Novel effect of helenalin on Akt signaling and Skp2 expression in 3T3-L1 preadipocytes
Section snippets
Materials and methods
Materials. Dulbecco’s modified Eagle’s medium (DMEM) was purchased from Cellgro by Mediatech. Calf bovine serum, fetal bovine serum (FBS), and trypsin-EDTA were from Invitrogen Corporation. Propidium iodide and RNase A were purchased from Sigma. Helenalin was purchased from Biomol. The following antibodies were used for immunoblotting: phospho-Akt (Ser473), total Akt, phospho-Erk1/2 (Thr202/Tyr204), and total Erk1/2 (Cell Signaling); Skp2, Skp1, and cyclin A (Santa Cruz Biotechnology); and p27
Helenalin inhibits hormonally induced Skp2 accumulation, p27 degradation, and G1/S phase transition
We have previously determined that Skp2 protein periodically accumulates during S/G2 phase progression of 3T3-L1 preadipocyte differentiation. To examine the effect of helenalin on Skp2 accumulation, density-arrested 3T3-L1 preadipocytes were stimulated with MDI in the presence or absence of helenalin (3 μM). Whole cell lysates were collected at 0 h (density arrest) and 20 h post-MDI and immunoblotted as indicated in Fig. 1A. We demonstrate that helenalin completely suppressed hormonally induced
Discussion
Positive energy balance can cause preadipocytes to undergo a transition from quiescence to proliferation during the development of hyperplastic obesity [14], [15]. The cyclin-dependent kinase inhibitors (CKIs), p27 and p21, govern this transition as potent inhibitors of the G1/S phase transition. Recent studies underscore the importance of these CKIs in adipose tissue development as mice defective in p27/p21 gene expression were shown to have a disproportionate increase in adipose tissue mass
Acknowledgments
We are grateful to Howard Green (Harvard Medical School) for the murine 3T3-L1 cell line. This work was supported by grants from the American Heart Association (0265418U) and National Institutes of Health (1R21DK072067-01) to R.F.M.
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2017, Human PathologyCitation Excerpt :Their data revealed that Akt results in the induction of NFκB and that the level of NFκB activation was mediated via the Akt signaling pathway. In previous studies Auld et al [45,46] analyzed the relationship between Akt and Skp2 (S-phase kinase–associated protein). Skp2 mRNA accumulation was found to precede the increase in Skp2 protein and succeed the activation of Akt.
The effect of dehydroleucodine in adipocyte differentiation
2011, European Journal of PharmacologyCitation Excerpt :Also, it has been found that sesquiterpene lactones inhibit the activation of cyclooxygenase and proinflammatory cytokines in macrophages (Hwang et al., 1996). Within the group of sesquiterpene lactones, helenalin, which occurs in the aerial portion of Arnica montana L., was also found to block the hormonally induced Sky2 mRNA and Akt phosphorylation during early stages of adipocyte differentiation (Auld et al., 2006). Inhibitory activities have been principally linked to the α-methylene-γ-lactone function (Heinrich et al., 1998).
Skp2 promotes adipocyte differentiation via a p27<sup>Kip1</sup>-independent mechanism in primary mouse embryonic fibroblasts
2009, Biochemical and Biophysical Research CommunicationsCitation Excerpt :These results indicated that mitotic clonal expansion of 3T3-L1 cells was inhibited by overexpression of p27Kip1, and they suggested that p27Kip1 may regulate adipocyte differentiation by controlling cell proliferation during mitotic clonal expansion in these cells. The Skp2-dependent degradation of p27Kip1 directly regulates cell division during mitotic clonal expansion in 3T3-L1 preadipocytes [22,23]. To determine whether Skp2 is required for adipocyte differentiation, we isolated MEFs from Skp2+/+, Skp2+/− and Skp2−/− littermates at embryonic day 13.5.
Cyclin-dependent kinase inhibitor, p21<sup>WAF1/CIP1</sup>, is involved in adipocyte differentiation and hypertrophy, linking to obesity, and insulin resistance
2008, Journal of Biological ChemistryCitation Excerpt :Further studies are needed to clarify the precise mechanism by which p53/p21 pathway is regulated and involved in obesity and insulin resistance in adipose tissue. Recent reports on another CDK inhibitor, p27, as well as Skp2, the F-box protein that controls ubiquitin-mediated degradation of p27, implicates the Skp2/p27 pathway in determining the cell number of adipocytes and pancreatic β cells (5, 22, 38–40). Mice that lack CDK4 develop insulin-dependent diabetes as a result of a reduction in islet mass, whereas deletion of p27 ameliorates hyperglycemia in diabetic mice by maintaining compensatory islet hyperplasia and hyperinsulinemia, suggesting that these factors are involved in cell cycle regulation and could also play a role in β cell mass and function (38, 41).