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Title: | 果蠅高基氏體蛋白質(Rotini)的發育遺傳功能角色探討 Developmental genetic functions of Drosophila Golgi phosphoprotein 3(GOLPH3), Rotini |
Authors: | Wei-Ling Chang 張瑋玲 |
Advisor: | 周子賓 |
Keyword: | 高基氏體蛋白質, GOLPH3,Rti, |
Publication Year : | 2013 |
Degree: | 博士 |
Abstract: | Rotini(Rti)為人類高基氏體蛋白GOLPH3在果蠅中的同源蛋白,藉由rti 突變造成的性狀,我們研究Rti在發育上扮演的角色。
exostosin (EXT)基因能合成醣基轉移酶,作用於多醣蛋白(HSPGs;Heparan Sulfate Proteoglycans)合成過程中幫助黏多醣(GAG)聚合。我們發現Rti能調控EXT在高基氏體的逆向運輸。當Rti減少時使EXTs的分佈轉移至靠近trans-Golgi的位置,此錯位累積的EXTs 將會被裂解,因而無法再次作用於GAGs長鏈的聚合;相反的,當 Rti大量表現時使EXTs的分佈轉移至靠近ER/cis-Golgi的位置。不管是缺少或大量表現Rti都會造成HSPGs合成出現問題而影響Hh訊息傳遞。 此模式同樣表現於人類的硬骨及軟骨細胞,意即GOLPH3能調控EXT1及EXT2在細胞內高基氏體的逆向運輸並影響EXT1及EXT2蛋白的穩定度。抑癌基因EXT1 或EXT2突變時會使HSPGs的合成出現問題而造成多發性硬軟骨癌(MO; Multiple Osteochondromas),因此我們的研究對多發性硬軟骨癌提供一新的致病機轉,意即GOLPH3調控抑癌基因EXT1及EXT2在高基式體內的分怖情形,錯位的分佈影響蛋白的穩定度,造成EXT1及EXT2蛋白的裂解,進而引發癌症。 rti 突變造成果蠅胚胎背腹軸性異常,為了解rti突變如何造成背腹軸性發育缺失,我們著重於Rti對三個蛋白質水解酶的影響,包括Gastrulation Defective (GD), Snake (Snk), 以及Easter (Ea)。研究發現三個蛋白質水解酶的酶原量在rti突變的胚胎內明顯增加,然而酶原激化後具活性的水解酶量卻減少,此外Snk酶原激化過成提早到卵子期發生。研究顯示Rti影響GD,Snk,以及Ea三個蛋白質水解酶的表現量及酶原激化過程。 簡而言之,Rti/GOLPH3 調控EXT在高基氏體的逆向運輸,此研究對多發性硬軟骨癌提供一新的致病機轉。此外,Rti藉由影響GD,Snk,以及Ea三個蛋白質水解酶來調控果蠅胚胎發育過程中背腹軸性的決定。 Rotini, the homologous of human GOLPH3, is a novel Golgi protein found in Drosophila. Based on the phenotypes display by rti GLC embryo, we studied the possible mechanisms of Rti during development. The exostosin (EXT) genes encode glycosyltransferases required for glycosaminoglycan (GAG) chain polymerization in the biosynthesis of heparan sulfate proteoglycans (HSPGs). As a Golgi protein, Rti mediates the retrograde trafficking of the EXTs glycotransferase enzymes within the Golgi. A reduction in Rti shifts the steady-state distribution of EXTs to the trans-Golgi. These accumulated EXTs tend to be degraded and their re-entrance towards the route for polymerizing GAG chains is disengaged. Conversely, EXTs are mislocalized towards the ER/cis-Golgi when Rti is over-expressed. Both loss of function and overexpression of rti result in incomplete HSPGs and perturb Hedgehog (Hh) signaling. This model is consistent with a role of GOLPH3 in human bone and cartilage cells, whereby GOLPH3 modulates the dynamic retention and protein stability of EXT1/2. Mutation in the tumor suppressor genes EXT1 and EXT2 disturb HSPG biosynthesis and cause multiple osteochondromas (MO). Our data demonstrate that GOLPH3 affects the sub-compartmental distribution of EXT1 and 2 in the Golgi, providing a putative function of GOLPH3 in MO etiology. To study the role of Rti in dorsoventral patterning formation in Drosophila embryo, we focused on three serine proteases, Gastrulation Defective (GD), Snake (Snk), and Easter (Ea). In rti GLC embryos, the protein levels of zymogens form of the three proteases significantly increased, but the processed/cleavage forms are barely detectable. When rti is mutated, the prematurely cleaved Snk has already existed in ovary. These suggest that Rti may affect protein level and cleavage processing of three serine proteases. In summary, Rti/GOLPH3 regulates the retrograde trafficking of EXTs to modulate the dynamic retention of EXTs within the Golgi. An effect of EXTs by GOLPH3 provides a putative role for GOLPH3 in the formation of MO. Besides, Rti affects GD, Snk, and Ea serine proteases to determine the dorsoventral patterning in the Drosophila embryo. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/62586 |
Fulltext Rights: | 有償授權 |
Appears in Collections: | 分子與細胞生物學研究所 |
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