Two subunits of the exocyst, Sec3p and Exo70p, can function exclusively on the plasma membrane.
Two subunits of the exocyst, Sec3p and Exo70p, can function exclusively on the plasma membrane.
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DOI：
10.1091/mbc.e17-08-0518
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发表时间：
2018-03-15
影响因子：
3.3
通讯作者：
Novick P
中科院分区：
文献类型：
--
作者：
Liu D;Li X;Shen D;Novick P
外囊是一种八聚体复合物，它将分泌囊泡拴在质膜上，为融合做准备。我们锚定每个亚基与跨膜（TM）结构域在其N-或C-末端。只有N-末端锚定的TM-Sec 3 p和C-末端锚定的Exo 70 p-TM被证明是功能性的。这些发现使复合物相对于膜定向，并确定Sec 3 p和Exo 70 p可以仅在膜上起作用。TM-Sec 3 p和Exo 70 p-TM的功能在很大程度上不受内吞再循环阻断的影响，这表明它们作用于质膜而不是分泌囊泡。其他外囊亚基的胞质池在TM-sec 3细胞中不受影响，而它们在exo 70-TM细胞中部分耗尽。阻断act 1 -3细胞中分泌囊泡的肌动蛋白依赖性递送导致纯化复合物中Sec 3 p的丢失。我们的研究结果是一致的模型，其中Sec 3 p和Exo 70 p可以专门在质膜上的功能，而其他亚基被带到他们的分泌囊泡。
The exocyst is an octameric complex that tethers secretory vesicles to the plasma membrane in preparation for fusion. We anchored each subunit with a transmembrane (TM) domain at its N- or C-terminus. Only N-terminally anchored TM-Sec3p and C-terminally anchored Exo70p-TM proved functional. These findings orient the complex with respect to the membrane and establish that Sec3p and Exo70p can function exclusively on the membrane. The functions of TM-Sec3p and Exo70p-TM were largely unaffected by blocks in endocytic recycling, suggesting that they act on the plasma membrane rather than on secretory vesicles. Cytosolic pools of the other exocyst subunits were unaffected in TM-sec3 cells, while they were partially depleted in exo70-TM cells. Blocking actin-dependent delivery of secretory vesicles in act1-3 cells results in loss of Sec3p from the purified complex. Our results are consistent with a model in which Sec3p and Exo70p can function exclusively on the plasma membrane while the other subunits are brought to them on secretory vesicles.