Abstract
摘要：Rotini，Rti，是人類高基氏體蛋白質Gpp34的果蠅同源物；rti突變會造成Hh 的表現量明顯下降以及胚胎呈現扭曲與背部化的性狀；此計劃將以釐清Rti參與調控這兩項發育遺傳的機制為目標。
硫醣蛋白(Heparan Sulfate Proteoglycans，HSPGs)由核心蛋白(core protein)攜帶多醣鏈(glycosaminoglycans，GAG)所組成。已知硫醣蛋白參與調控Hedgehog (Hh)的分佈及訊息傳遞；當核心蛋白Dally-like protein (Dlp) 突變或者聚合多醣鏈所需的酵素突變造成多醣鏈合成的缺損時，硫醣蛋白的生成異常因此會導致Hh的不表現以及訊息傳遞的缺損。
我們先前證實Rti並不是直接調控Hh的轉錄、轉譯及Hh的自我裂解程序，而是藉由調控硫醣蛋白的表現而後間接而影響Hh的行為。此計劃將驗證Rti是否為核心蛋白Dlp或聚合多醣鏈的酵素進入硫醣蛋白生成路徑之所需?實驗設計將詢問諸如：Rti 是否影響核心蛋白Dlp的表現或影響核心蛋白Dlp分泌輸送至細胞表面的行為? 或者，Rti是否為調控一系列多醣鏈聚合反應的聚合酵素進入高基氏體所需要的? 更者，經Two-hybrids搜尋，果蠅的v-SNARE蛋白質, dVti1, 被發現可能與Rti有交互作用。吾人將確定兩者是否為參與HSPGs生成的兩個直接作用成員。
由初步的背腹化標的蛋白質Twist的染色，Rti功能明顯的也影響胚胎背腹化的調控。由Rti對硫醣蛋白的可能影響，我們將先釐清Rti對胚胎的背腹化功能是作用於濾泡細胞(follicle cells)或者是胚胎本身，之後，Rti對於此項發育過程的調控機制將會被逐步解析。
Abstract: Rotinin (Rti) is the Drosophila homologue of human GPP34 Golgi protein. Hh expression level is clearly reduced in rti mutant cells. A twisted and partially dorsalized embryonic phenotype is observed in rti mutation. This project is aimed at to clarify the function of Rti on these two processes.
Heparan sulfate proteoglycans (HSPGs) are composed of core protein and glycosaminoglycans (GAGs) side chains. HSPGs regulate the expression level and signal transduction of Hedgehog (Hh) morphogen. Mutations involved in biogenesis of core protein Dally-like protein (Dlp) and in the synthesis of GAG side chains can cause the abnormal HSPGs expression and aberrant Hh expression and signaling.
We have first confirmed that Rti indirectly affects Hh behaviors by mediating HSPGs expression but not directly regulates the transcription, translation and auto-cleavage process of Hh. This project is planned to clarify whether Rti is required for the participation of core protein and/or of the enzyme(s) for the synthesis of GAG in the processes of HSPGs biogenesis. Experiments will be performed to understand whether Rti is required for the expression of Dlp protein and for its secretion to cell surface or whether Rti is involved in the formation of GAG chain by regulating the entrance of polymerases into HSPGs biogenesis.
From a two-hybrid screen for Rti interacting proteins, a Drosophila v-SNARE protein, dVti1, involved in Golgi retrograde trafficking in yeast has been identified. It will be critical to confirm that Rti and dVti1 may be two directly interacting components involved in the processes of HSPGs biogenesis.
Based on the staining pattern of Twist, the target gene of embryonic ventralization, it is suggested that Rti function also affects the formation of dorsal-ventral axis. We will first clearigy whether Rti acts in follicle cells or embryonic cell and then sequentially dissect its action mechanism.
Keyword(s)
硫醣蛋白
多醣鏈聚合酵素
高基氏體蛋白質
果蠅
Heparan sulfate proteoglycans
glycosaminoglycans
Golgi protein
Drosophila
