A type 2A protein phosphatase dephosphorylates the elongation factor 2 and is stimulated by the phorbol ester TPA in mouse epidermis in vivo.
Mouse epidermal cytosol contains a protein phosphatase with Mr 38,000, which dephosphorylates the elongation factor 2 (EF-2) of protein biosynthesis and is stimulated after topical application of TPA to mouse skin [(1988) Biochem. Biophys. Res. Commun. 153, 1129-1135]. Dephosphorylation of EF-2 by this phosphatase is inhibited by okadaic acid at concentrations as low as 10(-8) M, but not by heparin up to concentrations of 600.micrograms/ml. The catalytic subunit of protein phosphatase 2A (PP2Ac) with EF-2 as a substrate exhibits the same sensitivity towards okadaic acid and insensitivity towards heparin as the EF-2 phosphatase of epidermal cytosol. The catalytic subunit of protein phosphatase 1 (PP1c) is strongly suppressed by heparin and less sensitive towards okadaic acid than PP2Ac. PP2Ac is around 50 times more efficient in dephosphorylating EF-2 than PP1c. These data indicate that the TPA-stimulated EF-2 phosphatase in epidermal cytosol is a type 2A protein phosphatase.
Gschwendt
M
M
German Cancer Research Center, Institute of Biochemistry, Heidelberg.
Kittstein
W
W
Mieskes
G
G
Marks
F
F
D000818:Animals; D003600:Cytosol / Q000201:enzymology; D004789:Enzyme Activation / Q000187:drug effects; D004817:Epidermis / Q000378:metabolism*; D004988:Ethers, Cyclic / Q000494:pharmacology; D006493:Heparin / Q000494:pharmacology; D051379:Mice; D008970:Molecular Weight; D019319:Okadaic Acid; D020652:Peptide Elongation Factor 2; D010445:Peptide Elongation Factors / Q000378:metabolism*; D010749:Phosphoprotein Phosphatases / Q000378:metabolism*; D054645:Protein Phosphatase 1; D054648:Protein Phosphatase 2; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*
D004988:Ethers, Cyclic; D020652:Peptide Elongation Factor 2; D010445:Peptide Elongation Factors; D019319:Okadaic Acid; D006493:Heparin; D010749:Phosphoprotein Phosphatases; D054645:Protein Phosphatase 1; D054648:Protein Phosphatase 2; D013755:Tetradecanoylphorbol Acetate