Activation of 3-Phosphoinositide-dependent Kinase 1 (PDK1) and Serum-and Glucocorticoid-induced Protein Kinase 1 (SGK1) by Short-chain Sphingolipid C4-ceramide Rescues the Trafficking Defect of ΔF508-Cystic Fibrosis Transmembrane Conductance Regulator (ΔF508-CFTR)
Activation of 3-Phosphoinositide-dependent Kinase 1 (PDK1) and Serum-and Glucocorticoid-induced Protein Kinase 1 (SGK1) by Short-chain Sphingolipid C4-ceramide Rescues the Trafficking Defect of ΔF508-Cystic Fibrosis Transmembrane Conductance Regulator (ΔF508-CFTR)
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DOI：
10.1074/jbc.m114.598649
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发表时间：
2014-12-26
影响因子：
4.8
通讯作者：
Pollard, Harvey B.
中科院分区：
文献类型：
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作者：
Caohuy, Hung;Yang, Qingfeng;Pollard, Harvey B.
囊性纤维化（CF）是由于CF跨膜传导调节蛋白（CFTR）的折叠缺陷引起的。最常见的突变，Delta F508，阻止CFTR运输到顶端质膜。本研究表明，用c4 -神经酰胺（C4-CER）（一种无毒的小分子）激活PDK1/SGK1信号通路，从功能上纠正了CF患者培养的CF细胞和原代上皮细胞外植体的运输缺陷。C4-CER的作用机制涉及PDK1和SGK1之间一系列相互的自磷酸化和磷酸化事件。详细的机制研究表明，C4-CER最初诱导SGK1 Ser位点的自磷酸化（422）。SGK1[Ser(P)(422)]和C4-CER巧合地结合PDK1并允许PDK1在Ser位点自磷酸化（241）。然后PDK1[Ser(P)(241)]在Thr（256）位点磷酸化SGK1[Ser(P)(422)]，生成完全激活的SGK1[Ser(422), Thr(P)(256)]。SGK1[Ser(P)(422), Thr(P)(256)]磷酸化并使E3泛素连接酶Nedd4-2失活。因此Delta F508-CFTR可以自由地进入质膜。重要的是，c4 - cer介导的PDK1和SGK1的激活独立于雷帕霉素信号通路的PI3K/Akt/哺乳动物靶点。生理上，C4-CER显著提高Delta F508-CFTR的成熟度和稳定性（t1/2类似于10 h），增强camp激活的氯化物分泌，抑制白细胞介素-8 （IL-8）的高分泌。我们建议针对PDK1/SGK1信号通路的CF候选药物，如C4-CER，为平均每天影响一名儿童的限制性生命障碍提供了一种新的治疗策略。
Cystic fibrosis (CF) is due to a folding defect in the CF transmembrane conductance regulator (CFTR) protein. The most common mutation, Delta F508, prevents CFTR from trafficking to the apical plasma membrane. Here we show that activation of the PDK1/SGK1 signaling pathway with C4-ceramide (C4-CER), a non-toxic small molecule, functionally corrects the trafficking defect in both cultured CF cells and primary epithelial cell explants from CF patients. The mechanism of C4-CER action involves a series of mutual autophosphorylation and phosphorylation events between PDK1 and SGK1. Detailed mechanistic studies indicate that C4-CER initially induces autophosphorylation of SGK1 at Ser(422). SGK1[Ser(P)(422)] and C4-CER coincidently bind PDK1 and permit PDK1 to autophosphorylate at Ser(241). Then PDK1[Ser(P)(241)] phosphorylates SGK1[Ser(P)(422)] at Thr(256) to generate fully activated SGK1[Ser(422), Thr(P)(256)]. SGK1[Ser(P)(422), Thr(P)(256)] phosphorylates and inactivates the E3 ubiquitin ligase Nedd4-2. Delta F508-CFTR is thus free to traffic to the plasma membrane. Importantly, C4-CER-mediated activation of both PDK1 and SGK1 is independent of the PI3K/Akt/mammalian target of rapamycin signaling pathway. Physiologically, C4-CER significantly increases maturation and stability of Delta F508-CFTR (t1/2 similar to 10 h), enhances cAMP-activated chloride secretion, and suppresses hypersecretion of interleukin-8 (IL-8). We suggest that candidate drugs for CF directed against the PDK1/SGK1 signaling pathway, such as C4-CER, provide a novel therapeutic strategy for a life-limiting disorder that affects one child, on average, each day.