IGF-I stimulates intestinal muscle cell growth by activating distinct PI 3-kinase and MAP kinase pathways

The American Journal of Physiology
J F Kuemmerle, T L Bushman

Abstract

Insulin-like growth factor I (IGF-I), acting via its cognate receptor, plays an autocrine role in the regulation of growth of intestinal muscle cells. In the present study the signaling pathways mediating the growth effects of IGF-I were characterized in cultured human intestinal smooth muscle cells. Growth induced by a maximally effective concentration of IGF-I (100 nM), measured as [3H]thymidine incorporation, was only partially inhibited by LY-294002 [phosphatidylinositol 3-kinase (PI 3-kinase) inhibitor] or PD-98059 [mitogen-activated protein (MAP) kinase kinase (MEK) inhibitor] (86 +/- 7% and 35 +/- 6% inhibition, respectively) alone but was abolished by the two combined (114 +/- 18% inhibition), implying the participation of both pathways. IGF-I elicited time- and concentration-dependent increases in PI 3-kinase activity. This effect was inhibited only by LY-294002 (89 +/- 12%). IGF-I elicited time- and concentration-dependent phosphorylation of p44/p42 MAP kinase and increased MAP kinase activity. These effects were inhibited only by PD-98059 (78 +/- 9% and 98 +/- 7%, respectively). We conclude that in human intestinal muscle cells IGF-I activates distinct PI 3-kinase and MAP kinase signaling pathways, which act in conju...Continue Reading

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Citations

May 9, 2000·American Journal of Physiology. Gastrointestinal and Liver Physiology·J F Kuemmerle
Apr 8, 2004·American Journal of Physiology. Gastrointestinal and Liver Physiology·Xiping XinEllen M Zimmermann
Oct 29, 2000·American Journal of Physiology. Gastrointestinal and Liver Physiology·J F Kuemmerle, B Teng
Nov 1, 2003·American Journal of Physiology. Gastrointestinal and Liver Physiology·John F KuemmerleJennifer G Bowers
Nov 22, 2002·American Journal of Physiology. Gastrointestinal and Liver Physiology·John F Kuemmerle
Oct 1, 2005·American Journal of Physiology. Gastrointestinal and Liver Physiology·John F Kuemmerle
Sep 9, 2008·American Journal of Physiology. Gastrointestinal and Liver Physiology·Ling ChengJose Behar
Apr 30, 2008·JPEN. Journal of Parenteral and Enteral Nutrition·Prue M Pereira-FantiniJulie E Bines
Aug 7, 2004·American Journal of Physiology. Gastrointestinal and Liver Physiology·John F Kuemmerle
Apr 11, 2009·American Journal of Physiology. Gastrointestinal and Liver Physiology·Krystina B HazelgroveJohn F Kuemmerle
Jun 5, 2004·American Journal of Physiology. Gastrointestinal and Liver Physiology·John F KuemmerleJennifer G Bowers
Jul 16, 2010·American Journal of Physiology. Cell Physiology·Roger D P StanzelMichael G Blennerhassett
Sep 8, 2007·American Journal of Physiology. Gastrointestinal and Liver Physiology·J G SimmonsP K Lund

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