School of Medical Sciences, Faculty of Medicine and Health, The University of Sydney, Sydney, New South Wales, Australia.
J Morphol. 2022 Nov;283(11):1381-1389. doi: 10.1002/jmor.21504. Epub 2022 Oct 7.
Porosomes are plasma membrane structures in secretory cells that allow transient docking and/or partial fusion of vesicles during which they release their content then disengage. This is referred to as "kiss and run" exocytosis. During early pregnancy, at the time of receptivity, there is a high level of vesicle activity in uterine epithelial cells (UECs). One of the secretory pathways for these vesicles could be via porosomes, which have yet to be identified in UECs. This study identified porosomes in the apical plasma membrane of UECs for the first time. These structures were present on days 1, 5.5, and 6 of early pregnancy, where they likely facilitate partial secretion via "kiss and run" exocytosis. The porosomes were measured and quantified on days 1, 5.5, and 6, which showed there are significantly more porosomes on day 5.5 (receptive) compared to day 1 (nonreceptive) of pregnancy. This increase in porosome numbers may reflect major morphological and molecular changes in the apical plasma membrane at this time such as increased cholesterol and soluble NSF attachment protein receptor proteins, as these are structural and functional components of the porosome complex assembly. Porosomes were observed in both resting (inactive) and dilated (active) states on days 1, 5.5, and 6 of early pregnancy. Porosomes on day 5.5 are significantly more active than on day 1 as demonstrated by the dilation of their base diameter. Further two-way ANOVA analysis of base diameter in resting and dilated states found a significant increase in porosome activity in day 5.5 compared to day 1. This study therefore indicates an increase in the number and activity of porosomes at the time of uterine receptivity in the rat, revealing a mechanism by which the UECs modify the uterine luminal environment at this time.
质膜纳米通道（Porosomes）是分泌细胞中的一种质膜结构，允许囊泡短暂停靠和/或部分融合，在此过程中它们释放内容物然后脱离。这被称为“亲吻和跑开”胞吐作用。在妊娠早期，即接受期，子宫上皮细胞（UECs）中的囊泡活性水平很高。这些囊泡的一种分泌途径可能是通过质膜纳米通道，目前尚未在 UECs 中鉴定出这种通道。本研究首次在 UECs 的顶质膜中鉴定出质膜纳米通道。这些结构存在于妊娠第 1 天、第 5.5 天和第 6 天，它们可能通过“亲吻和跑开”胞吐作用促进部分分泌。在妊娠第 1 天、第 5.5 天和第 6 天测量和量化了这些质膜纳米通道，结果表明，在接受期（第 5.5 天）的质膜纳米通道数量明显多于非接受期（第 1 天）。此时顶质膜中质膜纳米通道数量的增加可能反映了主要的形态和分子变化，例如胆固醇和可溶性 NSF 附着蛋白受体蛋白的增加，因为这些是质膜纳米通道复合物组装的结构和功能组成部分。在妊娠第 1 天、第 5.5 天和第 6 天，观察到质膜纳米通道处于静止（非激活）和扩张（激活）状态。第 5.5 天的质膜纳米通道比第 1 天明显更活跃，这表现在它们基底直径的扩张上。进一步对静止和扩张状态下基底直径的双向方差分析发现，与第 1 天相比，第 5.5 天的质膜纳米通道活性显著增加。因此，本研究表明，在大鼠子宫接受期，质膜纳米通道的数量和活性增加，揭示了 UECs 在此时改变子宫腔环境的一种机制。
