The Memory Orchestra: Contribution of Astrocytes / 神经科学通报·英文版

For decades, memory research has centered on the role of neurons, which do not function in isolation. However, astrocytes play important roles in regulating neuronal recruitment and function at the local and network levels, forming the basis for information processing as well as memory formation and storage. In this review, we discuss the role of astrocytes in memory functions and their cellular underpinnings at multiple time points. We summarize important breakthroughs and controversies in the field as well as potential avenues to further illuminate the role of astrocytes in memory processes.

Central Regulation of Osteocalcin and Its Biological Mechanism / 中国生物化学与分子生物学报

Osteocalcin (OCN) regulates the physiological structure and function of various peripheral tissues and organs, and plays a central regulatory role, which is tightly associated with higher-level cognitive functions such as learning and memory. Studies have shown that OCN can enter the central nervous system through the blood-brain barrier and bind to GPR158 and GPR37, members of the G protein-coupled receptor (GPCR) family on the membrane of neurons or glial cells, activate or inhibit relevant intracellular signalling pathways, and then change the physiological activities of neurons or glial cells. In the brain, the role of OCN mainly includes regulating the synthesis and release of neurotransmitters such as serotonin, dopamine, norepinephrine and γ-aminobutyric acid, increasing the expression of brain-derived neurotrophic factor, promoting hippocampal neurogenesis, enhancing hippocampal neuron autophagy and maintaining myelin homeostasis, among others. Furthermore, OCN can also be involved in the regulation of the pathophysiological process of multiple neurodegenerative diseases. In Alzheimer's disease (AD), OCN treatment reduces β-amyloid protein (Aβ) deposition and Aβ-induced cytotoxicity in part, thereby improving learning and memory deficits; in Parkinson's disease (PD), OCN treatment inhibits the loss of substantia nigra and striatum dopaminergic neurons, increases the content of tyrosine hydroxylase and decreases neuroinflammation, thereby alleviating motor dysfunction. By analyzing the structure and function of GPR158 and GPR37, analyzing the role of OCN in the brain and its biological mechanism, and exploring the effect of OCN on neurodegenerative diseases such as AD and PD, this paper aims to provide a basis for further screening new targets to promote brain health.

Role of Helix 8 in Dopamine Receptor Signaling

G protein-coupled receptors (GPCRs) are membrane receptors whose agonist-induced dynamic conformational changes trigger heterotrimeric G protein activation, followed by GRK-mediated phosphorylation and arrestin-mediated desensitization. Cytosolic regions of GPCRs have been studied extensively because they are direct contact sites with G proteins, GRKs, and arrestins. Among various cytosolic regions, the role of helix 8 is least understood, although a few studies have suggested that it is involved in G protein activation, receptor localization, and/or internalization. In the present study, we investigated the role of helix 8 in dopamine receptor signaling focusing on dopamine D1 receptor (D1R) and dopamine D2 receptor (D2R). D1R couples exclusively to Gs, whereas D2R couples exclusively to Gi. Bioinformatic analysis implied that the sequences of helix 8 may affect GPCR-G protein coupling selectivity; therefore, we evaluated if swapping helix 8 between D1R and D2R changed G protein selectivity. Our results suggest that helix 8 is not involved in D1R-Gs or D2R-Gi coupling selectivity. Instead, we observed that D1R with D2R helix 8 or D1R with an increased number of hydrophobic residues in helix 8 relative to wild-type showed diminished β-arrestin-mediated desensitization, resulting in increased Gs signaling.

Pro-Inflammatory Role of S1P₃ in Macrophages

Sphingosine kinase 1 and its product, sphingosine 1-phosphate (S1P), as well as their receptors, have been implicated in inflammatory responses. The functions of receptors S1P₁ and S1P₂ on cell motility have been investigated. However, the function of S1P₃ has been poorly investigated. In this study, the roles of S1P₃ on inflammatory response were investigated in primary perito-neal macrophages. S1P₃ receptor was induced along with sphingosine kinase 1 by stimulation of lipopolysaccharide (LPS). LPS treatment induced inflammatory genes, such iNOS, COX-2, IL-1β, IL-6 and TNF-α. TY52156, an antagonist of S1P₃ suppressed the induction of inflammatory genes in a concentration dependent manner. Suppression of iNOS and COX-2 induction was further confirmed by western blotting and NO measurement. Suppression of IL-1β induction was also confirmed by western blotting and ELISA. Caspase 1, which is responsible for IL-1β production, was similarly induced by LPS and suppressed by TY52156. Therefore, we have shown S1P₃ induction in the inflammatory conditions and its pro-inflammatory roles. Targeting S1P₃ might be a strategy for regulating inflammatory diseases.

Lucy-tag promotes expression of sea lamprey (Petromyzon marinus) olfactory receptor on cell membrane / 中国药理学通报

Aim To elucidate the effect of Lucy-tag polypeptide label on the expression of olfactory receptor membrane in sea lamprey ( Petromyzon marinus). Methods Immunocytochemis-try, double luciferase system and calcium flow detection were used to verify the effect of polypeptide label Lucy-tag on olfactory receptors of sea lamprey. Results Polypeptide label Lucy-tag promoted the membrane expression of 13 olfactory receptors out of 20 olfactory receptors, and Lucy-tag did not affect the intrinsic activity of olfactory receptors, nor did it affect the IP3 signaling pathway of G protein coupled receptor (GPCR). Conclusions It provides a favorable technique for finding the ligand of olfactory receptor and lays a good theoretical foundation for the further study of the function of the GPCR and ligand.

Arrestins: structural disorder creates rich functionality

Arrestins are soluble relatively small 44-46 kDa proteins that specifically bind hundreds of active phosphorylated GPCRs and dozens of non-receptor partners. There are binding partners that demonstrate preference for each of the known arrestin conformations: free, receptor-bound, and microtubule-bound. Recent evidence suggests that conformational flexibility in every functional state is the defining characteristic of arrestins. Flexibility, or plasticity, of proteins is often described as structural disorder, in contrast to the fixed conformational order observed in high-resolution crystal structures. However, protein-protein interactions often involve highly flexible elements that can assume many distinct conformations upon binding to different partners. Existing evidence suggests that arrestins are no exception to this rule: their flexibility is necessary for functional versatility. The data on arrestins and many other multi-functional proteins indicate that in many cases, "order" might be artificially imposed by highly non-physiological crystallization conditions and/or crystal packing forces. In contrast, conformational flexibility (and its extreme case, intrinsic disorder) is a more natural state of proteins, representing true biological order that underlies their physiologically relevant functions.

Spinal Mechanisms of Itch Transmission / 神经科学通报·英文版

Peripheral itch stimuli are transmitted by sensory neurons to the spinal cord dorsal horn, which then transmits the information to the brain. The molecular and cellular mechanisms within the dorsal horn for itch transmission have only been investigated and identified during the past ten years. This review covers the progress that has been made in identifying the peptide families in sensory neurons and the receptor families in dorsal horn neurons as putative itch transmitters, with a focus on gastrin-releasing peptide (GRP)-GRP receptor signaling. Also discussed are the signaling mechanisms, including opioids, by which various types of itch are transmitted and modulated, as well as the many conflicting results arising from recent studies.

Molecular Signature That Determines the Acute Tolerance of G Protein-Coupled Receptors

Desensitization and acute tolerance are terms used to describe the attenuation of receptor responsiveness by prolonged or intermittent exposure to an agonist. Unlike desensitization of G protein-coupled receptors (GPCRs), which is commonly explained by steric hindrance caused by the β-arrestins that are translocated to the activated receptors, molecular mechanisms involved in the acute tolerance of GPCRs remain unclear. Our studies with several GPCRs and related mutants showed that the acute tolerance of GPCRs could occur independently of agonist-induced β-arrestin translocation. A series of co-immunoprecipitation experiments revealed a correlation between receptor tolerance and interactions among receptors, β-arrestin2, and Gβγ. Gβγ displayed a stable interaction with receptors and β-arrestin2 in cells expressing GPCRs that were prone to undergo tolerance compared to the GPCRs that were resistant to acute tolerance. Strengthening the interaction between Gβγ and β-arrestin rendered the GPCRs to acquire the tendency of acute tolerance. Overall, stable interaction between the receptor and Gβγ complex is required for the formation of a complex with β-arrestin, and determines the potential of a particular GPCR to undergo acute tolerance. Rather than turning off the signal, β-arrestins seem to contribute on continuous signaling when they are in the context of complex with receptor and Gβγ.

Calcium Signaling of Lysophosphatidylethanolamine through LPA1 in Human SH-SY5Y Neuroblastoma Cells

Lysophosphatidylethanolamine (LPE), a lyso-type metabolite of phosphatidylethanolamine, has been reported to be an intercellular signaling molecule. LPE mobilizes intracellular Ca²⁺ through G-protein-coupled receptor (GPCR) in some cells types. However, GPCRs for lysophosphatidic acid (LPA) were not implicated in the LPE-mediated activities in LPA GPCR overexpression systems or in SK-OV3 ovarian cancer cells. In the present study, in human SH-SY5Y neuroblastoma cells, experiments with LPA₁ antagonists showed LPE induced intracellular Ca²⁺ increases in an LPA₁ GPCR-dependent manner. Furthermore, LPE increased intracellular Ca²⁺ through pertussis-sensitive G proteins, edelfosine-sensitive-phospholipase C, 2-APB-sensitive IP₃ receptors, Ca²⁺ release from intracellular Ca²⁺ stores, and subsequent Ca²⁺ influx across plasma membranes, and LPA acted on LPA₁ and LPA₂ receptors to induce Ca²⁺ response in a 2-APB-sensitive and insensitive manner. These findings suggest novel involvements for LPE and LPA in calcium signaling in human SH-SY5Y neuroblastoma cells.

Rational design of GRK2 inhibitors for the treatment of heart failure / 中国药理学与毒理学杂志

G protein-coupled receptors (GPCRs) convert extracellular stimuli in the form of hormones, odorants and light into profound changes in cell homeostasis. Their timely desensitization is critical for cells to rapidly respond to changes in their environment and to avoid damage from sustained signaling. Seven GPCR kinases (GRKs) phosphorylate and regulate the activity of most of the ~800 GPCRs in the human genome. Although GRKs normally play an adaptive role, in conditions such as chronic heart failure they are overexpressed and linked to disease progression. GRK2 and GRK5 have thus become important targets for the treatment of heart failure and pathological cardiac hypertrophy, respectively. Our lab has determined atomic structures representing all three vertebrate GRK subfamilies, and is now in the midst of a campaign to develop selective inhibitors of these enzymes using structure-based rational design. We have identified the FDA approved drug paroxetine as a selective GRK2 inhibitor, determined the crystal structure of the GRK2·paroxetine complex and, in collaboration with the Koch lab, showed that the drug improves contractility in myocytes and, most impressively, recovery in post-myocardial infarcted mice. Since then, we have identified additional chemical scaffolds that exhibit even higher potency and/or selectivity for GRK5. Using a ″hybrid″ inhibitor design approach we have generated GRK selective chemical probes that exhibit improved potency and stability and are able to increase inotropy and dampen the hypertrophic response in cardiomyocytes and small animal models. Structural analysis has revealed the molecular basis for selectivity and potency in many of these compounds, allowing for the design of future generations of GRK chemical probes.

Research progress in multiple regulation pathways of STAT3 in cancer / 中国肿瘤临床

The activation of the proto-oncogene STAT3 is strongly controlled under physiological conditions. However, obtained evi-dence revealed that STAT3 is persistently activated in cancer cells and contributes to cancer initiation and progression. Studies demon-strated the various functions of activated STAT3 in promoting cancer development and aggravation, including cancer cell proliferation, invasion and metastasis, drug resistance, epithelial-mesenchymal transition, regulation of the tumor microenvironment, and promo-tion of the self-renewal and differentiation of cancer stem cells. Canonically, STAT3 is regulated by signaling pathways mediated by cy-tokines and growth factors. Many studies determined that STAT3 was also regulated by G protein-coupled receptors, cadherin engage-ment, Toll-like receptors, microRNA, and acetylation. We summarized the recent developments in the research on the regulation of STAT3 activation.

EP2 Induces p38 Phosphorylation via the Activation of Src in HEK 293 Cells

Prostaglandin E2 (PGE2), a major product of cyclooxygenase, binds to four different prostaglandin E2 receptors (EP1, EP2, EP3, and EP4) which are G-protein coupled transmembrane receptors (GPCRs). Although GPCRs including EP receptors have been shown to be associated with their specific G proteins, recent evidences suggest that GPCRs can regulate MAPK signaling via non-G protein coupled pathways including Src. EP2 is differentially expressed in various tissues and the expression of EP2 is induced by extracellular stimuli. We hypothesized that an increased level of EP2 expression may affect MAPK signaling. The overexpression of EP2 in HEK 293 cells resulted in significant increase in intracellular cAMP levels response to treatment with butaprost, a specific EP2 agonist, while overexpression of EP2 alone did not increase intracellular cAMP levels. However, EP2 overexpression in the absence of PGE2 induced an increase in the level of p38 phosphorylation as well as the kinase activity of p38, suggesting that up-regulation of EP2 may promote p38 activation via non-G protein coupled pathway. Inhibition of Src completely blocked EP2-induced p38 phosphorylation and overexpression of Src increased the level of p38 phosphorylation, indicating that Src is upstream kinase for EP2-induced p38 phosphorylation. EP2 overexpression also increased the Src activity and EP2 protein was co-immunoprecipitated with Src. Furthermore, sequential co-immunoprecipitation studies showed that EP2, Src, and beta-arrestin can form a complex. Our study found a novel pathway in which EP2 is associated with Src, regulating p38 pathway.

Development and evaluation of HEK293 cells stably expressing CRFR1 / 中国药理学通报

Aim ToconstructHEK293cellsstablyex-pressing corticotropin releasing factor receptor 1 ( CRFR1 ) , and evaluate its function by the cAMP as-say.Methods CulturedHEK293cellsweretransfect-ed with CRFR1-expressing vector by Lipofectamine 2000 and were selected by using G418 . CRFR1 ex-pression was detected by Western blot, RT-PCR and immunofluorescence.Results Westernblot,RT-PCR and immunofluorescence data revealed that the HEK293 cells expressed CRFR1 protein stably. The dose-responsive relationship experiment revealed that CRF induced a CRFR1-mediated cAMP production in HEK293 cells with EC50 =(5. 64 ± 0. 05) × 10 -10 mol ·L-1.Conclusion HEK293celllinesstablyex-pressing CRFR1 were constructed successfully, which would provide a cellular model to facilitate the research on the biological function of CRFR1 and CRFR1-targe-ted drug screening.

G protein-coupled receptor, family C, group 5 (GPRC5B) downregulation in spinal cord neurons is involved in neuropathic pain / 대한마취과학회지

BACKGROUND: G protein-coupled receptor, family C, group 5 (GPRC5B), a retinoic acid-inducible orphan G-protein-coupled receptor (GPCR), is a member of the group C metabotropic glutamate receptor family proteins presumably related in non-canonical Wnt signaling. In this study, we investigated altered GPRC5B expression in the dorsal horn of the spinal cord after spinal nerve injury and its involvement in the development of neuropathic pain. METHODS: After induction of anesthesia by intraperitoneal injection of pentobarbital (35 mg /kg), the left L5 spinal nerve at the level of 2 mm distal to the L5 DRG was tightly ligated with silk and cut just distal to the ligature. Seven days after nerve injury, animals were perfused with 4% paraformaldehyde, and the spinal cords were extracted and post-fixed at 4degrees C overnight. To identify the expression of GPRC5B and analyze the involvement of GPRC5B in neuropathic pain, immunofluorescence was performed using several markers for neurons and glial cells in spinal cord tissue. RESULTS: After L5 spinal nerve ligation (SNL), the expression of GPRC5B was decreased in the ipsilateral part, as compared to the contralateral part, of the spinal dorsal horn. SNL induced the downregulation of GPRC5B in NeuN-positive neurons in the spinal dorsal horn. However, CNPase-positive oligodendrocytes, OX42-positive microglia, and GFAP-positive astrocytes were not immunolabeled with GPRC5B antibody in the spinal dorsal horn. CONCLUSIONS: These results imply that L5 SNL-induced GPRC5B downregulation may affect microglial activation in the spinal dorsal horn and be involved in neuropathic pain.

Action and Signaling of Lysophosphatidylethanolamine in MDA-MB-231 Breast Cancer Cells

Previously, we reported that lysophosphatidylethanolamine (LPE), a lyso-type metabolite of phosphatidylethanolamine, can increase intracellular Ca2+ ([Ca2+]i) via type 1 lysophosphatidic acid (LPA) receptor (LPA1) and CD97, an adhesion G-protein-coupled receptor (GPCR), in MDA-MB-231 breast cancer cells. Furthermore, LPE signaling was suggested as like LPA1/CD97-Gi/o proteins-phospholipase C-IP3-Ca2+ increase in these cells. In the present study, we further investigated actions of LPE not only in the [Ca2+]i increasing effect but also in cell proliferation and migration in MDA-MB-231 breast cancer cells. We utilized chemically different LPEs and a specific inhibitor of LPA1, AM-095 in comparison with responses in SK-OV3 ovarian cancer cells. It was found that LPE-induced Ca2+ response in MDA-MB-231 cells was evoked in a different manner to that in SK-OV3 cells in terms of structural requirements. AM-095 inhibited LPE-induced Ca2+ response and cell proliferation in MDA-MB-231 cells, but not in SK-OV3 cells, supporting LPA1 involvement only in MDA-MB-231 cells. LPA had significant effects on cell proliferation and migration in MDA-MB-231 cells, whereas LPE had less or no significant effect. However, LPE modulations of MAPKs (ERK1/2, JNK and p38 MAPK) was not different to those by LPA in the cells. These data support the involvement of LPA1 in LPE-induced Ca2+ response and cell proliferation in breast MDA-MB-231 cells but unknown GPCRs (not LPA1) in LPE-induced responses in SK-OV3 cells. Furthermore, although LPE and LPA utilized LPA1, LPA utilized more signaling cascades than LPE, resulting in stronger responses by LPA in proliferation and migration than LPE in MDA-MB-231 cells.

Identification and Characterization of Dopamine D4 Receptor (DRD4) Gene Sequence within and Among Non Mammalian Species.

A number of polymorphic tandem repeats in human dopamine D4 receptor (DRD4) have been identified in the exons, including a 12-bp repeat in the first exon and a 48-bp repeat in exon III located in the third cytoplasmic loop. However, to determine whether the tandem repeats is specific to humans or not, we have identified and characterized dopamine receptor D4 (DRD4) Exon III tandem repeats in public available nucleotide sequences from 13 different non mammalian species. We found that the tandem repeat was composed of 21-bp modules in sequences from the Mycobacterium smegmatis str. MC2 155, Salinibacter ruber DSM 13855, Danio rerio, Parus major, Corvus macrorhynchos, and Coturnix japonica. A tandem repeat consisting of 30-bp modules was identified in sequence from Melopsittacus undulates while in the Phalacrocorax capillatus and Numida meleagris we identified tandem repeats composed of 3-bp modules. Tandem repeats could not be identified in sequences from Carassius auratus, Phasianus colchicus and Gallus gallus. To understand the evolutionary history of the Exon I region of DRD4—which in humans contains a polymorphic 12bp tandem duplication, a polymorphic 13bp deletion, and other rare variants—we examined the homologous exon in these different species. There was a low degree of similarity between the sequences of bacterial species and those from members of the piscean and avian and with human sequence. We identified transmembrane domain of DRD4 gene and signature of G-protein coupled receptors in the amino acid sequences. The number of transmembrane segments varied pronouncedly between species from 0 to 7 and signature of G-protein coupled receptors was found only in piscean species and was also identified in one avian species (parus major). These findings suggest that an association between Drd4 gene polymorphisms and animal personality variation predates the divergence of the non mammalian and mammalian lineages. Furthermore, the analysis of Drd4 polymorphisms within and among populations may provide information for elucidating the phylogenetic relationship and such data may also provide a clue toward understanding the relation between the genetic variation and behavioral variation in animals.

Intercellular Lipid Mediators and GPCR Drug Discovery

G-protein-coupled receptors (GPCR) are the largest superfamily of receptors responsible for signaling between cells and tissues, and because they play important physiological roles in homeostasis, they are major drug targets. New technologies have been developed for the identification of new ligands, new GPCR functions, and for drug discovery purposes. In particular, intercellular lipid mediators, such as, lysophosphatidic acid and sphingosine 1-phosphate have attracted much attention for drug discovery and this has resulted in the development of fingolimod (FTY-720) and AM095. The discovery of new intercellular lipid mediators and their GPCRs are discussed from the perspective of drug development. Lipid GPCRs for lysophospholipids, including lysophosphatidylserine, lysophosphatidylinositol, lysophosphatidylcholine, free fatty acids, fatty acid derivatives, and other lipid mediators are reviewed.

Structural Aspects of GPCR-G Protein Coupling

G protein-coupled receptors (GPCRs) are membrane receptors; approximately 40% of drugs on the market target GPCRs. A precise understanding of the activation mechanism of GPCRs would facilitate the development of more effective and less toxic drugs. Heterotrimeric G proteins are important molecular switches in GPCR-mediated signal transduction. An agonist-activated receptor interacts with specific sites on G proteins and promotes the release of GDP from the Galpha subunit. Because of the important biological role of the GPCR-G protein coupling, conformational changes in the G protein upon receptor coupling have been of great interest. One of the most important questions was the interface between the GPCR and G proteins and the structural mechanism of GPCR-induced G protein activation. A number of biochemical and biophysical studies have been performed since the late 80s to address these questions; there was a significant breakthrough in 2011 when the crystal structure of a GPCR-G protein complex was solved. This review discusses the structural aspects of GPCR-G protein coupling by comparing the results of previous biochemical and biophysical studies to the GPCR-G protein crystal structure.

High-throughput screening assays for G-protein-coupled receptors-targeted drug discovery / 国际药学研究杂志

G-protein-coupled receptors (GPCR), also known as 7 trans-membrane receptors. are the largest family of cell surface receptois. GPCR mediate many important physiological functions and are among the most successful therapeutic targets for a broad spectrum of diseases. These receptors are the targets of >50% of the current therapeutic agents on the market. Therefore, GPCR assay development and GPCR ligand screening remain the major focus of drug discovery research worldwide. In this review. we summarize the most widely used GPCR assays and recent advances in high-throughput screening technology for GPCR drug discovery. © 2006 Editorial office of Foreign Medical Sciences.

Characteristics of New Drugs as Ligands of G-Protein Coupled Receptor and Time-Dependent Changes of the New Drug Approvals over Three Decades from 1980 to 2009 in Japan / 医薬品情報学

<b>Objective: </b>We analyzed the characteristics of ligands of G-protein coupled receptor (GPCR) of new drugs approved, and the time dependent changes of these new drug approvals over three decades from 1980 to 2009 in Japan.<br><b>Methods: </b>The receptor therapeutic targets of 185 new drugs were distributed 20 receptor families of GPCR.  Most of new drugs which targeted GPCR were the ligands of class A receptors.  Among the class A receptors, the receptors of amine family, such as adrenaline, dopamine, histamine, serotonin and muscarinic receptor were the targets of new drugs.  One hundred and ten of 185 new drugs were the antagonist and other 75 were the agonist of GPCR.  Whether the new drug is agonist or antagonist depended on the receptor subtype.  The time dependent changes of new drug approval were different among the drugs depending on which GPCR was targeted.  Approval of new drugs which targeted some GPCR decreased time dependently.  In contrast, approval of new drugs which targeted other GPCR increased time dependently or continuously retained.<br><b>Results: </b>The results obtained in this study indicated characteristics of targeted GPCR, and time dependent changes of new drugs approvals, and suggest the future aspect of new drugs.