Phosphatidylinositol-3,4,5-Trisphosphate Is Required for Insulin-Like Growth Factor 1-Mediated Survival of 3T3-L1 Preadipocytes**This work was supported by a grant (to A.S.) from the Medical Research Council of Canada.

Abstract

Adipocyte number, a determinant of adipose tissue mass, reflects the balance between the rates of proliferation/differentiation vs. apoptosis of preadipocytes. The percentage of 3T3-L1 preadipocytes undergoing cell death following serum deprivation was reduced by 10 nM insulin-like growth factor (IGF)-1 (from 50.0 +/- 0.7% for control starved cells to 27.5 +/- 3.1%). TUNEL staining confirmed the apoptotic nature of the cell death. The protective effect of IGF-1 was blocked by phosphoinositide 3-kinase (PI3K) inhibitors, wortmannin, and LY294002, but was unaffected by rapamycin, PD98059, or SB203580, which inhibit mammalian target of rapamycin (mTOR), ERK kinase (MEK1), and p38 MAPK respectively. Exogenous PI(3,4,5)P3 (10 microM), the principal product of IGF-1-stimulated PI3K in 3T3-L1 preadipocytes, had a modest survival effect on its own, reducing cell death from 47.9 +/- 3.4% to 35.6 +/- 3.5%. When added to the combination of IGF-1 and LY294002, PI(3,4,5)P3 reversed most of the inhibitory effect of LY294002 on IGF-1-dependent cell survival, protein kinase B/Akt phosphorylation, and caspase-3 activity. Taken together, these results implicate PI(3,4,5)P3 as a necessary signal for the anti-apoptotic action of IGF-1 on 3T3-L1 preadipocytes.

Glucocorticoid Receptor Mutants Demonstrate Increased Motility Inside the Nucleus of Living Cells: Time of Fluorescence Recovery After Photobleaching (FRAP) Is an Integrated Measure of Receptor Function

“…Adipocyte number may be modulated by apoptosis of preadipocytes and adipocytes (22)(23)(24)(25), which is controlled by the PTEN-PI3K signaling pathway. AEBP1 promotes PTEN degradation, and AEBP1-null mice display reduced adipose tissue mass with enhanced apoptosis and suppressed survival signal (submitted).…”

Targeted Phosphoinositides Analysis Using High-Performance Ion Chromatography-Coupled Selected Reaction Monitoring Mass Spectrometry

“…The amounts of PtdIns3P + PtdIns5P, PtdIns4P, PtdIns­(3,4)­P 2 , PtdIns­(4,5)­P 2 , and PtdIns­(3,4,5)­P 3 are 11.1 ± 4.6, 160 ± 4, 21.8 ± 8.0, 630 ± 53, and 18.0 ± 5.4 pmol/mg protein, respectively. The higher variety and the detection of PtdIns­(3,4,5)­P 3 can be explained by the existence of insulin-like growth factor 1 (IGF1) in FBS in culture media, which stimulated the IGF1 receptor on pre-adipocyte surface and led to production of PtdIns­(3,4,5)­P 3 and derived species. , Previous studies have also reported the production of PtdIns­(3,4,5)­P 3 in other pre-adipocyte cell lines such as 3T3-L1 upon IGF1 stimulation, which induced pre-adipocytes growth and survival. , PtdIns3P, PtdIns5P, and PtdIns­(3,4)­P 2 were also detected in this study, as the dephosphorylation product of PtdIns­(3,4,5)­P 3 …”

Analysis of Transcriptome and miRNAome in the Muscle of Bamei Pigs at Different Developmental Stages

“…Skeletal myogenic cells respond to the IGF1 by differentiating or proliferating [55]. IGF1R gene as a receptor of IGF1 is much important for skeletal myogenic cells and is essential during prenatal [56]. The let-7a is the most abundant miRNA in porcine muscle development, which has been widely reported [43,44,57,58].…”