Phospholipase D2-Dependent Inhibition of the Nuclear Hormone Receptor PPARγ by Cyclic Phosphatidic Acid

Abstract

Summary Cyclic phosphatidic acid (1-acyl-2,3-cyclic-glycerophosphate, CPA), one of nature’s simplest phospholipids, is found in cells from slime mold to humans and has largely unknown function. We find here that CPA is generated in mammalian cells in a stimulus coupled-manner by Phospholipase D2 (PLD2), and binds to and inhibits the nuclear hormone receptor PPARγ with nanomolar affinity and high specificity through stabilizing its interaction with the corepressor SMRT. CPA production inhibits the PPARγ target-gene transcription that normally drives adipocytic differentiation of 3T3-L1 cells, lipid accumulation in RAW264.7 cells and primary mouse macrophages, and arterial wall remodeling in a rat model in vivo. Inhibition of PLD2 by shRNA, a dominant negative mutant, or a small molecule inhibitor blocks CPA production and relieves PPARγ inhibition. We conclude that CPA is a second messenger and a physiological inhibitor of PPARγ, revealing that PPARγ is regulated by endogenous agonists as well as by antagonists.

Cyclic phosphatidic acid inhibits the secretion of vascular endothelial growth factor from diabetic human coronary artery endothelial cells through peroxisome proliferator-activated receptor gamma

“…Brief exposure to AGP has been reported to induce progressive neointima formation [10] and, recently, LPA and its analog were shown to stimulate a new type of signaling by directly activating PPARγ [15]. A previous report suggested that neointima formation elicited by unsaturated LPA is not mediated by the LPA receptors (GPCRs) expressed in blood-vessel walls [13]; however, topical application of unsaturated LPA species into the non-injured carotid artery of rodents induced arterial-wall remodeling [13], and this response required PPARγ. LPA and AGP have also been reported to be agonists of PPARγ and have been implicated in atherogenesis [10].…”

“…Binding studies using the PPARγ ligand-binding domain showed that binding study of the AGP was similar to that of the TZD rosiglitazone [16]. We recently identified cyclic phosphatidic acid (cPA) is an endogenous PPARγ antagonist, and it is generated by phospholipase D2 (PLD2) [13]. These observations suggest that activation of PPARγ is likely to lead to a complex cellular response.…”

“…We previously reported that unsaturated LPA species induced arterial-wall remodeling in rat and mouse non-injury model, and this response required peroxisome proliferator-activated receptor gamma (PPARγ) [13]. The function of PPARγ has been studied extensively, and a variety of synthetic and physiological agonists of this receptor have been identified [14], including thiazolidinediones (TZDs) and numerous natural ligands containing fatty acids and phospholipids [14].…”

“…The migration of endothelial cells contributes to diverse aspects of vascular physiology such as the development of atherosclerosis. Currently, cPA plays a role in the anti-neointima activity of carotid arteries [13]; and, thus, it is important to understand the mechanisms that determine cPA sensitivity.…”

Cyclic phosphatidic acid influences the expression and regulation of cyclic nucleotide phosphodiesterase 3B and lipolysis in 3T3-L1 cells

“…T0070907 was identified as a potent and selective PPAR antagonist and it also inhibited lipid accumulation in 3T3-L1 cells [17]. We have been reported that cPA is a specific and high-affinity antagonist of PPARγ [18] [19] [20]. cPA is a naturally occurring analog of LPA in which the sn-2 hydroxy group forms a 5-membered ring with the sn-3 phosphate [21] [22,23].…”