Wright State University School of Medicine, Department of Biochemistry and Molecular Biology, OH 45435, USA.
Cell Signal. 2013 Jan;25(1):198-205. doi: 10.1016/j.cellsig.2012.08.010. Epub 2012 Aug 31.
We report the novel finding that Phospholipase D2 (PLD2), through its PX and PH domains, binds specifically to Ras and catalyzes the GDP/GTP exchange (i.e., is a GEF), with potency comparable to Ras-GRF-1, a known Ras-GEF. Cells overexpressing PLD2-GEF inactive mutants (F129Y and R172C/L173A) fail to stimulate cell proliferation compared to the wild type-expressing cells. The GEF effect on Ras follows a faster kinetics than other GTPase substrates (such as Rac2 or Rac1) and is a better substrate, too. The GEF action is due to PLD2 (protein) itself, independent of the lipase product PA. PA can still have a fine-tuning regulatory effect on Ras-GTP depending upon its cellular concentration. Rapidly growing human breast cancer cells MDA-MB 231 (but not the slow growing MCF7 counterpart) have high levels of endogenous PLD2-GEF which correlates with high Ras activation. The PLD2-"GEF" activity is even higher than the classical "lipase" activity and is abrogated with GEF single point mutants, particularly F129Y, and concomitantly with a slow rate of cell growth. This can be crucial to cancer biology in that not only Ras mutations explain abnormal growth, but the existence of a new GEF for Ras: a GEF molecule that happens to be a phospholipase.
我们报告了一个新的发现，即磷酸脂酶 D2（PLD2）通过其 PX 和 PH 结构域特异性地与 Ras 结合，并催化 GDP/GTP 交换（即 GEF），其效力可与 Ras-GRF-1 相媲美，后者是一种已知的 Ras-GEF。与表达野生型 PLD2-GEF 的细胞相比，过表达 PLD2-GEF 无活性突变体（F129Y 和 R172C/L173A）的细胞无法刺激细胞增殖。与其他 GTPase 底物（如 Rac2 或 Rac1）相比，PLD2 对 Ras 的 GEF 作用具有更快的动力学，并且也是更好的底物。PLD2 的 GEF 作用独立于脂酶产物 PA，与 PLD2（蛋白）本身有关，而不是与 PA 有关。PA 仍然可以根据其细胞浓度对 Ras-GTP 产生精细的调节作用。快速生长的人乳腺癌细胞 MDA-MB 231（而不是生长缓慢的 MCF7 细胞）具有高水平的内源性 PLD2-GEF，这与高 Ras 激活相关。PLD2-“GEF”活性甚至高于经典的“脂酶”活性，并且可以通过 GEF 单点突变（特别是 F129Y）来阻断，同时细胞生长速度也会变慢。这对于癌症生物学来说可能是至关重要的，因为不仅 Ras 突变可以解释异常生长，而且 Ras 还存在一种新的 GEF：碰巧是一种磷酸脂酶的 GEF 分子。
