Monovalent Cations and Striatal Tyrosine Hydroxylase

Kuczenski, Ronald

doi:10.1111/j.1471-4159.1982.tb12541.x

Cited by 11 publications

(4 citation statements)

References 11 publications

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“…Diffrrentiul qfects of hepurin. In agreement with Kuczenski (1981), we found that heparin (100 pLM) exerted a direct stimulatory effect on TH activity in soluble extracts from nondepolarized control striata ( Table 6). Previous TH activation by K +induced depolarization did not prevent this effect.…”

Section: Characteristics Of Th Extracted From Striatal Slices Incubatsupporting

confidence: 88%

Characteristics of Tyrosine Hydroxylase Activation by K⁺‐Induced Depolarization and/or Forskolin in Rat Striatal Slices

Mestikawy

Gozlan

Głowiński

et al. 1985

Journal of Neurochemistry

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The mechanisms of tyrosine hydroxylase (TH) activation by depolarization or exposure of dopaminergic terminals to cyclic AMP have been compared using rat striatal slices. Tissues were incubated with veratridine or 60 mM K+ (depolarizing conditions), on the one hand, and forskolin or dibutyryl cyclic AMP, on the other. K+-(or veratridine-)induced depolarization triggered an activation of TH (+75%) that persisted in soluble extracts of incubated tissues. This effect disappeared when drugs (EGTA, N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide, Gallopamil) preventing Ca2+- and calmodulin-dependent processes were included in the incubating medium. In contrast, prior in vivo reserpine treatment or in vitro addition of benztropine did not affect the depolarization-induced activation of TH. In vitro studies of soluble TH extracted from depolarized tissues indicated that activation was associated with a marked increase in the enzyme Vmax but with no change in its apparent affinity for the pteridin cofactor 6-methyl-5,6,7,8-tetrahydropterin (6-MPH4) or tyrosine. Furthermore, the activated enzyme from depolarized tissues exhibited the same optimal pH (5.8) as native TH extracted from control striatal slices. In contrast, TH activation resulting from tissue incubation in the presence of forskolin or dibutyryl cyclic AMP was associated with a selective increase in the apparent affinity for 6-MPH4 and a shift in the optimal pH from 5.8 to 7.0-7.2. Clear distinction between the two activating processes was further confirmed by the facts that heparin- and cyclic AMP-dependent phosphorylation stimulated TH activity from K+-exposed (and control) tissues but not that from striatal slices incubated with forskolin (or dibutyryl cyclic AMP). In contrast, the latter enzyme but not that from depolarized tissues could be activated by Ca2+-dependent phosphorylation. These data strongly support the concept that Ca2+- but not cyclic AMP-dependent phosphorylation is responsible for TH activation in depolarized dopaminergic terminals.

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Section: Characteristics Of Th Extracted From Striatal Slices Incubatsupporting

confidence: 88%

Characteristics of Tyrosine Hydroxylase Activation by K⁺‐Induced Depolarization and/or Forskolin in Rat Striatal Slices

Mestikawy

Gozlan

Głowiński

et al. 1985

Journal of Neurochemistry

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“…At high concentrations of 6-MPH4, however, a second kinetic component is manifested. This observation of biphasic double-reciprocal plots has been extensively characterized for adrenal tyrosine hydroxylase (Masserano and Weiner, 1979;1981; and recently described for rat striatal tyrosine hydroxylase (Lazar et al, 1982). The biphasic phenomenon can be explained by postulating a mixed population of enzyme molecules consisting of low-K, and high-K, forms (Masserano and Weiner, 1979).…”

Section: Enzyme Kinetic Analysis Of the Two Mechanisms Of Tyrosine Hysupporting

confidence: 53%

“…Tyrosine hydroxylase is directly controlled by end-product feedback inhibition (Ikeda et al, 1966), and both phospholipids (Lloyd and Kaufman, 1974;Lloyd, 1979) and anions (Kuczenski and Mandell, 1972) activate the enzyme. Both ionic strength and ionic composition, moreover, may also be important factors in determining tyrosine hydroxylase activity (Kuczenski, 1981).…”

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confidence: 99%

Tyrosine Hydroxylase Inactivation Following cAMP‐Dependent Phosphorylation Activation

Vrana

Roskoski

1983

Journal of Neurochemistry

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Tyrosine hydroxylase, the rate-limiting enzyme in catecholamine biosynthesis, is activated following phosphorylation by the cAMP-dependent protein kinase (largely by decreasing the Km of the enzyme for its pterin co-substrate). Following its phosphorylation activation in rat striatal homogenates, we find that tyrosine hydroxylase is inactivated by two distinct processes. Because cAMP is hydrolyzed in crude extracts by a phosphodiesterase, cAMP-dependent protein kinase activity declines following a single addition of cAMP. When tyrosine hydroxylase is activated under these transient phosphorylation conditions, inactivation is accompanied by a reversion of the activated kinetic form (low apparent Km for pterin co-substrate, less than or equal to 0.2 mM) to the kinetic form characteristic of the untreated enzyme (high apparent Km, greater than or equal to 1.0 mM). This inactivation is readily reversed by the subsequent addition of cAMP. When striatal tyrosine hydroxylase is activated under constant phosphorylation conditions (incubated with purified cAMP-dependent protein kinase catalytic subunit), however, it is also inactivated. This second inactivation process is irreversible and is characterized kinetically by a decreasing apparent Vmax with no change in the low apparent Km for pterin co-substrate (0.2 mM). The latter inactivation process is greatly attenuated by gel filtration which resolves a low-molecular-weight inactivating factor(s) from the tyrosine hydroxylase. These results are consistent with a regulatory mechanism for tyrosine hydroxylase involving two processes: in the first case, reversible phosphorylation and dephosphorylation and, in the second case, an irreversible loss of activity of the phosphorylated form of tyrosine hydroxylase.

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“…Αντίθετα, ο Mestikawy και οι συνεργάτες του (Mestikawy et al, 1983 (Kuczenski 1981), η ηπαρίνη Mandell 1972, Kuczenski 1973) και τα φωσφολιπίδια (Lloyd and Kaufman 1974) αυξάνουν την δραστηκότητα της υδροξυλάσης της τυροσίνης.…”

Section: γ To αβέβαιο-υποθαλαμικό Da-εργικό σύστημαunclassified

Βιοχημεια Της Συναψης: In Vitro Μελετη Των Συστηματων Μεταφορας Απελευθερωσης Και Του Μεταβολισμου Των Κατεχολαμινων Σε Κατεχολαμινεργικες Και Μη Περιοχες Τουκνς

Ευθυμιόπουλος¹,

Efthimiopoulos²

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Andrare R and Aghajanian GK,(1985): Opiate and a 2 -adrenoceptor-induced hyperpolarizations of locus coeruleus neurones in brain slices: reversal by cyclic adenosine 3':5'-monophosphate analogues. J. Neuronsci. 5: 2359-2364.Andrews DW, Langan TA and Weiner N, (1983): Evidence for the involvement of a cyclic AMP-independent protein kinase in the activation of soluble tyrosine hydroxylase from rat striatum.

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Monovalent Cations and Striatal Tyrosine Hydroxylase

Cited by 11 publications

References 11 publications

Characteristics of Tyrosine Hydroxylase Activation by K⁺‐Induced Depolarization and/or Forskolin in Rat Striatal Slices

Characteristics of Tyrosine Hydroxylase Activation by K⁺‐Induced Depolarization and/or Forskolin in Rat Striatal Slices

Tyrosine Hydroxylase Inactivation Following cAMP‐Dependent Phosphorylation Activation

Βιοχημεια Της Συναψης: In Vitro Μελετη Των Συστηματων Μεταφορας Απελευθερωσης Και Του Μεταβολισμου Των Κατεχολαμινων Σε Κατεχολαμινεργικες Και Μη Περιοχες Τουκνς

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Monovalent Cations and Striatal Tyrosine Hydroxylase

Cited by 11 publications

References 11 publications

Characteristics of Tyrosine Hydroxylase Activation by K+‐Induced Depolarization and/or Forskolin in Rat Striatal Slices

Characteristics of Tyrosine Hydroxylase Activation by K+‐Induced Depolarization and/or Forskolin in Rat Striatal Slices

Tyrosine Hydroxylase Inactivation Following cAMP‐Dependent Phosphorylation Activation

Βιοχημεια Της Συναψης: In Vitro Μελετη Των Συστηματων Μεταφορας Απελευθερωσης Και Του Μεταβολισμου Των Κατεχολαμινων Σε Κατεχολαμινεργικες Και Μη Περιοχες Τουκνς

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Characteristics of Tyrosine Hydroxylase Activation by K⁺‐Induced Depolarization and/or Forskolin in Rat Striatal Slices

Characteristics of Tyrosine Hydroxylase Activation by K⁺‐Induced Depolarization and/or Forskolin in Rat Striatal Slices