Stimulation of p70S6 kinase via a growth hormone-controlled phosphatidylinositol 3-kinase pathway leads to the activation of a PDE4A cyclic AMP-specific phosphodiesterase in 3T3-F442A preadipocytes

Stimulation of p70S6 kinase via a growth hormone-controlled phosphatidylinositol 3-kinase pathway leads to the activation of a PDE4A cyclic AMP-specific phosphodiesterase in 3T3-F442A preadipocytes

^*Division of Biochemistry, Davidson and Wolfson Buildings, University of Glasgow, Glasgow G12 8QQ, Scotland, United Kingdom; ^†Huntsman Cancer Institute, University of Utah Health Science Center, Salt Lake City, UT 84148; ^§Celgene Corporation, 7 Powder Horn Drive, Warren, NJ 07059; and ^‡The Hannah Research Institute, Ayr KA6 5HL, Scotland, United Kingdom

Communicated by Joseph A. Beavo, University of Washington School of Medicine, Seattle, WA (received for review December 11, 1997)

Abstract

The challenge of 3T3-F442A fibroblasts with growth hormone led to both a decrease in the mobility on SDS/PAGE and activation of the PDE4A cyclic AMP-specific phosphodiesterase isoform PDE4A5. Activation was mediated by a JAK-2-dependent pathway coupled to the activation of phosphatidylinositol 3-kinase and p70S6 kinase. Activation was not dependent on the ability of growth hormone to stimulate ERK2 or protein kinase C or any effect on transcription. Blockade of activation of murine PDE4A5 ablated the ability of growth hormone to decrease intracellular cAMP levels. Antisense depletion of murine PDE4A5 mimicked the ability of rolipram to enhance the growth hormone-stimulated differentiation of 3T3-F442A cells to adipocytes. It is suggested that activation of PDE4A5 by growth hormone serves as a brake on the differentiation processes.

Footnotes

↵ ¶ To whom reprint requests should be addressed at the University of Glasgow. e-mail: gbca29{at}udcf.gla.ac.uk.
Data deposition: The sequences reported in this paper have been deposited in the GenBank database (accession nos. AF038895 and AF038896).
ABBREVIATIONS:

GH,

growth hormone;

PI,

phosphatidylinositol;

MAPK,

mitogen-activated protein kinase;

DOTAP,

N-[1-(2,3-dioleoyloxy)propyl]-N,N,N-trimethylammonium methylsulfate;

GPDH,

glycerol-3-phosphate dehydrogenase;

PDE,

cyclic nucleotide phosphodiesterase;

PDE4,

rolipram-inhibited cyclic AMP-specific family 4 phosphodiesterase of which there are four gene families (4A, 4B, 4C, and 4D);

RT-PCR,

reverse transcription–PCR;

PKC,

protein kinase C