Effects of okadaic acid on insulin-sensitive cAMP phosphodiesterase in rat adipocytes

Evidence that insulin may stimulate the enzyme by phosphorylation

Hiroshi Shibata, Frances W. Robinson, Thomas Soderling, Tetsuro Kono

Research output: Contribution to journalArticle

25 Citations (Scopus)

Abstract

Okadaic acid, a potent inhibitor of Type 1 and Type 2A protein phosphatases, was used to investigate the mechanism of insulin action on membrane-bound low Km cAMP phosphodiesterase in rat adipocytes. Upon incubation of cells with 1 μM okadaic acid for 20 min, phosphodiesterase was stimulated 3.7- to 3.9-fold. This stimulation was larger than that elicited by insulin (2.5- to 3.0-fold). Although okadaic acid enhanced the effect of insulin, the maximum effects of the two agents were not additive. When cells were pretreated with 1-(5-isoquinolinylsulfonyl)-2-methylpiperazine (H-7) (see below), the level of phosphodiesterase stimulation by okadaic acid was rendered smaller, similar to that attained by insulin. In cells that had been treated with 2 mM KCN, okadaic acid (like insulin) failed to stimulate phosphodiesterase, suggesting that ATP was essential. Also, as reported previously, the effect of insulin on phosphodiesterase was reversed upon exposure of hormone-treated cells to KCN. This deactivation of previously-stimulated phosphodiesterase was blocked by okadaic acid, but not by insulin. The above KCN experiments were carried out with cells in which A-kinase activity was minimized by pretreatment with H-7. Okadaic acid mildly stimulated basal glucose transport and, at the same time, strongly inhibited the action of insulin thereon. It is suggested that insulin may stimulate phosphodiesterase by promoting its phosphorylation and that the hormonal effect may be reversed by a protein phosphatase which is sensitive to okadaic acid. The hypothetical protein kinase thought to be involved in the insulin-dependent stimulation of phosphodiesterase appears to be more H-7-resistant than A-kinase.

Original languageEnglish (US)
Pages (from-to)17948-17953
Number of pages6
JournalJournal of Biological Chemistry
Volume266
Issue number27
StatePublished - Sep 25 1991
Externally publishedYes

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Okadaic Acid
Phosphorylation
Phosphoric Diester Hydrolases
Adipocytes
Rats
Insulin
1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine
Enzymes
Phosphotransferases
Cells
Protein Phosphatase 2
Phosphoprotein Phosphatases
Protein Kinases
Adenosine Triphosphate
Hormones
Membranes
Glucose

ASJC Scopus subject areas

  • Biochemistry

Cite this

Effects of okadaic acid on insulin-sensitive cAMP phosphodiesterase in rat adipocytes : Evidence that insulin may stimulate the enzyme by phosphorylation. / Shibata, Hiroshi; Robinson, Frances W.; Soderling, Thomas; Kono, Tetsuro.

In: Journal of Biological Chemistry, Vol. 266, No. 27, 25.09.1991, p. 17948-17953.

Research output: Contribution to journalArticle

Shibata, Hiroshi ; Robinson, Frances W. ; Soderling, Thomas ; Kono, Tetsuro. / Effects of okadaic acid on insulin-sensitive cAMP phosphodiesterase in rat adipocytes : Evidence that insulin may stimulate the enzyme by phosphorylation. In: Journal of Biological Chemistry. 1991 ; Vol. 266, No. 27. pp. 17948-17953.
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abstract = "Okadaic acid, a potent inhibitor of Type 1 and Type 2A protein phosphatases, was used to investigate the mechanism of insulin action on membrane-bound low Km cAMP phosphodiesterase in rat adipocytes. Upon incubation of cells with 1 μM okadaic acid for 20 min, phosphodiesterase was stimulated 3.7- to 3.9-fold. This stimulation was larger than that elicited by insulin (2.5- to 3.0-fold). Although okadaic acid enhanced the effect of insulin, the maximum effects of the two agents were not additive. When cells were pretreated with 1-(5-isoquinolinylsulfonyl)-2-methylpiperazine (H-7) (see below), the level of phosphodiesterase stimulation by okadaic acid was rendered smaller, similar to that attained by insulin. In cells that had been treated with 2 mM KCN, okadaic acid (like insulin) failed to stimulate phosphodiesterase, suggesting that ATP was essential. Also, as reported previously, the effect of insulin on phosphodiesterase was reversed upon exposure of hormone-treated cells to KCN. This deactivation of previously-stimulated phosphodiesterase was blocked by okadaic acid, but not by insulin. The above KCN experiments were carried out with cells in which A-kinase activity was minimized by pretreatment with H-7. Okadaic acid mildly stimulated basal glucose transport and, at the same time, strongly inhibited the action of insulin thereon. It is suggested that insulin may stimulate phosphodiesterase by promoting its phosphorylation and that the hormonal effect may be reversed by a protein phosphatase which is sensitive to okadaic acid. The hypothetical protein kinase thought to be involved in the insulin-dependent stimulation of phosphodiesterase appears to be more H-7-resistant than A-kinase.",
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