Enhancement of arachidonic acid signaling pathway by nicotinic acid receptor HM74A

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• 作者：Yuting Tang ; Lubing Zhou ; Joseph W. Gunnet ; Pamela G. Wines ; Ellen V. Cryan and Keith T. Demarest
• 关键词：G protein-coupled receptor (GPCR) ; Nicotinic acid (niacin) ; HM74A ; Arachidonic acid (AA) ; Extracellular-signal-regulated kinases 1 and 2 (ERK1/2) ; Peroxisome-proliferator activated receptors (PPAR)
• 刊名：Biochemical and Biophysical Research Communications
• 出版年：2006
• 出版时间：23 June 2006
• 年：2006
• 卷：345
• 期：1
• 页码：29-37
• 全文大小：180 K

文摘

HM74A is a G protein-coupled receptor for nicotinic acid (niacin), which has been used clinically to treat dyslipidemia for decades. The molecular mechanisms whereby niacin exerts its pleiotropic effects on lipid metabolism remain largely unknown. In addition, the most common side effect in niacin therapy is skin flushing that is caused by prostaglandin release, suggesting that the phospholipase A₂ (PLA₂)/arachidonic acid (AA) pathway is involved. Various eicosanoids have been shown to activate peroxisome-proliferator activated receptors (PPAR) that play a diverse array of roles in lipid metabolism. To further elucidate the potential roles of HM74A in mediating the therapeutic effects and/or side effects of niacin, we sought to explore the signaling events upon HM74A activation. Here we demonstrated that HM74A synergistically enhanced UTP- and bradykinin-mediated AA release in a pertussis toxin-sensitive manner in A431 cells. Activation of HM74A also led to Ca²⁺-mobilization and enhanced bradykinin-promoted Ca²⁺-mobilization through Gi protein. While HM74A increased ERK1/2 activation by the bradykinin receptor, it had no effects on UTP-promoted ERK1/2 activation.Furthermore, UTP- and bradykinin-mediated AA release was significantly decreased in the presence of both MAPK kinase inhibitor PD 098059 and PKC inhibitor GF 109203X. However, the synergistic effects of HM74A were not dramatically affected by co-treatment with both inhibitors, indicating the cross-talk occurred at the receptor level. Finally, stimulation of A431 cells transiently transfected with PPRE-luciferase with AA significantly induced luciferase activity, mimicking the effects of PPARγ agonist rosiglitazone, suggesting that alteration of AA signaling pathway can regulate gene expression via endogenous PPARs.