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Dunkley PR, Dickson PW. Tyrosine hydroxylase phosphorylation
in vivo. J Neurochem 2019; 149:706-728. [DOI: 10.1111/jnc.14675] [Citation(s) in RCA: 36] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2018] [Revised: 01/23/2019] [Accepted: 01/29/2019] [Indexed: 12/31/2022]
Affiliation(s)
- Peter R. Dunkley
- The School of Biomedical Sciences and Pharmacy and The Hunter Medical Research Institute The University of Newcastle University Drive Callaghan NSW Australia
| | - Phillip W. Dickson
- The School of Biomedical Sciences and Pharmacy and The Hunter Medical Research Institute The University of Newcastle University Drive Callaghan NSW Australia
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2
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Sahu BS, Mahata S, Bandyopadhyay K, Mahata M, Avolio E, Pasqua T, Sahu C, Bandyopadhyay GK, Bartolomucci A, Webster NJG, Van Den Bogaart G, Fischer-Colbrie R, Corti A, Eiden LE, Mahata SK. Catestatin regulates vesicular quanta through modulation of cholinergic and peptidergic (PACAPergic) stimulation in PC12 cells. Cell Tissue Res 2018; 376:51-70. [PMID: 30467710 DOI: 10.1007/s00441-018-2956-1] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2018] [Accepted: 10/30/2018] [Indexed: 12/23/2022]
Abstract
We have previously shown that the chromogranin A (CgA)-derived peptide catestatin (CST: hCgA352-372) inhibits nicotine-induced secretion of catecholamines from the adrenal medulla and chromaffin cells. In the present study, we seek to determine whether CST regulates dense core (DC) vesicle (DCV) quanta (catecholamine and chromogranin/secretogranin proteins) during acute (0.5-h treatment) or chronic (24-h treatment) cholinergic (nicotine) or peptidergic (PACAP, pituitary adenylyl cyclase activating polypeptide) stimulation of PC12 cells. In acute experiments, we found that both nicotine (60 μM) and PACAP (0.1 μM) decreased intracellular norepinephrine (NE) content and increased 3H-NE secretion, with both effects markedly inhibited by co-treatment with CST (2 μM). In chronic experiments, we found that nicotine and PACAP both reduced DCV and DC diameters and that this effect was likewise prevented by CST. Nicotine or CST alone increased expression of CgA protein and together elicited an additional increase in CgA protein, implying that nicotine and CST utilize separate signaling pathways to activate CgA expression. In contrast, PACAP increased expression of CgB and SgII proteins, with a further potentiation by CST. CST augmented the expression of tyrosine hydroxylase (TH) but did not increase intracellular NE levels, presumably due to its inability to cause post-translational activation of TH through serine phosphorylation. Co-treatment of CST with nicotine or PACAP increased quantal size, plausibly due to increased synthesis of CgA, CgB and SgII by CST. We conclude that CST regulates DCV quanta by acutely inhibiting catecholamine secretion and chronically increasing expression of CgA after nicotinic stimulation and CgB and SgII after PACAPergic stimulation.
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Affiliation(s)
- Bhavani Shankar Sahu
- Department of Integrative Biology and Physiology, University of Minnesota, Minneapolis, MN, USA. .,Department of Medicine, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA, 92093-0732, USA.
| | - Sumana Mahata
- California Institute of Technology, Pasadena, CA, USA
| | - Keya Bandyopadhyay
- Department of Medicine, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA, 92093-0732, USA
| | - Manjula Mahata
- Department of Medicine, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA, 92093-0732, USA
| | | | | | - Chinmayi Sahu
- Department of Integrative Biology and Physiology, University of Minnesota, Minneapolis, MN, USA
| | - Gautam K Bandyopadhyay
- Department of Medicine, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA, 92093-0732, USA
| | - Alessandro Bartolomucci
- Department of Integrative Biology and Physiology, University of Minnesota, Minneapolis, MN, USA
| | - Nicholas J G Webster
- Department of Medicine, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA, 92093-0732, USA.,VA San Diego Healthcare System, San Diego, CA, USA
| | | | | | - Angelo Corti
- IRCCS San Raffaele Scientific Institute, San Raffaele Vita-Salute University, Milan, Italy
| | - Lee E Eiden
- Section on Molecular Neuroscience, NIMH-IRP, Bethesda, MD, USA
| | - Sushil K Mahata
- Department of Medicine, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA, 92093-0732, USA. .,VA San Diego Healthcare System, San Diego, CA, USA.
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3
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Johnson M, Salvatore M, Maiolo S, Bobrovskaya L. Tyrosine hydroxylase as a sentinel for central and peripheral tissue responses in Parkinson’s progression: Evidence from clinical studies and neurotoxin models. Prog Neurobiol 2018; 165-167:1-25. [DOI: 10.1016/j.pneurobio.2018.01.002] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2017] [Revised: 12/07/2017] [Accepted: 01/10/2018] [Indexed: 12/25/2022]
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4
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Complex molecular regulation of tyrosine hydroxylase. J Neural Transm (Vienna) 2014; 121:1451-81. [PMID: 24866693 DOI: 10.1007/s00702-014-1238-7] [Citation(s) in RCA: 66] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2014] [Accepted: 05/04/2014] [Indexed: 12/16/2022]
Abstract
Tyrosine hydroxylase, the rate-limiting enzyme in catecholamine biosynthesis, is strictly controlled by several interrelated regulatory mechanisms. Enzyme synthesis is controlled by epigenetic factors, transcription factors, and mRNA levels. Enzyme activity is regulated by end-product feedback inhibition. Phosphorylation of the enzyme is catalyzed by several protein kinases and dephosphorylation is mediated by two protein phosphatases that establish a sensitive process for regulating enzyme activity on a minute-to-minute basis. Interactions between tyrosine hydroxylase and other proteins introduce additional layers to the already tightly controlled production of catecholamines. Tyrosine hydroxylase degradation by the ubiquitin-proteasome coupled pathway represents yet another mechanism of regulation. Here, we revisit the myriad mechanisms that regulate tyrosine hydroxylase expression and activity and highlight their physiological importance in the control of catecholamine biosynthesis.
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Abstract
Endothelin-1 (ET-1) is a locally acting vasoactive peptide that also has profound effects on the contractile properties and growth of the cardiac myocyte. Binding of ET-1 to its transmembrane heptahelical receptors activates G proteins of the G(q) and G(i) classes. Activation of G(q) stimulates hydrolysis of phosphatidylinositol-4,5-bisphosphate, and the diacylglycerol thus formed stimulates protein kinase C. Subsequently, the protein kinase Raf is activated and this leads to activation of the extracellular signal-regulated protein kinase (ERK) subfamily of mitogen-activated protein kinases. Activation of G(i) counteracts β-adrenoceptor-mediated increases in cAMP concentrations. We have attempted to rationalize the established physiological consequences of ET-1 agonism in the cardiac myocyte (that is, on contraction and growth) in terms of activation of these signaling pathways.
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Affiliation(s)
- P H Sugden
- Peter H. Sugden is at the National Heart and Lung Institute (Cardiac Medicine), Imperial College of Science, Technology and Medicine, London SW3 6LY, United Kingdom
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6
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Izumi Y, Yamamoto N, Matsuo T, Wakita S, Takeuchi H, Kume T, Katsuki H, Sawada H, Akaike A. Vulnerability to glutamate toxicity of dopaminergic neurons is dependent on endogenous dopamine and MAPK activation. J Neurochem 2009; 110:745-55. [DOI: 10.1111/j.1471-4159.2009.06178.x] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Marques Pereira P, Gruss M, Braun K, Foos N, Pannetier S, Hanauer A. Dopaminergic system dysregulation in themrsk2_KO mouse, an animal model of the Coffin-Lowry syndrome. J Neurochem 2008; 107:1325-34. [DOI: 10.1111/j.1471-4159.2008.05703.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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8
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Yanagihara N, Toyohira Y, Shinohara Y. Insights into the Pharmacological Potential of Estrogens and Phytoestrogens on Catecholamine Signaling. Ann N Y Acad Sci 2008; 1129:96-104. [DOI: 10.1196/annals.1417.008] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Liu M, Yanagihara N, Toyohira Y, Tsutsui M, Ueno S, Shinohara Y. Dual effects of daidzein, a soy isoflavone, on catecholamine synthesis and secretion in cultured bovine adrenal medullary cells. Endocrinology 2007; 148:5348-54. [PMID: 17717056 DOI: 10.1210/en.2007-0073] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
We recently demonstrated the occurrence and functional roles of plasma membrane estrogen receptors in cultured bovine adrenal medullary cells. Here we report the effects of daidzein, a phytoestrogen of soybeans, on catecholamine synthesis and secretion in the cells. Incubation of cells with daidzein for 20 min increased the synthesis of (14)C-catecholamines from [(14)C]tyrosine but not [(14)C]dihydroxyphenylalanine, in a concentration-dependent manner (10-1000 nm). The stimulatory effect of daidzein on (14)C-catecholamine synthesis was not inhibited by ICI182,780, a classical estrogen receptor inhibitor. Acetylcholine, a physiological secretagogue, stimulated the synthesis of (14)C-catecholamines, which was suppressed by daidzein at 1 mum. Daidzein at high concentrations (1-100 microm) suppressed catecholamine secretion induced by acetylcholine. Furthermore, daidzein (10-1000 nm) inhibited the specific binding of [(3)H]17beta-estradiol to plasma membranes isolated from bovine adrenal medulla. The present findings suggest that daidzein at low concentrations stimulates catecholamine synthesis through plasma membrane estrogen receptors but at high concentrations inhibits catecholamine synthesis and secretion induced by acetylcholine in bovine adrenal medulla. The latter effect of daidzein may be a beneficial action on the cardiovascular system.
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Affiliation(s)
- Minhui Liu
- Department of Pharmacology, University of Occupational and Environmental Health, School of Medicine, 1-1, Iseigaoka, Kitakyushu, Japan
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Shinkai K, Toyohira Y, Yoshimura R, Tsutsui M, Ueno S, Nakamura J, Yanagihara N. Stimulation of catecholamine synthesis via activation of p44/42 MAPK in cultured bovine adrenal medullary cells by milnacipran. Naunyn Schmiedebergs Arch Pharmacol 2007; 375:65-72. [PMID: 17211600 DOI: 10.1007/s00210-006-0128-4] [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] [Received: 06/07/2006] [Accepted: 11/28/2006] [Indexed: 11/25/2022]
Abstract
Milnacipran is a serotonin noradrenaline reuptake inhibitor (SNRI) and is used clinically as an antidepressant. We report here the effect of milnacipran on catecholamine synthesis in cultured bovine adrenal medullary cells. Incubation of adrenal medullary cells with milnacipran (300 ng/ml, 1,065 nM) for 20 min resulted in a significant increase in 14C-catecholamine synthesis from [14C]tyrosine, but not from [14C]DOPA, whereas the selective serotonin reuptake inhibitors (SSRIs), paroxetine (300 ng/ml, 800 nM) and fluvoxamine (300 ng/ml, 691 nM), had little effect. Milnacipran, but not paroxetine or fluvoxamine, increased the activity of tyrosine hydroxylase, the rate-limiting step of catecholamine biosynthesis, in a concentration-dependent manner (100-300 ng/ml, 355-1,065 nM). U0126 (1 microM), an inhibitor of p44/42 mitogen-activated protein kinase (MAPK) kinase, abolished the stimulatory effects of milnacipran on tyrosine hydroxylase activity. Furthermore, incubation of cells with milnacipran (30-100 ng/ml) for 5 min activated p44/42 MAPK, whereas paroxetine and fluvoxamine did not. The present findings suggest that milnacipran activates tyrosine hydroxylase and then stimulates catecholamine synthesis through a p44/42 MAPK-dependent pathway in cultured bovine adrenal medullary cells.
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Affiliation(s)
- Koji Shinkai
- Department of Psychiatry, University of Occupational and Environmental Health, School of Medicine, Kitakyushu, 807-8555, Japan
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11
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Lehmann IT, Bobrovskaya L, Gordon SL, Dunkley PR, Dickson PW. Differential Regulation of the Human Tyrosine Hydroxylase Isoforms via Hierarchical Phosphorylation. J Biol Chem 2006; 281:17644-51. [PMID: 16644734 DOI: 10.1074/jbc.m512194200] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Tyrosine hydroxylase (TH) is the rate-limiting enzyme in the biosynthesis of the catecholamines dopamine, noradrenaline, and adrenaline. In response to short term stimuli TH activity is primarily controlled by phosphorylation of serine 40. We have previously shown that phosphorylation of serine 19 in TH can indirectly activate TH via a hierarchical mechanism by increasing the rate of phosphorylation of serine 40. Here we show that phosphorylation of serine 31 in rat TH increases the rate of serine 40 phosphorylation 9-fold in vitro. Phosphorylation of serine 31 in intact bovine chromaffin cells potentiated the forskolin-induced increase in serine 40 phosphorylation and TH activity more than 2-fold. Humans are unique in that they contain four TH isoforms but to date no significant differences have been shown in the regulation of these isoforms. Phosphorylation of the human TH isoform 1 at serine 31 by extracellular signal-regulated protein kinase (ERK) also produced a 9-fold increase in the rate of phosphorylation of serine 40, whereas little effect was seen in the TH isoforms 3 and 4. ERK did not phosphorylate human TH isoform 2. The effect of serine 19 phosphorylation on serine 40 (44 in TH2) phosphorylation is stronger in TH2 than in TH1. Thus hierarchical phosphorylation provides a mechanism whereby the two major human TH isoforms (1 and 2) can be differentially regulated with only isoform 1 responding to the ERK pathway, whereas isoform 2 is more sensitive to calcium-mediated events.
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Affiliation(s)
- Ingo T Lehmann
- School of Biomedical Sciences and The Hunter Medical Research Institute, Faculty of Health, The University of Newcastle, Callaghan, NSW 2308, Australia
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Royo M, Colette Daubner S. Kinetics of regulatory serine variants of tyrosine hydroxylase with cyclic AMP-dependent protein kinase and extracellular signal-regulated protein kinase 2. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2006; 1764:786-92. [PMID: 16503426 PMCID: PMC1855258 DOI: 10.1016/j.bbapap.2006.01.019] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/13/2005] [Revised: 01/24/2006] [Accepted: 01/24/2006] [Indexed: 11/24/2022]
Abstract
Rat tyrosine hydroxylase is phosphorylated at four serine residues, at positions 8, 19, 31, and 40 in its amino terminal regulatory domain by multiple protein kinases. Cyclic AMP-dependent protein kinase phosphorylates S40, which results in alleviation of inhibition by dopamine. Extracellular signal-regulated protein kinase 2 phosphorylates S8 and S31. Site-directed serine-to-glutamate mutations were introduced into tyrosine hydroxylase to mimic prior phosphorylation of the regulatory serines; these proteins were used as substrates for cAMP-dependent kinase and extracellular signal-regulated kinase 2. The activity of cAMP-dependent kinase was unaffected by the substitution of serines 8, 19 or 31 with glutamate and the activity of extracellular signal-regulated kinase 2 was unaffected by substitution of serines 19 or 40 with glutamate. Cyclic AMP-dependent kinase was less active in phosphorylating S40 if dopamine was bound to tyrosine hydroxylase, but extracellular signal-regulated kinase 2 phosphorylation at S31 was unaffected by the presence of dopamine.
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Affiliation(s)
- Montserrat Royo
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, TX 77843-2128, USA
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13
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Drolet RE, Behrouz B, Lookingland KJ, Goudreau JL. Substrate-mediated enhancement of phosphorylated tyrosine hydroxylase in nigrostriatal dopamine neurons: evidence for a role of alpha-synuclein. J Neurochem 2006; 96:950-9. [PMID: 16412098 DOI: 10.1111/j.1471-4159.2005.03606.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Tyrosine hydroxylase (TH) protein, phosphorylated at serine-40, serine-31 and serine-19, and enzyme catalytic activity were compared under basal conditions and in activated nigrostriatal dopamine (NSDA) neurons of wild-type and homozygous alpha-synuclein knockout mice. Mice were injected with the D2 antagonist raclopride to stimulate NSDA neuronal activity in the presence or absence of supplemental l-tyrosine. There was no difference in phosphorylated TH levels or TH catalytic activity between wild-type and alpha-synuclein knockout mice under basal conditions or following raclopride-induced acceleration of NSDA activity. In wild-type animals, tyrosine administration potentiated the raclopride-induced increase in phosphorylated TH and enzyme activity. However, tyrosine administration did not enhance phosphorylated TH levels or enzyme catalytic activity in raclopride-stimulated NSDA neurons in alpha-synuclein knockout mice. These findings suggest that alpha-synuclein plays a role in the ability of tyrosine to either enhance TH phosphorylation or hinder TH inactivation during accelerated neuronal activity. The present study supports the hypothesis that alpha-synuclein functions as a molecular chaperone protein that regulates the phosphorylation state of TH in a substrate and activity-dependent manner.
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Affiliation(s)
- Robert E Drolet
- Neuroscience Program, Michigan State University, East Lansing, Michigan 48823, USA
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Yanagihara N, Liu M, Toyohira Y, Tsutsui M, Ueno S, Shinohara Y, Takahashi K, Tanaka K. Stimulation of catecholamine synthesis through unique estrogen receptors in the bovine adrenomedullary plasma membrane by 17beta-estradiol. Biochem Biophys Res Commun 2005; 339:548-53. [PMID: 16307725 DOI: 10.1016/j.bbrc.2005.11.047] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2005] [Accepted: 11/09/2005] [Indexed: 11/28/2022]
Abstract
Incubation of cultured bovine adrenal medullary cells with 17beta-estradiol (E(2)) (0.3-100nM) or membrane-impermeable E(2)-bovine serum albumin (100nM) acutely increased (14)C-catecholamine synthesis from [(14)C]tyrosine. The stimulatory effect of E(2) was not inhibited by ICI182,780, a nuclear estrogen receptor inhibitor. E(2) also increased tyrosine hydroxylase activity and p44/42MAPK phosphorylation, the former of which was attenuated by U0126, an inhibitor of p44/42MAPK kinase. The plasma membrane isolated from the gland showed two classes of specific binding sites of [(3)H]E(2) with apparent K(d)s of 3.2 and 106nM, and B(max)s of 0.44 and 8.5pmol/mg protein, respectively. The high-affinity binding of [(3)H]E(2) was most strongly inhibited by E(2) and phytoestrogens, and to lesser extents by other steroid hormones, while it was enhanced by ICI182,780 and environmental estrogenic pollutants. These findings suggest that E(2) acutely stimulates catecholamine synthesis via activation of p44/42MAPK through unique estrogen receptors in the plasma membrane of bovine adrenal medulla.
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Affiliation(s)
- Nobuyuki Yanagihara
- Department of Pharmacology, University of Occupational and Environmental Health, School of Medicine, 1-1, Iseigaoka, Yahatanishi-ku, Kitakyushu 807-8555, Japan.
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Gozal E, Shah ZA, Pequignot JM, Pequignot J, Sachleben LR, Czyzyk-Krzeska MF, Li RC, Guo SZ, Gozal D. Tyrosine hydroxylase expression and activity in the rat brain: differential regulation after long-term intermittent or sustained hypoxia. J Appl Physiol (1985) 2005; 99:642-9. [PMID: 15817718 DOI: 10.1152/japplphysiol.00880.2004] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Tyrosine hydroxylase, a hypoxia-regulated gene, may be involved in tissue adaptation to hypoxia. Intermittent hypoxia, a characteristic feature of sleep apnea, leads to significant memory deficits, as well as to cortex and hippocampal apoptosis that are absent after sustained hypoxia. To examine the hypothesis that sustained and intermittent hypoxia induce different catecholaminergic responses, changes in tyrosine hydroxylase mRNA, protein expression, and activity were compared in various brain regions of male rats exposed for 6 h, 1 day, 3 days, and 7 days to sustained hypoxia (10% O2), intermittent hypoxia (alternating room air and 10% O2), or normoxia. Tyrosine hydroxylase activity, measured at 7 days, increased in the cortex as follows: sustained > intermittent > normoxia. Furthermore, activity decreased in the brain stem and was unchanged in other brain regions of sustained hypoxia-exposed rats, as well as in all regions from animals exposed to intermittent hypoxia, suggesting stimulus-specific and heterotopic catecholamine regulation. In the cortex, tyrosine hydroxylase mRNA expression was increased, whereas protein expression remained unchanged. In addition, significant differences in the time course of cortical Ser40tyrosine hydroxylase phosphorylation were present in the cortex, suggesting that intermittent and sustained hypoxia-induced enzymatic activity differences are related to different phosphorylation patterns. We conclude that long-term hypoxia induces site-specific changes in tyrosine hydroxylase activity and that intermittent hypoxia elicits reduced tyrosine hydroxylase recruitment and phosphorylation compared with sustained hypoxia. Such changes may not only account for differences in enzyme activity but also suggest that, with differential regional brain susceptibility to hypoxia, recruitment of different mechanisms in response to hypoxia will elicit region-specific modulation of catecholamine response.
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Affiliation(s)
- Evelyne Gozal
- Kosair Children's Hospital Research Institute, 570 S. Preston Street, Suite 321, Louisville, KY 40202, USA.
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16
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Royo M, Fitzpatrick PF, Daubner SC. Mutation of regulatory serines of rat tyrosine hydroxylase to glutamate: effects on enzyme stability and activity. Arch Biochem Biophys 2005; 434:266-74. [PMID: 15639226 DOI: 10.1016/j.abb.2004.11.007] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2004] [Revised: 11/03/2004] [Indexed: 10/26/2022]
Abstract
Tyrosine hydroxylase is phosphorylated at four serine residues in its amino-terminus by multiple kinases. Phosphorylation of serine 40 by cAMP-dependent protein kinase results in alleviation of dopamine inhibition [J. Biol. Chem. 267 (1992) 12639]. The other serines are at positions 8, 19, and 31. The effect of phosphorylation at these serines has been investigated using mutated forms of tyrosine hydroxylase containing glutamates at the positions of the serines. The S8E, S19E, and S31E tyrosine hydroxylase variants have similar steady-state kinetic parameters and similar binding affinity for catecholamines to wild-type enzyme. The S8E, S19E, S31E, and S40E variants differ in stability at elevated temperatures. The S40E variant is the least stable, while the others are all more stable than wild-type enzyme. The increased stability of S8E, S19E, and S31E tyrosine hydroxylases may be one of the physiological effects of phosphorylation. It may also have implications for the interpretation of activities of heterogeneous mixtures of tyrosine hydroxylase which have been phosphorylated.
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Affiliation(s)
- Montserrat Royo
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, TX 77843, USA
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Moy LY, Tsai LH. Cyclin-dependent Kinase 5 Phosphorylates Serine 31 of Tyrosine Hydroxylase and Regulates Its Stability. J Biol Chem 2004; 279:54487-93. [PMID: 15471880 DOI: 10.1074/jbc.m406636200] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Tyrosine hydroxylase (TH) is the rate-limiting enzyme in catecholamine biosynthesis, and its activity is regulated by phosphorylation in the N-terminal regulatory domain. The proline-directed serine/threonine kinase cyclin-dependent kinase 5 (cdk5) plays an important role in diverse neuronal processes. In the present study, we identify TH as a novel substrate of cdk5. We show that cdk5 phosphorylates TH at serine 31 and that this phosphorylation is associated with an increase in total TH activity. In transgenic mice with increased cdk5 activity, the immunoreactivity for phosphorylated TH at Ser-31 is enhanced in neurons of the substantia nigra, a brain region enriched with TH-positive neurons. In addition, we demonstrate that co-expression of cdk5 and its regulatory activator p35 with TH increases the stability of TH. Consistent with these findings, TH protein levels are reduced in cdk5 knock-out mice. Importantly, the TH activity and protein turnover of the phosphorylation-defective mutant TH S31A was not altered by cdk5 activity. Taken together, these data suggest that cdk5 phosphorylation of TH is an important regulator of TH activity through stabilization of TH protein levels.
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Affiliation(s)
- Lily Y Moy
- Department of Pathology and Howard Hughes Medical Institute, Harvard Medical School, Boston, Massachusetts 02115, USA.
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Dunkley PR, Bobrovskaya L, Graham ME, von Nagy-Felsobuki EI, Dickson PW. Tyrosine hydroxylase phosphorylation: regulation and consequences. J Neurochem 2004; 91:1025-43. [PMID: 15569247 DOI: 10.1111/j.1471-4159.2004.02797.x] [Citation(s) in RCA: 351] [Impact Index Per Article: 17.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The rate-limiting enzyme in catecholamine synthesis is tyrosine hydroxylase. It is phosphorylated at serine (Ser) residues Ser8, Ser19, Ser31 and Ser40 in vitro, in situ and in vivo. A range of protein kinases and protein phosphatases are able to phosphorylate or dephosphorylate these sites in vitro. Some of these enzymes are able to regulate tyrosine hydroxylase phosphorylation in situ and in vivo but the identity of the kinases and phosphatases is incomplete, especially for physiologically relevant stimuli. The stoichiometry of tyrosine hydroxylase phosphorylation in situ and in vivo is low. The phosphorylation of tyrosine hydroxylase at Ser40 increases the enzyme's activity in vitro, in situ and in vivo. Phosphorylation at Ser31 also increases the activity but to a much lesser extent than for Ser40 phosphorylation. The phosphorylation of tyrosine hydroxylase at Ser19 or Ser8 has no direct effect on tyrosine hydroxylase activity. Hierarchical phosphorylation of tyrosine hydroxylase occurs both in vitro and in situ, whereby the phosphorylation at Ser19 increases the rate of Ser40 phosphorylation leading to an increase in enzyme activity. Hierarchical phosphorylation depends on the state of the substrate providing a novel form of control of tyrosine hydroxylase activation.
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Affiliation(s)
- Peter R Dunkley
- School of Biomedical Sciences, The University of Newcastle, Callaghan, New South Wales, Australia.
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Royo M, Daubner SC, Fitzpatrick PF. Specificity of the MAP kinase ERK2 for phosphorylation of tyrosine hydroxylase. Arch Biochem Biophys 2004; 423:247-52. [PMID: 15001389 DOI: 10.1016/j.abb.2003.12.027] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2003] [Revised: 12/23/2003] [Indexed: 01/15/2023]
Abstract
Short-term regulation of catecholamine biosynthesis involves reversible phosphorylation of several serine residues in the N-terminal regulatory domain of tyrosine hydroxylase. The MAP kinases ERK1/2 have been identified as responsible for phosphorylation of Ser31. As an initial step in elucidating the effects of phosphorylation of Ser31 on the structure and activity of tyrosine hydroxylase, the kinetics of phosphorylation of the rat enzyme by recombinant rat ERK2 have been characterized. Complete phosphorylation results in incorporation of 2mol of phosphate into each subunit of tyrosine hydroxylase. The S8A and S31A enzymes only incorporate a single phosphate, while the S19A and S40A enzymes incorporate two. Phosphorylation of S8A tyrosine hydroxylase is nine times as rapid as phosphorylation of the S31A enzyme, consistent with a ninefold preference of ERK2 for Ser31 over Ser8.
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Affiliation(s)
- Montserrat Royo
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, TX 77843-2128, USA.
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20
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Kumar GK, Kim DK, Lee MS, Ramachandran R, Prabhakar NR. Activation of tyrosine hydroxylase by intermittent hypoxia: involvement of serine phosphorylation. J Appl Physiol (1985) 2003; 95:536-44. [PMID: 12692140 DOI: 10.1152/japplphysiol.00186.2003] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Regulation of tyrosine hydroxylase (TH) by intermittent hypoxia (IH) was investigated in rat pheochromocytoma 12 (PC-12) cells by exposing them to alternating cycles of hypoxia (1% O2, 15 s) and normoxia (21% O2, 3 min) for up to 60 cycles; controls were exposed to normoxia for a similar duration. IH exposure increased dopamine content and TH activity by approximately 42 and approximately 56%, respectively. Immunoblot analysis revealed that comparable levels of TH protein were expressed in normoxic and IH cells. Removal of TH-bound catecholamines and in vitro phosphorylation of TH in cell-free extracts by the catalytic subunit of protein kinase A (PKA) increased TH activity in normoxic but not in IH cells, suggesting possible induction of TH phosphorylation and removal of endogenous inhibition of TH by IH. To assess the role of serine phosphorylation in IH-induced TH activation, TH immunoprecipitates and extracts derived from normoxic and IH cells were probed with anti-phosphoserine and anti-phospho-TH (Ser-40) antibody, respectively. Compared with normoxic cells, total serine and Ser-40-specific phosphorylation of TH were increased in IH cells. IH-induced activation of TH and the increase in total serine and Ser-40-specific phosphorylation of TH were inhibited by Ca2+/calmodulin-dependent protein kinase (CaMK) and PKA-specific inhibitors but not by inhibitors of the extracellular signal-regulated protein kinase pathway, suggesting that IH activates TH in PC-12 cells via phosphorylation of serine residues including Ser-40, in part, by CaMK and PKA. Our results also suggest that IH-induced phosphorylation of TH facilitates the removal of endogenous inhibition of TH, leading to increased synthesis of dopamine.
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Affiliation(s)
- Ganesh K Kumar
- Department of Biochemistry,Western Reserve University, Cleveland, OH 44106-4935, USA.
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21
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Brunzell DH, Russell DS, Picciotto MR. In vivo nicotine treatment regulates mesocorticolimbic CREB and ERK signaling in C57Bl/6J mice. J Neurochem 2003; 84:1431-41. [PMID: 12614343 DOI: 10.1046/j.1471-4159.2003.01640.x] [Citation(s) in RCA: 159] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The extracellular regulated kinase (ERK) pathway was studied to determine its role in neuronal plasticity related to the development of nicotine dependence. Levels and phosphorylation state of ERK, cAMP response element binding protein (CREB) and proline-rich/Ca2+-activated tyrosine kinase (PYK2), and levels of tyrosine hydroxylase (TH), were determined using western blotting. C57Bl/6J mice received acute or chronic nicotine (200 microg/mL) in their drinking water or were withdrawn from nicotine for 24 h following chronic exposure. CREB phosphorylation was reduced in the nucleus accumbens following chronic nicotine, consistent with previous reports that decreased accumbens CREB activity increases drug reinforcement. In contrast, CREB phosphorylation was increased in the prefrontal cortex following chronic nicotine exposure and in the ventral tegmental area during nicotine withdrawal. In addition, total and phosphorylated ERK decreased in the amygdala following chronic nicotine exposure, but ERK phosphorylation increased in the prefrontal cortex. TH levels increased in both the amygdala and prefrontal cortex, supporting the hypothesis that increased catecholaminergic tone contributes to nicotine reinforcement. Overall, these results support a role for ERK and CREB activity in neural plasticity associated with nicotine dependence.
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Affiliation(s)
- Darlene H Brunzell
- Department of Psychiatry, Yale University School of Medicine, New Haven, Connecticut, USA
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22
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Lindgren N, Goiny M, Herrera-Marschitz M, Haycock JW, Hökfelt T, Fisone G. Activation of extracellular signal-regulated kinases 1 and 2 by depolarization stimulates tyrosine hydroxylase phosphorylation and dopamine synthesis in rat brain. Eur J Neurosci 2002; 15:769-73. [PMID: 11886455 DOI: 10.1046/j.1460-9568.2002.01901.x] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Production of dopamine is regulated via phosphorylation of tyrosine hydroxylase (TH), the rate-limiting enzyme in the synthesis of catecholamines. Here we have used a preparation of rat striatal slices to examine the involvement of two mitogen-activated protein kinases (MAPKs), extracellular signal-regulated protein kinases 1 and 2 (ERK1/2), in the depolarization-dependent regulation of TH phosphorylation and dopamine synthesis. Depolarization with elevated KCl (45 mm) caused an increase in the phosphorylation state and, thereby, activation of ERK1/2. The same stimulus also increased TH phosphorylation at Ser19, Ser31 and Ser40 (measured using site- and phospho-specific antibodies) and TH activity [measured as 3,4-dihydroxyphenylalanine (DOPA) accumulation]. A MAPK/ERK kinase inhibitor, PD098059, decreased the basal levels of phospho-ERK1/2 and prevented the increase in ERK1/2 phosphorylation induced by depolarization. PD098059 also decreased both basal and depolarization-induced phosphorylation of TH at Ser31 and reduced the increase in Ser40 phosphorylation induced by high potassium, but did not affect Ser19 phosphorylation. PD098059 alone inhibited basal TH activity and decreased the accumulation of DOPA induced by depolarization. These data provide evidence for the involvement of ERK1/2 in the regulation of the state of phosphorylation of TH at Ser31 and Ser40 and a correlation between ERK1/2-dependent phosphorylation of TH and stimulation of dopamine synthesis in the brain.
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Affiliation(s)
- Niklas Lindgren
- Department of Neuroscience, Karolinska Institutet, Stockholm, Sweden
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Salvatore MF, Waymire JC, Haycock JW. Depolarization-stimulated catecholamine biosynthesis: involvement of protein kinases and tyrosine hydroxylase phosphorylation sites in situ. J Neurochem 2001; 79:349-60. [PMID: 11677263 DOI: 10.1046/j.1471-4159.2001.00593.x] [Citation(s) in RCA: 82] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Depolarizing stimuli increase catecholamine (CA) biosynthesis, tyrosine hydroxylase (TH) activity, and TH phosphorylation at Ser19, Ser31, and Ser40 in a Ca(2+)-dependent manner. However, the identities of the protein kinases that phosphorylate TH under depolarizing conditions are not known. Furthermore, although increases in Ser31 or Ser40 phosphorylation increase TH activity in vitro, the relative influence of phosphorylation at these sites on CA biosynthesis under depolarizing conditions is not known. We investigated the participation of extracellular signal-regulated protein kinase (ERK) and cAMP-dependent protein kinase (PKA) in elevated K(+)-stimulated TH phosphorylation in PC12 cells using an ERK pathway inhibitor, PD98059, and PKA-deficient PC12 cells (A126-B1). In the same paradigm, we measured CA biosynthesis. TH phosphorylation stoichiometry (PS) was determined by quantitative blot-immunolabeling using site- and phosphorylation state-specific antibodies. Treatment with elevated K(+) (+ 58 mM) for 5 min increased TH PS at each site in a Ca(2+)-dependent manner. Pretreatment with PD98059 prevented elevated K(+)-stimulated increases in ERK phosphorylation and Ser31 PS. In A126-B1 cells, Ser40 PS was not significantly increased by forskolin, and elevated K(+)-stimulated Ser40 PS was three- to five-fold less than that in PC12 cells. In both cell lines, CA biosynthesis was increased 1.5-fold after treatment with elevated K(+) and was prevented by pretreatment with PD98059. These results suggest that ERK phosphorylates TH at Ser31 and that PKA phosphorylates TH at Ser40 under depolarizing conditions. They also suggest that the increases in CA biosynthesis under depolarizing conditions are associated with the ERK-mediated increases in Ser31 PS.
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Affiliation(s)
- M F Salvatore
- Department of Biochemistry and Molecular Biology and Neuroscience Center of Excellence, Louisiana State University Health Sciences Center, New Orleans, Louisiana, USA.
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24
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Abstract
Tyrosine hydroxylase (TOH) activity is regulated acutely by phosphorylation of serines 8, 19, 31 and 40. The only kinases known to phosphorylate Ser31 are the mitogen-activated protein kinases MAPK-1 and 2. The involvement of these kinases in TOH activation in situ was therefore investigated using intact bovine chromaffin cells. Nicotine, K+ and A23187 increased TOH activity over 10 min in a Ca2+-dependent manner. The response to all three was reduced by PD098059, a selective inhibitor of the upstream activator of MAPK, MEK1. In contrast, TOH activation by forskolin and phorbol dibutyrate were unaffected by PD098059. The results support a key role for MEK1/MAPK in the acute activation of TOH by nicotinic receptors and by other agonists that increase cytosolic Ca2+.
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Affiliation(s)
- J Griffiths
- Department of Pharmacology, University of Melbourne, Victoria 3010, Australia
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25
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Bobrovskaya L, Odell A, Leal RB, Dunkley PR. Tyrosine hydroxylase phosphorylation in bovine adrenal chromaffin cells: the role of MAPKs after angiotensin II stimulation. J Neurochem 2001; 78:490-8. [PMID: 11483651 DOI: 10.1046/j.1471-4159.2001.00445.x] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Angiotensin II (AII, 100 nM) stimulation of bovine adrenal chromaffin cells (BACCs) produced angiotensin II receptor subtype 1 (AT1)-mediated increases in extracellular regulated protein kinase 1/2 (ERK1/2) and stress-activated p38MAPK (p38 kinase) phosphorylation over a period of 10 min. ERK1/2 and p38 kinase phosphorylation preceded Ser31 phosphorylation on tyrosine hydroxylase (TOH). The inhibitors of mitogen-activated protein kinase kinase 1/2 (MEK1/2) activation, PD98059 (0.1-50 microM) and UO126 (0.1-10 microM), dose-dependently inhibited both ERK2 and Ser31 phosphorylation on TOH in response to AII, suggesting MEK1/2 involvement. The p38 kinase inhibitor SB203580 (20 microM, 30 min) abolished Ser31 and Ser19 phosphorylation on TOH and partially inhibited ERK2 phosphorylation produced by AII. In contrast, 1 microM SB203580 did not affect AII-stimulated TOH phosphorylation, but fully inhibited heat shock protein 27 (HSP27) phosphorylation produced by AII. Also, 1 microM SB203580 fully inhibited Ser19 phosphorylation on TOH and HSP27 phosphorylation in response to anisomycin (30 min, 10 microg/mL). The results suggest that ERKs mediate Ser31 phosphorylation on TOH in response to AII, but p38 kinase is not involved. Previous studies suggesting a role for p38 kinase in the phosphorylation of Ser31 are explained by the non-specific effects of 20 microM SB203580 in BACCs. The p38 kinase pathway is able to phosphorylate Ser19 on TOH in response to anisomycin, but does not do so in response to AII.
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Affiliation(s)
- L Bobrovskaya
- The Neuroscience Group, Discipline of Medical Biochemistry, Faculty of Medicine and Health Sciences, The University of Newcastle, Callaghan, New South Wales, Australia
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Utsunomiya K, Yanagihara N, Tachikawa E, Cheah TB, Kajiwara K, Toyohira Y, Ueno S, Izumi F. Stimulation of catecholamine synthesis in cultured bovine adrenal medullary cells by leptin. J Neurochem 2001; 76:926-34. [PMID: 11158265 DOI: 10.1046/j.1471-4159.2001.00123.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Recently, we characterized leptin receptors in bovine adrenal medullary cells (Yanagihara et al. 2000). Here we report the stimulatory effect of leptin on catecholamine synthesis in the cells. Incubating cells with leptin (10 nM) for 20 min increased the synthesis of 14C-catecholamines from [14C]tyrosine, but not from L-3,4-dihydroxyphenyl [3-14C]alanine. The stimulation of catecholamine synthesis in the cells by leptin was associated with the phosphorylation and activation of tyrosine hydroxylase, the rate-limiting enzyme of catecholamine biosynthesis. The incubation of cells with leptin resulted in a rapid activation of the mitogen-activated protein kinases (MAPKs). An inhibitor of MAPK kinase, U0126, nullified the stimulatory effect of leptin on the synthesis of 14C-catecholamines. Leptin potentiated the stimulatory effect of acetylcholine on 14C-catecholamine synthesis, whereas leptin failed to enhance the phosphorylation and activation of tyrosine hydroxylase induced by acetylcholine. These findings suggest that leptin stimulates catecholamine synthesis via the activation of tyrosine hydroxylase by two different mechanisms, i.e., one is dependent on tyrosine hydroxylase phosphorylation mediated through the MAPK pathway and the second is independent of enzyme phosphorylation.
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Affiliation(s)
- K Utsunomiya
- Department of Pharmacology, University of Occupational and Environmental Health, School of Medicine, Kitakyushu, Japan
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Abstract
Phenylalanine hydroxylase, tyrosine hydroxylase, and tryptophan hydroxylase constitute a small family of monooxygenases that utilize tetrahydropterins as substrates. When from eukaryotic sources, these enzymes are composed of a homologous catalytic domain to which are attached discrete N-terminal regulatory domains and short C-terminal tetramerization domains, whereas the bacterial enzymes lack the N-terminal and C-terminal domains. Each enzyme contains a single ferrous iron atom bound to two histidines and a glutamate. Recent mechanistic studies have begun to provide insights into the mechanisms of oxygen activation and hydroxylation. Although the hydroxylating intermediate in these enzymes has not been identified, the iron is likely to be involved. Reversible phosphorylation of serine residues in the regulatory domains affects the activities of all three enzymes. In addition, phenylalanine hydroxylase is allosterically regulated by its substrates, phenylalanine and tetrahydrobiopterin.
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Affiliation(s)
- P F Fitzpatrick
- Department of Biochemistry and Biophysics, Texas A&M University, College Station 77843-2128, USA.
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Fitzpatrick PF. The aromatic amino acid hydroxylases. ADVANCES IN ENZYMOLOGY AND RELATED AREAS OF MOLECULAR BIOLOGY 2000; 74:235-94. [PMID: 10800597 DOI: 10.1002/9780470123201.ch6] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/16/2023]
Abstract
The enzymes phenylalanine hydroxylase, tyrosine hydroxylase, and tryptophan hydroxylase constitute the family of pterin-dependent aromatic amino acid hydroxylases. Each enzyme catalyzes the hydroxylation of the aromatic side chain of its respective amino acid substrate using molecular oxygen and a tetrahydropterin as substrates. Recent advances have provided insights into the structures, mechanisms, and regulation of these enzymes. The eukaryotic enzymes are homotetramers comprised of homologous catalytic domains and discrete regulatory domains. The ligands to the active site iron atom as well as residues involved in substrate binding have been identified from a combination of structural studies and site-directed mutagenesis. Mechanistic studies with nonphysiological and isotopically substituted substrates have provided details of the mechanism of hydroxylation. While the complex regulatory properties of phenylalanine and tyrosine hydroxylase are still not fully understood, effects of regulation on key kinetic parameters have been identified. Phenylalanine hydroxylase is regulated by an interaction between phosphorylation and allosteric regulation by substrates. Tyrosine hydroxylase is regulated by phosphorylation and feedback inhibition by catecholamines.
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Affiliation(s)
- P F Fitzpatrick
- Department of Biochemistry and Biophysics, Texas A&M University, College Station 77843-2128, USA
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Ramsey AJ, Fitzpatrick PF. Effects of phosphorylation on binding of catecholamines to tyrosine hydroxylase: specificity and thermodynamics. Biochemistry 2000; 39:773-8. [PMID: 10651643 DOI: 10.1021/bi991901r] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
As the catalyst for the rate-limiting step in the biosynthesis of the catecholamine neurotransmitters, the activity of tyrosine hydroxylase is tightly regulated. A principle means of posttranslational regulation is reversible phosphorylation of serine residues in an N-terminal regulatory domain. Phosphorylation of serine 40 has been shown to have a large effect on the rate constant for dissociation of dopamine and a much smaller effect on that for DOPA [Ramsey, A. J., and Fitzpatrick, P. F. (1998) Biochemistry 37, 8980-8986]. To determine the structural basis for the differences in affinity and to further test the validity of the previously proposed model for regulation, the effects of phosphorylation of serine 40 on the affinities for a series of catechols have been determined. The affinities of the unphosphorylated enzyme vary by 3 orders of magnitude due to differences in the rates of dissociation. The highest affinities are found with catecholamines which lack a carboxylate. The affinities of the phosphorylated enzyme show a much smaller range. In the case of binding of dihydroxyphenylalanine, the decrease in affinity upon phosphorylation is due primarily to a decrease in the enthalpy of the interaction. Based upon these results, a structural model for the effect of phosphorylation is proposed.
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Affiliation(s)
- A J Ramsey
- Department of Biochemistry, Department of Chemistry, Texas A&M University, College Station, Texas 77843-2128, USA
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30
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Sugden PH, Clerk A. Regulation of the ERK subgroup of MAP kinase cascades through G protein-coupled receptors. Cell Signal 1997; 9:337-51. [PMID: 9376213 DOI: 10.1016/s0898-6568(96)00191-x] [Citation(s) in RCA: 250] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The extracellularly-responsive kinase (ERK) subfamily of mitogen-activated protein kinases (MAPKs) has been implicated in the regulation of cell growth and differentiation. Activation of ERKs involves a two-step protein kinase cascade lying upstream from ERK, in which the Raf family are the MAPK kinase kinases and the MEK1/MEK2 isoforms are the MAPK kinases. The linear sequence of Raf --> MEK --> ERK constitutes the ERK cascade. Although the ERK cascade is activated through growth factor-regulated receptor protein tyrosine kinases, they are also modulated through G protein-coupled receptors (GPCRs). All four G protein subfamilies (Gq/11 Gi/o, Gs and G12/13) influence the activation state of ERKs. In this review, we describe the ERK cascade and characteristics of its activation through GPCRs. We also discuss the identity of the intervening steps that may couple agonist binding at GPCRs to activation of the ERK cascade.
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Affiliation(s)
- P H Sugden
- National Heart and Lung Institute (Cardiac Medicine), Imperial College School of Medicine, London, United Kingdom
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Haycock JW. Short- and long-term regulation of tyrosine hydroxylase in chromaffin cells by VIP and PACAP. Ann N Y Acad Sci 1996; 805:219-30; discussion 230-1. [PMID: 8993405 DOI: 10.1111/j.1749-6632.1996.tb17485.x] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Whereas cholinergic neurotransmitters are responsible for the release of a substantial portion of the CAs released from rat chromaffin cells by activation of the splanchinc nerves, the present data suggest that noncholinergic neurotransmission appears to play a more substantial role in the short- and long-term homeostatic regulation of TH activity, which serves to maintain the stores of CAs for subsequent release. In addition, studies using the PKA-deficient PC12 cells provided the first direct evidence that PKA actually mediates the phosphorylation of Ser40 in situ.
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Affiliation(s)
- J W Haycock
- Department of Biochemistry and Molecular Biology, Louisiana State University Medical Center, New Orleans 70199, USA.
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