LONG-TERM GOAL: to characterize the events/mechanisms of the adipocyte differentiation program and verify these events in physiological context. The immediate goal is to understand """"""""mitotic clonal expansion"""""""" (MCE), which is required for adipogenesis. The well-characterized 3T3-L1 preadipocyte --) adipocyte differentiation system will serve as primary model. Wild-type and mutant/knockout mouse embryo fibroblasts (MEFs) and a preadipocyte """"""""in vivo implantation"""""""" system will test ex vivo results in physiological context.
SPECIFIC AIMS : to determine the: 1) roles of C/EBPbeta/delta and Calpain: C/EBPbeta/delta lack DNA binding activity early in the program. After a long lag this function is acquired concomitant with phosphorylation and release from inhibitory constraint. As the cells synchronously enter S-phase of MCE. Once C/EBPbeta/delta acquire DNA binding activity, they transcriptionally activate the C/EBPalpha and PPARgamma genes which transcriptionally activate genes that produce the adipocyte phenotype. Relevant phosphorylation sites on C/EBPbeta/delta will be identified, the responsible kinase(s) and interaction partners identified and effects on C/EBPbeta/delta function determined. MCE will be characterized along with converging events at the G1-S checkpoint that are responsible for progression of MCE and differentiation. Among these is the activation of Calpain which we showed plays a crucial role in initiating p27/KIP1 turnover, an essential event in the activation of Cdk2-cyclinA/entry of S-phase. The mechanism(s) by which calpain activation is triggered and its possible role in the transcriptionally activating the Cdk2 gene, a unique feature of adipogenic MCE, will be explored, and 2) roles of CUP/AP-2alpha and Spl: Previous studies identified repressive regulatory elements for, i.e. CUP/AP-2(_and Spl, in the C/EBP( gene promoter. Down-regulation of these repressors occurs concomitant with the onset of MCE just prior to the transcriptional activation of the C/EBPalpha gene. The mechanisms by which these repressors are down-regulated and the effects of forced expression and """"""""knockdown"""""""" on MCE/differentiation and/or de-differentiation will be determined. The 32kDa CUP/AP-2alpha- interacting protein, p32, previously identified in our lab, will be characterized and its role determined.
|Huang, Haiyan; Song, Tan-Jing; Li, Xi et al. (2009) BMP signaling pathway is required for commitment of C3H10T1/2 pluripotent stem cells to the adipocyte lineage. Proc Natl Acad Sci U S A 106:12670-5|
|Li, Xi; Kim, Jae Woo; Gronborg, Mads et al. (2007) Role of cdk2 in the sequential phosphorylation/activation of C/EBPbeta during adipocyte differentiation. Proc Natl Acad Sci U S A 104:11597-602|
|Kim, Jae-woo; Monila, Henrik; Pandey, Akhilesh et al. (2007) Upstream stimulatory factors regulate the C/EBP alpha gene during differentiation of 3T3-L1 preadipocytes. Biochem Biophys Res Commun 354:517-21|
|Wolfgang, Michael J; Cha, Seung Hun; Sidhaye, Aniket et al. (2007) Regulation of hypothalamic malonyl-CoA by central glucose and leptin. Proc Natl Acad Sci U S A 104:19285-90|
|Kim, Jae-Woo; Tang, Qi-Qun; Li, Xi et al. (2007) Effect of phosphorylation and S-S bond-induced dimerization on DNA binding and transcriptional activation by C/EBPbeta. Proc Natl Acad Sci U S A 104:1800-4|
|Huang, Haiyan; Lane, M Daniel; Tang, Qi-Qun (2005) Effect of serum on the down-regulation of CHOP-10 during differentiation of 3T3-L1 preadipocytes. Biochem Biophys Res Commun 338:1185-8|
|Tang, Qi-Qun; Gronborg, Mads; Huang, Haiyan et al. (2005) Sequential phosphorylation of CCAAT enhancer-binding protein beta by MAPK and glycogen synthase kinase 3beta is required for adipogenesis. Proc Natl Acad Sci U S A 102:9766-71|
|Tang, Qi-Qun; Zhang, Jiang-Wen; Daniel Lane, M (2004) Sequential gene promoter interactions of C/EBPbeta, C/EBPalpha, and PPARgamma during adipogenesis. Biochem Biophys Res Commun 319:235-9|
|Zhang, Jiang-Wen; Tang, Qi-Qun; Vinson, Charles et al. (2004) Dominant-negative C/EBP disrupts mitotic clonal expansion and differentiation of 3T3-L1 preadipocytes. Proc Natl Acad Sci U S A 101:43-7|
|Zhang, Jiang-Wen; Klemm, Dwight J; Vinson, Charles et al. (2004) Role of CREB in transcriptional regulation of CCAAT/enhancer-binding protein beta gene during adipogenesis. J Biol Chem 279:4471-8|
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