Inhibition of Akt Signaling by Exclusion from Lipid Rafts in Normal and Transformed Epidermal Keratinocytes
Inhibition of Akt Signaling by Exclusion from Lipid Rafts in Normal and Transformed Epidermal Keratinocytes
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DOI：
10.1038/jid.2009.415
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发表时间：
2010-04-01
影响因子：
6.5
通讯作者：
Gniadecki, Robert
中科院分区：
文献类型：
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作者：
Calay, Damien;Vind-Kezunovic, Dina;Gniadecki, Robert
脂筏是富含胆固醇的质膜结构域，调节信号转导。由于我们早期的工作表明，筏破坏抑制增殖，并导致细胞死亡，我们在这里调查的膜胆固醇，关键筏成分，在调节磷脂酰肌醇-3激酶（PI 3 K）/Akt途径的作用。在正常人角质形成细胞和癌前（HaCaT）或转化（A431）的角质形成细胞中，通过胆固醇提取或用甲基-β-环糊精、菲律宾蛋白III或5-胡萝卜烯-5-β-醇灭活，实现筏破坏。脂筏破坏不影响PI 3 K与其主要靶点表皮生长因子受体的结合，也不影响其将磷脂酰肌醇4，5-二磷酸转化为磷脂酰肌醇3，4，5-三磷酸的能力，但损害调节位点Thr（308）和Ser（473）处的Akt磷酸化。Akt活性降低导致雷帕霉素的哺乳动物靶标失活，FoxO 3a活化，并增加对凋亡刺激的敏感性。脂筏破坏废除Akt和主要的Akt激酶，磷脂酰肌醇依赖性激酶1，通过pleckstrin同源结构域的膜的结合。因此，脂筏的完整性是Akt活性和细胞存活所必需的，并且可以作为治疗表皮癌的潜在药理学靶点。
Lipid rafts are cholesterol-rich plasma membrane domains that regulate signal transduction. Because our earlier work indicated that raft disruption inhibited proliferation and caused cell death, we investigated here the role of membrane cholesterol, the crucial raft constituent, in the regulation of the phosphatidylinositol-3 kinase (PI3K)/Akt pathway. Raft disruption was achieved in normal human keratinocytes and precancerous (HaCaT) or transformed (A431) keratinocytes by cholesterol extraction or inactivation with methyl-beta-cyclodextrin, filipin III, or 5-cholestene-5-beta-ol. Lipid raft disruption did not affect PI3K binding to its main target, the epidermal growth factor receptor, nor its ability to convert phosphatidylinositol 4,5-bisphosphate to phosphatidylinositol 3,4,5-trisphosphate but impaired Akt phosphorylation at the regulatory sites Thr(308) and Ser(473). Diminished Akt activity resulted in deactivation of mammalian target of rapamycin, activation of FoxO3a, and increased sensitivity to apoptosis stimuli. Lipid raft disruption abrogated the binding of Akt and the major Akt kinase, phosphatidylinositol-dependent kinase 1, to the membrane by pleckstrin-homology domains. Thus, the integrity of lipid rafts is required for the activity of Akt and cell survival and may serve as a potential pharmacological target in the treatment of epidermal cancers.