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Identification and regulation of novel PPAR-gamma splice variants in human THP-1 macrophages
Ye Chen1, Anna R Jimenez, Jheem D Medh
1Department of Chemistry and Biochemistry, Sc3112B, California State University at Northridge, 18111 Nordhoff Street, Northridge, CA 91330, USA.
Abstract:
We have previously identified four novel isoforms of PPAR-gamma transcripts in monkey macrophages (J. Zhou, K.M. Wilson, J.D. Medh, Genetic analysis of four novel peroxisome proliferator receptor-gamma splice variants in monkey macrophages. Biochem. Biophys. Res. Commun., 293 (2002) 274-283). The purpose of this study was to ascertain that these isoforms are also present in humans. Specific primers were designed to amplify individual isoform transcripts. The presence of PPAR-gamma4, PPAR-gamma5, and PPAR-gamma7 transcripts in human THP-1 macrophages was confirmed by RT-PCR and sequencing. A transcript corresponding to PPAR-gamma6 was not detected. The presence of novel full-length transcripts and protein was also ascertained by Northern and Western blot analysis. Treatment of THP-1 cells with 15-deoxy-Delta12,14-prostaglandin J2 (15d-PGJ2) resulted in more than 20% induction in the expression of PPAR-gamma5 and PPAR-gamma7 transcripts by both Northern blot analysis and RT-PCR. Another PPAR-gamma ligand, troglitazone, induced expression of only PPAR-gamma5. Both ligands inhibited the expression of PPAR-gamma1 and PPAR-gamma2. Additionally, 15d-PGJ2 and troglitazone increased the level of apolipoprotein E transcript by 60% but decreased lipoprotein lipase expression by 15% in THP-1 cells. The differential regulation of PPAR-gamma transcripts suggests that each transcript isoform may contribute to macrophage function.
Insights
Researchers confirmed novel peroxisome proliferator-activated receptor-gamma (PPAR-gamma) isoforms in human macrophages. These PPAR-gamma variants show differential responses to ligands, suggesting distinct roles in macrophage function.
Area of Science:
- Molecular Biology
- Cell Biology
- Genetics
Background:
- Previous research identified four novel peroxisome proliferator-activated receptor-gamma (PPAR-gamma) transcript isoforms in monkey macrophages.
- The biological significance and presence of these isoforms in human cells remained to be determined.
Purpose of the Study:
- To investigate the presence and expression of novel PPAR-gamma transcript isoforms in human macrophages.
- To determine the differential regulation of these isoforms by PPAR-gamma ligands.
Main Methods:
- Reverse transcription-polymerase chain reaction (RT-PCR) and sequencing were used to detect specific PPAR-gamma isoforms.
- Northern and Western blot analyses confirmed the presence of full-length transcripts and proteins.
- Human THP-1 macrophages were treated with 15-deoxy-Delta12,14-prostaglandin J2 (15d-PGJ2) and troglitazone.
Main Results:
- PPAR-gamma4, PPAR-gamma5, and PPAR-gamma7 transcripts were detected in human THP-1 macrophages; PPAR-gamma6 was not found.
- Ligand treatment showed differential effects: 15d-PGJ2 induced PPAR-gamma5 and PPAR-gamma7, while troglitazone induced only PPAR-gamma5.
- Both ligands inhibited PPAR-gamma1 and PPAR-gamma2 expression and altered apolipoprotein E and lipoprotein lipase expression.
Conclusions:
- Novel PPAR-gamma transcript isoforms are present in human macrophages.
- The differential regulation of these isoforms by ligands suggests distinct functional roles in macrophage biology.
- Further research into these isoforms could elucidate specific contributions to macrophage function.
