Insulin/IGF-I rescues immortalized brown adipocytes from apoptosis down-regulating Bcl-xS expression, in a PI 3-kinase- and map kinase-dependent manner.
Serum deprivation of immortalized brown adipocyte cell line resulted in growth arrest in G0/G1 phases of the cell cycle and apoptosis, as detected either by DNA laddering or by increase in the percentage of hypodiploid cells. Furthermore, apoptosis is concurrent with a dramatic increase in the expression of the proapoptotic protein Bcl-xS, the expression of Bcl-xL remaining almost undetectable. Insulin/insulin-like growth factor (IGF-I) rescued serum-deprived brown adipocytes from apoptosis, decreasing the number of hypodiploid cells and increasing the number of cells undergoing cell cycle progression throughout S and G2/M phases of the cell cycle. Moreover, insulin down-regulated Bcl-xS expression without inducing the expression of Bcl-xL. Both phosphatidylinositol (PI) 3-kinase and mitogen-activated protein kinase (MAPK) pathways are necessary for insulin/IGF-I full survival effect, since the use of specific inhibitors of PI 3-kinase activity (wortmannin or LY294002, at the dose that inhibits PI 3-kinase activity induced by insulin) or MAPK kinase activity inhibitor (PD098059, at the dose that inhibits insulin-induced phosphorylation of MAPK) totally blocked the antiapoptotic effect induced by insulin/IGF-I, respectively. In conclusion, insulin survival effect on immortalized brown adipocytes is associated with inhibition of the Bcl-xS content without changing Bcl-xL, in a PI 3-kinase- and MAP kinase-dependent manner.
Navarro
P
P
Facultad de Farmacia, Universidad Complutense, Madrid, 28040, Spain.
Valverde
A M
AM
Benito
M
M
Lorenzo
M
M
D017667:Adipocytes / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism; D002001:Adipose Tissue, Brown / Q000166:cytology; D017209:Apoptosis; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D002453:Cell Cycle; D002460:Cell Line; D015536:Down-Regulation; D016193:G1 Phase; D007328:Insulin / Q000378:metabolism* / Q000494:pharmacology; D007334:Insulin-Like Growth Factor I / Q000378:metabolism* / Q000494:pharmacology; D048369:MAP Kinase Kinase 1; D020929:Mitogen-Activated Protein Kinase Kinases; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D000081082:Phosphoinositide-3 Kinase Inhibitors; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism*; D016192:Resting Phase, Cell Cycle; D051020:bcl-X Protein
D017871:Calcium-Calmodulin-Dependent Protein Kinases; D007328:Insulin; D007334:Insulin-Like Growth Factor I; D048369:MAP Kinase Kinase 1; D020929:Mitogen-Activated Protein Kinase Kinases; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D017346:Protein Serine-Threonine Kinases; D011505:Protein-Tyrosine Kinases; D019253:Proto-Oncogene Proteins c-bcl-2; D051020:bcl-X Protein