Plant exocytosis: Weaving distinct pathways to the plant plasma membrane
Plant exocytosis: Weaving distinct pathways to the plant plasma membrane
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植物胞吐作用：编织通往植物质膜的不同途径
DOI：
10.1016/j.molp.2022.02.003
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发表时间：
2022
期刊：
影响因子：
27.5
通讯作者：
Nielsen, Erik
中科院分区：
文献类型：
--
作者：
Nielsen, Erik
在植物生长和发育过程中，新合成的蛋白质和其他货物分子必须选择性地靶向各种细胞区室。也许最重要的靶向涉及蛋白质向质膜的运输，在那里它们控制与环境和邻近细胞的相互作用。在此过程中，进入分泌途径的蛋白质被输入到内质网中，在那里它们被折叠和加工。然后，它们被分类并运送到高尔基复合体，在那里它们被进一步加工和修改。在这一点上，蛋白质和货物被递送到trans-Golgi网络（TGN），在那里它们最终被分选到不同的囊泡群体中，然后靶向不同的晚期内体，液泡区室和质膜（Nielsen，2020）。在极化细胞中，膜运输到质膜也可能被分成额外的，离散的膜运输途径，可能到不同的质膜域。在酵母和动物中，在这些分泌区室之间转运蛋白质和货物的分子机制是进化保守的（图1）。货物分选和囊泡出芽事件由ADP-核糖基化因子GTP酶（ARF GTP酶）调节，而囊泡转运和融合由Rab GTP酶调节（Anders和Jurgens，2008; Nielsen，2020）。已显示Rab GTP酶通过募集束缚因子来调节膜融合的各个方面，束缚因子是长卷曲螺旋蛋白或保守的多亚基复合物，其保持囊泡与其靶膜紧密结合，直到SNAP受体（SNARE）蛋白复合物形成并启动囊泡融合（Stenmark，2009）。其中一种多亚基束缚复合物称为外囊复合物，包含八个进化上保守的亚基（Sec 3、Sec 5、Sec 6、Sec 8、Sec 10、Sec 15、Exo 70和Exo 84; Lepore等人，二〇一八年; Polgar和Fogelgren，2018），并被认为有助于在组装SNARE蛋白融合复合物之前将分泌囊泡拴系到质膜上（Saeed et al.，2019）在酵母的极化分泌期间。当Sec 2从TGN中出现时，Rab GTpt 31（及其同源物Ypt 32）将Sec 2招募到新形成的分泌囊泡中（图1）。Sec 2为这些囊泡招募并激活第二个Rab GT3，Sec 4。Sec 4又通过与Sec 15的相互作用募集外囊复合物。外囊复合物通过Exo 70和Sec 3亚基与磷酸肌醇PI-4，5 P2的相互作用帮助将分泌囊泡束缚到质膜上。同样，在动物中，Rab 8（Sec 4样）和Rab 11（Ypt 31/32样）也通过Sec 15相互作用招募外囊，Sec 3和Exo 70亚基也结合PI-4，5 P2（Polgar和Fogelgren，2018）。此外，在酵母中，外囊复合物可能通过以下途径参与SNARE蛋白融合复合物的组装：
During plant growth and development newly synthesized proteins and other cargo molecules must be selectively targeted to a variety of cellular compartments. Perhaps the most important targeting involves the trafficking of proteins to the plasma membrane, where they control interactions with the environment and neighboring cells. During this process, proteins entering the secretory pathway are imported into the endoplasmic reticulum where they are folded and processed. They are then sorted and delivered to the Golgi complex, where they are further processed and modified. At this point, the proteins and cargo are delivered to the trans-Golgi network (TGN), where they are finally sorted into distinct vesicle populations that are then targeted to distinct late endosomes, vacuolar compartments, and the plasma membrane (Nielsen, 2020). In polarized cells, membrane trafficking to the plasma membrane may also be split into additional, discrete membrane trafficking pathways potentially to distinct plasma membrane domains.In yeast and animals, the molecular machinery that functions to transport protein and cargo between these secretory compartments is evolutionarily conserved (Figure 1). Cargo sorting and vesicle budding events are regulated by ADP-ribosylation factor GTPases (ARF GTPases), while vesicle transport and fusion are regulated by Rab GTPases (Anders and Jurgens, 2008; Nielsen, 2020). Rab GTPases have been shown to regulate aspects of membrane fusion through the recruitment of tethering factors, which are either long coiled-coil proteins or conserved multisubunit complexes that hold the vesicle in close association with their target membrane until SNAP receptor (SNARE) protein complexes form and initiate vesicle fusion (Stenmark, 2009). One of these multi-subunit tethering complexes, called the exocyst complex, contains eight evolutionarily conserved subunits (Sec3, Sec5, Sec6, Sec8, Sec10, Sec15, Exo70, and Exo84; Lepore et al., 2018; Polgar and Fogelgren, 2018) and is thought to assist in tethering of secretory vesicles to the plasma membrane prior to the assembly of SNARE protein fusion complexes (Saeed et al., 2019) during polarized secretion in yeast. The Rab GTPase Ypt31 (and its homolog, Ypt32) recruits Sec2 to newly formed secretory vesicles as they emerge from the TGN (Figure 1). Sec2 recruits and activates a second Rab GTPase, Sec4, to these vesicles. Sec4, in turn, recruits the exocyst complex through interaction with Sec15. The exocyst complex assists in tethering the secretory vesicle to the plasma membrane through the interaction of the Exo70 and Sec3 subunits with phosphoinositide PI-4, 5P2. Similarly, in animals, Rab8 (Sec4-like) and Rab11 (Ypt31/32-like) also recruit the exocyst through Sec15 interactions, and Sec3 and Exo70 subunits also bind PI-4, 5P2(Polgar and Fogelgren, 2018). Furthermore, in yeast, the exocyst complex likely participates in the assembly of SNARE protein fusion complexes through