DOCSLIB.ORG

Small G-Protein They Bind GTP, and “OFF” After the GTP Has Been Hydrolyzed to GDP (Which in Turn Remains Bound)

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Small G-Protein They Bind GTP, and “OFF” After the GTP Has Been Hydrolyzed to GDP (Which in Turn Remains Bound) MONOMERIC G-PROTEINS (GTPases) In addition to heterotrimeric G-proteins, there is a superfamily of small monomeric G-proteins. Their size is around 21 kDa, approximately one half of the average size of the subunits of heterotrimeric proteins. These small proteins also operate as switches, which are “ON” when Small G-protein they bind GTP, and “OFF” after the GTP has been hydrolyzed to GDP (which in turn remains bound). There is a larger family of small GTP-binding switch proteins, related to G Monomeric G-proteins are activated by proteins which induce a conformational change resulting in reduced affinity to GDP, and thus in G-protein : heterotrimeric G proteins GDP release. The general term for such proteins is GEF (guanine nucleotide exchange factor). The GEFs of the small G-proteins are not the activated receptors, but rather proteins downstream the signaling cascade. GEFs vary with regard to their mode of activation and their selectivity for specific monomeric G-proteins. Small GTP-binding proteins include (roles indicated): initiation & elongation factors (protein synthesis). Compared to the subunit of heterotrimeric G-proteins, GTPase activity Ras (growth factor signal cascades). of the monomeric G-proteins is very low in the absence of interference. Rab (vesicle targeting and fusion). However, association with a protein of the GAP (GTPase-activating ARF (forming vesicle coatomer coats). protein) type results in very rapid GTP hydrolysis. Ran (transport of proteins into & out of the nucleus). As in the case of GEFs, the activation state of GAPs can be regulated, and Rho (regulation of actin cytoskeleton) GAPs are selective with regard to the small G-proteins they affect. All GTP-binding proteins differ in conformation depending on whether GDP or GTP is present at their nucleotide binding site. Generally, GTP binding induces the active state. Ras was the first small G-protein discovered 1 protein-GTP (active) G of a heterotrimeric G protein has innate capability for GTP hydrolysis. Most GTP-binding proteins It has the essential arginine residue normally provided by a GAP for depend on helper proteins: GDP small GTP-binding proteins. However, RGS proteins, which are negative regulators of G protein GAPs, GTPase Activating GEF GAP signaling, stimulate GTP hydrolysis by G. Proteins, promote GTP hydrolysis. GTP Pi GEFs, Guanine Nucleotide Exchange Factors, promote GDP/GTP exchange. protein-GDP (inactive) An activated receptor (GPCR) normally serves as GEF for a heterotrimeric G-protein. A GAP may provide an essential active site residue, while Alternatively, AGS (Activator of G-protein Signaling) promoting the correct positioning of the glutamine residue of proteins may activate some heterotrimeric G- proteins, independent of a receptor. the switch II domain. protein-GTP (active) Some AGS proteins have GEF activity. Frequently a (+) charged arginine residue of a GAP inserts GDP into the active site and helps to stabilize the transition state by interacting with () charged O atoms of the terminal GEF GAP RGS: Regulators of G-protein signaling phosphate of GTP during hydrolysis. GTP Pi protein-GDP (inactive) Ras Monomeric G-proteins are activated by proteins which induce a conformational change resulting in reduced affinity to GDP, and thus in GDP release. A single amino acid mutation of Ras is found in more than 30% of all cancers! The general term for such proteins is GEF (guanine nucleotide exchange As many as 90% of certain human tumors like pancreatic carcinomas factor). The GEFs of the small G-proteins are not the activated receptors, have mutant Ras! but rather proteins downstream the signaling cascade. GEFs vary with Ras controls both proliferation and differentiation pathways. regard to their mode of activation and their selectivity for specific monomeric G-proteins. Compared to the subunit of heterotrimeric G-proteins, GTPase activity of the GEF=Guanine nucleotide Exchange monomeric G-proteins is very low in the absence of interference. However, Factor association with a protein of the GAP (GTPase-activating protein) type GAP=GTPase Activating Proteins results in very rapid GTP hydrolysis. As in the case of GEFs, the activation state of GAPs can be regulated, and The cytosol concentration of GTP is GAPs are selective with regard to the small G-proteins they affect. 10x that of GDP 2 G proteins and Ras-Common Signaling switch The regulation of GTP/GDP binding protein small monomeric GTP-binding form is active, while GDP-binding form is inactive G-proteins. Intrinsic GTPase activity Ras was the first GAPs increase GTPase activity small G-protein Tethered to cell membrane discovered, and is presented here as G proteins and Ras-Difference an example. G Proteins Ras Subunit: Trimeric (and Monomeric () Activation: Dissociation (and ) GEFs Receptor: Direct binding No Signaling: cAMP (PKA) MAP kinase PLC-: DAG (PKC) IP3 (Ca 2+) Dissociated may also activate MAP kinase, and Ras may indirectly induce PLC- (via PI3K). 19 Ras activation Mutations of the ras oncogene are associated with a wide range of human cancers The ras oncogene causes oncogenic transformation. Mutations in the ras oncogene are found in a wide range of human cancer Number of % samples with a ras gene Tumor samples tested mutated ras gene found to be mutated Pancreas adenocarcinoma 156 84 K Lung adenocarcinoma 45 33 K Colon adenocarcinoma 277 44 K Thyroid follicular carcinoma 15 53 H, K, N Myeloid disorder (AML) 412 35 N, K Discovered Bos, JL (1989) Cancer Res. 49, 4682 In Dros.: Sevenless Drk SOS These mutations lead to constitutive activation of the Ras signaling pathway. RAS蛋白有三 種H-ras ，分別為、K-ras和N-ras，位於細胞膜上 3 Downstream of Ras Ras plays critical roles in the signaling pathway 18 leading to transformation Raf RTK GAP GRB2 SOS1,2 Erk Ras NF1 Ras GTP GDP Raf -1, A-, B- PI3K RalGEFs Ral MEK1,2 AKT Fos /Jun ERK1,2 Survival Transcription Muegge et al (1996) Structure 4, 475 Factors Ras/MAP Kinase Cascade Oncogenic Ras mutations in ~30% of all MAPKKK /MAP3K cancers. MAPKK -Oncogenic Raf mutations in ~70% of /MAP2K malignant melanomas. MAPK -Over-expression / activation of RTK in many MAP kinase cascade cancers Serine/threonine kinases Activate transcription factor Highly conserved cascade 4 Rho GTPases and Signaling networks Small GTP-binding proteins include (roles indicated): initiation & elongation factors (protein synthesis). 彎曲形受體 Ras (growth factor signal cascades). Rab (vesicle targeting and fusion). ARF (forming vesicle coatomer coats). Ran (transport of proteins into & out of the nucleus). Rho (regulation of actin cytoskeleton) All GTP-binding proteins differ in conformation depending on whether GDP or GTP is present at their nucleotide binding site. Generally, GTP binding induces the active state. Ras was the first small G-protein discovered Rho Family: Regulators of the actin cytoskeleton Extracellular signals induce global actin filament rearrangements via the Rho protein family – cdc42, Rac, and Rho. 溶血性磷脂酸 (lysophosphatidic acid,LPA 休止 5 Active nuclear transport is driven by Ran G protein Ran is a small GTPase- binds and hydrolyses guanine nucleotide Rho GEF triphosphate (GTP) – Ran exists in two conformational forms: Ran - GTP and Ran- WASp Rho kinase GDP – Ran has weak GTPase activity that is stimulated by RanGAP (GTPase activating protein) – A guanine nucleotide exchange factor (GEF), called RCC1 突起的構造 板狀偽足 stimulates the release of GDP and binding of GTP (higher concentration of GTP in the cell assures preferential binding of GTP) – The cycle of GTP binding, hydrolysis, release provides energy for nuclear transport – asymmetric localization of RanGAP and RCC1 assure Role of signal transduction pathways in cell locomotion and the organization of directionality of transport the cytoskeleton Protein import to nucleus nuclear localization signal Low affinity to NLS After import to nucleoplasm → high concentration → export Transport without ATP Interact with FG-nucleoprins Ran = GTPase GAP = GTPase-activing protein GEF = Guanine exchange factor GTPase accelerating protein Has FG (phenylalanine glycine) amino acids repeat (hydrophobic) Also called FG-nucleoporins 6 cargo export from nucleus to nucleus nuclear export signal Rab proteins (monomeric GTPase) help ensure the specificity of vesicle docking Interact with Conformal FG- change→ high nucleoprins affinity to NES hnRNP and mRNA by the same mechanism Exportin-t : bind to tRNA and interact with Ran → export tRNA to cytoplasm B. Machinery Involved: Plasma Membrane: Vesicle Transport and Rab-GTPases - small GTP binding proteins on vesicles. Fusion Related to the oncogene product Ras. A. Steps in Vesicular Act as tethering factors that mediate initial interaction between membrane Targeting: Bind to Rab effectors on target membrane. 1. Transport vesicle Over 30 diferent Rab proteins specific to different membranes. with v-SNARE is tethered Another protein (guanine-nuc. exchange factor) catalyzes exchange of GDP to target mb by a Rab bound to cytosolic Rab for GTP, which allows Rab to bind to the transport GTPase. vesicle. NSF - (N-ethylmaleimide sensitive factor) a tetramer of identical subunits that 2. If v-SNARE on binds and hydrolyzes ATP. Required for disassembly of SNARE complex. vesicle and t-SNARE on target match, then SNAPs - (soluble NSF attachment protein). Act as a cofactor mediating NSF attachment to SNAREs. loosely tethered vesicle SNAP-NSF Receptors (SNAREs) - a family of cognate membrane proteins. becomes tightly "docked". Vesicular (v)-SNAREs on vesicles form
Load more

Recommended publications
  • Dynamin Functions and Ligands: Classical Mechanisms Behind
    1521-0111/91/2/123–134$25.00 http://dx.doi.org/10.1124/mol.116.105064 MOLECULAR PHARMACOLOGY Mol Pharmacol 91:123–134, February 2017 Copyright ª 2017 by The American Society for Pharmacology and Experimental Therapeutics MINIREVIEW Dynamin Functions and Ligands: Classical Mechanisms Behind Mahaveer Singh, Hemant R. Jadhav, and Tanya Bhatt Department of Pharmacy, Birla Institute of Technology and Sciences Pilani, Pilani Campus, Rajasthan, India Received May 5, 2016; accepted November 17, 2016 Downloaded from ABSTRACT Dynamin is a GTPase that plays a vital role in clathrin-dependent pathophysiology of various disorders, such as Alzheimer’s disease, endocytosis and other vesicular trafficking processes by acting Parkinson’s disease, Huntington’s disease, Charcot-Marie-Tooth as a pair of molecular scissors for newly formed vesicles originating disease, heart failure, schizophrenia, epilepsy, cancer, dominant ’ from the plasma membrane. Dynamins and related proteins are optic atrophy, osteoporosis, and Down s syndrome. This review is molpharm.aspetjournals.org important components for the cleavage of clathrin-coated vesicles, an attempt to illustrate the dynamin-related mechanisms involved phagosomes, and mitochondria. These proteins help in organelle in the above-mentioned disorders and to help medicinal chemists division, viral resistance, and mitochondrial fusion/fission. Dys- to design novel dynamin ligands, which could be useful in the function and mutations in dynamin have been implicated in the treatment of dynamin-related disorders. Introduction GTP hydrolysis–dependent conformational change of GTPase dynamin assists in membrane fission, leading to the generation Dynamins were originally discovered in the brain and identi- of endocytic vesicles (Praefcke and McMahon, 2004; Ferguson at ASPET Journals on September 23, 2021 fied as microtubule binding partners.
    [Show full text]
  • G Protein Alpha 13 (GNA13) (NM 006572) Human Tagged ORF Clone Lentiviral Particle Product Data
    OriGene Technologies, Inc. 9620 Medical Center Drive, Ste 200 Rockville, MD 20850, US Phone: +1-888-267-4436 [email protected] EU: [email protected] CN: [email protected] Product datasheet for RC207762L3V G protein alpha 13 (GNA13) (NM_006572) Human Tagged ORF Clone Lentiviral Particle Product data: Product Type: Lentiviral Particles Product Name: G protein alpha 13 (GNA13) (NM_006572) Human Tagged ORF Clone Lentiviral Particle Symbol: GNA13 Synonyms: G13 Vector: pLenti-C-Myc-DDK-P2A-Puro (PS100092) ACCN: NM_006572 ORF Size: 1131 bp ORF Nucleotide The ORF insert of this clone is exactly the same as(RC207762). Sequence: OTI Disclaimer: The molecular sequence of this clone aligns with the gene accession number as a point of reference only. However, individual transcript sequences of the same gene can differ through naturally occurring variations (e.g. polymorphisms), each with its own valid existence. This clone is substantially in agreement with the reference, but a complete review of all prevailing variants is recommended prior to use. More info OTI Annotation: This clone was engineered to express the complete ORF with an expression tag. Expression varies depending on the nature of the gene. RefSeq: NM_006572.3 RefSeq Size: 4744 bp RefSeq ORF: 1134 bp Locus ID: 10672 UniProt ID: Q14344, A0A024R8M0 Domains: G-alpha Protein Families: Druggable Genome Protein Pathways: Long-term depression, Regulation of actin cytoskeleton, Vascular smooth muscle contraction MW: 44 kDa This product is to be used for laboratory only. Not for diagnostic or therapeutic use. View online » ©2021 OriGene Technologies, Inc., 9620 Medical Center Drive, Ste 200, Rockville, MD 20850, US 1 / 2 G protein alpha 13 (GNA13) (NM_006572) Human Tagged ORF Clone Lentiviral Particle – RC207762L3V Gene Summary: Guanine nucleotide-binding proteins (G proteins) are involved as modulators or transducers in various transmembrane signaling systems (PubMed:15240885, PubMed:16787920, PubMed:16705036, PubMed:27084452).
    [Show full text]
  • Crystal Structure of a Small G Protein in Complex with the Gtpase
    letters to nature of apolipoproteins2,12–14. However, our results show that the residues lipoprotein metabolism involving cell surface heparan sulfate proteoglycans. J. Biol. Chem. 269, 2764– 2+ 2772 (1994). in the conserved acidic motif of LR5 are buried to participate in Ca 16. Innerarity, T. L., Pitas, R. E. & Mahley, R. W. Binding of arginine-rich (E) apoprotein after coordination, instead of being exposed on the surface of the domain recombination with phospholipid vesicles to the low density lipoprotein receptors of fibroblasts. J. Biol. Chem. 254, 4186–4190 (1979). (Fig. 4a). Although lipoprotein uptake by members of the LDLR 17. Otwinowski, Z. & Minor, W. Data Collection and Processing (eds Sawyer, L., Isaacs, N. & Bailey, S.) family may involve an electrostatic component, perhaps through 556–562 (SERC Daresbury Laboratory, Warrington, UK, 1993). association of the lipoproteins with cell-surface proteoglycans15, the 18. CCP4. The SERC (UK) Collaborative Computing Project No. 4 A Suite of Programs for Protein Crystallography (SERC Daresbury Laboratory, Warrington, UK, 1979). LR5 structure demonstrates that the primary role for the conserved 19. Cowtan, K. D. Joint CCP4 and ESF-EACBM Newsletter on Protein Crystallography 31, 34–38 (1994). acidic residues in LDL-A modules is structural. It has been noted 20. Jones, T. A., Zou, J. Y., Cowan, S. W. & Kjeldgaard, M. Improved methods for binding protein models in electron density maps and the location of errors in these models. Acta Crystallogr. A 47, 110–119 previously that only lipid-associated apolipoproteins bind with (1991). 16 high affinity to the LDLR ; the LR5 structure suggests an alternative 21.
    [Show full text]
  • Ras Gtpase Chemi ELISA Kit Catalog No
    Ras GTPase Chemi ELISA Kit Catalog No. 52097 (Version B3) Active Motif North America 1914 Palomar Oaks Way, Suite 150 Carlsbad, California 92008, USA Toll free: 877 222 9543 Telephone: 760 431 1263 Fax: 760 431 1351 Active Motif Europe Waterloo Atrium Drève Richelle 167 – boîte 4 BE-1410 Waterloo, Belgium UK Free Phone: 0800 169 31 47 France Free Phone: 0800 90 99 79 Germany Free Phone: 0800 181 99 10 Telephone: +32 (0)2 653 0001 Fax: +32 (0)2 653 0050 Active Motif Japan Azuma Bldg, 7th Floor 2-21 Ageba-Cho, Shinjuku-Ku Tokyo, 162-0824, Japan Telephone: +81 3 5225 3638 Fax: +81 3 5261 8733 Active Motif China 787 Kangqiao Road Building 10, Suite 202, Pudong District Shanghai, 201315, China Telephone: (86)-21-20926090 Hotline: 400-018-8123 Copyright 2021 Active Motif, Inc. www.activemotif.com Information in this manual is subject to change without notice and does not constitute a commit- ment on the part of Active Motif, Inc. It is supplied on an “as is” basis without any warranty of any kind, either explicit or implied. Information may be changed or updated in this manual at any time. This documentation may not be copied, transferred, reproduced, disclosed, or duplicated, in whole or in part, without the prior written consent of Active Motif, Inc. This documentation is proprietary information and protected by the copyright laws of the United States and interna- tional treaties. The manufacturer of this documentation is Active Motif, Inc. © 2021 Active Motif, Inc., 1914 Palomar Oaks Way, Suite 150; Carlsbad, CA 92008.
    [Show full text]
  • Role of Excess Inorganic Pyrophosphate in Primer-Extension Genotyping Assays
    Methods Role of Excess Inorganic Pyrophosphate in Primer-Extension Genotyping Assays Ming Xiao,1 Angie Phong,1 Kristen L. Lum,1 Richard A. Greene,2 Philip R. Buzby,2,3 and Pui-Yan Kwok1,4,5 1Cardiovascular Research Institute, University of California, San Francisco, San Francisco, California 94143-0130, USA; 2PerkinElmer Life and Analytical Sciences, Inc., Boston, Massachusetts 02118-2512, USA We have developed and genotyped >15,000 SNP assays by using a primer extension genotyping assay with fluorescence polarization (FP) detection. Although the 80% success rate of this assay is similar to those of other SNP genotyping assays, we wanted to determine the reasons for the failures and find ways to improve the assay. We observed that the failed assays fell into three general patterns: PCR failure, excess of heterozygous genotypes, and loss of FP signal for one of the dye labels. After analyzing several hundred failed assays, we concluded that 5% of the assays had PCR failure and had to be redesigned. We also discovered that the other two categories of failures were due to misincorporation of one of the dye-terminators during the primer extension reaction as a result of primer shortening with a reverse reaction involving inorganic pyrophosphate, and to the quenching of R110-terminator after its incorporation onto the SNP primer. The relatively slow incorporation of R110 acycloterminators by AcycloPol compounds the problem with the R110 label. In this report, we describe the source of the problems and simple ways to correct these problems by adding pyrophosphatase, using quenching as part of the analysis, and replacing R110 by Texas red as one of the dye labels.
    [Show full text]
  • Predicting Coupling Probabilities of G-Protein Coupled Receptors Gurdeep Singh1,2,†, Asuka Inoue3,*,†, J
    Published online 30 May 2019 Nucleic Acids Research, 2019, Vol. 47, Web Server issue W395–W401 doi: 10.1093/nar/gkz392 PRECOG: PREdicting COupling probabilities of G-protein coupled receptors Gurdeep Singh1,2,†, Asuka Inoue3,*,†, J. Silvio Gutkind4, Robert B. Russell1,2,* and Francesco Raimondi1,2,* 1CellNetworks, Bioquant, Heidelberg University, Im Neuenheimer Feld 267, 69120 Heidelberg, Germany, 2Biochemie Zentrum Heidelberg (BZH), Heidelberg University, Im Neuenheimer Feld 328, 69120 Heidelberg, Germany, 3Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai, Miyagi 980-8578, Japan and 4Department of Pharmacology and Moores Cancer Center, University of California, San Diego, La Jolla, CA 92093, USA Received February 10, 2019; Revised April 13, 2019; Editorial Decision April 24, 2019; Accepted May 01, 2019 ABSTRACT great use in tinkering with signalling pathways in living sys- tems (5). G-protein coupled receptors (GPCRs) control multi- Ligand binding to GPCRs induces conformational ple physiological states by transducing a multitude changes that lead to binding and activation of G-proteins of extracellular stimuli into the cell via coupling to situated on the inner cell membrane. Most of mammalian intra-cellular heterotrimeric G-proteins. Deciphering GPCRs couple with more than one G-protein giving each which G-proteins couple to each of the hundreds receptor a distinct coupling profile (6) and thus specific of GPCRs present in a typical eukaryotic organism downstream cellular responses. Determining these coupling is therefore critical to understand signalling. Here, profiles is critical to understand GPCR biology and phar- we present PRECOG (precog.russelllab.org): a web- macology. Despite decades of research and hundreds of ob- server for predicting GPCR coupling, which allows served interactions, coupling information is still missing for users to: (i) predict coupling probabilities for GPCRs many receptors and sequence determinants of coupling- specificity are still largely unknown.
    [Show full text]
  • ADP-Ribosylation Factor, a Small GTP-Binding Protein, Is Required for Binding of the Coatomer Protein Fl-COP to Golgi Membranes JULIE G
    Proc. Natl. Acad. Sci. USA Vol. 89, pp. 6408-6412, July 1992 Biochemistry ADP-ribosylation factor, a small GTP-binding protein, is required for binding of the coatomer protein fl-COP to Golgi membranes JULIE G. DONALDSON*, DAN CASSEL*t, RICHARD A. KAHN*, AND RICHARD D. KLAUSNER* *Cell Biology and Metabolism Branch, National Institute of Child Health and Human Development, and tLaboratory of Biological Chemistry, Division of Cancer Treatment, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892 Communicated by Marc Kirschner, April 20, 1992 (receivedfor review February 11, 1992) ABSTRACT The coatomer is a cytosolic protein complex localized to the Golgi complex, although their functions have that reversibly associates with Golgi membranes and is Impli- not been defined. Distinct among these proteins is the ADP- cated in modulating Golgi membrane transport. The associa- ribosylation factor (ARF), originally identified as a cofactor tion of 13-COP, a component of coatomer, with Golgi mem- required for in vitro cholera toxin-catalyzed ADP- branes is enhanced by guanosine 5'-[v-thioltriphosphate ribosylation of the a subunit of the trimeric GTP-binding (GTP[yS]), a nonhydrolyzable analogue of GTP, and by a protein G, (G,.) (19). ARF is an abundant cytosolic protein mixture of aluminum and fluoride ions (Al/F). Here we show that reversibly associates with Golgi membranes (20, 21). that the ADP-ribosylation factor (ARF) is required for the ARF has been shown to be present on Golgi coated vesicles binding of (-COP. Thus, 13-COP contained in a coatomer generated in the presence of GTP[yS], but it is not a com- fraction that has been resolved from ARF does not bind to Golgi ponent of the cytosolic coatomer (22).
    [Show full text]
  • Neuropeptidergic Signaling Partitions Arousal Behaviors in Zebrafish
    3142 • The Journal of Neuroscience, February 26, 2014 • 34(9):3142–3160 Behavioral/Cognitive Neuropeptidergic Signaling Partitions Arousal Behaviors in Zebrafish Ian G. Woods,1,2 David Schoppik,2 Veronica J. Shi,2 Steven Zimmerman,2 Haley A. Coleman,1 Joel Greenwood,3 Edward R. Soucy,3 and Alexander F. Schier2,3 1Department of Biology, Ithaca College, Ithaca, New York 14850, and 2Department of Molecular and Cellular Biology and 3Center for Brain Science, Harvard University, Cambridge, Massachusetts 02138 Animals modulate their arousal state to ensure that their sensory responsiveness and locomotor activity match environmental demands. Neuropeptides can regulate arousal, but studies of their roles in vertebrates have been constrained by the vast array of neuropeptides and their pleiotropic effects. To overcome these limitations, we systematically dissected the neuropeptidergic modulation of arousal in larval zebrafish. We quantified spontaneous locomotor activity and responsiveness to sensory stimuli after genetically induced expression of seven evolutionarily conserved neuropeptides, including adenylate cyclase activating polypeptide 1b (adcyap1b), cocaine-related and amphetamine-related transcript (cart), cholecystokinin (cck), calcitonin gene-related peptide (cgrp), galanin, hypocretin, and nocicep- tin. Our study reveals that arousal behaviors are dissociable: neuropeptide expression uncoupled spontaneous activity from sensory responsiveness, and uncovered modality-specific effects upon sensory responsiveness. Principal components analysis and phenotypic clustering revealed both shared and divergent features of neuropeptidergic functions: hypocretin and cgrp stimulated spontaneous locomotor activity, whereas galanin and nociceptin attenuated these behaviors. In contrast, cart and adcyap1b enhanced sensory respon- siveness yet had minimal impacts on spontaneous activity, and cck expression induced the opposite effects. Furthermore, hypocretin and nociceptin induced modality-specific differences in responsiveness to changes in illumination.
    [Show full text]
  • G-Protein ␤␥-Complex Is Crucial for Efficient Signal Amplification in Vision
    The Journal of Neuroscience, June 1, 2011 • 31(22):8067–8077 • 8067 Cellular/Molecular G-Protein ␤␥-Complex Is Crucial for Efficient Signal Amplification in Vision Alexander V. Kolesnikov,1 Loryn Rikimaru,2 Anne K. Hennig,1 Peter D. Lukasiewicz,1 Steven J. Fliesler,4,5,6,7 Victor I. Govardovskii,8 Vladimir J. Kefalov,1 and Oleg G. Kisselev2,3 1Department of Ophthalmology and Visual Sciences, Washington University School of Medicine, St. Louis, Missouri 63110, Departments of 2Ophthalmology and 3Biochemistry and Molecular Biology, Saint Louis University School of Medicine, Saint Louis, Missouri 63104, 4Research Service, Veterans Administration Western New York Healthcare System, and Departments of 5Ophthalmology (Ross Eye Institute) and 6Biochemistry, University at Buffalo/The State University of New York (SUNY), and 7SUNY Eye Institute, Buffalo, New York 14215, and 8Sechenov Institute for Evolutionary Physiology and Biochemistry, Russian Academy of Sciences, Saint Petersburg 194223, Russia A fundamental question of cell signaling biology is how faint external signals produce robust physiological responses. One universal mechanism relies on signal amplification via intracellular cascades mediated by heterotrimeric G-proteins. This high amplification system allows retinal rod photoreceptors to detect single photons of light. Although much is now known about the role of the ␣-subunit of the rod-specific G-protein transducin in phototransduction, the physiological function of the auxiliary ␤␥-complex in this process remains a mystery. Here, we show that elimination of the transducin ␥-subunit drastically reduces signal amplification in intact mouse rods. The consequence is a striking decline in rod visual sensitivity and severe impairment of nocturnal vision. Our findings demonstrate that transducin ␤␥-complex controls signal amplification of the rod phototransduction cascade and is critical for the ability of rod photoreceptors to function in low light conditions.
    [Show full text]
  • H-Ras Gtpase
    H-Ras GTPase Key to Understanding Cancer? Marquette University High School SMART Team: Mohammed Ayesh, Wesley Borden, Andrew Bray, Brian Digiacinto, Patrick Jordan, David Moldenhauer, Thomas Niswonger, Joseph Radke, Amit Singh, Alex Vincent, and Caleb Vogt Teachers: Keith Klestinski and David Vogt Mentor: Evgenii Kovrigin, Ph.D., Medical College of Wisconsin Abstract Cell Cycle Control The protein known as H-Ras GTPase is essential to H-ras is activated late in the G1 phase. proper biological functioning in the entire web of life. The Once H-ras is activated, the cell advances main function of this protein is giving the "stop" signal to past the G1 checkpoint and is compelled to the process of cell reproduction. Unfortunately, this protein complete mitosis. is not perfect and severe consequences, such as cancer, can arise when H-Ras GTPase malfunctions. H-Ras GTPase is a protein from the large family of enzymes that bind and split GTP. H-Ras GTPase is vital in processes like cell-to-cell communication, protein translation in ribosomes, and programmed cell death Ras GTPase Ras GDPase (apoptosis). Its main fields of operation are determining Active Inactive stem cell into specific functioning cells, as well as replicating preexisting "specialized" cells. All G domain based proteins have a universal structure and two Controlling the “Switch” between universal switch mechanisms, which consist of a mixed, six-stranded beta sheet and five alpha helices. H-Ras Active and Inactive States GTPase works by first dissociating from GDP and binding In the graphics (above and below), H-ras is shown in both © 2008, Physiomics, Corp.
    [Show full text]
  • Transducin ␤-Subunit Can Interact with Multiple G-Protein ␥-Subunits to Enable Light Detection by Rod Photoreceptors
    New Research Sensory and Motor Systems Transducin ␤-Subunit Can Interact with Multiple G-Protein ␥-Subunits to Enable Light Detection by Rod Photoreceptors Paige M. Dexter,1 Ekaterina S. Lobanova,2 Stella Finkelstein,2 William J. Spencer,1 Nikolai P. Skiba,2 and Vadim Y. Arshavsky1,2 DOI:http://dx.doi.org/10.1523/ENEURO.0144-18.2018 1Department of Pharmacology and Cancer Biology, Duke University School of Medicine, Durham, North Carolina 27710 and 2Albert Eye Research Institute, Duke University, Durham, North Carolina 27710 Visual Overview The heterotrimeric G-protein transducin mediates visual signaling in vertebrate photoreceptor cells. Many aspects of the function of transducin were learned from knock-out mice lacking its individual subunits. Of particular interest is ␥ ␥ the knockout of its rod-specific -subunit (G 1). Two stud- ies using independently generated mice documented that this knockout results in a considerable Ͼ60-fold reduction in the light sensitivity of affected rods, but provided dif- ␣ ␣ ferent interpretations of how the remaining -subunit (G t) ␤ ␥ mediates phototransduction without its cognate G 1 1- subunit partner. One study found that the light sensitivity ␣ reduction matched a corresponding reduction in G t con- tent in the light-sensing rod outer segments and proposed ␣ ␤ that G t activation is supported by remaining G 1 asso- ciating with other G␥ subunits naturally expressed in pho- toreceptors. In contrast, the second study reported the same light sensitivity loss but a much lower, only approx- ␣ imately sixfold, reduction of G t and proposed that the light responses of these rods do not require G␤␥ at all. To resolve this controversy and elucidate the mechanism ␥ driving visual signaling in G 1 knock-out rods, we analyzed both mouse lines side by side.
    [Show full text]
  • GNAI3 Gene G Protein Subunit Alpha I3
    GNAI3 gene G protein subunit alpha i3 Normal Function The GNAI3 gene provides instructions for making one component, the inhibitory alpha subunit, of a protein complex called a guanine nucleotide-binding protein (G protein). G proteins are composed of three protein subunits: alpha, beta, and gamma. Each of these subunits is produced from a different gene. Through a process called signal transduction, G proteins trigger a complex network of signaling pathways within cells. These pathways help transmit information from outside the cell to inside the cell. Specifically, G proteins made with the GNAI3 inhibitory alpha subunit reduce (inhibit) the activity of an enzyme called adenylyl cyclase, which is an important chemical messenger within cells. G protein signaling ultimately influences many cell activities, instructing the cell to grow, divide, or take on specialized functions. Studies suggest that G protein signaling involving the GNAI3 inhibitory alpha subunit contributes to the development of the first and second pharyngeal arches. These embryonic structures ultimately develop into the jawbones, facial muscles, middle ear bones, ear canals, outer ears, and related tissues. Health Conditions Related to Genetic Changes Auriculo-condylar syndrome At least two mutations in the GNAI3 gene have been found to cause auriculo-condylar syndrome, a disorder that primarily affects the development of the ears and lower jaw ( mandible). The identified mutations change single protein building blocks (amino acids) in the inhibitory alpha subunit. These mutations likely alter the structure of the inhibitory alpha subunit and impair G protein signaling. Abnormal signaling alters the formation of the lower jaw: instead of developing normally, the lower jaw becomes shaped more like the smaller upper jaw (maxilla).
    [Show full text]