PT  - JOURNAL ARTICLE
AU  - Li Quan Yang
AU  - Anja Seifert
AU  - Dai Fei Wu
AU  - Xiaoquan Wang
AU  - Vladan Rankovic
AU  - Helmut Schroeder
AU  - Lars Ove Brandenburg
AU  - Volker Hoellt
AU  - Thomas Koch
TI  - Role of phospholipase D2/phosphatidic acid signal transduction in μ- and δ-opioid receptor endocytosis
AID  - 10.1124/mol.109.063107
DP  - 2010 Mar 30
TA  - Molecular Pharmacology
PG  - mol.109.063107
4099  - http://molpharm.aspetjournals.org/content/early/2010/03/30/mol.109.063107.short
4100  - http://molpharm.aspetjournals.org/content/early/2010/03/30/mol.109.063107.full
AB  - We recently demonstrated that opioid-induced activation of Phospholipase D2 (PLD2) enhances μ- and δ-opioid receptor (MOPr and DOPr) endocytosis/recycling and thus reduces the development of opioid receptor desensitization and tolerance. However, the mechanistic basis for the PLD2-mediated induction of opioid receptor endocytosis is currently unknown. Here we show that PLD2-generated phosphatidic acid (PA) might play a key role in facilitating the endocytosis of opioid receptors. However, PLD2-derived PA is known to be further converted to diacylglycerol (DAG) by PA phosphohydrolase (PPAP2). In fact, blocking of PA phosphohydrolase activity by propranolol or PPAP2-siRNA transfection, both significantly attenuated agonist-induced opioid receptor endocytosis. The primary importance of PA-derived DAG in the induction of opioid receptor endocytosis was further supported by the finding that increasing the DAG level by inhibiting the reconversion of DAG into PA with the DAG kinase inhibitor R59949 or the addition of the synthetic cell-permeable DAG analog DOG, further increased the agonist-induced opioid receptor endocytosis. Moreover, addition of DOG bypasses the PLD2-siRNA- or PPAP2-siRNA-mediated impairment of DAG synthesis and resulted in a restoration of agonist-induced opioid receptor internalization. Further studies established a functional link between PA-derived DAG and the activation of p38 MAPK and the subsequent phosphorylation of the Rab5 effector EEA1, which has been recently demonstrated to be required for the induction of MOPr endocytosis. Taken together, our results revealed that the regulation of opioid receptor endocytosis by PLD2 involves the conversion of its product PA to DAG resulting in an activation of the p38 MAPK pathway.The American Society for Pharmacology and Experimental Therapeutics