Nox4 mediates angiotensin II-induced activation of Akt/protein kinase B in mesangial cells.
ANG II induces protein synthesis through the serine-threonine kinase Akt/protein kinase B (PKB) in mesangial cells (MCs). The mechanism(s) of activation of Akt/PKB particularly by G protein-coupled receptors, however, is not well characterized. We explored the role of the small GTPase Rac1, a component of the phagocyte NADPH oxidase, and the gp91phox homologue Nox4/Renox in this signaling pathway. ANG II causes rapid activation of Rac1, an effect abrogated by phospholipase A2 inhibition and mimicked by arachidonic acid (AA). Northern blot analysis revealed high levels of Nox4 transcript in MCs and transfection with antisense (AS) oligonucleotides for Nox4 markedly decreased NADPH-dependent reactive oxygen species (ROS)-producing activity. Dominant negative Rac1 (N17Rac1) as well as AS Nox4 inhibited ROS generation in response to ANG II and AA, whereas constitutively active Rac1 stimulated ROS formation. Moreover, N17Rac1 blocked stimulation of NADPH oxidase activity by AA. N17Rac1 or AS Nox4 abolished ANG II- or AA-induced activation of the hypertrophic kinase Akt/PKB. In addition, AS Nox4 inhibited ANG II-induced protein synthesis. These data provide the first evidence that activation by AA of a Rac1-regulated, Nox4-based NAD(P)H oxidase and subsequent generation of ROS mediate the effect of ANG II on Akt/PKB activation and protein synthesis in MCs.
Gorin
Yves
Y
Department of Medicine, The University of Texas Health Science Center, San Antonio, TX 78229-3900, USA.
Ricono
Jill M
JM
Kim
Nam-Ho
NH
Bhandari
Basant
B
Choudhury
Goutam Ghosh
GG
Abboud
Hanna E
HE
D000804:Angiotensin II / Q000494:pharmacology*; D000818:Animals; D016718:Arachidonic Acid / Q000096:biosynthesis; D002478:Cells, Cultured; D004789:Enzyme Activation / Q000187:drug effects; D005920:Glomerular Mesangium / Q000166:cytology / Q000187:drug effects / Q000201:enzymology*; D000074663:NADPH Oxidase 4; D019255:NADPH Oxidases / Q000378:metabolism*; D010084:Oxidation-Reduction; D010741:Phospholipases A / Q000378:metabolism; D054467:Phospholipases A2; D014176:Protein Biosynthesis; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt; D051381:Rats; D017382:Reactive Oxygen Species / Q000378:metabolism; D014662:Vasoconstrictor Agents / Q000494:pharmacology*; D020830:rac1 GTP-Binding Protein / Q000378:metabolism
D011518:Proto-Oncogene Proteins; D017382:Reactive Oxygen Species; D014662:Vasoconstrictor Agents; D000804:Angiotensin II; D016718:Arachidonic Acid; D000074663:NADPH Oxidase 4; D019255:NADPH Oxidases; C498911:Nox4 protein, rat; C494920:Akt1 protein, rat; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D010741:Phospholipases A; D054467:Phospholipases A2; D020830:rac1 GTP-Binding Protein