Kiss Z, Mukherjee J J, Crilly K S, Chung T
Hormel Institute, University of Minnesota, Austin 55912, USA.
Eur J Biochem. 1997 Dec 1;250(2):395-402. doi: 10.1111/j.1432-1033.1997.0395a.x.
NIH 3T3 fibroblasts express a phospholipase D activity hydrolyzing phosphatidylethanolamine (PtdEtn) which produces ethanolamine (Etn) in response to a variety of growth regulating agents. The main objective of this work was to evaluate the effects of Etn on mitogenesis and to determine whether these effects require its metabolism to phosphoethanolamine (PEtn) or PtdEtn. To increase conversion of Etn to PEtn, an Etn-specific kinase derived from Drosophila was highly expressed in NIH 3T3 cells. Overexpression of this Etn kinase resulted in large (10-12.5-fold) increases in PEtn formation, but only in modest (1.2-1.7-fold) increases in PtdEtn synthesis. In both vector control and Etn kinase overexpressor cells, Etn had biphasic effects on insulin-induced DNA synthesis with maximal (approximately 2-fold) potentiating effects being observed at 0.5-1 mM concentrations, followed by an inhibitory phase at higher Etn concentrations. In the Etn kinase overexpressor lines, the inhibitory phase was elicited by lower Etn concentrations and it was partially blocked by 5 mM choline due to decreased formation of PEtn. In both vector control and Etn kinase overexpressor cells, phosphocholine (PCho) and insulin synergistically stimulated DNA synthesis; their effects were further enhanced by physiologically relevant (5-60 microM) concentrations of Etn by a mechanism independent of mitogen-activated protein (MAP) kinase. Concentrations of Etn >50 microM also enhanced the effects of both PCho and the synergistic effects of PCho plus ATP; however, in the latter case 20 microM Etn was inhibitory. The magnitude of both the potentiating and inhibitory effects of Etn on PCho-induced as well as PCho + ATP-induced DNA synthesis were similar in the vector control and Etn kinase overexpressor cells; they were associated with stimulation and inhibition, respectively, of p42 MAP kinase activity. The results indicate that in NIH 3T3 cells Etn exerts significant effects on DNA synthesis which, except inhibition of insulin-induced DNA synthesis by higher concentrations of Etn, do not correlate with the metabolism of Etn to PEtn or PtdEtn.
NIH 3T3成纤维细胞表达一种磷脂酶D活性，可水解磷脂酰乙醇胺（PtdEtn），在多种生长调节因子的作用下产生乙醇胺（Etn）。这项工作的主要目的是评估Etn对有丝分裂的影响，并确定这些影响是否需要其代谢为磷酸乙醇胺（PEtn）或PtdEtn。为了增加Etn向PEtn的转化，一种源自果蝇的Etn特异性激酶在NIH 3T3细胞中高表达。这种Etn激酶的过表达导致PEtn形成大幅增加（10 - 12.5倍），但PtdEtn合成仅适度增加（1.2 - 1.7倍）。在载体对照和Etn激酶过表达细胞中，Etn对胰岛素诱导的DNA合成具有双相作用，在0.5 - 1 mM浓度下观察到最大（约2倍）的增强作用，随后在更高的Etn浓度下进入抑制阶段。在Etn激酶过表达细胞系中，较低的Etn浓度引发抑制阶段，并且由于PEtn形成减少，该阶段被5 mM胆碱部分阻断。在载体对照和Etn激酶过表达细胞中，磷酸胆碱（PCho）和胰岛素协同刺激DNA合成；它们的作用通过生理相关浓度（5 - 60 microM）的Etn通过一种独立于丝裂原活化蛋白（MAP）激酶的机制进一步增强。Etn浓度>50 microM也增强了PCho的作用以及PCho加ATP的协同作用；然而，在后一种情况下，20 microM Etn具有抑制作用。Etn对PCho诱导以及PCho + ATP诱导的DNA合成的增强和抑制作用的幅度在载体对照和Etn激酶过表达细胞中相似；它们分别与p42 MAP激酶活性的刺激和抑制相关。结果表明，在NIH 3T3细胞中，Etn对DNA合成有显著影响，除了高浓度Etn抑制胰岛素诱导的DNA合成外，这些影响与Etn代谢为PEtn或PtdEtn无关。
