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  • 學位論文

低氧引發GCM1降解的機制與子癲前症發病的關係

Mechanism of hypoxia-induced GCM1 degradation: Implications for the pathogenesis of preeclampsia

指導教授 : 陳宏文

摘要


GCM1 (Glial cells missing homolog 1)是調控胎盤發育的重要轉錄因子(transcription factor),根據過去我們實驗室對GCM1研究發現:(1) GCM1可調控融合蛋白syncytin基因的表現,促使滋養葉胞層細胞(cytotrophoblast)融合成滋養葉融合層細胞(syncytiotrophoblast);(2) SCFFBW2複合體(complex)與磷酸化的GCM1作用促進GCM1汎素化(ubiquitination),進而由26S proteasome 進行蛋白質降解(degradation);(3) cAMP/PKA訊息路徑(signaling pathway)可促進CBP蛋白對GCM1蛋白質進行乙醯化(acetylation)修飾,使GCM1蛋白質免於被汎素化;(4)GCM1在子癲前症(preeclampsia)的胎盤組織表現減少。 子癲前症(preeclampsia)是一懷孕特有疾病,約有5-7%的妊娠婦女患此疾病。胎盤滋養葉細胞(trophoblast)的侵入和子宮螺旋形動脈(spiral arterial)的重塑(remodeling)不完整可能會導致胎盤細胞處於低氧狀態(hypoxia)。這些現象也被認為是引起子癲前症的主要原因,但低氧與子癲前症之間的關係目前並不清楚。GCM1及其調控的基因syncytin 1、syncytin 2和PGF (placental growth factor),在子癲前症胎盤組織皆減少。而PGF也是GCM1的調控基因,其對胎盤血管的新生扮演著重要的角色。 胎盤細胞BeWo和JEG-3在低氧狀態下,內生性的GCM1、syncytin 1、syncytin 2的mRNA明顯減少,而GCM1的蛋白量也隨之減少。BeWo細胞在CMV啟動子(cytomegalovirus promoter)之下,可穩定持續表現HA-GCM1的細胞株BeWo31,進行低氧或以CoCl2藥物模擬低氧狀態之實驗,其HA-GCM1的mRNA量不變;但HA-GCM1的蛋白量減少,由此實驗結果我們證明低氧造成GCM1蛋白質的降解。在低氧狀態下,胎盤細胞內活化型態的Akt (p-Thr308-Akt和p-Ser473-Akt)的蛋白量皆明顯減少,同時不活化型態的GSK-3β (p-Ser9-GSK-3β)也顯著減少。PI3K的抑制劑LY294002可以使HA-GCM1的蛋白量減少,在低氧下更為明顯,但GSK-3β的抑制劑LiCl可以制止因低氧引發GCM1的降解。我們證明低氧造成GCM1降解是藉抑制PI3K-Akt的訊息路徑,導致GSK-3β的活化。活化的GSK-3β對GCM1的Ser322磷酸化,促使磷酸化的GCM1與F-box protein FBW2作用,導致GCM1汎素化進而降解。因此,GCM1所調控的轉錄網絡受到抑制,進而在子癲前症的形成過程中,扮演重要的角色。

並列摘要


Glial cells missing homolog 1 (GCM1) is a transcription factor critical for placental development. Our previous studies have demonstrated that (1) GCM1 is able to regulate syncytin gene expression in order to mediate fusion of cytotrophoblasts into multinucleated syncytiotrophoblasts, (2) the SCFFBW2 complex interacts with GCM1 in a phosphorylation-dependent manner and promotes GCM1 ubiquitination, (3) the cAMP-PKA pathway is able to enhance CBP-mediated acetylation of GCM1 to prevent GCM1 from ubiquitination, and (4) GCM1 gene expression is decreased in preeclampsia. Preeclampsia is a major pregnancy-specific disorder affecting 5-7% of pregnancies worldwide. While hypoxia caused by incomplete trophoblast invasion and impaired spiral arterial remodeling is thought to be a major cause of preeclampsia, how hypoxia affects placental development remains uncertain. In preeclampsia, GCM1 and its target genes syncytin 1 and placental growth factor (PGF), important for syncytiotrophoblast formation and placental vasculogenesis, are all decreased. In this study, I present evidence that GCM1 is a major target of hypoxia associated with preeclampsia. Furthermore, hypoxia triggers GCM1 degradation by suppressing the PI3K-Akt signaling pathway, leading to GSK-3β activation. Activated GSK-3β phosphorylates GCM1 on Ser322, which in turn recruits the F-box protein FBW2, leading to GCM1 ubiquitination and degradation. Importantly, the GSK-3β inhibitor LiCl prevented hypoxia-induced GCM1 degradation. Overall, this study identifies a molecular basis for the disrupted GCM1 transcription network in preeclampsia and provides a potential avenue for therapeutic intervention.

並列關鍵字

GCM1 preeclampsia hypoxia

參考文獻


Akiyama, Y., T. Hosoya, A. M. Poole and Y. Hotta (1996). "The gcm-motif: a novel DNA-binding motif conserved in Drosophila and mammals." Proc Natl Acad Sci U S A 93(25): 14912-14916.
Alvarez-Tejado, M., A. Alfranca, J. Aragones, A. Vara, M. O. Landazuri and L. del Peso (2002). "Lack of evidence for the involvement of the phosphoinositide 3-kinase/Akt pathway in the activation of hypoxia-inducible factors by low oxygen tension." J Biol Chem 277(16): 13508-13517.
Anson-Cartwright, L., K. Dawson, D. Holmyard, S. J. Fisher, R. A. Lazzarini and J. C. Cross (2000). "The glial cells missing-1 protein is essential for branching morphogenesis in the chorioallantoic placenta." Nat Genet 25(3): 311-314.
Beitner-Johnson, D., R. T. Rust, T. C. Hsieh and D. E. Millhorn (2001). "Hypoxia activates Akt and induces phosphorylation of GSK-3β in PC12 cells." Cell Signal 13(1): 23-27.
Blaise, S., N. de Parseval, L. Benit and T. Heidmann (2003). "Genomewide screening for fusogenic human endogenous retrovirus envelopes identifies syncytin 2, a gene conserved on primate evolution." Proc Natl Acad Sci U S A 100(22): 13013-13018.

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