2015-08-012024-05-13https://scholars.lib.ntu.edu.tw/handle/123456789/648542摘要：Liver receptor homologue-1 (LRH-1) 屬於核受器NR5A家族之成員主要表現於肝臟、胰臟、小腸、卵巢及脂肪組織。LRH-1為一轉錄因子調控很多基因的表現，影響了各種不同的生物反應，包括發育、代謝、類固醇荷爾蒙生成與腫瘤生成。LRH-1會促進雌激素相關的乳癌細胞的增生，此作用與類固醇荷爾蒙生成以及受ERα調控有正關聯性。此外，LRH-1亦會促進乳癌細胞的移動與轉移，而此作用與雌激素無關。研究顯示LRH-1會與β-catenin作用調控細胞週期重要分子cyclin D1與cyclin E1的表現，此作用對小腸細胞更新具重要性。研究發現LRH-1異常過量表現發生於乳癌、胰臟癌、胃癌等腫瘤組織，而降低LRH-1的表現可顯著抑制癌細胞株的生長。顯見LRH-1參與並影響腫瘤生成，但其作用機制尚未真正了解。泛素-蛋白酶體路徑是一重要的蛋白質降解系統，以維持細胞蛋白質的恆定。我們先前的研究顯示，LRH-1蛋白質相當不穩定且會經由泛素-蛋白酶體而被降解。我們進一步找到與LRH-1有交互作用的蛋白質DDB2，其藉由CUL4-DDB1 E3泛素連接酶的作用，會促進LRH-1蛋白質降解。此外，我們發現更多與LRH-1有交互作用的E3泛素連接酶分子，如RNF128、RNF138與RNF115，皆是屬於具有RING結構類型的E3泛素連接酶。有趣的是，這些分子並不會造成LRH-1蛋白質降解；相反地，LRH-1會顯著降低這些蛋白質的量。已知RNF138會促進TCF/LEE蛋白質降解，因而抑制了Wnt/β-catenin的訊息路徑。Wnt/β-catenin異常活化與癌症的發生有關，特別在大腸癌與肝癌最為顯著。由於LRH-1與Wnt/β-catenin訊息傳遞在大腸癌與肝癌皆扮演重要角色，促使我們深入探討LRH-1調控RNF138蛋白質穩定性的機制。我們假設此作用在Wnt相關的腫瘤生成具有相當程度的重要性。此計畫的主要研究目標包括：目標一：確認的穩定性會受到LRH-1所調控目標二：研究LRH-1調控RNF138蛋白質穩定性的機制目標三：探討LRH-1與RNF138在腫瘤生成的角色透過此研究，我們將可清楚了解LRH-1調控RNF138蛋白質穩定性的機制，並對相關的腫瘤之了解與治療也可有所貢獻。<br> Abstract: Liver receptor homologue-1 (LRH-1; NR5A2), a member of the orphan nuclear receptor NR5A subfamily, is mainly expressed in liver, pancreas, intestine, ovary and adipose tissue. LRH-1 functions as a transcription factor to regulate the expression of numerous genes associated with diverse biological processes, including development, metabolism, steroidogenesis and carcinogenesis. In breast cancer, LRH-1 promotes estrogen-dependent cell proliferation that is correlated to steroid synthesis and ERα regulation. It also regulates breast cancer migration and invasion independent of estrogen. LRH-1 has been shown to promote cell proliferation through the interaction with the β-catenin to regulate the expression of cell-cycle regulators cyclin D1 and E1 that contributes to intestinal cell renewal. The aberrant overexpression of LRH-1 occurs in human breast, pancreatic and gastric cancers and blocking of LRH-1 inhibits cancer cell proliferation in vitro. However, despite the critical involvement of LRH-1 in development and progression of cancer, the contribution of LRH-1 to tumorigenesis remains unclear.Ubiquitin-proteasome pathway is an important proteolytic system to maintain the homeostasis of cellular proteins. We previously found that LRH-1 is extremely unstable and is destroyed by ubiquitin-mediated proteolysis. Our ongoing study showed that DDB2 is a LRH-1 interacting protein and mediates LRH-1 ubiquitination/degradation by CUL4-DDB1 E3 ligase. In addition, we found more RING-type E3 ligases including RNF128, RNF138 and RNF115 interact with LRH-1. Interestingly, these E3 proteins have no effect on LRH-1 protein degradation; on the contrary, their protein levels are negatively regulated by LRH-1. Recently, RNF138 has been shown to regulate the degradation of TCF/LEE transcription factor and hence acts as an inhibitor of Wnt/β-catenin signaling. Activation of Wnt/β-catenin pathway is linked to different types of cancer, most notably colorectal and liver cancers. Due to the important roles of LRH-1 and Wnt/β-catenin signaling in liver and colon cancers, we therefore focus on underlying mechanism by which LRH-1 regulate RNF138 protein levels in this proposal. We speculate that LRH-1-mediated RNF138 protein stability may contribute a part to the Wnt related tumorigenesis. The specific aims are:Aim 1: To verify the regulation of RFN138 protein stability by LRH-1Aim 2: To investigate the mechanism by which LRH-1 modulate RNF138 stabilityAim 3: To explore the roles for LRH-1 and RNF138 in tumorigenesisThis study will gain insight into the regulation of RNF138 stability by LRH-1 that should contribute to the understanding and therapeutic approaches in LRH-1 associated carcinogenesis.核受器LRH-1RING 泛素連接酶RNF138蛋白質Wnt/β-catenin路徑腫瘤生成Liver receptor homologue-1 (LRH-1)RING ubiquitin ligaseRNF138Wnt/β-catenin pathwaytumorigenesis