Protein Phosphatase 2A Is Involved in the Regulation of Protein Kinase A Signaling Pathway during in Vitro Chondrogenesis

doi:10.1006/excr.2002.5487

Experimental Cell Research

Volume 275, Issue 1, 15 April 2002, Pages 1-8

https://doi.org/10.1006/excr.2002.5487 Get rights and content

Abstract

We have evaluated the importance of the Ser/Thr protein phosphorylation and dephosphorylation for chondrogenesis in high-density chicken limb bud mesenchymal cell cultures (HDCs) by using H89, a cell-permeable protein kinase inhibitor, and okadaic acid (OA), a phosphoprotein phosphatase (PP)-specific inhibitor molecule. When 20 nM OA was applied to the HDCs on Days 2 and 3 of culturing, it significantly inhibited protein phosphatase 2A (PP2A), enhanced cartilage formation, and elevated the activity of cAMP-dependent protein kinase (PKA). Application of 20 μM H89 significantly decreased the activity of PKA and blocked the chondrogenesis in HDCs. Furthermore, OA enhanced cartilage formation and elevated the suppressed activity of PKA even in the H89-pretreated HDCs. cGMP-dependent protein kinase was not detected in HDCs, while protein kinase Cμ (PKCμ), which is also inhibited by nanomolar concentrations of H89, was present throughout the culturing period. Neither OA nor H89 influenced the expression of the catalytic subunit of PKA or the cAMP response element binding protein, CREB. However, a significantly elevated amount of Ser-133-phosphorylated-CREB (P-CREB) was detected following addition of OA, while H89 treatment resulted in a decrease of the amount of P-CREB. Our results demonstrate that PP2A plays a role in the regulation of the PKA signaling pathway and that the phosphorylation level of CREB is influenced by the activity of both enzymes during in vitro chondrogenesis.

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Citation Excerpt :
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¹: To whom correspondence and reprint requests should be addressed at the Department of Medical Chemistry, Medical and Health Science Centre, University of Debrecen, Bem tér 18/B, H-4026 Debrecen, Hungary. Fax: +36-52-412566. E-mail: [email protected].

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Regular ArticleProtein Phosphatase 2A Is Involved in the Regulation of Protein Kinase A Signaling Pathway during in Vitro Chondrogenesis

Abstract

Osteoarthritis Cartilage

Cell

Dev. Biol.

J. Biol. Chem.

J. Biol. Chem.

Trends Biochem. Sci.

Trends Biochem. Sci.

J. Biol. Chem.

Trends Biochem. Sci.

Trends Biochem. Sci.

J. Biol Chem.

Dev. Biol.

Meth. Enzymol.

Biochem. Biophys. Res. Commun.

Differentiation

Differentiation

Differentiation

Int. J. Biochem. Cell Biol.

Cell

J. Biol. Chem.

Matrix Biol.

Regular Article
Protein Phosphatase 2A Is Involved in the Regulation of Protein Kinase A Signaling Pathway during in Vitro Chondrogenesis