Peroxisome proliferator-activated receptor gamma (PPAR-γ or PPARG), also known as the glitazone reverse insulin resistance receptor, or NR1C3 (nuclear receptor subfamily 1, group C, member 3) is a type II nuclear receptor functioning as a transcription factor that in humans is encoded by the PPARGgene.[5][6][7]
Tissue distribution
PPARG is mainly present in adipose tissue, colon and macrophages. Two isoforms of PPARG are detected in the human and in the mouse: PPAR-γ1 (found in nearly all tissues except muscle) and PPAR-γ2 (mostly found in adipose tissue and the intestine).[8][9]
Gene expression
This gene encodes a member of the peroxisome proliferator-activated receptor (PPAR) subfamily of nuclear receptors. PPARs form heterodimers with retinoid X receptors (RXRs) and these heterodimers regulate transcription of various genes. Three subtypes of PPARs are known: PPAR-alpha, PPAR-delta, and PPAR-gamma. The protein encoded by this gene is PPAR-gamma and is a regulator of adipocyte differentiation. Alternatively spliced transcript variants that encode different isoforms have been described.[10]
The activity of PPARG can be regulated via phosphorylation through the MEK/ERK pathway. This modification decreases transcriptional activity of PPARG and leads to diabetic gene modifications, and results in insulin insensitivity. For example, the phosphorylation of serine 112 will inhibit PPARG function, and enhance adipogenic potential of fibroblasts.[11]
Function
PPARG regulates fatty acid storage and glucose metabolism. The genes activated by PPARG stimulate lipid uptake and adipogenesis by fat cells. PPARG knockout mice are devoid of adipose tissue, establishing PPARG as a master regulator of adipocyte differentiation.[12]
During embryogenesis, PPARG first substantially expresses in interscapular brown fat pad.[23] The depletion of PPARG will result in embryonic lethality at E10.5, due to the vascular anomalies in placenta, with no permeation of fetal blood vessels and dilation and rupture of maternal blood sinuses.[24] The expression PPARG can be detected in placenta as early as E8.5 and through the remainder of gestation, mainly located in the primary trophoblast cell in the human placenta.[23] PPARG is required for epithelial differentiation of trophoblast tissue, which is critical for proper placenta vascularization. PPARG agonists inhibit extravillous cytotrophoblast invasion. PPARG is also required for the accumulation of lipid droplets by the placenta.[11]
Interactions
Peroxisome proliferator-activated receptor gamma has been shown to interact with:
Many insulin sensitizing drugs (namely, the thiazolidinediones) used in the treatment of diabetes activate PPARG as a means to lower serum glucose without increasing pancreatic insulin secretion. Activation of PPARG is more effective for skeletal muscle insulin resistance than for insulin resistance of the liver.[37]
^Elbrecht A, Chen Y, Cullinan CA, Hayes N, Leibowitz MD, Moller DE, Berger J (July 1996). "Molecular cloning, expression and characterization of human peroxisome proliferator activated receptors gamma 1 and gamma 2". Biochemical and Biophysical Research Communications. 224 (2): 431–7. doi:10.1006/bbrc.1996.1044. PMID8702406.
^ abPeluso I, Morabito G, Urban L, Ioannone F, Serafini M (December 2012). "Oxidative stress in atherosclerosis development: the central role of LDL and oxidative burst". Endocrine, Metabolic & Immune Disorders Drug Targets. 12 (4): 351–60. doi:10.2174/187153012803832602. PMID23061409.
^Dreyer C, Keller H, Mahfoudi A, Laudet V, Krey G, Wahli W (1993). "Positive regulation of the peroxisomal beta-oxidation pathway by fatty acids through activation of peroxisome proliferator-activated receptors (PPAR)". Biology of the Cell. 77 (1): 67–76. doi:10.1016/s0248-4900(05)80176-5. PMID8390886. S2CID10746292.
^O'Flaherty JT, Rogers LC, Paumi CM, Hantgan RR, Thomas LR, Clay CE, et al. (October 2005). "5-Oxo-ETE analogs and the proliferation of cancer cells". Biochimica et Biophysica Acta (BBA) - Molecular and Cell Biology of Lipids. 1736 (3): 228–36. doi:10.1016/j.bbalip.2005.08.009. PMID16154383.
^Naruhn S, Meissner W, Adhikary T, Kaddatz K, Klein T, Watzer B, et al. (February 2010). "15-hydroxyeicosatetraenoic acid is a preferential peroxisome proliferator-activated receptor beta/delta agonist". Molecular Pharmacology. 77 (2): 171–84. doi:10.1124/mol.109.060541. PMID19903832. S2CID30996954.
^O'Sullivan SE, Tarling EJ, Bennett AJ, Kendall DA, Randall MD (November 2005). "Novel time-dependent vascular actions of Delta9-tetrahydrocannabinol mediated by peroxisome proliferator-activated receptor gamma". Biochemical and Biophysical Research Communications. 337 (3): 824–31. doi:10.1016/j.bbrc.2005.09.121. PMID16213464.
^Liu J, Li H, Burstein SH, Zurier RB, Chen JD (May 2003). "Activation and binding of peroxisome proliferator-activated receptor gamma by synthetic cannabinoid ajulemic acid". Molecular Pharmacology. 63 (5): 983–92. doi:10.1124/mol.63.5.983. PMID12695526. S2CID22671555.
^Krishnan A, Nair SA, Pillai MR (September 2007). "Biology of PPAR gamma in cancer: a critical review on existing lacunae". Current Molecular Medicine. 7 (6): 532–40. doi:10.2174/156652407781695765. PMID17896990.
^Schaiff WT, Barak Y, Sadovsky Y (April 2006). "The pleiotropic function of PPAR gamma in the placenta". Molecular and Cellular Endocrinology. 249 (1–2): 10–5. doi:10.1016/j.mce.2006.02.009. PMID16574314. S2CID54322301.
^Berger J, Patel HV, Woods J, Hayes NS, Parent SA, Clemas J, et al. (April 2000). "A PPARgamma mutant serves as a dominant negative inhibitor of PPAR signaling and is localized in the nucleus". Molecular and Cellular Endocrinology. 162 (1–2): 57–67. doi:10.1016/S0303-7207(00)00211-2. PMID10854698. S2CID20343538.
1fm6: THE 2.1 ANGSTROM RESOLUTION CRYSTAL STRUCTURE OF THE HETERODIMER OF THE HUMAN RXRALPHA AND PPARGAMMA LIGAND BINDING DOMAINS RESPECTIVELY BOUND WITH 9-CIS RETINOIC ACID AND ROSIGLITAZONE AND CO-ACTIVATOR PEPTIDES.
1fm9: THE 2.1 ANGSTROM RESOLUTION CRYSTAL STRUCTURE OF THE HETERODIMER OF THE HUMAN RXRALPHA AND PPARGAMMA LIGAND BINDING DOMAINS RESPECTIVELY BOUND WITH 9-CIS RETINOIC ACID AND GI262570 AND CO-ACTIVATOR PEPTIDES.
1i7i: CRYSTAL STRUCTURE OF THE LIGAND BINDING DOMAIN OF HUMAN PPAR-GAMMA IN COMPLEX WITH THE AGONIST AZ 242
1k74: The 2.3 Angstrom resolution crystal structure of the heterodimer of the human PPARgamma and RXRalpha ligand binding domains respectively bound with GW409544 and 9-cis retinoic acid and co-activator peptides.
1knu: LIGAND BINDING DOMAIN OF THE HUMAN PEROXISOME PROLIFERATOR ACTIVATED RECEPTOR GAMMA IN COMPLEX WITH A SYNTHETIC AGONIST
1nyx: Ligand binding domain of the human peroxisome proliferator activated receptor gamma in complex with an agonist
1prg: LIGAND BINDING DOMAIN OF THE HUMAN PEROXISOME PROLIFERATOR ACTIVATED RECEPTOR GAMMA
1rdt: Crystal Structure of a new rexinoid bound to the RXRalpha ligand binding doamin in the RXRalpha/PPARgamma heterodimer
1wm0: PPARgamma in complex with a 2-BABA compound
1zeo: Crystal Structure of Human PPAR-gamma Ligand Binding Domain Complexed with an Alpha-Aryloxyphenylacetic Acid Agonist
1zgy: Structural and Biochemical Basis for Selective Repression of the Orphan Nuclear Receptor LRH-1 by SHP
2ath: Crystal structure of the ligand binding domain of human PPAR-gamma im complex with an agonist
2f4b: Crystal structure of the ligand binding domain of human PPAR-gamma in complex with an agonist
2fvj: A novel anti-adipogenic partial agonist of peroxisome proliferator-activated receptor-gamma (PPARG) recruits pparg-coactivator-1 alpha (PGC1A) but potentiates insulin signaling in vitro
2g0g: Structure-based drug design of a novel family of PPAR partial agonists: virtual screening, x-ray crystallography and in vitro/in vivo biological activities
2g0h: Structure-based drug design of a novel family of PPAR partial agonists: virtual screening, x-ray crystallography and in vitro/in vivo biological activities
2gtk: Structure-based Design of Indole Propionic Acids as Novel PPARag CO-Agonists
2hfp: Crystal Structure of PPAR Gamma with N-sulfonyl-2-indole carboxamide ligands
2i4j: Crystal structure of the complex between PPARgamma and the agonist LT160 (ureidofibrate derivative)
2i4p: Crystal structure of the complex between PPARgamma and the partial agonist LT127 (ureidofibrate derivative). Structure obtained from crystals of the apo-form soaked for 30 days.
2i4z: Crystal structure of the complex between PPARgamma and the partial agonist LT127 (ureidofibrate derivative). This structure has been obtained from crystals soaked for 6 hours.
2om9: Ajulemic acid, a synthetic cannabinoid bound to PPAR gamma
2prg: LIGAND-BINDING DOMAIN OF THE HUMAN PEROXISOME PROLIFERATOR ACTIVATED RECEPTOR GAMMA
3prg: LIGAND BINDING DOMAIN OF HUMAN PEROXISOME PROLIFERATOR ACTIVATED RECEPTOR