小柯机器人

细胞内相分离组分依赖性的热力学
2020-05-07 13:14

美国普林斯顿大学Clifford P. Brangwynne和圣裘德儿童研究医院Richard W. Kriwacki课题组合作在研究中取得进展。他们揭示了细胞内相分离组分依赖性的热力学。相关论文在线发表在2020年5月6日出版的《自然》杂志上。

研究人员发现异型多组分相互作用主导内源性液-液相分离(LLPS),并引起核仁素和其他不具有固定饱和浓度的缩合物。随着各个组分浓度的变化,它们的分配系数以一种可用于确定形成LLPS热力学自由能的方式变化。

研究发现,蛋白质和RNA成分之间的异型相互作用可稳定细胞内各种典型的缩合物(包括核仁、Cajal体、应力颗粒和P体),这意味着缩合物的组成可以通过基本生物分子相互作用网络的热力学进行微调。在加工RNA的缩合物(例如核仁)中,这表现为选择性排除完全组装的核糖核蛋白复合物,为载体核糖体RNA从核仁中流出提供了热力学基础。

该方法在概念上简单明了、易于实施、可广泛用于从显微镜图像中提取热力学参数。这些方法为深入了解细胞内多组分相行为的热力学及其与内源性缩合物非平衡活性之间的相互作用铺平了道路。

据介绍,胞内体如核仁、Cajal体和各种信号传导组件通过LLPS形成代表性的无膜细胞器或缩合物。生物分子的相互作用(尤其是由自缔合、内在无序蛋白质区域介导的同型相互作用)被认为是引起LLPS热力学的基础,形成的缩合物可以促进生物化学活性复合物(例如核仁内核糖体亚基)的组装和加工。简化模型系统产生了一个概念,即单一固定的饱和浓度是内源性LLPS的固有特征,并被认为是细胞内浓度缓冲的一种机制。但是,在活细胞内未对固定饱和浓度这一假设进行过测定。在活细胞内,聚合物丰富的多组分性质可能会使这一简单情况复杂化。

附:英文原文

Title: Composition-dependent thermodynamics of intracellular phase separation

Author: Joshua A. Riback, Lian Zhu, Mylene C. Ferrolino, Michele Tolbert, Diana M. Mitrea, David W. Sanders, Ming-Tzo Wei, Richard W. Kriwacki, Clifford P. Brangwynne

Issue&Volume: 2020-05-06

Abstract: Intracellular bodies such as nucleoli, Cajal bodies and various signalling assemblies represent membraneless organelles, or condensates, that form via liquid–liquid phase separation (LLPS)1,2. Biomolecular interactions—particularly homotypic interactions mediated by self-associating intrinsically disordered protein regions—are thought to underlie the thermodynamic driving forces for LLPS, forming condensates that can facilitate the assembly and processing of biochemically active complexes, such as ribosomal subunits within the nucleolus. Simplified model systems3,4,5,6 have led to the concept that a single fixed saturation concentration is a defining feature of endogenous LLPS7,8,9, and has been suggested as a mechanism for intracellular concentration buffering2,7,8,10. However, the assumption of a fixed saturation concentration remains largely untested within living cells, in which the richly multicomponent nature of condensates could complicate this simple picture. Here we show that heterotypic multicomponent interactions dominate endogenous LLPS, and give rise to nucleoli and other condensates that do not exhibit a fixed saturation concentration. As the concentration of individual components is varied, their partition coefficients change in a manner that can be used to determine the thermodynamic free energies that underlie LLPS. We find that heterotypic interactions among protein and RNA components stabilize various archetypal intracellular condensates—including the nucleolus, Cajal bodies, stress granules and P-bodies—implying that the composition of condensates is finely tuned by the thermodynamics of the underlying biomolecular interaction network. In the context of RNA-processing condensates such as the nucleolus, this manifests in the selective exclusion of fully assembled ribonucleoprotein complexes, providing a thermodynamic basis for vectorial ribosomal RNA flux out of the nucleolus. This methodology is conceptually straightforward and readily implemented, and can be broadly used to extract thermodynamic parameters from microscopy images. These approaches pave the way for a deeper understanding of the thermodynamics of multicomponent intracellular phase behaviour and its interplay with the nonequilibrium activity that is characteristic of endogenous condensates.

DOI: 10.1038/s41586-020-2256-2

Source: https://www.nature.com/articles/s41586-020-2256-2

Nature:《自然》,创刊于1869年。隶属于施普林格·自然出版集团,最新IF:69.504
官方网址:http://www.nature.com/
投稿链接:http://www.nature.com/authors/submit_manuscript.html


本期文章:《自然》:Online/在线发表

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