The adipose tissue triglyceride lipase ATGL/PNPLA2 is downregulated by insulin and TNF-{alpha} in 3T3-L1 adipocytes and is a target for transactivation by PPAR{gamma}

Department of Biochemistry and Cancer Biology, Medical University of Ohio, Toledo, Ohio Submitted 14 July 2005 ; accepted in final form 30 January 2006 The minimal adipose phenotype of hormone-sensitive lipase (HSL)-null mice suggested that other hormonally responsive lipase(s) were present in adipocytes. Recent studies have characterized a new adipose tissue triglyceride lipase, ATGL/PNPLA2/destnutrin/iPLA2 /TTS2.2 (ATGL). We had previously cloned a novel adipose-enriched transcript by differential screening and recently determined its identity with murine ATGL. We report here on the regulation of ATGL by TNF- and insulin in 3T3-L1 adipocytes and identify ATGL as a target for transcriptional activation by the key adipogenic transcription factor PPAR . Insulin at 100 nM resulted in a marked decrease in ATGL transcript that was effectively blocked by inhibitors for PI 3-kinase and p70 ribosomal protein S6 kinase. TNF- treatment decreased ATGL transcript in a time-dependent manner that paralleled TNF- downregulation of PPAR with a maximal decrease noted by 6 h. TNF- effects on ATGL were attenuated by pretreatment with PD-98059, LY-294002, or rapamycin, suggesting involvement of the p44/42 MAP kinase, PI 3-kinase, and p70 ribosomal protein S6 kinase signals. To study transcriptional regulation of ATGL, we cloned 2,979 bp of the murine ATGL 5'-flanking region. Compared with promoterless pGL2-Basic, the –2979/+21 ATGL luciferase construct demonstrated 120- and 40-fold increases in activity in white and brown adipocytes, respectively. Luciferase reporter activities for a series of eight ATGL promoter deletions revealed that the –928/+21, –1738/+21, –1979/+21, and –2979/+21 constructs were transactivated by PPAR . Our findings identify the novel lipase ATGL to be a target gene for TNF- and insulin action in adipocytes and reveal that it is subject to transcriptional control by PPAR -mediated signals. gene regulation; adipogenesis; promoter activity; tumor necrosis factor- ; peroxisome proliferator-activated receptor- ; patatin-like phospholipase domain containing 2 Address for reprint requests and other correspondence: C. M. Smas, Dept. of Biochemistry and Cancer Biology, Medical University of Ohio, Toledo, OH 43614 (e-mail: csmas{at}meduohio.edu )