The Ubiquitin-like Protein LC3 Regulates the Rho-GEF Activity of AKAP-Lbc
The Ubiquitin-like Protein LC3 Regulates the Rho-GEF Activity of AKAP-Lbc
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DOI：
10.1074/jbc.m109.054668
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发表时间：
2009-10-09
影响因子：
4.8
通讯作者：
Diviani, Dario
中科院分区：
文献类型：
--
作者：
Baisamy, Laurent;Cavin, Sabrina;Diviani, Dario
AKAP-Lbc 是 A 激酶锚定蛋白 (AKAP) 家族的成员，最近发现该家族与心脏肥大和癌症等病理学的发展有关。我们之前已经证明，在分子水平上，AKAP-Lbc 作为鸟嘌呤核苷酸交换因子 (GEF) 发挥作用，促进 RhoA 的特异性激活。在本研究中，我们确定了类泛素蛋白 LC3 是一种与 AKAP-Lbc 相互作用的新型调节蛋白。诱变研究表明，LC3 通过其 NH2 末端 α 螺旋结构域与位于 AKAP-Lbc NH2 末端调节区内的两个结合位点相互作用。有趣的是，LC3 过表达强烈降低了 AKAP-Lbc 与 RhoA 相互作用的能力，严重损害了锚定蛋白的 Rho-GEF 活性，从而损害了其促进与肌动蛋白应力纤维形成相关的细胞骨架重排的能力。此外，与野生型蛋白相比，无法与 LC3 相互作用的 AKAP-Lbc 突变体表现出更高的基础 Rho-GEF 活性，并且对 LC3 的抑制作用变得难以抵抗。这表明 LC3 结合使 AKAP-Lbc 维持在非活性状态，从而显示出促进下游信号传导的能力降低。总的来说，这些发现为 LC3 在 Rho 信号传导调节和肌动蛋白细胞骨架重组中的先前未表征的作用提供了证据。
AKAP-Lbc is a member of the A-kinase anchoring protein (AKAP) family that has been recently associated with the development of pathologies, such as cardiac hypertrophy and cancer. We have previously demonstrated that, at the molecular level, AKAP-Lbc functions as a guanine nucleotide exchange factor (GEF) that promotes the specific activation of RhoA. In the present study, we identified the ubiquitin-like protein LC3 as a novel regulatory protein interacting with AKAP-Lbc. Mutagenesis studies revealed that LC3, through its NH2-terminal alpha-helical domain, interacts with two binding sites located within the NH2-terminal regulatory region of AKAP-Lbc. Interestingly, LC3 overexpression strongly reduced the ability of AKAP-Lbc to interact with RhoA, profoundly impairing the Rho-GEF activity of the anchoring protein and, as a consequence, its ability to promote cytoskeletal rearrangements associated with the formation of actin stress fibers. Moreover, AKAP-Lbc mutants that fail to interact with LC3 show a higher basal Rho-GEF activity as compared with the wild type protein and become refractory to the inhibitory effect of LC3. This suggests that LC3 binding maintains AKAP-Lbc in an inactive state that displays a reduced ability to promote downstream signaling. Collectively, these findings provide evidence for a previously uncharacterized role of LC3 in the regulation of Rho signaling and in the reorganization of the actin cytoskeleton.