Xu L, Shen Y, Joseph T, Bryant A, Luo J Q, Frankel P, Rotunda T, Foster D A
Department of Biological Sciences, Hunter College of the City University of New York, 695 Park Avenue, New York, New York, 10021 USA.
Biochem Biophys Res Commun. 2000 Jun 24;273(1):77-83. doi: 10.1006/bbrc.2000.2907.
Phospholipase D (PLD) activity is elevated in response to the oncogenic stimulus of several signaling oncogenes. PLD activity is also elevated in response to peptide growth factors, indicating that PLD likely plays an important role in mitogenic signaling. Many proteins that mediate mitogenic signaling are localized in caveolin-enriched membrane microdomains (CEMMs). We report here that the elevated PLD activity in NIH 3T3 cells transformed by activated oncogenic forms of Src, Ras, and Raf is largely restricted to the CEMMs. Likewise, the PLD activity stimulated by epidermal growth factor is also restricted to the CEMMs. Although both PLD1 and PLD2 were found in CEMMs, neither was particularly enriched in the CEMMs of the transformed relative to the parental cells, indicating that it is the specific activity of PLD that is increased in the CEMMs. An apparent PLD substrate specificity in transformed cells for phosphatidylcholine lacking arachidonate acyl groups is also explained by the localization of activity in the CEMMs where [(3)H]arachidonate-labeled PC was excluded. These data indicate that mitogenic signals through PLD are initiated in CEMMs where many signaling molecules colocalize.
磷脂酶D（PLD）的活性会因多种信号癌基因的致癌刺激而升高。PLD的活性也会因肽生长因子而升高，这表明PLD可能在有丝分裂信号传导中发挥重要作用。许多介导有丝分裂信号传导的蛋白质定位于富含小窝蛋白的膜微区（CEMM）。我们在此报告，由激活的致癌形式的Src、Ras和Raf转化的NIH 3T3细胞中升高的PLD活性主要局限于CEMM。同样，表皮生长因子刺激的PLD活性也局限于CEMM。尽管在CEMM中发现了PLD1和PLD2，但相对于亲代细胞，在转化细胞的CEMM中两者均未特别富集，这表明在CEMM中增加的是PLD的比活性。转化细胞中对缺乏花生四烯酸酰基的磷脂酰胆碱具有明显的PLD底物特异性，这也可以通过活性定位于排除了[(3)H]花生四烯酸标记的PC的CEMM来解释。这些数据表明，通过PLD的有丝分裂信号在许多信号分子共定位的CEMM中启动。
