Laboratoire de Biogenèse Membranaire, UMR5200, CNRS, Université de Bordeaux, Villenave d'Ornon, France.
Laboratoire de Biophysique Moléculaire aux Interfaces, TERRA Research Centre, GX ABT, Université de Liège, Gembloux, Belgium.
EMBO Rep. 2019 Aug;20(8):e47182. doi: 10.15252/embr.201847182. Epub 2019 Jul 9.
In eukaryotes, membrane contact sites (MCS) allow direct communication between organelles. Plants have evolved a unique type of MCS, inside intercellular pores, the plasmodesmata, where endoplasmic reticulum (ER)-plasma membrane (PM) contacts coincide with regulation of cell-to-cell signalling. The molecular mechanism and function of membrane tethering within plasmodesmata remain unknown. Here, we show that the multiple C2 domains and transmembrane region protein (MCTP) family, key regulators of cell-to-cell signalling in plants, act as ER-PM tethers specifically at plasmodesmata. We report that MCTPs are plasmodesmata proteins that insert into the ER via their transmembrane region while their C2 domains dock to the PM through interaction with anionic phospholipids. A Atmctp3/Atmctp4 loss of function mutant induces plant developmental defects, impaired plasmodesmata function and composition, while MCTP4 expression in a yeast Δtether mutant partially restores ER-PM tethering. Our data suggest that MCTPs are unique membrane tethers controlling both ER-PM contacts and cell-to-cell signalling.
在真核生物中，膜接触位点（MCS）允许细胞器之间的直接通讯。植物进化出了一种独特的 MCS，位于细胞间孔隙——胞间连丝中，其中内质网（ER）-质膜（PM）接触与细胞间信号转导的调节相吻合。胞间连丝中膜连接的分子机制和功能仍不清楚。在这里，我们表明，作为植物细胞间信号转导关键调节剂的多 C2 结构域和跨膜区蛋白（MCTP）家族，特异性作为 ER-PM 系链存在于胞间连丝中。我们报告称，MCTP 是通过其跨膜区插入 ER 的胞间连丝蛋白，而其 C2 结构域通过与阴离子磷脂相互作用与 PM 对接。 Atmctp3/Atmctp4 功能丧失突变体诱导植物发育缺陷、胞间连丝功能和组成受损，而在酵母 Δtether 突变体中表达 MCTP4 部分恢复了 ER-PM 系链。我们的数据表明，MCTP 是独特的膜系链，控制 ER-PM 接触和细胞间信号转导。
