探討BLMP-1在線蟲腸道細胞內之膜囊泡運輸過程中扮演的角色

Abstract

囊泡運輸作用對於生物體來說是極為重要又複雜的機制。細胞透過胞吞作用、胞吐作用，以及物質運輸，來維持膜上物質的動態平衡，包括膜上蛋白質的量及位置。然而，細胞內物質運輸機制還有許多細節尚未被釐清。BLMP-1(B細胞成熟因子)是一個轉錄因子，在演化上高度被保留下來，代表其對於生物體具有重要性。先前研究指出，BLMP-1在生物體的發育過程中，決定特定時間的發育事件，這包含了小鼠免疫細胞的分化作用、果蠅蛻皮激素的分泌以及線蟲遠頂細胞的移動。我們的研究發現blmp-1(s71)線蟲突變株其表皮的鈣黏蛋白(E-cadherin)有錯位的情形。我們猜測這可能源自細胞內囊泡物質運輸情形出現了問題。透過觀察各種細胞內物質運輸相關的蛋白標定線蟲，確實發現到在blmp-1(RNAi)突變種腸道細胞囊泡運輸作用有變異，包含負責將物質運輸到細胞膜表面的RAB-11-related回收囊泡數量減少，以及跟降解作用的囊泡數量異常累積，也可能造成分泌到細胞膜上的P-糖蛋白(P-glycoprotein)的量可能有減少，指向BLMP-1可能透過影響囊泡運輸作用，而調控運送物質到細胞膜上的機制。

Membrane trafficking is an important and complicated mechanism in all cells. The counterbalancing action of endocytosis and exocytosis maintains a dynamic equilibrium that regulates the composition of the plasma membrane as well as the level and localization of membrane proteins. E-cadherins which are regulated by membrane trafficking are adherens junctional molecules important for tissue organization and integrity. BLMP-1 is an evolutionarily conserved transcriptional factor which mostly functions as a repressor. Previous studies have shown that BLMP-1 regulates the timing of specific developmental events including ecdysone induced developmental pathway in Drosophila and distal tip cells migration in C. elegans. In our studies, we used investigated blmp-1 function in C. elegans. Interestingly, we observed that E-cadherin proteins are mislocalized in the epidermis of the blmp-1 mutant. We hypothesized the E-cadherin abnormality might be due to defects in vesicle trafficking. We employed RAB-related reporters to dissect vesicle trafficking steps. The data showed that inactivation of blmp-1 by RNA interference caused the decrease of rab-11-related recycling vesicles, theaccumulation of lysosome-related organelles and the increase of late endosomal vesicles as well as lysosomes. Further, we found that the P-glycoprotein, which localizes to the apical surface of intestinal cells, were decreased in blmp-1(RNAi) mutants. This result indicated that the defects of vesicle trafficking in blmp-1(RNAi) mutants affected the localization of membrane proteins. Altogether, our results suggested that BLMP-1 affects vesicles trafficking in the intestine.