Light Chain 3 associates with a Sos1 guanine nucleotide exchange factor: its significance in the Sos1-mediated Rac1 signaling leading to membrane ruffling
Light Chain 3 associates with a Sos1 guanine nucleotide exchange factor: its significance in the Sos1-mediated Rac1 signaling leading to membrane ruffling
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DOI：
10.1038/sj.onc.1205790
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发表时间：
2002-10-10
期刊：
影响因子：
8
通讯作者：
Kamata, T
中科院分区：
文献类型：
--
作者：
Furuta, S;Miura, K;Kamata, T
通过GST-Sos-DH亲和层析从大鼠脑中纯化出一个与Sos1的Dbl癌基因同源结构域（Sos-DH）相关的19 kDa蛋白。肽测序显示该蛋白与轻链3 （LC3）相同，LC3是微管相关蛋白。在体外GST-pull - down实验中，LC3与Sos1共免疫沉淀，GST-LC3能够与Sos1形成复合物。此外，通过免疫组织化学测定，LC3在细胞中与Sos1共定位。在体外COS细胞裂解物实验中，Sos1刺激了Rac1上的鸟嘌呤核苷酸交换反应，而LC3抑制了Sos1激活Rac1的能力。与此一致的是，LC3的过表达降低了COS细胞中活性gtp结合的Rac1的水平。Sos1表达可诱导膜褶皱，这是Rac1的下游靶点，但LC3表达可抑制Sos1的这种生物学效应。这些发现表明LC3与Sos1相互作用，从而负调控Sos1依赖性的Rac1激活，导致膜褶皱。
A 19 kDa protein was identified to associate with the Dbl oncogene homology domain of Sos1 (Sos-DH) and was purified from rat brains by GST-Sos-DH affinity chromatography. Peptide sequencing revealed that the protein is identical to light chain 3 (LC3), a microtubule-associated protein. LC3 coimmunoprecipitated with Sos1, and GST-LC3 was capable of forming complexes with Sos1 in in vitro GST-pull down assay. Furthermore, LC3 was colocalized with Sos1 in cells, as determined by immunohistochemistry. While Sos1 stimulated the guanine nucleotide exchange reaction on Rac1, LC3 suppressed the ability of Sos1 to activate Rac1 in in vitro experiments using COS cell lysates. Consistent with this, overexpression of LC3 decreased the level of active GTP-bound Rac1 in COS cells. Sos1 expression induced membrane ruffling, a downstream target for Rac1, but LC3 expression inhibited this biological effect of Sos1. These findings suggest that LC3 interacts with Sos1 and thereby negatively regulates the Sos1-dependent Rac1 activation leading to membrane ruffling.