IGF-I inhibits apoptosis through the activation of the phosphatidylinositol 3-kinase/Akt pathway in pituitary cells.
In previous studies we demonstrated that IGF-I induces proliferation of pituitary lactotrophs. In addition to its mitotrophic actions, IGF-I is known to prevent apoptosis induced by diverse stimuli in several cell types. In this study, we investigated the action of IGF-I on pituitary cell survival and the intracellular signaling transduction pathway implicated in this effect. Treatment of cultured male rat pituitary cells with IGF-I (10(-7) M) for 24 h prevented pituitary cell death induced by serum deprivation. The protective effect of IGF-I was blocked by phosphoinositide 3-kinase (PI3-kinase) inhibitor, LY294002, but was unaffected by PD98059, which inhibits MAP/ERK kinase (MEK1). IGF-I activation of PI3-kinase induced the phosphorylation and activation of the serine/threonine kinase Akt. Moreover, IGF-I increased the phosphorylation of the pro-apoptotic factor Bad and the levels of the anti-apoptotic protein Bcl-2 through the PI3-kinase pathway in primary pituitary cells.
Fernández
M
M
Servicio de Endocrinología, Hospital Ramón y Cajal, Carretera de Colmenar, Km 9, 28034 Madrid, Spain.
Sánchez-Franco
F
F
Palacios
N
N
Sánchez
I
I
Fernández
C
C
Cacicedo
L
L
D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D002478:Cells, Cultured; D004789:Enzyme Activation; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D010903:Pituitary Gland, Anterior / Q000166:cytology* / Q000201:enzymology; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt; D051381:Rats; D011994:Recombinant Proteins / Q000494:pharmacology
D007334:Insulin-Like Growth Factor I; D019869:Phosphatidylinositol 3-Kinases; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt; D011994:Recombinant Proteins; C494920:Akt1 protein, rat