Navegando por Palavras-chave "G-protein"

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    Conditional Deletion of Ric-8b in Olfactory Sensory Neurons Leads to Olfactory Impairment
    (Soc Neuroscience, 2017) Machado, Cleiton F.; Nagai, Maria H.; Lyra, Cassandra S.; Reis-Silva, Thiago M.; Machado, Andre M. [UNIFESP]; Glezer, Isaias [UNIFESP]; Felicio, Luciano F.; Malnic, Bettina
    The olfactory system can discriminate a vast number of odorants. This ability derives from the existence of a large family of odorant receptors expressed in the cilia of the olfactory sensory neurons. Odorant receptors signal through the olfactory-specific G-protein subunit, G alpha olf. Ric-8b, a guanine nucleotide exchange factor, interacts with G alpha olf and can amplify odorant receptor signal transduction in vitro. To explore the function of Ric-8b in vivo, we generated a tissue specific knock-out mouse by crossing OMP-Cre transgenic mice to Ric-8b floxed mice. We found that olfactory-specific Ric-8b knock-out mice of mixed sex do not express the G alpha olf protein in the olfactory epithelium. We also found that in these mice, the mature olfactory sensory neuron layer is reduced, and that olfactory sensory neurons show increased rate of cell death compared with wild-type mice. Finally, behavioral tests showed that the olfactory-specific Ric-8b knock-out mice show an impaired sense of smell, even though their motivation and mobility behaviors remain normal.
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    Conformational flexibility of three cytoplasmic segments of the angiotensin II AT(1A) receptor: A circular dichroism and fluorescence spectroscopy study
    (Wiley-Blackwell, 2002-01-01) Pertinhez, Thelma A.; Krybus, Regina; Cilli, Eduardo Maffud [UNIFESP]; Paiva, Antonio Cechelli de Mattos [UNIFESP]; Nakaie, Clovis Ryuichi [UNIFESP]; Franzoni, Lorella; Sartor, Giorgio; Spisni, Alberto; Schreier, Shirley; Univ Parma; LNLS; Universidade de São Paulo (USP); Universidade Federal de São Paulo (UNIFESP)
    The conformation of three synthetic peptides encompassing the proximal and distal half of the third intracellular loop (Ni3 and Ci3) and a portion of the cytoplasmic tail (fCT) of the angiotensin II AT(1A) receptor has been studied using circular dischroism and fluorescence spectroscopies. the results show that the conformation of the peptides is modulated in various ways by the environmental conditions (pH, ionic strength and dielectric constant). Indeed, Ni3 and fCT fold into helical structures that possess distinct stability and polarity due to the diverse forces involved: mainly polar interactions in the first case and a combination of polar and hydrophobic interactions in the second. the presence of these various features also produce distinct intermolecular interactions. Ci3, instead, exists as an ensemble of partially folded states in equilibrium. Since the corresponding regions of the angiotensin II AT(1A) receptor are known to play an important role in the receptor function, due to their ability to undergo conformational changes, these data provide some new clues about their different conformational plasticity. Copyright (C) 2002 European Peptide Society and John Wiley Sons, Ltd.
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    Functional characterization of heterotrimeric G-proteins in rat diaphragm muscle
    (Elsevier B.V., 2011-02-15) Andrade-Lopes, Ana Luiza [UNIFESP]; Pires-Oliveira, Marcelo [UNIFESP]; Sandro Menezes-Rodrigues, Francisco [UNIFESP]; Godinho, Rosely Oliveira [UNIFESP]; Universidade Federal de São Paulo (UNIFESP)
    Seven-transmembrane receptors mediate diverse skeletal muscle responses for a wide variety of stimuli, via activation of heterotrimeric G-proteins. Herein we evaluate the expression and activation of rat diaphragm or cultured skeletal muscle G-proteins using [(35)S]GTP gamma S. Total membrane G alpha subunit content was 4-7 times higher in rat primary cultured myotubes and L6 cell line than in diaphragm (32.6 +/- 1.2 fmol/mg protein) and 7-27% of them were in the active conformational state. Immunoprecipitation assay showed equal expression of diaphragm G alpha s, G alpha q and G alpha i/o. Addition of GDP allowed the measurement of G-protein activation by different GPCR, including adrenoceptor, adenosine, melatonin and muscarinic receptors. Diaphragm denervation resulted in a marked increase in both total and active state G-protein levels. Together, the results show that [(35)S]GTP gamma S binding assay is a sensitive and valuable method to evaluate GPCR activity in skeletal muscle cells, which is of particular interest for pharmacological analysis of drugs with potential use in the management of respiratory muscle failure. (C) 2010 Elsevier B.V. All rights reserved.
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    Mutational analysis of the interaction of the N- and C-terminal ends of angiotensin II with the rat AT(1A) receptor
    (Nature Publishing Group, 2000-07-01) Costa-Neto, Claudio M.; Mikakawa, Ayumi A.; Oliveira, Laerte; Hjorth, Siv A.; Schwartz, Thue W.; Paiva, Antonio Cechelli de Mattos [UNIFESP]; Universidade Federal de São Paulo (UNIFESP); Univ Copenhagen
    1. the role of different residues of the rat AT(1A) receptor in the interaction with the N- and C-terminal ends of angiotensin II (AngII) was studied by determining ligand binding and production of inositol phosphates (IP) in COS-7 cells transiently expressing the following AT(1A) mutants: T88H, Y92H, G196I, G196W and D278E.2 G196W and G196I retained significant binding and IF-production properties, indicating that bulky substituents in position 196 did not affect the interaction of AngII's C-terminal carboxyl with Lys(199) located three residues below.3 Although the T88A mutation did not affect binding, the T88H mutant had greatly decreased affinity for AngII, suggesting that substitution of Thr(88) by His might hinder binding through an indirect effect.4 the Y92H mutation caused loss of affinity for AngII that was much less pronounced than that reported for Y92A, indicating that His in that position can fulfil part of the requirements for binding.5 Replacing Asp(278) by Glu caused a much smaller reduction in affinity than replacing it by Ala, indicating the importance of Asp's beta-carboxyl group for AngII binding.6 Mutations in residues Thr(88), Tyr(92) and Asp(278) greatly reduced affinity for AngII but not for Sar(1) Leu(8)-AngII, suggesting unfavourable interactions between these residues and AngII's aspartic acid side-chain or N-terminal amino group, which might account for the proposed role of the N-terminal amino group of AngII in the agonist-induced desensitization (tachyphylaxis) of smooth muscles.