Regulation of cell death-inducing DFFA-like effector A (CideA) expression by SUMO-Specific Protease SENP2 in adipocyte

Abstract

The cell death-inducing DFFA (DNA fragmentation factor )-like effector A (CideA), which is expressed abundantly in brown adipose tissue of mouse, is an important regulatory factor in metabolism of adipocyte and programmed cell death. When sentrin/SUMO-specific protease 2 (SENP2) adenovirus was infected to fully differentiated 3T3-L1 adipocytes, the expression level of CideA was increased. In this study, the mechanism by which CideA expression was increased via SENP2 was investigated. CideA gene promoter has binding sites for several transcription factors, such as Peroxisome proliferator-activated receptor gamma (PPAR, Nuclear respiratory factor 1 (NRF1), and Estrogen-related receptor alpha (ERR. These transcription factors can be co-activated with Peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC1. To elucidate which transcription factor was regulated by SENP2, transient transfection assays were performed. The promoter activity of CideA was not increased when PPAR, NRF1, ERR, PGC1 was transfected alone. However, the CideA promoter activity was increased only when PGC1 and ERR were co-transfected, while co-transfection of PGC1 with PPAR or NRF1 did not changed CideA promoter activity. Furthermore, transfection of SENP2 with PGC1 and ERR additionally increased the CideA promoter activity. Both PGC1 and ERR can be sumoylated and SENP2 efficiently removed SUMO from these proteins. PGC1 was thought to be a major target of SENP2 which elevates the CideA promoter activity. In the promoter assay data, however, there is no difference between PGC1 and PGC1 K183R, which was a mutated form of PGC1 sumoylation site. And small interfering RNA-mediated knockdown of PGC1 decrease RNA level of CideA, but, still induce CideA level by SENP2. To examine the effect of ERR desumoylation on CideA activity, promoter assay with the wild type of PGC1 and ERR or the sumoylation sit mutant form of PGC1 and ERR was performed. The promoter activity of CideA was significantly increased when both of PGC1 and ERR mutant forms were transfected. Also there is no difference between of CideA promoter activity when SENP2 was co-transfected with both of mutant forms. In summary, CideA promoter activity was significantly increased only when PGC1 and ERR were co-transfected and the expression level of CideA was increased by SENP2 in adipocyte. The increase of CideA expression by SENP2 could be through both of PGC1 and ERR desumoylation.