THE ROLES OF PROHIBITINS (PHBS) IN 3T3-L1 ADIPOCYTE DIFFERENTIATION

点击翻译按钮获取中文摘要

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. PROJECT SUMMARY (See instructions): In the past 20 years, the number of overweight and obese individuals has increased significantly in the United States. Being overweight or obese increases the risk of the development of many diseases such as hypertension and diabetes. Elucidating the mechanisms of the proliferation, differentiation and apoptosis in preadipocytes will be essential for the development of therapies for obesity. Our current proposal will focus on the following two long-term goals: 1). Characterizing the roles of the upregulated mitochondrial proteins during adipocyte differentiation; 2). Characterizing the transcriptional regulation of the prohibitins (PHBs) genes. Prohibitins (PHB1 and PHB2) are two intracellular molecules that display interdependence and together form a high molecular weight PHB complex. Our preliminary data showed that both of these PHBs were significantly increased during the adipocyte differentiation of 3T3-L1 preadipocytes. Moreover, 3T3-L1 adipocyte differentiation was impaired after the simultaneous knockdown of either PHBs protein by siRNAPHB1 or siRNA-PHB2. These results lead to the hypothesis that both PHBs are critical in 3T3-L1 adipocyte differentiation. Based on the bioinformatics analyses, we found some putative Egr-1 transcription factor binding sites in the mouse and human PHBs promoters. In addition, we observed that Egr-1 expression was induced prior to the increase of PHBs during 3T3-L1 adipocyte differentiation. Furthermore, the expression of PHBs proteins was upregulated in the adipose tissue in Adipose-transgenic Egr-1 mice. These results lead to a second hypothesis that Egr-1 is a critical modulator of PHBs upregulation during 3T3-L1 adipocyte differentiation. Two specific aims in this proposal are: 1). Test the hypothesis that PHBs are critical in 3T3-L1 adipocyte differentiation. "loss-of-PHBs-function" and "gain-of-PHBs-function" studies will be employed in this aim; 2). Test the hypothesis that Egr-1 modulates PHBs upregulation during 3T3-L1 adipocyte differentiation. PHBs expression analyses after "loss-of-function" and "gain-of-function" of Egr-1, and promoter activity analyses for the mouse PHBs genes will be tested in this aim. Prohibitins may be used as effective drug targets against obesity if the results support the hypothesis that prohibitins are critical in fat cell differentiation.