Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, MD 20742, USA.
Department of Cell Biology, University of Texas Southwestern Medical Center, 6000 Harry Hines Boulevard, Dallas, TX 75390-9039, USA.
Dev Cell. 2021 Dec 20;56(24):3380-3392.e9. doi: 10.1016/j.devcel.2021.10.023. Epub 2021 Nov 22.
Union of two gametes to form a zygote is a defining event in the life of sexual eukaryotes, yet the mechanisms that underlie cell-cell fusion during fertilization remain poorly characterized. Here, in studies of fertilization in the green alga, Chlamydomonas, we report identification of a membrane protein on minus gametes, Minus Adhesion Receptor 1 (MAR1), that is essential for the membrane attachment with plus gametes that immediately precedes lipid bilayer merger. We show that MAR1 forms a receptor pair with previously identified receptor FUS1 on plus gametes, whose ectodomain architecture we find is identical to a sperm adhesion protein conserved throughout plant lineages. Strikingly, before fusion, MAR1 is biochemically and functionally associated with the ancient, evolutionarily conserved eukaryotic Class II fusion protein HAP2 on minus gametes. Thus, the integral membrane protein MAR1 provides a molecular link between membrane adhesion and bilayer merger during fertilization in Chlamydomonas.
两个配子融合形成受精卵是有性真核生物生命中的一个决定性事件，但受精过程中细胞融合的机制仍未得到很好的描述。在这里，我们在绿藻衣藻的受精研究中报告了一种位于负配子上的膜蛋白，即负配子黏附受体 1（MAR1）的鉴定，该蛋白对于在脂质双层融合之前与正配子进行膜附着是必需的。我们表明 MAR1 在正配子上与先前鉴定的受体 FUS1 形成受体对，我们发现其细胞外结构域的结构与整个植物谱系中保守的精子黏附蛋白相同。引人注目的是，在融合之前，MAR1 在生化和功能上与负配子上的古老的、进化上保守的真核 II 类融合蛋白 HAP2 相关联。因此，在衣藻的受精过程中，整合膜蛋白 MAR1 为膜黏附和双层融合提供了分子联系。
