The Experts below are selected from a list of 4092 Experts worldwide ranked by ideXlab platform
Teresa Duda - One of the best experts on this subject based on the ideXlab platform.
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Structure and Ca^2+ regulation of frog photoreceptor guanylate cyclase, ROS-GC1
Molecular and Cellular Biochemistry, 2003Co-Authors: Iswari Subbaraya, Chong Zhao, Teresa DudaAbstract:Rod outer segment membrane guanylate cyclase (ROS-GC) is a critical component of the vertebrate phototransduction machinery. In response to photoillumination, it senses a decline in free Ca^2+ levels from 500 to below 100 nM, becomes activated, and replenishes the depleted cyclic GMP pool to restore the dark state of the photoreceptor cell. It exists in two forms, ROS-GC1 and ROS-GC2. In outer segments, ROS-GCs sense fluctuations in Ca^2+ via two Ca^2+-binding proteins, which have been termed GCAP1 and GCAP2. In the present study we report on the cloning of two ROS-GCs from the frog retinal cDNA library. These cyclases are the structural and functional counterparts of the mammalian ROS-GC1 and ROS-GC2. There is, however, an important difference between the regulation of mammalian and frog ROS-GC1: In contrast to the mammalian, the frog form does not require the myristoylated form of GCAP1 for its Ca^2+-dependent modulation. This feature is not dependent upon the ability of frog GCAP1 to bind Ca^2+ because unmyristoylated GCAP1 mutants which do not bind Ca^2+, activate frog ROS-GC1. The findings establish frog as a suitable phototransduction model and show a facet of frog ROS-GC signaling, which is not shared by the mammalian form.
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rod outer segment membrane guanylate cyclase type 1 ros gc1 gene structure organization and regulation by phorbol ester a protein kinase c activator
Molecular and Cellular Biochemistry, 1998Co-Authors: Teresa Duda, Venkateswar Venkataraman, Anuradha Krishnan, Rameshwar K SharmaAbstract:At present there are two recognized members of the ROS-GC subfamily of membrane guanylate cyclases. They are ROS-GC1 and ROS-GC2. A distinctive feature of this family is that its members are not switched on by the extracellular peptide hormones; instead, they are modulated by intracellular Ca2+ signals, consistent to their linkage with phototransduction. An intriguing feature of ROS-GC1, which distinguishes it from ROS-GC2, is that it has two Ca2+ switches. One switch inhibits the enzyme at micromolar concentrations of Ca2+, as in phototransduction; the other, stimulates. The stimulatory switch, most likely, is linked to retinal synaptic activity. Thus, ROS-GC1 is linked to both phototransduction and the synaptic activity. The present study describes (1) the almost complete structural identity of 18.5 kb ROS-GC1 gene; (2) its structural organization: the gene is composed of 20 exons and 19 introns with classical GT/AG boundaries; (3) the activity of the ROS-GC1 promoter assayed through luciferase reporter in COS cells; and (4) induction of the gene by phorbol ester, a protein kinase C (PKC) activator. The co-presence of PKC and ROS-GC1 in photoreceptors suggests that regulation of the ROS-GC1 gene by PKC might be a physiologically relevant phenomenon.
Yu-may Lee - One of the best experts on this subject based on the ideXlab platform.
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Hsp27 decreases inclusion body formation from mutated GTP-cyclohydrolase I protein
Biochimica et biophysica acta, 2008Co-Authors: Yu-wei Chiou, Wuh-liang Hwu, Yu-may LeeAbstract:GTP cyclohydrolase I (GCH), an oligomeric protein composed of 10 identical subunits, is required for the synthesis of neurotransmitters; mutations in GCH are associated with dopa-responsive dystonia (DRD) and hyperphenylalaninemia. Mutated GCH proteins are unstable and prone to dominant-negative effect. We show herein that expression of the GCH mutant GCH-201E or the splicing variant GCH-II caused intracellular inclusion bodies. When Hsp27 was expressed together with the GCH mutants, Hsp27 expression decreased the formation of inclusion bodies by GCH (as assessed by immunofluorescence) and decreased the amount of insoluble GCH mutant proteins (as assessed by Western blot). Transfection of pcDNA-Hsp27-S3D, a phosphorylation-mimicry Hsp27 mutant, was more effective at the mutated GCH proteins than transfection with pcDNA-Hsp27, but okadaic acid, a phosphatase inhibitor, enhanced the effect of pcDNA-Hsp27. Hsp27-S3D also abolished the dominant-negative action of GCH-II. The mutated GCH proteins interacted with the wild-type GCH protein; the inclusion bodies were positive for lysosomal marker LAMP1, soluble in 2% SDS, and were not ubiquitinated. Phophorlyated Hsp27 also decreased the inclusion body formation by the huntingtin polyglutamines. Therefore, diseases involving mutated oligomeric proteins would be manageable by chaperone therapies.
Rameshwar K Sharma - One of the best experts on this subject based on the ideXlab platform.
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rod outer segment membrane guanylate cyclase type 1 ros gc1 gene structure organization and regulation by phorbol ester a protein kinase c activator
Molecular and Cellular Biochemistry, 1998Co-Authors: Teresa Duda, Venkateswar Venkataraman, Anuradha Krishnan, Rameshwar K SharmaAbstract:At present there are two recognized members of the ROS-GC subfamily of membrane guanylate cyclases. They are ROS-GC1 and ROS-GC2. A distinctive feature of this family is that its members are not switched on by the extracellular peptide hormones; instead, they are modulated by intracellular Ca2+ signals, consistent to their linkage with phototransduction. An intriguing feature of ROS-GC1, which distinguishes it from ROS-GC2, is that it has two Ca2+ switches. One switch inhibits the enzyme at micromolar concentrations of Ca2+, as in phototransduction; the other, stimulates. The stimulatory switch, most likely, is linked to retinal synaptic activity. Thus, ROS-GC1 is linked to both phototransduction and the synaptic activity. The present study describes (1) the almost complete structural identity of 18.5 kb ROS-GC1 gene; (2) its structural organization: the gene is composed of 20 exons and 19 introns with classical GT/AG boundaries; (3) the activity of the ROS-GC1 promoter assayed through luciferase reporter in COS cells; and (4) induction of the gene by phorbol ester, a protein kinase C (PKC) activator. The co-presence of PKC and ROS-GC1 in photoreceptors suggests that regulation of the ROS-GC1 gene by PKC might be a physiologically relevant phenomenon.
Yang Shi - One of the best experts on this subject based on the ideXlab platform.
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Identification of proteins interacting with GTP cyclohydrolase I.
Biochemical and biophysical research communications, 2009Co-Authors: Na Wei, Bassam T. Wakim, Brian D. Halligan, Kirkwood A. Pritchard, Yang ShiAbstract:GTP cyclohydrolase I (GCH-1) is the rate-limiting enzyme in the biosynthesis of tetrahydrobiopterin, an essential cofactor for nitric oxide synthase and aromatic amino acid hydroxylase. To explore the interactome of GCH-1, we established a HEK 293 cell line stably expressing tetracycline-inducible FLAG-GCH-1. FLAG-GCH-1 and associated proteins were immunoprecipitated and analyzed by liquid chromatography/tandem mass spectrometry. Twenty-nine proteins, derived from different subcellular components such as cytosol, membranes, nucleus and mitochondria were identified to interact with GCH-1. Cell fractionation studies also showed that GCH-1 was present in the cytosol, membranes and nucleus. Gene ontology analysis revealed that GCH-1 interactome was involved in a variety of biological processes such as signal transduction, apoptosis, metabolism, transport and cell organization. To our knowledge, this study is the first to provide a comprehensive analysis of the GCH-1 interactome. Findings expand the number and diversity of proteins that are known to associate with GCH-1.
Toshiharu Nagatsu - One of the best experts on this subject based on the ideXlab platform.
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cGMP inhibits GTP cyclohydrolase I activity and biosynthesis of tetrahydrobiopterin in human umbilical vein endothelial cells.
Journal of pharmacological sciences, 2003Co-Authors: Hiroaki Shiraishi, Taiya Kato, Koji Atsuta, Chiho Sumi-ichinose, Masatsugu Ohtsuki, Mitsuyasu Itoh, Hitoshi Hishida, Shin Tada, Yasuhiro Udagawa, Toshiharu NagatsuAbstract:Tetrahydrobiopterin (BH4) acts as an essential cofactor for the enzymatic activity of nitric oxide (NO) synthases. Biosynthesis of the cofactor BH4 starts from GTP and requires 3 enzymatic steps, which include GTP cyclohydrolase I (GCH I) catalysis of the first and rate-limiting step. In this study we examined the effects of cGMP on GCH I activity in human umbilical vein endothelial cells under inflammatory conditions. Exogenous application of the cGMP analogue 8-bromo-cGMP markedly inhibited GCH I activity in the short term, whereas an cAMP analogue had no effect on GCH I activity under the same condition. NO donors, NOR3 and sodium nitroprusside, elevated the intracellular cGMP level and reduced GCH I activity in the short term. This inhibition of GCH I activity was obliterated in the presence of an NO trapper carboxy-PTIO. NO donors had no effect on GCH I mRNA expression in the short term. Moreover, cycloheximide did not alter the inhibition by NO donors of GCH I activity. These findings suggest that stimulation of the cGMP signaling cascade down-regulates GCH I activity through post translational modification of the GCH I enzyme.
