PDF(Pubmed)
Abstract：
Solution structures and biochemical data have provided a wealth of mechanistic insight into Ras GTPases. However, information on how much the membrane organization of these lipid-modified proteins impacts on their signaling is still scarce. Ras proteins are organized into membrane nanoclusters, which are necessary for Ras-MAPK signaling. Using quantitative conventional and super-resolution fluorescence methods, as well as mathematical modeling, we investigated nanoclustering of H-ras helix α4 and hypervariable region mutants that have different bona fide conformations on the membrane. By following the emergence of conformer-specific nanoclusters in the plasma membrane of mammalian cells, we found that conformers impart distinct nanoclustering responses depending on the cytoplasmic levels of the nanocluster scaffold galectin-1. Computational modeling revealed that complexes containing H-ras conformers and galectin-1 affect both the number and lifetime of nanoclusters and thus determine the specific Raf effector recruitment. Our results show that mutations in Ras can affect its nanoclustering response and thus allosterically effector recruitment and downstream signaling. We postulate that cancer- and developmental disease-linked mutations that are associated with the Ras membrane conformation may exhibit so far unrecognized Ras nanoclustering and therefore signaling alterations.
摘要：
溶液结构和生化数据为RasGTP酶提供了丰富的机械见解。然而,关于这些脂质修饰蛋白的膜组织对其信号传导有多大影响的信息仍然很少。ras蛋白被组织成膜纳米簇，这是必要的Ras-MAPK信号。使用定量常规和超分辨率荧光法，以及数学建模，我们研究了在膜上具有不同真实构象的H-ras螺旋α4和高变区突变体的纳米聚类。随着哺乳动物细胞质膜中构象异构体特异性纳米簇的出现，我们发现构象赋予不同的纳米簇反应取决于纳米簇支架半乳糖凝集素-1的细胞质水平。计算模型表明，含有H-ras构象异构体和半乳糖凝集素-1的复合物会影响纳米簇的数量和寿命，从而确定特定的Raf效应子募集。我们的结果表明，Ras中的突变可以影响其纳米聚类反应，从而影响变构效应子募集和下游信号传导。我们推测，与Ras膜构象相关的癌症和发育疾病相关的突变可能表现出迄今为止尚未识别的Ras纳米聚类，因此信号改变。
