DIFFERENTIAL REGULATION OF RASGAP AND NEUROFIBROMATOSIS GENE-PRODUCT ACTIVITIES
DIFFERENTIAL REGULATION OF RASGAP AND NEUROFIBROMATOSIS GENE-PRODUCT ACTIVITIES
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DOI：
10.1038/351576a0
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发表时间：
1991-06-13
期刊：
影响因子：
64.8
通讯作者：
MCCORMICK, F
中科院分区：
文献类型：
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作者：
BOLLAG, G;MCCORMICK, F
ras编码的p21ras蛋白与GTP结合非常紧密，但催化水解成GDP的速度非常慢。在人类中，有两个基因编码刺激这种GTPase活性的蛋白质（GAP，或GTPase激活蛋白）2，一个相对分子质量为120,000，称为p120-GAP，另一个由神经纤维瘤病1型基因3-5编码的NF1-GAP。这两种gap在哺乳动物组织中广泛表达6,7。在这里，我们表明，尽管它们都能结合p21ras的致癌突变体，但都不会刺激它们的GTPase活性。NF1-GAP结合p21ras蛋白的效率是p120-GAP的300倍。某些脂质在不同程度上抑制了这两种gap：花生四烯酸酯、磷脂酸酯和磷脂酰肌醇4,5-二磷酸的微摩尔浓度仅影响NF1-GAP。这种抑制作用不与p21ras竞争，并且脂质失活的NF1-GAP仍然可以结合p21ras。我们使用仅抑制NF1-GAP的洗涤剂十二烷基麦芽糖苷来区分细胞提取物中的两种活性，并发现这两种类型同时存在于几种哺乳动物细胞系中。十二烷基麦芽糖甙对爪蟾卵母细胞提取物中GAP活性无明显影响。根据这些标准，哺乳动物细胞同时具有GAP活性，而卵母细胞仅具有p120样GAP活性。这些结果表明，在同一细胞中，不止一个GAP调控p21ras。
THE ras-encoded p21ras proteins bind GTP very tightly, but catalyse hydrolysis to GDP very slowly 1. In humans, two genes encode proteins that stimulate this GTPase activity (GAP, or GTPase-activating proteins)2, one of relative molecular mass 120,000, referred to as p120-GAP, and another NF1-GAP, which is encoded by the neurofibromatosis type-1 gene 3-5. Both GAPs are widely expressed in mammalian tissues 6,7. Here we show that although they will both bind oncogenic mutants of p21ras, neither will stimulate their GTPase activity. NF1-GAP binds to the p21ras proteins up to 300 times more efficiently than p120-GAP. The two GAPs are inhibited to different extents by certain lipids: micromolar concentrations of arachidonate, phosphatidate and phosphatidylinositol-4,5-bisphosphate affect only NF1-GAP. This inhibition does not compete with p21ras, and lipid-inactivated NF1-GAP can still bind p21ras. We used the detergent dodecyl maltoside, which inhibits only NF1-GAP, to distinguish between the two activities in cell extracts and found both types present together in several mammalian cell lines. In contrast, GAP activity in extracts of Xenopus oocytes was not affected by dodecyl maltoside. By these criteria, the mammalian cells contain both GAP activities and the oocytes have only p120-like GAP activity. These results indicate that more than one GAP regulates p21ras in the same cell.