodopsinlike Class A, secretin-like Class B1, adhesion GPCRs Class B2, glutamate receptors Class C, Frizzled receptors Class F, and Taste-2 receptors. Within these receptors, peptides interact with the GPCRs of Class A and Class B1. Our previous work identified a C type of Allatostatin receptor (AlstR) from Class A in the laboratory stick insect, Carausius morosus (Duan Sahbaz et al., 2017). All types of AlstRs (A, B, and C) have a common function, which is inhibition of juvenile hormone (JH) secretion. However, their expression profiles differ in a stage-specific, tissuespecific, and species-specific manner. In addition, their inhibitory effect varies between species. The laboratory stick insect is an organism defined as an agricultural pest in some countries but fed as a pet in others. Its locomotion behavior is widely studied and modeled (Bläsing and Cruse, 2004; Gruhn et al., 2016; Dallmann et al., 2017). Additionally, other peptidergic mechanisms, such as ecdysis behavior, circadian rhythm, and heartbeat frequency, are as well studied (Wadsworth et al., 2014; Marco et al., 2018). Although the most researched mechanisms of the stick insect rely on peptidergic pathways, there is limited information on its neuropeptides and GPCRs. Even though its neuropeptidome was revealed recently (Liessem et al., 2018), we need to uncover the GPCRs they target and activate in order to understand the mechanism of action of the neuropeptides. There are well-fitted approaches and tools for GPCR prediction from RNA sequencing (RNAseq) data. For instance, the RNAseq approach has been recently used to predict the GPCR profiles of different arthropods (Buckley et al., 2016; Guerrero et al., 2016). These studies utilized the open reading frame and 7TM domain prediction tools to predict GPCR candidates. Then they filtered the reliable GPCRs with the help of the GPCRPred tool, which annotates and predicts GPCRs from other proteins with an accuracy of Abstract: G protein-coupled receptors (GPCRs) are 7-transmembrane proteins that transduce various extracellular signals into intracellular pathways. They are the major target of neuropeptides, which regulate the development, feeding behavior, mating behavior, circadian rhythm, and many other physiological functions of insects. In the present study, we performed RNA sequencing and de novo transcriptome assembly to uncover the GPCRs expressed in the stick insect Carausius morosus. The transcript assemblies were predicted for the presence of 7-transmembrane GPCR domains. As a result, 430 putative GPCR transcripts were obtained and 43 of these revealed full-length sequences with highly significant similarity to known GPCR sequences in the databases. Thirteen different GPCRs were chosen for tissue expression analysis. Some of these receptors, such as calcitonin, inotocin, and tyramine receptors, showed specific expression in some of the tissues. Additionally, GPCR prediction yielded a novel uncharacterized GPCR sequence, which was specifically expressed in the central nervous system and ganglia. Previously, the only information about the anatomy of the stick insect was on its gastrointestinal system. This study provides complete anatomical information about the adult insect.
Scientific Reports, 2017
Allatostatins (AST) are neuropeptides with variable function ranging from regulation of developme... more Allatostatins (AST) are neuropeptides with variable function ranging from regulation of developmental processes to the feeding behavior in insects. They exert their effects by binding to cognate GPCRs, called Allatostatin receptors (AlstR), which emerge as promising targets for pesticide design. However, AlstRs are rarely studied. This study is the first reported structural study on AlstR-AST interaction. In this work, the first C type AlstR from the stick insect Carausius morosus (CamAlstR-C) was identified and its interaction with type C AST peptide was shown to be physically consistent with the experimental results. The proposed structure of CamAlstR-C revealed a conserved motif within the third extracellular loop, which, together with the N-terminus is essential for ligand binding. In this work, computational studies were combined with molecular and nano-scale approaches in order to introduce an unknown GPCR-ligand system. Consequently, the data obtained provided a reliable target region for future agonist/inverse agonist studies on AlstRs.
ABSTRACTAge-related hearing loss (ARHL) is the most common sensory disability associated with hum... more ABSTRACTAge-related hearing loss (ARHL) is the most common sensory disability associated with human aging. Yet, there are no approved measures for preventing or treating this debilitating condition. With its slow progression, continuous and safe approaches are critical for ARHL treatment. Nicotinamide Riboside (NR), a NAD+ precursor, is well tolerated even for long-term use and is already shown effective in various disease models including Alzheimer’s and Parkinson’s Disease. It has also been beneficial against noise induced hearing loss and in hearing loss associated with premature aging. However, its beneficial impact on ARHL is not known. Using two different wild-type mouse strains, we show that long-term NR administration prevents the progression of ARHL. Through transcriptomic and biochemical analysis, we find that NR administration restores age-associated reduction in cochlear NAD+ levels, upregulates biological pathways associated with synaptic transmission and PPAR signaling...
Turkish neurosurgery, 2021
AIM We aimed to study the changes in the distribution of and the transcriptional levels associate... more AIM We aimed to study the changes in the distribution of and the transcriptional levels associated with α4- and α7-subtype nicotinic acetylcholine receptors (nAChRs) in the primary somatosensory (S1) and motor (M1) cortices of rats after electrical stimulation of the basal forebrain (BF). MATERIAL AND METHODS Immunofluorescence (IF) analyses were performed on brain sections from 20 rats (experimental groups: controls, contralateral, and ipsilateral to BF stimulation). The nAChR receptor complexes were labeled with antibodies and counted (N) in the cortical layers of the hindlimb representation (S1HL), barrel field (S1BF), and M1. To determine the relative transcriptional mRNA levels, qRT-PCR was performed with tissue from the associated brain regions of 14 different animals in two groups, controls and BF stimulation. RESULTS For all three tested brain regions, N and D (density) of the α7-subtype nAChR increased in both ipsilateral and contralateral hemispheres after BF stimulation. ...
Turkish Journal of Biology, 2019
G protein-coupled receptors (GPCRs) are 7-transmembrane proteins that transduce various extracell... more G protein-coupled receptors (GPCRs) are 7-transmembrane proteins that transduce various extracellular signals into
intracellular pathways. They are the major target of neuropeptides, which regulate the development, feeding behavior, mating behavior,
circadian rhythm, and many other physiological functions of insects. In the present study, we performed RNA sequencing and de
novo transcriptome assembly to uncover the GPCRs expressed in the stick insect Carausius morosus. The transcript assemblies were
predicted for the presence of 7-transmembrane GPCR domains. As a result, 430 putative GPCR transcripts were obtained and 43 of
these revealed full-length sequences with highly significant similarity to known GPCR sequences in the databases. Thirteen different
GPCRs were chosen for tissue expression analysis. Some of these receptors, such as calcitonin, inotocin, and tyramine receptors, showed
specific expression in some of the tissues. Additionally, GPCR prediction yielded a novel uncharacterized GPCR sequence, which was
specifically expressed in the central nervous system and ganglia. Previously, the only information about the anatomy of the stick insect
was on its gastrointestinal system. This study provides complete anatomical information about the adult insect.
Allatostatins (AST) are neuropeptides with variable function ranging from regulation of developme... more Allatostatins (AST) are neuropeptides with variable function ranging from regulation of developmental processes to the feeding behavior in insects. They exert their effects by binding to cognate GPCRs, called Allatostatin receptors (AlstR), which emerge as promising targets for pesticide design. However, AlstRs are rarely studied. This study is the first reported structural study on AlstR-AST interaction. In this work, the first C type AlstR from the stick insect Carausius morosus (CamAlstR-C) was identified and its interaction with type C AST peptide was shown to be physically consistent with the experimental results. The proposed structure of CamAlstR-C revealed a conserved motif within the third extracellular loop, which, together with the N-terminus is essential for ligand binding. In this work, computational studies were combined with molecular and nano-scale approaches in order to introduce an unknown GPCR-ligand system. Consequently, the data obtained provided a reliable target region for future agonist/inverse agonist studies on AlstRs. Allatostatin receptors (AlstR) are insect GPCRs, which function in inhibition of Juvenile Hormone (JH) synthesis in corpora allata during development. They also play a role during oogenesis, vitellogenesis and muscle contraction in midgut, either directly or indirectly via inhibiting JH 1–3. It has been shown that oral administration of Allatostatin (AST) or its analogs reduce survival and nymph production in pea aphids 4. Thus, the crucial role of AlstRs during key developmental and metabolic processes renders them potential targets for pesticide design. AlstRs identified so far have been grouped in three distinct classes (A, B and C types) according to their activating ligands. Type C AlstRs are homologous to mammalian somatostatin receptors (SSTR) which are known to inhibit growth hormone secretion in the hypothalamus 5. Type A and B AlstRs are closely related to galanin and bombe-sin receptors, respectively. The physiological function of AlstR-AST systems varies according to species-specific, tissue-specific and developmental stage-specific expression. For instance, even though there are two AlstR-C paralogs in D. melanogaster, their cognate peptide AST-C does not inhibit JH in larval stage of the organism 6. On the other hand, Manduca sexta AST-C peptides are shown to inhibit JH synthesis in different species and at developmental stages 7. AlstRs belong to the rhodopsin-like family of GPCRs (Family A). Rhodopsin is the first GPCR for which the 3D structure was resolved by X-ray crystallography 8 and therefore became a model for subsequent structural studies. Yet, X-ray and NMR approaches to reveal protein structure are very challenging for GPCRs due to their hydrophobic properties. Recent developments in bioinformatics have facilitated structural studies on GPCRs. For instance, Constanzi compared the crystal structure of the beta-2 adrenergic receptor with in silico models and proved its applicability to drug design 9. In order to support bioinformatics predictions and to identify the ligand binding pocket of GPCRs, random mutagenesis and subsequent activity assays are performed. In addition, molecular-physical approaches, such as Atomic Force Microscopy (AFM), enable quantitative analysis of the binding concept. However, working with purified GPCR molecules is not feasible because their dynamic properties may change when isolated from the lipid bilayer. Intermediate solutions such as integrating them into liposomes may provide a solution 10,11. Yet, in order to understand their proper physiological responses GPCRs should be examined directly on the cell surface. Single molecule force spectroscopy via AFM has been used successfully on living cells to measure the strength of ligand binding of transporter proteins 12 and integrins 13 while the same studies on GPCRs are limited 14 .
Books by Burcin Duan Sahbaz
InTechOpen, 2018
Neuropeptides constitute an important part of the nervous system, since the simple nerve nets (i.... more Neuropeptides constitute an important part of the nervous system, since the simple nerve nets (i.e. of Hydra). The assigned functions of these peptides vary enormously. For instance, besides inhibiting or stimulating the release of some hormones, they can be responsible for tentacle contraction of the Hydra, dropping the tail of the lizard, postnatal care of the beetles and also aggressiveness of humans. They perform these tasks via activating their cognate GPCRs, which are hypothesized to be coevolved with their ligand neuropeptides. In this chapter, we will introduce the concept of neuropeptide, its intracel-lular maturation process, characteristics of some typical neuropeptide families and the common properties of their cognate GPCRs. At last, we will try to give information about the widely used methods for studying GPCR-neuropeptide interactions.
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Papers by Burcin Duan Sahbaz
intracellular pathways. They are the major target of neuropeptides, which regulate the development, feeding behavior, mating behavior,
circadian rhythm, and many other physiological functions of insects. In the present study, we performed RNA sequencing and de
novo transcriptome assembly to uncover the GPCRs expressed in the stick insect Carausius morosus. The transcript assemblies were
predicted for the presence of 7-transmembrane GPCR domains. As a result, 430 putative GPCR transcripts were obtained and 43 of
these revealed full-length sequences with highly significant similarity to known GPCR sequences in the databases. Thirteen different
GPCRs were chosen for tissue expression analysis. Some of these receptors, such as calcitonin, inotocin, and tyramine receptors, showed
specific expression in some of the tissues. Additionally, GPCR prediction yielded a novel uncharacterized GPCR sequence, which was
specifically expressed in the central nervous system and ganglia. Previously, the only information about the anatomy of the stick insect
was on its gastrointestinal system. This study provides complete anatomical information about the adult insect.
Books by Burcin Duan Sahbaz
intracellular pathways. They are the major target of neuropeptides, which regulate the development, feeding behavior, mating behavior,
circadian rhythm, and many other physiological functions of insects. In the present study, we performed RNA sequencing and de
novo transcriptome assembly to uncover the GPCRs expressed in the stick insect Carausius morosus. The transcript assemblies were
predicted for the presence of 7-transmembrane GPCR domains. As a result, 430 putative GPCR transcripts were obtained and 43 of
these revealed full-length sequences with highly significant similarity to known GPCR sequences in the databases. Thirteen different
GPCRs were chosen for tissue expression analysis. Some of these receptors, such as calcitonin, inotocin, and tyramine receptors, showed
specific expression in some of the tissues. Additionally, GPCR prediction yielded a novel uncharacterized GPCR sequence, which was
specifically expressed in the central nervous system and ganglia. Previously, the only information about the anatomy of the stick insect
was on its gastrointestinal system. This study provides complete anatomical information about the adult insect.