Laboratoire Physico Chimie Curie, Institut Curie, Université PSL, Sorbonne Université, CNRS UMR168, 75005, Paris, France.
Moleculaire Biofysica, Zernike Instituut, Rijksuniversiteit Groningen, Nijenborgh 4, 9747 AG, Groningen, The Netherlands.
BMC Biol. 2021 Apr 8;19(1):66. doi: 10.1186/s12915-021-00983-9.
ESCRT-III proteins are involved in many membrane remodeling processes including multivesicular body biogenesis as first discovered in yeast. In humans, ESCRT-III CHMP2 exists as two isoforms, CHMP2A and CHMP2B, but their physical characteristics have not been compared yet.
Here, we use a combination of techniques on biomimetic systems and purified proteins to study their affinity and effects on membranes. We establish that CHMP2B binding is enhanced in the presence of PI(4,5)P2 lipids. In contrast, CHMP2A does not display lipid specificity and requires CHMP3 for binding significantly to membranes. On the micrometer scale and at moderate bulk concentrations, CHMP2B forms a reticular structure on membranes whereas CHMP2A (+CHMP3) binds homogeneously. Thus, CHMP2A and CHMP2B unexpectedly induce different mechanical effects to membranes: CHMP2B strongly rigidifies them while CHMP2A (+CHMP3) has no significant effect.
We therefore conclude that CHMP2B and CHMP2A exhibit different mechanical properties and might thus contribute differently to the diverse ESCRT-III-catalyzed membrane remodeling processes.
ESCRT-III 蛋白参与许多膜重塑过程，包括多泡体的生物发生，这首先在酵母中被发现。在人类中，ESCRT-III CHMP2 存在两种异构体，CHMP2A 和 CHMP2B，但它们的物理特性尚未被比较。
在这里，我们使用仿生系统和纯化蛋白的组合技术来研究它们与膜的亲和力和作用。我们确定 CHMP2B 的结合在存在 PI(4,5)P2 脂质的情况下增强。相比之下，CHMP2A 没有显示出脂质特异性，并且需要 CHMP3 才能显著结合到膜上。在微米尺度和中等体相浓度下，CHMP2B 在膜上形成网状结构，而 CHMP2A(+CHMP3)均匀地结合。因此，CHMP2A 和 CHMP2B 出人意料地对膜产生不同的机械效应：CHMP2B 强烈地使其刚性化，而 CHMP2A(+CHMP3)则没有显著影响。
因此，我们得出结论，CHMP2B 和 CHMP2A 表现出不同的力学特性，因此可能对 ESCRT-III 催化的不同膜重塑过程有不同的贡献。
