Activation of aromatic l‐amino acid decarboxylase by calcium/calmodulin kinase II (original) (raw)
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Journal of Neurochemistry, 1988
The concentration requirements of calmodulin in altering basal, GTP-, and dopamine-stimulated adenylate cyclase activities in an EGTA-washed particulate fraction from bovine striatum were examined. In the bovine striatal particulate fraction, calmodulin activated basal adenylate cyclase activity 3.5-fold, with an ECSO of 110 nM. Calmodulin also potentiated the activation of adenylate cyclase by GTP by decreasing the ECso for GTP from 303 k 56 nM to 60 f 10 nM. Calmodulin did not alter the maximal response to GTP. The EC50 for calmodulin in potentiating the GTP response was only 1 1 nM as compared to 1 10 nM for activation of basal activity. Similarly, calmodulin increased the maximal stimulation of adenylate cyclase by dopamine by 50-60%. The EC5o for calmodulin in eliciting this response was 35 nM. These data demonstrate that calmodulin can both activate basal adenylate cyclase and po-tentiate adenylate cyclase activities that involve the activating GTP-binding protein, N,. Mechanisms that involve potentiation of N,-mediated effects are much more sensitive to calmodulin than is the activation of basal adenylate cyclase activity. Potentiation of GTP-stimulated adenylate cyclase activity by calmodulin was apparent at 3 and 5 mM MgClz, but not at 1 or 10 mM MgC12. These data further support a role for calmodulin in hormonal signalling and suggest that calmodulin can regulate cyclic AMP formation by more than one mechanism. Key Words: Basal ganglia-Guanyl nucleotides-Calcium-Dopamine-Adenylate cyclase. Harrison J. K. et al. Differential regulation by calmodulin of basal, GTP-, and dopamine-stimulated adenylate cyclase activities in bovine striatum. J. Neurochem. 51, 345-352 (1988). A limited number of mammalian tissues display an adenylate cyclase activity that is sensitive to an endogenous Ca2+-binding protein, calmodulin (CaM). These include brain, retina, pancreatic islets, adrenal medulla, kidney, and heart (Manalan and Nee, 1984; MacNeil et al., 1985). The response of adenylate cyclase to CaM in nervous tissue, however, is significantly greater than that in other tissues. Much of the evidence to date suggests that CaM stimulates adenylate cyclase activity by binding directly to the catalytic moiety of the enzyme (Salter et al., 198 1 ; Yeager et al., 1985). Although guanyl nucleotides are not required for stimulation of adenylate cyclase by CaM (Heideman et al., 1982; Seamon and Daly, 1982), CaM can affect the activation of guanyl nucleotidemediated activities of adenylate cyclase (Brostrom et
Journal of Neurochemistry, 1989
Tryptophan hydroxylase is activated in a crude extract by addition of ATP and Mg2+. This activation is reversible and requires in addition both Ca2+ and calmodulin. Thus, phosphorylation by an endogenous calmodulin-dependent protein kinase has long been suspected. Now that we have prepared a specific polyclonal antibody to rat brain tryptophan hydroxylase, we have been able to prove that this hypothesis is correct. After incubation of purified tryptophan hydroxylase with Ca*+/calmodulin-dependent protein kinase together with [y-32P]ATP, Mg2+, Ca2+, and calmodulin, followed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and blotting of the enzymes onto nitrocellulose sheets, we could label the band of tryptophan hydroxylase by the antiserum and the peroxidase technique and show by autoradiography that ' ' P was incorporated into this band. By measuring the radioactivity, we calculated that about 1 mol of phosphate was incorporated per 8 mol of subunits of the enzyme (2 mol of native enzyme). Because the concentration of ATP which we employed (50 p M ) gives about halfmaximal activation in crude extract compared to saturating ATP conditions (about 1 m M ) , this result indicates that the incorporation of at least 1 mol of phosphate/mol of tetramer of native tryptophan hydroxylase is required for maximal activation. Key Words: Rat brain tryptophan hydroxylase-Phosphorylation-Activation-Ca2+/calmodulin-dependent protein kinase. Ehret M. et al. Formal demonstration of the phosphorylation of rat brain tryptophan hydroxylase by Ca2+/ calmodulin-dependent protein kinase.
Aromatic L-Amino Acid Decarboxylase Activity of Mouse Striatum Is Modulated via Dopamine Receptors
Journal of Neurochemistry, 1993
Aromatic L-amino acid decarboxylase (AAAD) activity is enhanced in the striatum of control and MPTPtreated mice after administration of a single dose of the dopamine receptor antagonists haloperidol, sulpiride, and SCH 23390. MPTP-treated mice appear more sensitive to the antagonists, i.e., respond earlier and to lower doses of antagonists than control mice. The rise of AAAD activity induced by the antagonists is prevented by pretreatment with cycloheximide. The apparent K , values for ~-3,4-dihydroxyphenylalanine (L-DOPA) and pyridoxal 5-phosphate appear unchanged after treatment with the antagonists. Increased AAAD activity was observed also after subchronic administration of dopamine receptor antagonists or treatment with reserpine. A single dose of a selective dopamine receptor agonists had no effect on AAAD activity. In contrast, administration of L-DOPA, quinpirole, or SKF 23390 for 7 days lowers AAAD activity in the striatum. We conclude that AAAD is modulated in striaturn via dopaminergic receptors.
Proceedings of the National Academy of Sciences, 1987
High-affinity antibodies against calmodulin (CaM)-dependent cyclic nucleotide phosphodiesterase and protein phosphatase (calcineurin) were purified and characterized. Rabbit anti-phosphodiesterase antibody did not react with other phosphodiesterases or with the regulatory subunits of cAMP-dependent protein kinase. Affinity-puriflied goat anti-calcineurin antibody recognized both the 61-kDa catalytic subunit and the 18-kDa Ca2+-binding subunit of the phospha-The publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. §1734 solely to indicate this fact.
Brain Research, 2000
The present study examined whether the O-methylated derivative of L-DOPA, 3-O-methyl-L-DOPA (3-OM-L-DOPA), inhibits neuronal (brain) and non-neuronal (liver and kidney) aromatic L-amino acid decarboxylase (AADC) activity. The incubation of brain, liver and kidney homogenates with 3-OM-L-DOPA (5 mM) did not result in the formation of 3-methoxytyramine, the compound expected to result from the decarboxylation of 3-OM-L-DOPA. Incubation of tissue homogenates with L-DOPA resulted in a concentration-dependent formation of dopamine, revealing K values (in mM) of similar magnitude for brain (0.8), liver (1.6) and kidney (1.0). Both benserazide m and L-5-hydroxytryptophan (L-5-HTP) were found to produce concentration dependent decreases in AADC activity with K values in the i mM range. By contrast, 3-OM-L-DOPA did not reduce the activity of either neuronal AADC (brain) or non-neuronal AADC (liver and kidney). The administration of benserazide in vivo (1, 3 and 10 mg / kg) produced marked reductions in AADC activity in both liver and kidney, but had no effect upon brain AADC. The effect of increasing the dose of benserazide up to 30 mg / kg (p.o.) was an almost complete inhibition (.95% reduction) in liver and kidney AADC activity accompanied by a marked decrease (49% reduction) in brain AADC activity. By contrast, the administration of 30 mg / kg (p.o.) 3-OM-L-DOPA, which generates levels in brain, liver and kidney six-fold those in L-DOPA-treated rats, was found to change neither neuronal nor non-neuronal AADC activity. In conclusion, 3-OM-L-DOPA fails to interact with neuronal and non-neuronal AADC, either as substrate or inhibitor.
Journal of Cellular Biochemistry, 1988
Ca2+, through the mediation of calmodulin, stimulates the activity of brain adenylate cyclase. The growing awareness that fluctuating Ca2+ concentrations play a major role in intracellular signalling prompted the present study, which aimed to investigate the implications for neurotransmitter (receptor) regulation of enzymatic activity of this calmodulin regulation. The role of Ca2+/calmodulin in regulating neurotransmitter-mediated inhibition and stimulation was assessed in a number of rat brain areas. Ca*+/calmodulin stimulated adenylate cyclase activity in EGTA-washed plasma preparations from each region studied-from 1 .%fold (in striatum) to 3.4-fold (in cerebral cortex). The fold-stimulation produced by Ca2+/calmodulin was decreased in the presence of GTP, forskolin, or Mn2'. In EGTA-washed membranes, receptor-mediated inhibition of adenylate cyclase was strictly dependent upon Ca*+/calmodulin stimulation in all regions, except striatum. A requirement for Mg2+ in combination with Ca*+/calmodulin to observe neurotransmitter-mediated inhibition was also observed. In contrast, receptormediated stimulation of activity was much greater in the absence of Ca2+/ calmodulin. The findings demonstrate that ambient Ca*' concentrations, in concert with endogenous calmodulin, may play a central role in dictating whether inhibition or stimulation of adenylate cyclase by neurotransmitters may proceed.
Neuroscience, 2003
Alpha Calcium/calmodulin-dependent protein kinase type II (CaMKII-␣) expression is regulated in an activitydependent manner, but it is not known whether other CaMKII isoforms (, ␦, and ␥) are similarly regulated. We examined the activity-dependent regulation of these CaMKII isoforms in vivo, using a model of generalized seizures caused by i.p. injection of kainic acid. Following seizure induction, CaMKII-␣ expression was downregulated and CaMKII-␦ expression upregulated while CaMKII- and CaMKII-␥ expression was unaffected. A transient downregulation in CaMKII-␣ and a transient increase in CaMKII-␦ occurred throughout neocortex in the same temporal order. Although CaMKII-␣ mRNA was decreased by seizure activity, the less abundant, alternatively spliced, CaMKII-␣33 mRNA was unaffected. Organotypic cortical slice cultures treated with bicuculline and 4-aminopyridine to induce seizure activity also showed a downregulation of CaMKII-␣ mRNA and an upregulation of CaMKII-␦ mRNA. Prior exposure to tetrodotoxin prevented the changes in CaMKII-␣ and CaMKII-␦ mRNA regulation and this was mimicked by D-L-2amino-5-phosphonovaleric acid, but not by 6-cyano-2,3-dihydroxy-7-nitro-quinoxaline, suggesting that CaMKII-␣ and CaMKII-␦ mRNA expression is regulated in an N-methyl-D-aspartate receptor-dependent manner. Regulation was also transcription dependent. Blocking transcription with actinomycin-D prevented activity-dependent changes in CaMKII-␣ and CaMKII-␦ mRNA, but produced opposite effects on basal transcription, resulting in more stabilized CaMKII-␣ mRNA and less stabilized CaMKII-␦ mRNA. These results reveal unique patterns of seizure-induced alterations in CaMKII mRNAs. Activity-dependent changes in subunit composition could, therefore, differentially influence the functional attributes of the CaMKII holoenzyme.
Molecular pharmacology, 2004
A brain dopamine receptor that modulates phosphatidylinositol (PI) metabolism via the activation of phospholipase Cbeta (PLCbeta) has been described previously. The present study aims to define the downstream signaling cascade initiated by the PI-linked dopamine receptor. Incubation of rat brain frontal cortical slices with 6-chloro-7,8-dihydroxy-3-methyl-1-(3-methylphenyl)-2,3,4,5-tetrahydro-1H-3-benzazepine (SKF83959), a recently identified selective agonist of the PI-linked D1-like dopamine receptor, elicited transient time- and dose-dependent stimulations of cyclin-dependent kinase 5 (cdk5) and calcium/calmodulin-dependent protein kinase II (CaMK II) activities. The stimulation of these kinases is blocked by 20 microM R-(+)-7-chloro-8-hydroxy-3-methyl-1-phenyl-2,3,4,5-tetrahydro-1H-3-benzazepine (SCH23390) or the PLCbeta antagonist 1-[6-[[17beta-methoxyestra-1,3,5(10)-trien-17-yl]amino]hexyl]-1H-pyrrole-2,5-dione (U-73122) and is attenuated by the protein kinase inhibitor calpho...
Clozapine Modulates Aromatic l-Amino Acid Decarboxylase Activity in Mouse Striatum
Journal of Pharmacology and Experimental Therapeutics, 2006
Clozapine is efficacious for treating dopaminergic psychosis in Parkinson's disease and ameliorates L-DOPA-induced motor complications. Based on its pharmacology and reported enhancing effects on dopamine metabolism and tyrosine hydroxylase activity, we investigated whether it could modulate the activity of aromatic L-amino acid decarboxylase (AAAD), the second enzyme for the biosynthesis of catecholamines and indoleamines. A single dose of clozapine increased AAAD activity of striatum in a dose-and time-dependent manner. At 1 h, enhanced enzyme activity was characterized by an increased V max for substrate and cofactor and was accompanied by elevated levels of protein in striatum and mRNA in substantia nigra, ventral tegmental area, locus coeruleus, and raphe nuclei. Acute clozapine increased tyrosine hydroxylase activity in striatum but with differing temporal patterns from AAAD and heightened dopamine metabolism. Interestingly, the response