Akt as a mediator of secretory phospholipase A2 receptor-involved inducible nitric oxide synthase expression.
The induction of inducible NO synthase (iNOS) by group IIA phospholipase A(2) (PLA(2)) involves the stimulation of a novel signaling cascade. In this study, we demonstrate that group IIA PLA(2) up-regulates the expression of iNOS through a novel pathway that includes M-type secretory PLA(2) receptor (sPLA(2)R), phosphatidylinositol 3-kinase (PI3K), and Akt. Group IIA PLA(2) stimulated iNOS expression and promoted nitrite production in a dose- and time-dependent manner in Raw264.7 cells. Upon treating with group IIA PLA(2), Akt is phosphorylated in a PI3K-dependent manner. Pretreatment with LY294002, a PI3K inhibitor, strongly suppressed group IIA PLA(2)-induced iNOS expression and PI3K/Akt activation. The promoter activity of iNOS was stimulated by group IIA PLA(2), and this was suppressed by LY294002. Transfection with Akt cDNA resulted in Akt protein overexpression in Raw264.7 cells and effectively enhanced the group IIA PLA(2)-induced reporter activity of the iNOS promoter. M-type sPLA(2)R was highly expressed in Raw264.7 cells. Overexpression of M-type sPLA(2)R enhanced group IIA PLA(2)-induced promoter activity and iNOS protein expression, and these effects were abolished by LY294002. However, site-directed mutation in residue responsible for PLA(2) catalytic activity markedly reduced their ability to production of nitrites and expression of iNOS. These results suggest that group IIA PLA(2) induces nitrite production by involving of M-type sPLA(2)R, which then mediates signal transduction events that lead to PI3K/Akt activation.
Park
Dae-Won
DW
Department of Biochemistry and Molecular Biology, College of Medicine, Yeungnam University, 317-1 Daemyung-5 Dong, Nam-Gu, Daegu 705-035, Korea.
Kim
Jae-Ryong
JR
Kim
Seong-Yong
SY
Sonn
Jong-Kyung
JK
Bang
Ok-Sun
OS
Kang
Shin-Sung
SS
Kim
Jung-Hye
JH
Baek
Suk-Hwan
SH
D016475:3T3 Cells; D000818:Animals; D002460:Cell Line; D002867:Chromones / Q000494:pharmacology; D004790:Enzyme Induction / Q000502:physiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D054501:Group II Phospholipases A2; D006801:Humans; D051379:Mice; D008807:Mice, Inbred BALB C; D009025:Morpholines / Q000494:pharmacology; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors / Q000096:biosynthesis* / Q000235:genetics; D052247:Nitric Oxide Synthase Type II; D009573:Nitrites / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000502:physiology; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010741:Phospholipases A / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D054467:Phospholipases A2; D011401:Promoter Regions, Genetic / Q000187:drug effects / Q000502:physiology; D047428:Protein Kinase Inhibitors; D011494:Protein Kinases / Q000502:physiology*; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins / Q000502:physiology*; D051057:Proto-Oncogene Proteins c-akt; D011817:Rabbits; D011956:Receptors, Cell Surface / Q000378:metabolism / Q000502:physiology*; D054507:Receptors, Phospholipase A2; D014162:Transfection
D002867:Chromones; D004791:Enzyme Inhibitors; D054501:Group II Phospholipases A2; D009025:Morpholines; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; D009573:Nitrites; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010741:Phospholipases A; D054467:Phospholipases A2; D047428:Protein Kinase Inhibitors; D011494:Protein Kinases; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt; D011956:Receptors, Cell Surface; D054507:Receptors, Phospholipase A2; C516360:PLA2R1 protein, human; C516357:Pla2r1 protein, mouse; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; C496319:NOS2 protein, human; C496317:Nos2 protein, mouse; C494918:AKT1 protein, human