P3: REGULATION OF PPARGAMMA IN ADIPOCYTES BY THE UBIQUITIN-PROTEASOME SYSTEM

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This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. A. Specific Aims In March 2009, the external reviewers indicated that our project "has the potential to reveal new mechanistic insights" into the regulation of PPARgamma and that our initial screen of ubiquitin E3 ligases has identified "E3 ligases that appear to influence steady state levels of PPARgamma within cells". The reviewers also advised that "successfully competing for an R01 in this area is likely to require narrowing the focus to one or two enzymes that play functional roles in PPARgamma action". A primary concern continued to be linking PPARgamma ubiquitylation and degradation to PPARgamma transcriptional function or a down-stream metabolic alteration. Recommendations for achieving these goals centered on continuing our experiments with the E3 ligases by focusing on one or two ligases, determining whether the effect of the E3 ligase on PPARgamma protein levels is direct or indirect and considering the effect of the selected E3 ligase on adipogenesis. In addition, the reviewers recommended we focus on ubiquitin proteasome modification of PPARgamma as a regulated posttranslational modification of PPARgamma. In response to the reviewers' suggestions, we pursued the following aims: Specific Aim 1: Complete the secondary screen to identify ubiquitin E3 ligases that regulate PPARgamma protein levels in mature adipocytes. Specific Aim 2: Examine the effect of the selected ligase or ligases on ligand-enhanced ubiquitylation and proteasome-dependent degradation of PPARgamma. Specific Aim 3: Determine the effect of the identified ligase or ligases on adipogenesis.