通过体外和细胞内的生化重组，研究人员证明了兴奋性和抑制性突触后细胞基质或密度（e/iPSD），通过相分离自发地分离成不同的凝聚分子组装体。用PSD-95胞内抗体（解离常数约为4nM）标记iPSD支架桥尾蛋白会导致桥尾蛋白与ePSD凝聚物错位。
意想不到的是，iPSD凝聚物的形成迫使体内标记的桥尾蛋白脱离ePSD凝聚物。因此，生物分子在凝聚物中的默认过程不是由扩散控制的自发混合，而是去混合。相分离可以产生稀释溶液中无法产生的生物分子区室化特异性。
据介绍，即使是在一个亚微米大小的树突突起上形成的兴奋性突触和抑制性突触也不会重叠。e/iPSD是如何分离的，目前尚不清楚。从广义上讲，无膜细胞器在细胞亚区中自然分隔的原因也不清楚。
附：英文原文
Title: Demixing is a default process for biological condensates formed via phase separation
Author: Shihan Zhu, Zeyu Shen, Xiandeng Wu, Wenyan Han, Bowen Jia, Wei Lu, Mingjie Zhang
Issue&Volume: 2024-05-24
Abstract: Excitatory and inhibitory synapses do not overlap even when formed on one submicron-sized dendritic protrusion. How excitatory and inhibitory postsynaptic cytomatrices or densities (e/iPSDs) are segregated is not understood. Broadly, why membraneless organelles are naturally segregated in cellular subcompartments is unclear. Using biochemical reconstitutions in vitro and in cells, we demonstrate that ePSDs and iPSDs spontaneously segregate into distinct condensed molecular assemblies through phase separation. Tagging iPSD scaffold gephyrin with a PSD-95 intrabody (dissociation constant ~4 nM) leads to mistargeting of gephyrin to ePSD condensates. Unexpectedly, formation of iPSD condensates forces the intrabody-tagged gephyrin out of ePSD condensates. Thus, instead of diffusion-governed spontaneous mixing, demixing is a default process for biomolecules in condensates. Phase separation can generate biomolecular compartmentalization specificities that cannot occur in dilute solutions.
DOI: adj7066
Source: https://www.science.org/doi/10.1126/science.adj7066