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 PPARgamma.
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/iPLA2zeta/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-alpha and insulin in 3T3-L1 adipocytes and identify ATGL as a target for transcriptional activation by the key adipogenic transcription factor PPARgamma. 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-alpha treatment decreased ATGL transcript in a time-dependent manner that paralleled TNF-alpha downregulation of PPARgamma with a maximal decrease noted by 6 h. TNF-alpha 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 PPARgamma. Our findings identify the novel lipase ATGL to be a target gene for TNF-alpha and insulin action in adipocytes and reveal that it is subject to transcriptional control by PPARgamma-mediated signals.
Kim
Ji Young
JY
Dept. of Biochemistry and Cancer Biology, Medical University of Ohio, Toledo, OH 43614, USA. csmas@meduohio.edu
Tillison
Kristin
K
Lee
Jun-Ho
JH
Rearick
David A
DA
Smas
Cynthia M
CM
D041721:3T3-L1 Cells; D017667:Adipocytes / Q000201:enzymology / Q000502:physiology; D000273:Adipose Tissue / Q000201:enzymology* / Q000502:physiology; D000818:Animals; D015152:Blotting, Northern; D015536:Down-Regulation / Q000187:drug effects / Q000502:physiology; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects / Q000502:physiology; D007328:Insulin / Q000494:pharmacology*; D008049:Lipase / Q000235:genetics / Q000378:metabolism*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008814:Mice, Inbred NZB; D008820:Mice, Obese; D008856:Microscopy, Fluorescence; D020411:Oligonucleotide Array Sequence Analysis; D047495:PPAR gamma / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D015533:Transcriptional Activation / Q000187:drug effects / Q000502:physiology; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*
D007328:Insulin; D047495:PPAR gamma; D012333:RNA, Messenger; D014409:Tumor Necrosis Factor-alpha; D008049:Lipase