Insulin-induced phosphorylation of a 38 kDa DNA-binding protein in ventricular cardiomyocytes: Possible implication of nuclear protein phosphatase activity

Maria Von Holtey, P. Csermely, Jörg Niggemann, Jürgen Eckel

Research output: Contribution to journalArticle

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Abstract

Ventricular cardiomyocytes isolated from adult rat heart were used to analyze the effect of insulin on the phosphorylation of DNA-binding nuclear proteins and to elucidate the potential involvement of protein phosphatase-1 (PP-1) and PP-2A in this hormonal action. Cells were labelled with [33P]orthophosphate, stimulated with insulin (1.7 x 10-7 M) and processed for the isolation of nuclei and extraction of DNA-binding proteins. Insulin was found to induce a rapid and constant increase in the serine/threonine phosphorylation of a 38 kDa DNA-binding protein, reaching 150% of control after 15 min and 180% after 150 min. Immunoprecipitation and Western blotting experiments revealed the presence of phosphorylated numatrin in the nuclear extract, however, insulin did not modify its phosphorylation state. Treatment of cardiomyocytes with okadaic acid (1 μM) resulted in a large increase (246 ± 30%) in the phosphorylation of the 38 kDa protein. Using 32P-labelled phosphorylase as a substrate, we observed a significant inhibition of nuclear PP-1 activity to 38.5 ± 7% (n = 3) of control after incubation of cardiomyocytes with insulin for 15 min. PP-2A, which corresponds to about 25% of total phosphatase activity, was also inhibited to the same extent. These data show the presence of an insulin-responsive 38 kDa DNA-binding phosphoprotein in the nucleus of cardiomyocytes, which is at least partly regulated by nuclear phosphatase activity. It is suggested that inhibition of nuclear PP-1 and PP-2A represents a possible mechanism of insulin signalling to the nucleus of target cells.

Original languageEnglish
Pages (from-to)107-114
Number of pages8
JournalMolecular and Cellular Endocrinology
Volume120
Issue number2
DOIs
Publication statusPublished - Jul 1 1996

Fingerprint

Phosphorylation
Phosphoprotein Phosphatases
DNA-Binding Proteins
Cardiac Myocytes
Insulin
Protein Phosphatase 1
Phosphoric Monoester Hydrolases
Okadaic Acid
Phosphorylases
Phosphoproteins
DNA
Threonine
Nuclear Proteins
Cell Nucleus
Immunoprecipitation
Serine
Rats
Western Blotting
Phosphates
Substrates

Keywords

  • Cardiomyocytes
  • Insulin
  • Nucleus
  • Protein phosphatase

ASJC Scopus subject areas

  • Endocrinology
  • Endocrinology, Diabetes and Metabolism

Cite this

Insulin-induced phosphorylation of a 38 kDa DNA-binding protein in ventricular cardiomyocytes : Possible implication of nuclear protein phosphatase activity. / Von Holtey, Maria; Csermely, P.; Niggemann, Jörg; Eckel, Jürgen.

In: Molecular and Cellular Endocrinology, Vol. 120, No. 2, 01.07.1996, p. 107-114.

Research output: Contribution to journalArticle

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