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Selvaraj C, Rudhra O, Alothaim AS, Alkhanani M, Singh SK. Structure and chemistry of enzymatic active sites that play a role in the switch and conformation mechanism. ADVANCES IN PROTEIN CHEMISTRY AND STRUCTURAL BIOLOGY 2022; 130:59-83. [PMID: 35534116 DOI: 10.1016/bs.apcsb.2022.02.002] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Enzymes, which are biological molecules, are constructed from polypeptide chains, and these molecules are activated through reaction mechanisms. It is the role of enzymes to speed up chemical reactions that are used to build or break down cell structures. Activation energy is reduced by the enzymes' selective binding of substrates in a protected environment. In enzyme tertiary structures, the active sites are commonly situated in a "cleft," which necessitates the diffusion of substrates and products. The amino acid residues of the active site may be far apart in the primary structure owing to the folding required for tertiary structure. Due to their critical role in substrate binding and attraction, changes in amino acid structure at or near the enzyme's active site usually alter enzyme activity. At the enzyme's active site, or where the chemical reactions occur, the substrate is bound. Enzyme substrates are the primary targets of the enzyme's active site, which is designed to assist in the chemical reaction. This chapter elucidates the summary of structure and chemistry of enzymes, their active site features, charges and role of water in the structures to clarify the biochemistry of the enzymes in the depth of atomic features.
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Affiliation(s)
- Chandrabose Selvaraj
- Computer Aided Drug Design and Molecular Modelling Lab, Department of Bioinformatics, Science Block, Alagappa University, Karaikudi, Tamil Nadu, India.
| | - Ondipilliraja Rudhra
- Computer Aided Drug Design and Molecular Modelling Lab, Department of Bioinformatics, Science Block, Alagappa University, Karaikudi, Tamil Nadu, India
| | - Abdulaziz S Alothaim
- Department of Biology, College of Science in Zulfi, Majmaah University, Majmaah, Saudi Arabia
| | - Mustfa Alkhanani
- Emergency Service Department, College of Applied Sciences, Al Maarefa University, Riyadh, Saudi Arabia
| | - Sanjeev Kumar Singh
- Computer Aided Drug Design and Molecular Modelling Lab, Department of Bioinformatics, Science Block, Alagappa University, Karaikudi, Tamil Nadu, India.
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Li D, Bao P, Yin Z, Sun L, Feng J, He Z, Jin M, Liu C. Exploration of the involvement of LncRNA in HIV-associated encephalitis using bioinformatics. PeerJ 2018; 6:e5721. [PMID: 30345171 PMCID: PMC6187992 DOI: 10.7717/peerj.5721] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2018] [Accepted: 09/05/2018] [Indexed: 01/25/2023] Open
Abstract
Background HIV-associated encephalitis (HIVE) is one of the common complications of HIV infection, and the pathogenesis of HIVE remains unclear, while lncRNA might be involved it. In this study, we made re-annotation on the expression profiling from the HIVE study in the public database, identified the lncRNA that might be involved in HIVE, and explored the possible mechanism. Methods In the GEO public database, the microarray expression profile (GSE35864) of three regions of brain tissues (white matter, frontal cortex and basal ganglia brain tissues) was chosen, updated annotation was performed to construct the non-cording-RNA (ncRNA) microarray data. Morpheus was used to identify the differential expressed ncRNA, and Genbank of NCBI was used to identify lncRNAs. The StarBase, PITA and miRDB databases were used to predict the target miRNAs of lncRNA. The TargetScan, PicTar and MiRanda databases were used to predict the target genes of miRNAs. The GO and KEGG pathway analysis were used to make function analysis on the targets genes. Results Seventeen differentially expressed lncRNAs were observed in the white matter of brain tissues, for which 352 target miRNAs and 6,659 target genes were predicted. The GO function analysis indicated that the lncRNAs were mainly involved in the nuclear transcription and translation processes. The KEGG pathway analysis showed that the target genes were significantly enriched in 33 signal pathways, of which 11 were clearly related to the nervous system function. Discussion The brand-new and different microarray results can be obtained through the updated annotation of the chips, and it is feasible to identify lncRNAs from ordinary chips. The results suggest that lncRNA may be involved in the occurrence and development of HIVE, which provides a new direction for further research on the diagnosis and treatment of HIVE.
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Affiliation(s)
- Diangeng Li
- Chinese PLA General Hospital, Nanlou Respiratory Diseases Department, Beijing, China
| | - Pengtao Bao
- Chinese PLA General Hospital, Nanlou Respiratory Diseases Department, Beijing, China.,Department of Respiratory Medicine, The 309th Hospital of People's Liberation Army, Beijing, China
| | - Zhiwei Yin
- Chinese PLA General Hospital, Department of Nephrology, Beijing, China
| | - Lei Sun
- Chinese PLA General Hospital, Editorial Office of Chinese Journal of Otology, Beijing, China
| | - Jin Feng
- Chinese PLA General Hospital, Department of stomotology, Beijing, China
| | - Zheng He
- Chinese PLA General Hospital, Department of Clinical Laboratory, Beijing, China
| | - Meiling Jin
- Beijing Chao-yang Hospital, Department of Nephrology, Beijing, China
| | - Changting Liu
- Chinese PLA General Hospital, Nanlou Respiratory Diseases Department, Beijing, China
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3
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Mitochondrial proteomics investigation of frontal cortex in an animal model of depression: Focus on chronic antidepressant drugs treatment. Pharmacol Rep 2018; 70:322-330. [DOI: 10.1016/j.pharep.2017.11.016] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2017] [Revised: 11/15/2017] [Accepted: 11/24/2017] [Indexed: 12/31/2022]
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4
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Xifró X, Miñano-Molina AJ, Saura CA, Rodríguez-Álvarez J. Ras protein activation is a key event in activity-dependent survival of cerebellar granule neurons. J Biol Chem 2014; 289:8462-72. [PMID: 24523415 DOI: 10.1074/jbc.m113.536375] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Neuronal activity promotes the survival of cerebellar granule neurons (CGNs) during the postnatal development of cerebellum. CGNs that fail to receive excitatory inputs will die by apoptosis. This process could be mimicked in culture by exposing CGNs to either a physiological concentration of KCl (5 mm or K5) plus N-methyl-d-aspartate (NMDA) or to 25 mm KCl (K25). We have previously described that a 24-h exposure to NMDA (100 μm) or K25 at 2 days in vitro induced long term survival of CGNs in K5 conditions. Here we have studied the molecular mechanisms activated at 2 days in vitro in these conditions. First we showed that NMDA or K25 addition promoted a rapid stimulation of PI3K and a biphasic phosphorylation on Ser-473 of Akt, a PI3K substrate. Interestingly, we demonstrated that only the first wave of Akt phosphorylation is necessary for the NMDA- and K25-mediated survival. Additionally, we detected that both NMDA and K25 increased ERK activity with a similar time-course. Moreover, our results showed that NMDA-mediated activation of the small G-protein Ras is necessary for PI3K/Akt pathway activation, whereas Rap1 was involved in NMDA phosphorylation of ERK. On the other hand, Ras, but not Rap1, mediates K25 activation of PI3K/Akt and MEK/ERK pathways. Because neuroprotection by NMDA or K25 is mediated by Ras (and not by Rap1) activation, we propose that Ras stimulation is a crucial event in NMDA- and K25-mediated survival of CGNs through the activation of PI3K/Akt and MEK/ERK pathways.
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Affiliation(s)
- Xavier Xifró
- From the Institut de Neurociencies and Department of Bioquímica i Biología Molecular, Universitat Autònoma de Barcelona, 08193 Cerdanyola del Vallès, Spain
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Duarte DB, Duan JH, Nicol GD, Vasko MR, Hingtgen CM. Reduced expression of SynGAP, a neuronal GTPase-activating protein, enhances capsaicin-induced peripheral sensitization. J Neurophysiol 2011; 106:309-18. [PMID: 21525372 DOI: 10.1152/jn.00963.2010] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Synaptic GTPase-activating protein (SynGAP) is a neuronal-specific Ras/Rap-GAP that increases the hydrolysis rate of GTP to GDP, converting Ras/Rap from the active into the inactive form. The Ras protein family modulates a wide range of cellular pathways including those involved in sensitization of sensory neurons. Since GAPs regulate Ras activity, SynGAP might be an important regulator of peripheral sensitization and pain. Therefore, we evaluated excitability, stimulus-evoked release of the neuropeptide calcitonin gene-related peptide (CGRP), and nociception from wild-type (WT) mice and those with a heterozygous mutation of the SynGAP gene (SynGAP(+/-)). Our results demonstrate that SynGAP is expressed in primary afferent sensory neurons and that the capsaicin-stimulated CGRP release from spinal cord slices was two-fold higher from SynGAP(+/-) mice than that observed from WT mouse tissue, consistent with an increase in expression of the capsaicin receptor, transient receptor potential cation channel subfamily V member 1 (TRPV1), in SynGAP(+/-) dorsal root ganglia. However, there was no difference between the two genotypes in potassium-stimulated release of CGRP, the number of action potentials generated by a ramp of depolarizing current, or mechanical hypernociception elicited by intraplantar injection of capsaicin. In contrast, capsaicin-induced thermal hypernociception occurred at lower doses of capsaicin and had a longer duration in SynGAP(+/-) mice than WT mice. These results provide the first evidence that SynGAP is an important regulator of neuropeptide release from primary sensory neurons and can modulate capsaicin-induced hypernociception, demonstrating the importance of GAP regulation in signaling pathways that play a role in peripheral sensitization.
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Affiliation(s)
- Djane Braz Duarte
- Department of Pharmacology and Toxicology and 2Neurology, Indiana University School of Medicine, Indianapolis, Indiana 46202, USA
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Duan JH, Wang Y, Duarte D, Vasko MR, Nicol GD, Hingtgen CM. Ras signaling pathways mediate NGF-induced enhancement of excitability of small-diameter capsaicin-sensitive sensory neurons from wildtype but not Nf1+/- mice. Neurosci Lett 2011; 496:70-4. [PMID: 21501659 DOI: 10.1016/j.neulet.2011.03.083] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2011] [Revised: 03/18/2011] [Accepted: 03/28/2011] [Indexed: 11/30/2022]
Abstract
Nerve growth factor (NGF) activates multiple downstream effectors, including Ras, phosphoinositide-3 kinase, and sphingomyelins. However, pathway mediating the NGF-induced augmentation of sensory neuronal excitability remains largely unknown. We previously reported that small-diameter sensory neurons with a heterozygous mutation of the Nf1 gene (Nf1+/-) exhibited increased excitability. The protein product of the Nf1 gene is neurofibromin, a guanosine triphosphatase-activating protein (GAP) for p21ras (Ras) that accelerates the conversion of active Ras-GTP to inactive Ras-GDP. Thus, Nf1+/- cells have augmented basal and stimulated Ras activity. To investigate whether NGF-induced increases in excitability of small-diameter sensory neurons are dependent on Ras signaling, an antibody that blocks the activation of Ras, Y13-259, was perfused into the cell. Under these conditions, the enhanced excitability produced by NGF was suppressed in wildtype neurons but the excitability of Nf1+/- neurons was unaltered. In addition, expression of a dominant-negative form of Ras abolished the ability of NGF to increase the excitability of small-diameter sensory neurons. These results demonstrate that NGF enhances excitability of small-diameter sensory neurons in a Ras-dependent manner while the consequences of decreased expression of neurofibromin cannot be restored by blocking Ras signaling; suggesting that Ras-initiated signaling pathways can regulate both transcriptional and posttranslational control of ion channels important in neuronal excitability.
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Affiliation(s)
- J-H Duan
- Department of Pharmacology and Toxicology, School of Medicine, Indiana University, Indianapolis, IN 46202, United States
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7
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Penzes P, Woolfrey KM, Srivastava DP. Epac2-mediated dendritic spine remodeling: implications for disease. Mol Cell Neurosci 2010; 46:368-80. [PMID: 21115118 DOI: 10.1016/j.mcn.2010.11.008] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2010] [Accepted: 11/11/2010] [Indexed: 12/12/2022] Open
Abstract
In the mammalian forebrain, most glutamatergic excitatory synapses occur on small dendritic protrusions called dendritic spines. Dendritic spines are highly plastic and can rapidly change morphology in response to numerous stimuli. This dynamic remodeling of dendritic spines is thought to be critical for information processing, memory and cognition. Conversely, multiple studies have revealed that neuropathologies such as autism spectrum disorders (ASDs) are linked with alterations in dendritic spine morphologies and miswiring of neural circuitry. One compelling hypothesis is that abnormal dendritic spine remodeling is a key contributing factor for this miswiring. Ongoing research has identified a number of mechanisms that are critical for the control of dendritic spine remodeling. Among these mechanisms, regulation of small GTPase signaling by guanine-nucleotide exchange factors (GEFs) is emerging as a critical mechanism for integrating physiological signals in the control of dendritic spine remodeling. Furthermore, multiple proteins associated with regulation of dendritic spine remodeling have also been implicated with multiple neuropathologies, including ASDs. Epac2, a GEF for the small GTPase Rap, has recently been described as a novel cAMP (yet PKA-independent) target localized to dendritic spines. Signaling via this protein in response to pharmacological stimulation or cAMP accumulation, via the dopamine D1/5 receptor, results in Rap activation, promotes structural destabilization, in the form of dendritic spine shrinkage, and functional depression due to removal of GluR2/3-containing AMPA receptors. In addition, Epac2 forms macromolecular complexes with ASD-associated proteins, which are sufficient to regulate Epac2 localization and function. Furthermore, rare non-synonymous variants of the EPAC2 gene associated with the ASD phenotype alter protein function, synaptic protein distribution, and spine morphology. We review here the role of Epac2 in the remodeling of dendritic spines under normal conditions, the mechanisms that underlie these effects, and the implications these disease-associated variants have on our understanding of the pathophysiology of ASD.
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Affiliation(s)
- Peter Penzes
- Department of Physiology, Northwestern University Feinberg School of Medicine, Chicago, IL 60611, USA.
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Wang H, Imamura Y, Ishibashi R, Chandana EPS, Yamamoto M, Noda M. The Reck tumor suppressor protein alleviates tissue damage and promotes functional recovery after transient cerebral ischemia in mice. J Neurochem 2010; 115:385-98. [PMID: 20796170 DOI: 10.1111/j.1471-4159.2010.06933.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
The extracellular matrix (ECM) is important for both structural integrity and functions of the brain. Matrix metalloproteinases (MMPs) play major roles in ECM-remodeling under both physiological and pathological conditions. Reversion-inducing cysteine-rich protein with Kazal motifs (Reck) is a membrane-anchored MMP-regulator implicated in coordinated regulation of pericellular proteolysis. Although patho-physiological importance of MMPs and another group of MMP-regulators, tissue inhibitor of metalloproteinases, in brain ischemia has been demonstrated, little is known about the role of Reck in this process. In this study, we found that Reck is up-regulated in hippocampus and penumbra of subventricular zone after transient cerebral ischemia in mice. Most of the Reck-positive cells found at day 2 after ischemia are positive for Nestin as well as Ki67 and localized to the CA2 region of the hippocampus. At day 7 after ischemia, the Reck-positive cells increased in number, extended processes, expressed the reactive astrocyte marker GFAP and the neuronal marker NF200, and were widely distributed in the hippocampus. In the mutant mice carrying single functional Reck allele (Reck+/-), tissue damage and cell death after cerebral ischemia were augmented, the recovery of long-term potentiation in the hippocampus was compromised, NR2C subunit of NMDA receptor was up-regulated, gelatinolytic activity of MMPs were up-regulated and laminin-immunoreactivity was reduced. Our data implicate Reck in protection of ECM/tissue integrity and promotion of functional recovery in the brain after transient cerebral ischemia.
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Affiliation(s)
- Huan Wang
- Department of Molecular Oncology, Kyoto University Graduate School of Medicine, Sakyo-ku, Kyoto, Japan
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9
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Yaman E, Gasper R, Koerner C, Wittinghofer A, Tazebay UH. RasGEF1A and RasGEF1B are guanine nucleotide exchange factors that discriminate between Rap GTP-binding proteins and mediate Rap2-specific nucleotide exchange. FEBS J 2009; 276:4607-16. [DOI: 10.1111/j.1742-4658.2009.07166.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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10
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Pochynyuk O, Stockand JD, Staruschenko A. Ion channel regulation by Ras, Rho, and Rab small GTPases. Exp Biol Med (Maywood) 2008; 232:1258-65. [PMID: 17959838 DOI: 10.3181/0703-mr-76] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Regulation of ion channels by heterotrimeric guanosine triphosphatases (GTPases), activated by heptathelical membrane receptors, has been the focus of several recent reviews. In comparison, regulation of ion channels by small monomeric G proteins, activated by cytoplasmic guanine nucleotide exchange factors, has been less well reviewed. Small G proteins, molecular switches that control the activity of cellular and membrane proteins, regulate a wide variety of cell functions. Many upstream regulators and downstream effectors of small G proteins now have been isolated. Their modes of activation and action are understood. Recently, ion channels were recognized as physiologically important effectors of small GTPases. Recent advances in understanding how small G proteins regulate the intracellular trafficking and activity of ion channels are discussed here. We aim to provide critical insight into physiological control of ion channel function and the biological consequences of regulation of these important proteins by small, monomeric G proteins.
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Affiliation(s)
- Oleh Pochynyuk
- Department of Physiology, University of Texas Health Science Center, San Antonio, Texas 78229-3900, USA
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Fu Z, Lee SH, Simonetta A, Hansen J, Sheng M, Pak DTS. Differential roles of Rap1 and Rap2 small GTPases in neurite retraction and synapse elimination in hippocampal spiny neurons. J Neurochem 2007; 100:118-31. [PMID: 17227435 DOI: 10.1111/j.1471-4159.2006.04195.x] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The Rap family of small GTPases is implicated in the mechanisms of synaptic plasticity, particularly synaptic depression. Here we studied the role of Rap in neuronal morphogenesis and synaptic transmission in cultured neurons. Constitutively active Rap2 expressed in hippocampal pyramidal neurons caused decreased length and complexity of both axonal and dendritic branches. In addition, Rap2 caused loss of dendritic spines and spiny synapses, and an increase in filopodia-like protrusions and shaft synapses. These Rap2 morphological effects were absent in aspiny interneurons. In contrast, constitutively active Rap1 had no significant effect on axon or dendrite morphology. Dominant-negative Rap mutants increased dendrite length, indicating that endogenous Rap restrains dendritic outgrowth. The amplitude and frequency of alpha-amino-3-hydroxy-5-methylisoxazole-4-propionate (AMPA)-mediated miniature excitatory postsynaptic currents (mEPSCs) decreased in hippocampal neurons transfected with active Rap1 or Rap2, associated with reduced surface and total levels of AMPA receptor subunit GluR2. Finally, increasing synaptic activity with GABA(A) receptor antagonists counteracted Rap2's inhibitory effect on dendrite growth, and masked the effects of Rap1 and Rap2 on AMPA-mediated mEPSCs. Rap1 and Rap2 thus have overlapping but distinct actions that potentially link the inhibition of synaptic transmission with the retraction of axons and dendrites.
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Affiliation(s)
- Zhanyan Fu
- Georgetown University Medical School, Department of Physiology and Biophysics, Washington, DC 20057, USA
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Pochynyuk O, Medina J, Gamper N, Genth H, Stockand JD, Staruschenko A. Rapid translocation and insertion of the epithelial Na+ channel in response to RhoA signaling. J Biol Chem 2006; 281:26520-7. [PMID: 16829523 DOI: 10.1074/jbc.m603716200] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Activity of the epithelial Na+ channel (ENaC) is limiting for Na+ absorption across many epithelia. Consequently, ENaC is a central effector impacting systemic blood volume and pressure. Two members of the Ras superfamily of small GTPases, K-Ras and RhoA, activate ENaC. K-Ras activates ENaC via a signaling pathway involving phosphatidylinositol 3-kinase and production of phosphatidylinositol 3,4,5-trisphosphate with the phospholipid directly interacting with the channel to increase open probability. How RhoA increases ENaC activity is less clear. Here we report that RhoA and K-Ras activate ENaC through independent signaling pathways and final mechanisms of action. Activation of RhoA signaling rapidly increases the membrane levels of ENaC likely by promoting channel insertion. This process dramatically increases functional ENaC current, resulting in tight spatial-temporal control of these channels. RhoA signals to ENaC via a transduction pathway, including the downstream effectors Rho kinase and phosphatidylinositol-4-phosphate 5-kinase. Phosphatidylinositol 4,5-biphosphate produced by activated phosphatidylinositol 4-phosphate 5-kinase may play a role in targeting vesicles containing ENaC to the plasma membrane.
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Affiliation(s)
- Oleh Pochynyuk
- Department of Physiology, University of Texas Health Science Center, San Antonio, Texas 78229, USA
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Xie Z, Huganir RL, Penzes P. Activity-dependent dendritic spine structural plasticity is regulated by small GTPase Rap1 and its target AF-6. Neuron 2006; 48:605-18. [PMID: 16301177 DOI: 10.1016/j.neuron.2005.09.027] [Citation(s) in RCA: 96] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2005] [Revised: 09/16/2005] [Accepted: 09/28/2005] [Indexed: 12/11/2022]
Abstract
Activity-dependent remodeling of dendritic spines is essential for neural circuit development and synaptic plasticity, but the mechanisms that coordinate synaptic structural and functional plasticity are not well understood. Here we investigate the signaling pathways that enable excitatory synapses to undergo activity-dependent structural modifications. We report that activation of NMDA receptors in cultured cortical neurons induces spine morphogenesis and activation of the small GTPase Rap1. Rap1 bimodally regulates spine morphology: activated Rap1 recruits the PDZ domain-containing protein AF-6 to the plasma membrane and induces spine neck elongation, while inactive Rap1 dissociates AF-6 from the membrane and induces spine enlargement. Rap1 also regulates spine content of AMPA receptors: thin spines induced by Rap1 activation have reduced GluR1-containing AMPA receptor content, while large spines induced by Rap1 inactivation are rich in AMPA receptors. These results identify a signaling pathway that regulates activity-dependent synaptic structural plasticity and coordinates it with functional plasticity.
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Affiliation(s)
- Zhong Xie
- Department of Physiology, Northwestern University Feinberg School of Medicine, 303 East Chicago Avenue, Chicago, Illinois 60611
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Sans N, Wang PY, Du Q, Petralia RS, Wang YX, Nakka S, Blumer JB, Macara IG, Wenthold RJ. mPins modulates PSD-95 and SAP102 trafficking and influences NMDA receptor surface expression. Nat Cell Biol 2005; 7:1179-90. [PMID: 16299499 DOI: 10.1038/ncb1325] [Citation(s) in RCA: 94] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2005] [Accepted: 09/26/2005] [Indexed: 02/06/2023]
Abstract
Appropriate trafficking and targeting of glutamate receptors (GluRs) to the postsynaptic density is crucial for synaptic function. We show that mPins (mammalian homologue of Drosophila melanogaster partner of inscuteable) interacts with SAP102 and PSD-95 (two PDZ proteins present in neurons), and functions in the formation of the NMDAR-MAGUK (N-methyl-D-aspartate receptor-membrane-associated guanylate kinase) complex. mPins enhances trafficking of SAP102 and NMDARs to the plasma membrane in neurons. Expression of dominant-negative constructs and short-interfering RNA (siRNA)-mediated knockdown of mPins decreases SAP102 in dendrites and modifies surface expression of NMDARs. mPins changes the number and morphology of dendritic spines and these effects depend on its Galphai interaction domain, thus implicating G-protein signalling in the regulation of postsynaptic structure and trafficking of GluRs.
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Affiliation(s)
- Nathalie Sans
- Laboratory of Neurochemistry, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Building 50, Room 4146, 50 South Drive, Bethesda, MD 20892-8027, USA.
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Shi S, Noda M, Kitayama H. Rap1 mutants with increased affinity for the guanine-nucleotide exchange factor C3G. Oncogene 2005; 23:8711-9. [PMID: 15480424 DOI: 10.1038/sj.onc.1208132] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The mutant of Ras protein with serine to asparagine mutation at residue 17 (Ras-17N) is known to interfere with the signaling function of the wild-type Ras protein by sequestering its guanine-nucleotide exchange factors (GEFs). The similar mutant of another Ras family protein Rap1 (Rap1-17N) fails to effectively interfere with the interaction between the wild-type Rap1 and one of its GEFs, C3G, in vitro. In the present study, we have attempted to isolate Rap1 mutants with increased affinity for C3G using random mutagenesis and yeast two-hybrid screening. Based on the pattern of mutations found among these mutants, we could design a potent C3G-binder, named Rap1-AGE, harboring mutations in three sites (17A, 29G, and 117E). The association of Rap1-AGE with C3G in the cells was confirmed by co-immunoprecipitation experiments. The ability of Rap1-AGE to inhibit C3G-mediated Rap1-activation and cell spreading was also demonstrated. On the other hand, Rap1 activation mediated by two other GEFs, Epac and smgGDS, was not inhibited by Rap1-AGE. These results suggest that Rap1-AGE acts as a dominant interfering factor against C3G and serves as a useful tool in analyzing the roles of C3G-Rap1 signaling pathway in various biological processes.
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Affiliation(s)
- Shuliang Shi
- Department of Molecular Oncology, Kyoto University Graduate School of Medicine, Yoshida-Konoe-cho, Sakyo-ku, Kyoto 606-8501, Japan
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Murray HJ, O'Connor JJ. A role for monomeric G-proteins in synaptic plasticity in the rat dentate gyrus in vitro. Brain Res 2004; 1000:85-91. [PMID: 15053956 DOI: 10.1016/j.brainres.2003.11.044] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/20/2003] [Indexed: 11/21/2022]
Abstract
Recent studies have implicated Ras signalling in synaptic plasticity. In this study we have investigated a role for the low molecular weight G proteins Ras, Rap, Ra1 and Rac in long-term potentiation and depression using Clostridium Sordelli Lethal Toxin-82 (LT-82), which inactivates Ras, Rap, Ra1 and Rac, and manumycin A, a Ras inhibitor. Perfusion of hippocampal slices with LT-82 (200 ng/ml) attenuated LTP (83+/-10%, n=5, P<0.01, compared with controls of 160+/-11% at 60 min post HFS, n=5). LT-82 had no effect on LTD (63+/-1% at 100 ng/ml, n=5 and 66+/-1% at 200 ng/ml, n=4, compared to controls of 56+/-6%, n=6). Manumycin A (2 microM) had no effect on LTP (162+/-2%, n=5, compared to controls of 167+/-13%, n=5), but significantly attenuated LTD (88+/-6%, n=5, P<0.01, compared to controls of 63+/-9%, n=7). LT-82 (200 ng/ml) significantly increased the amplitude of the isolated NMDA-EPSP at 60 min post-drug application (240+/-40%, n=5, P<0.01, compared with controls of 100+/-4%, n=5). However, manumycin A, had no significant effect on NMDAR-EPSP amplitude (92+/-2%, n=5, compared with controls). These results demonstrate an important role for Ras in LTD and a role for Rap, Ra1 and Rac in LTP.
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Affiliation(s)
- Hilary J Murray
- Department of Human Anatomy and Physiology, Conway Institute of Biomolecular and Biomedical Research, National Neuroscience Network, University College Dublin, Belfield, Dublin 4, Ireland
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Imamura Y, Matsumoto N, Kondo S, Kitayama H, Noda M. Effects of ras and rap1 on electrical excitability of differentiated ng108-15 cells. Neuroscience 2004; 127:973-81. [PMID: 15312909 DOI: 10.1016/j.neuroscience.2004.05.051] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/28/2004] [Indexed: 11/15/2022]
Abstract
Effects of two small G-proteins, Rap1 and Ras, on the sodium channel activity in NG108-15 cells were studied using sindbis virus-mediated gene transfer. When an activated Rap1A mutant (Rap1-12V, the activated mutant of Rap1 carrying glycine to valine substitution at codon 12) or a dominant-negative H-Ras mutant (Ras-17N, carrying serine to asparagine substitution at codon 17) was expressed in differentiated NG108-15 cells, the proportion of cells generating action potential decreased and the amplitudes of sodium current diminished. This effect was sensitive to an inhibitor of protein kinase A. The effects of a cyclic AMP (cAMP) analog (dibutyl cAMP) on sodium current in these cells were biphasic: inhibitory at lower concentrations (<100 microM) and enhancing at higher concentrations (200-500 microM). The inhibitory phase of cAMP effect was suppressed by an activated Ras mutant (Ras-12V) while the enhancing phase was suppressed by Rap1-12V. These data are consistent with the model that Rap1 and Ras function as counteracting regulators of voltage-gated sodium current through cAMP-dependent mechanisms.
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Affiliation(s)
- Y Imamura
- Department of Molecular Oncology, Kyoto University Graduate School of Medicine, Yoshida, Konoe-cho, Sakyo-Ku, Kyoto 606-8501, Japan
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