Tyrosine hydroxylase phosphorylation

Haycock, J.W. Multiple signaling pathways in bovine chromaffin cells regulate tyrosine hydroxylase phosphorylation at Serl9, Ser31, and Ser40. Neurochem. Res. 18 15, 1993. 

The regulation of phosphorylation of tyrosine hydroxylase is affected by stimuli that increase Ca2+ or cAMP concentrations in neurons, including nerve impulse conduction and certain neurotransmitters in well-defined regions of the nervous system, in the adrenal medulla and in cultured pheochromocytoma cells. In addition, tyrosine hydroxylase phosphorylation is stimulated by nerve growth factor in certain cell types, possibly via the activation of ERKs. These changes in the phosphorylation of tyrosine hydroxylase have been shown to correlate with changes in the catalytic activity of the enzyme and in the rate of catecholamine biosynthesis. 

Haeusler G, Lues I, Minck KO, Schelling P, Seyfried CA (1992) Pharmacological basis for antihypertensive therapy with a novel dopamine agonist. Eur Heart J 13 Suppl D 129-35 Hakansson K, Pozzi L, Usiello A, Haycock J, Borrelli E, Fisone G (2004) Regulation of striatal tyrosine hydroxylase phosphorylation by acute and chronic haloperidol. Eur J Neurosci 20 1108-12... 

Kobori, N., Waymire, J. C., Haycock, J. W., Qifton, G. L., and Dash, P. K. (2004) Enhancement of tyrosine hydroxylase phosphorylation and activity by glial cell line-derived neurotrophic factor. J. Biol Chem. 279, 2182-2191... 

The dopamine is then concentrated in storage vesicles via an ATP-dependent process. Here the rate-limiting step appears not to be precursor uptake, under normal conditions, but tyrosine hydroxylase activity. This is regulated by protein phosphorylation and by de novo enzyme synthesis. The enzyme requites oxygen, ferrous iron, and tetrahydrobiopterin (BH. The enzymatic conversion of the precursor to the active agent and its subsequent storage in a vesicle are energy-dependent processes. 

Table 8.2 The effects of phosphorylation of tyrosine hydroxylase on enz3nne kinetics (based on Kaufman 1995)...

Starke, K (1987) Presynaptic a-autoreceptors. Rev. Physiol. Biochem. Pharmacol. 107 73-146. Zhong, H and Minneman, KP (1999) i-Adrenoceptor subtypes Eur. J. Pharmacol. 375 261-276. Zigmond, RE, Schwarzschild, MA and Rittenhouse, AR (1989) Acute regulation of tyrosine hydroxylase by nerve activity and by neurotransmitters via phosphorylation. Ann. Rev. Neurosci. 12 451-461. 

Ramsey A., Fitzpatrick P. (1998). Effects of phosphorylation of serine 40 of tyrosine hydroxylase on binding of catecholamines evidence for a novel regulatory mechanism. Biochemistry 37, 8980-6. 

Sutherland, C., Alterio, J., Campbell, D. G., Le Bourdelles, B., Mallet, J., Haavik, J., and Cohen, P. (1993). Phosphorylation and activation of human tyrosine hydroxylase in vitro by mitogen-activated protein (MAP) kinase and MAP-kinase-activated kinases 1 and 2. Em.J. Biodiem. 217, 715-722. 

FIGURE 1 2-2 Schematic diagram of the phosphorylation sites on each of the four 60kDa subunits of tyrosine hydroxylase (TOHase). Serine residues at the N-terminus of each of the four subunits of TOHase can be phosphorylated by at least five protein kinases. (J), Calcium/calmodulin-dependent protein kinase II (CaM KII) phosphorylates serine residue 19 and to a lesser extent serine 40. (2), cAMP-dependent protein kinase (PKA) phosphorylates serine residue 40. (3), Calcium/phosphatidylserine-activated protein kinase (PKC) phosphorylates serine 40. (4), Extracellular receptor-activated protein kinase (ERK) phosphorylates serine 31. (5), A cdc-like protein kinase phosphorylates serine 8. Phosphorylation on either serine 19 or 40 increases the activity of TOHase. Serine 19 phosphorylation requires the presence of an activator protein , also known as 14-3-3 protein, for the expression of increased activity. Phosphorylation of serines 8 and 31 has little effect on catalytic activity. The model shown includes the activation of ERK by an ERK kinase. The ERK kinase is activated by phosphorylation by PKC. (With permission from reference [72].)... 

Waymire, J. C. and Craviso, G. L. Multiple site phosphorylation and activation of tyrosine hydroxylase. Adv. Protein Phosphatases 7 501-513,1993. 

TABLE 23-3 Examples of proteins regulated by phosphorylation Enzymes involved in neurotransmitter biosynthesis Tyrosine hydroxylase Tryptophan hydroxylase Neurotransmitter receptors Adrenergic receptors Dopamine receptors Opioid receptors Glutamate receptors Many others... 

FIGURE 23-5 Schematic diagram of tyrosine hydroxylase with sites of phosphorylation indicated (yellow) along with the protein kinases. 

Several key questions remain with regard to the regulation of tyrosine hydroxylase by phosphorylation. What is the precise effect of the phosphorylation of each of these serine residues on the catalytic activity of the enzyme How does the phosphorylation of multiple residues affect enzyme activity Does the phosphorylation of one residue affect the ability of the others to be phosphorylated Tyrosine hydroxylase provides a striking example as to how multiple intracellular messengers and protein kinases converge functionally through the phosphorylation of a single substrate protein. Phosphorylation of tyrosine hydroxylase by cAMP-dependent and Ca2+-dependent protein kinases and by MAPK cascades... 

Pigeon, D. Ferrara, P. Gros, E Thibault, J. Rat pheochromocytoma tyrosine hydroxylase is phosphorylated on serine 40 by an associated protein kinase. J. Biol. Chem., 262, 6155-6158 (1987)... 

The hereditary absence of phenylalanine hydroxylase, which is found principally in the liver, is the cause of the biochemical defect phenylketonuria (Chapter 25, Section B).430 4308 Especially important in the metabolism of the brain are tyrosine hydroxylase, which converts tyrosine to 3,4-dihydroxyphenylalanine, the rate-limiting step in biosynthesis of the catecholamines (Chapter 25), and tryptophan hydroxylase, which catalyzes formation of 5-hydroxytryptophan, the first step in synthesis of the neurotransmitter 5-hydroxytryptamine (Chapter 25). All three of the pterin-dependent hydroxylases are under complex regulatory control.431 432 For example, tyrosine hydroxylase is acted on by at least four kinases with phosphorylation occurring at several sites.431 433 4338 The kinases are responsive to nerve growth factor and epidermal growth factor,434 cAMP,435 Ca2+ + calmodulin, and Ca2+ + phospholipid (protein kinase C).436 The hydroxylase is inhibited by its endproducts, the catecholamines,435 and its activity is also affected by the availability of tetrahydrobiopterin.436... 

Daubner SC, Lauriano C, Haycock JW, Fitzpatrick PF (1992) Site-directed mutagenesis of serine 40 of rat tyrosine hydroxylase. Effects of dopamine and cAMP-dependent phosphorylation on enzyme activity. J Biol Chem 267 12639 16... 

PAH, a nonheme iron-containing enzyme, is a member of a larger BI Independent amino acid hydroxylase family. In addition to PAH, the enzyme family includes tyrosine hydroxylase and tryptophan hydroxylase. The enzymes in this family participate in critical metabolic steps and are tissue specific. PAH catabolizes excess dietary PA and synthesizes tyrosine. In adrenal and nervous tissue, tyrosine hydroxylase catalyzes the initial steps in the synthesis of dihydrox-yphenylalanine. In the brain, tryptophan is converted to 5-hydroxytryptophan as the first step of serotonin synthesis. Consequently, these enzymes are highly regulated not only by their expression in different tissues but also by reversible phosphorylation of a critical serine residue found in regulatory domains of the three enzymes. Since all three enzymes are phosphorylated and dephosphorylated by different kinases and phosphatases in response to the need for the different synthetic products, it is not unexpected that the exact regulatory signal for each member of the enzyme family is unique. 

Lindgren N, Xu ZQ, Herrera-Marschitz M, Haycock J, Hokfelt T, Fisone G (2001) Dopamine D(2) receptors regulate tyrosine hydroxylase activity and phosphorylation at Ser40 in rat striatum. Eur J Neurosci 73 773-780. 

There are numerous data that peroxynitrite is involved in cell death and tissue injuries in many clinical conditions. An important mechanism underlying peroxynitrite toxicity is the reaction of tyrosine nitration. Tyrosine nitration inactivates certain enzymes, as was postulated for prostacyclin (PGI2) synthase (M14), cytochrome P450 2B1 (RIO), tyrosine hydroxylase (A 14), and MnSOD (Yl). Moreover, nitration blocks tyrosine phosphorylation, and thus interferes with the tyrosine kinase signaling pathways (K18). The peroxynitrite treatment of rat liver epithelial cells stimulates mitogen-activated protein kinases p38 MAPK, JNK1/2, and ERK1/2 the mechanism of this effect awaits elucidation (S9). 

Norepinephrine (NE), a catecholamine, was first identified as a neurotransmitter in 1946. In the peripheral nervous system, it is found as a neuro transmitter in the sympathetic postganglionic synapse. NE is synthesized by the enzyme dopamine-p-hydroxylase (DbH) from the precursor dopamine (which is derived from tyrosine via DOPA). The rate-limiting step is the production of DOPA by tyrosine hydroxylase, which can be activated through phosphorylation. NE is removed from the synapse by two mechanisms (1) catechol-O-methyl-transferase (COMT), which degrades intrasynaptic NE, and (2) the norepinephrine transporter (NET), the primary way of removing NE from the synapse. Once internalized, NE can be degraded by the intracellular enzyme monoamine oxidase (MAO). 

Cytosolic Ca can modulate the activity of serine/threonine CaMKs via calmodulin. For instance, neuronal CaMK stimulates phosphorylation and activates tyrosine hydroxylase, the limiting enzyme in the synthesis of catecholamine neurotransmitters. Ca also regulates the activation of the conventional PKC isoforms. Increased Ca " promotes binding of Ca " to... 

L-Dopa is normally a trace intermediary metabolite in the biosynthesis of catecholamines, formed from L-tyrosine in a rate-limiting hydroxylation step by tyrosine hydroxylase, a phosphorylation-activated cytoplasmic mono-oxygenase. L-Dopa is readily decar-boxy ated by the cytoplasmic enzyme L-aro-matic amino acid decarboxylase ("dopa decarboxylase ) to form DA (2). The effects observed after systemic administration of l-... 

Zigmond RE, Schwarzschild MA, Rittenhouse AR. Acute regulation of tyrosine hydroxylase by nerve activity and by neurotransmitters via phosphorylation. Annu Rev Neurosci 1989 12 415-61. 

Tyrosine hydroxylase is a substrate for protein kinases (see following section on second messengers), and once phosphorylated, the enzyme is less sensitive to end-product inhibition and thereby appears to have a greater affinity for hydroxylase cofactor. One study suggests that under physiologic... 

Cyclic AMP can affect the synthesis of catecholamines by two separate modes of action on the rate-limiting catecholamine-synthesizing enzyme tyrosine hydroxylase. Cyclic AMP-dependent kinase can phosphorylate tyrosine hydroxylase, which in turn results in activation of the enzyme. Furthermore, in peripheral tissues such as the adrenal medulla, cAMP can result in the de novo synthesis of tyrosine hydroxylase by causing a derepression of gene expression due to the translocation of the catalytic subunit of the kinase to the chromaffin cell nucleus. 

As with cAMP-stimulated protein kinase, the specific cellular responses to protein kinase C activation depend on the ensemble of target proteins that become phosphorylated in a given cell. Known target proteins include calmodulin, the insulin receptor, the adrenergic receptor (see here), the glucose transporter, HMG-CoA reductase, cytochrome P450, and tyrosine hydroxylase. 

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