Galectin-3 augments K-Ras activation and triggers a Ras signal that attenuates ERK but not phosphoinositide 3-kinase activity
Galectin-3 augments K-Ras activation and triggers a Ras signal that attenuates ERK but not phosphoinositide 3-kinase activity
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DOI：
10.1074/jbc.m312697200
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发表时间：
2004-08-13
影响因子：
4.8
通讯作者：
Kloog, Y
中科院分区：
文献类型：
--
作者：
Elad-Sfadia, G;Haklai, R;Kloog, Y
取决于细胞环境，Ras可以激活的机制仍然知之甚少的特征性效应器。半乳糖凝集素-1促进Ras激活Raf-1，而非PI3-K （phosphoinositide 3-kinase, PI3-K）是其中一种机制。在本报告中，我们描述了一种控制K-Ras4B （K-Ras）选择性的机制，K-Ras是最重要的Ras癌蛋白。我们发现半乳糖凝集素-3作为活化的K-Ras的选择性结合伙伴。半乳糖凝集素-3与K-Ras-GTP共免疫沉淀明显优于与K-Ras-GDP、H-Ras或N-Ras共免疫沉淀，并且在细胞膜上与绿色荧光蛋白k - ras （G12V）共定位，而不是与绿色荧光蛋白H-Ras（G12V）共定位。K-Ras/半乳糖凝集素-3共转染，而H-Ras/半乳糖凝集素-3不转染，表现出表皮生长因子刺激下Ras-GTP、Raf-1活性和PI3-K活性的增强和延长。然而，细胞外信号调节激酶（ERK）活性在K-Ras/半乳糖凝集素-3和K-Ras(G12V)/半乳糖凝集素-3共转染中减弱。半乳糖凝集素-3反义RNA抑制表皮生长因子刺激下K-Ras- gtp的增加，但增强ERK的激活和K-Ras（G12V）转化活性。因此，与半乳糖凝集素-1延长Ras对ERK的激活并抑制PI3-K不同，K-Ras-GTP/半乳糖凝集素-3的相互作用除了促进PI3-K和Raf-1的激活外，还促进第三种抑制信号，即减弱活性ERK。这些实验建立了一种新的特异性机制来控制活性K-Ras信号的持续时间和选择性，这在许多人类肿瘤中非常重要。
Depending on the cellular context, Ras can activate characteristic effectors by mechanisms still poorly understood. Promotion by galectin-1 of Ras activation of Raf-1 but not of phosphoinositide 3-kinase (PI3-K) is one such mechanism. In this report, we describe a mechanism controlling selectivity of K-Ras4B (K-Ras), the most important Ras oncoprotein. We show that galectin-3 acts as a selective binding partner of activated K-Ras. Galectin-3 co-immunoprecipitated significantly better with K-Ras-GTP than with K-Ras-GDP, H-Ras, or N-Ras and colocalized with green fluorescent protein-K-Ras(G12V), not with green fluorescent protein-H-Ras(G12V), in the cell membrane. Co-transfectants of K-Ras/galectin-3, but not of H-Ras/galectin-3, exhibited enhanced and prolonged epidermal growth factor-stimulated increases in Ras-GTP, Raf-1 activity, and PI3-K activity. Extracellular signal-regulated kinase (ERK) activity, however, was attenuated in K-Ras/galectin-3 and in K-Ras(G12V)/galectin-3 co-transfectants. Galectin-3 antisense RNA inhibited the epidermal growth factor-stimulated increase in K-Ras-GTP but enhanced ERK activation and augmented K-Ras(G12V) transformation activity. Thus, unlike galectin-1, which prolongs Ras activation of ERK and inhibits PI3-K, K-Ras-GTP/galectin-3 interactions promote, in addition to PI3-K and Raf-1 activation, a third inhibitory signal that attenuates active ERK. These experiments established a novel and specific mechanism controlling the duration and selectivity of signals of active K-Ras, which is extremely important in many human tumors.