Smith Jean A, Hall Allison E, Rose Mark D
Department of Molecular Biology, Princeton University, Princeton, NJ.
Department of Molecular Biology, Princeton University, Princeton, NJ
J Cell Biol. 2017 Dec 4;216(12):3971-3980. doi: 10.1083/jcb.201703169. Epub 2017 Oct 24.
Cell fusion is ubiquitous in eukaryotic fertilization and development. The highly conserved Rho-GTPase Cdc42p promotes yeast fusion through interaction with Fus2p, a pheromone-induced amphiphysin-like protein. We show that in prezygotes, Cdc42p forms a novel Fus2p-dependent focus at the center of the zone of cell fusion (ZCF) and remains associated with remnant cell walls after initial fusion. At the ZCF and during fusion, Cdc42p and Fus2p colocalized. In contrast, in shmoos, both proteins were near the cortex but spatially separate. Cdc42p focus formation depends on ZCF membrane curvature: mutant analysis showed that Cdc42p localization is negatively affected by shmoo-like positive ZCF curvature, consistent with the flattening of the ZCF during fusion. BAR-domain proteins such as the fusion proteins Fus2p and Rvs161p are known to recognize membrane curvature. We find that mutations that disrupt binding of the Fus2p/Rvs161p heterodimer to membranes affect Cdc42p ZCF localization. We propose that Fus2p localizes Cdc42p to the flat ZCF to promote cell wall degradation.
细胞融合在真核生物受精和发育过程中普遍存在。高度保守的Rho-GTP酶Cdc42p通过与Fus2p相互作用促进酵母融合，Fus2p是一种信息素诱导的发动蛋白样蛋白。我们发现，在合子前期，Cdc42p在细胞融合区（ZCF）中心形成一个新的依赖于Fus2p的焦点，并在初始融合后与残余细胞壁保持关联。在ZCF处及融合过程中，Cdc42p和Fus2p共定位。相比之下，在接合芽中，这两种蛋白都靠近皮层，但在空间上是分开的。Cdc42p焦点的形成取决于ZCF膜的曲率：突变分析表明，Cdc42p的定位受到接合芽样正ZCF曲率的负面影响，这与融合过程中ZCF变平一致。已知诸如融合蛋白Fus2p和Rvs161p等BAR结构域蛋白可识别膜曲率。我们发现，破坏Fus2p/Rvs161p异二聚体与膜结合的突变会影响Cdc42p在ZCF的定位。我们提出，Fus2p将Cdc42p定位到扁平的ZCF以促进细胞壁降解。
