IndraLab
Statements
rlimsp
"Insulin-stimulated activation of eNOS is independent of Ca2+ but requires phosphorylation by Akt at Ser(1179). Vasodilator actions of insulin are mediated by activation of endothelial nitric-oxide synthase (eNOS) and subsequent production of NO. Phosphatidylinositol 3-kinase and Akt play important roles in insulin-signaling pathways leading to production of NO in vascular endothelium. Here we dissected mechanisms whereby insulin activates eNOS by using the fluorescent dye DAF-2 to directly measure NO production in single cells. Insulin caused a rapid increase in intracellular NO in NIH-3T3(IR) cells transiently transfected with eNOS. The stimulation of NO production by lysophosphatidic acid (LPA) was abrogated by pretreatment of cells with the calcium chelator 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid. Remarkably, in the same cells, insulin-stimulated production of NO was unaffected. However, cells expressing the eNOS-S1179A mutant (disrupted Akt phosphorylation site) did not produce detectable NO in response to insulin, whereas the response to LPA was similar to that observed in cells expressing wild-type eNOS. Moreover, production of NO in response to insulin was blocked by coexpression of an inhibitory mutant of Akt, whereas the response to LPA was unaffected. Phosphorylation of eNOS at Ser(1179) was observed only in response to treatment with insulin, but not with LPA."
rlimsp
"The serine/ threonine protein kinase Akt has been shown to increase human eNOS activity by Akt phosphorylation at Ser1179 and then lead to increase NO production, whereas mutant eNOS (Ser 1179A and Ser 1177) is resistant to phosphorylation and Akt-dependent activation [37, 38]. Reduced phosphorylation of eNOS at Ser1179 has previously been reported in diabetic rats [39]."
rlimsp
"Akt can directly phosphorylate eNOS on serine 1179 (based on the bovine eNOS sequence and equivalent to human eNOS-serine 1177) and activate the enzyme, leading to NO production. [38] Studies have shown that a crosstalk between RhoA–ROCK and Akt regulates eNOS phosphorylation independent of the RhoA/ROCK actions on the downregulation of eNOS expression."