Synthetic Protein Condensates That Inducibly Recruit and Release Protein Activity in Living Cells.
23 Apr 2021-Journal of the American Chemical Society (American Chemical Society (ACS))-Vol. 143, Iss: 17, pp 6434-6446
TL;DR: In this article, a modular combination of a tandem fusion of two oligomeric proteins, which forms phase-separated synthetic protein condensates in cells, with a chemically induced dimerization tool, was presented.
Abstract: Compartmentation of proteins into biomolecular condensates or membraneless organelles formed by phase separation is an emerging principle for the regulation of cellular processes. Creating synthetic condensates that accommodate specific intracellular proteins on demand would have various applications in chemical biology, cell engineering, and synthetic biology. Here, we report the construction of synthetic protein condensates capable of recruiting and/or releasing proteins of interest in living mammalian cells in response to a small molecule or light. By a modular combination of a tandem fusion of two oligomeric proteins, which forms phase-separated synthetic protein condensates in cells, with a chemically induced dimerization tool, we first created a chemogenetic protein condensate system that can rapidly recruit target proteins from the cytoplasm to the condensates by addition of a small-molecule dimerizer. We next coupled the protein-recruiting condensate system with an engineered proximity-dependent protease, which gave a second protein condensate system wherein target proteins previously expressed inside the condensates are released into the cytoplasm by small-molecule-triggered protease recruitment. Furthermore, an optogenetic condensate system that allows reversible release and sequestration of protein activity in a repeatable manner using light was constructed successfully. These condensate systems were applicable to control protein activity and cellular processes such as membrane ruffling and ERK signaling in a time scale of minutes. This proof-of-principle work provides a new platform for chemogenetic and optogenetic control of protein activity in mammalian cells and represents a step toward tailor-made engineering of synthetic protein condensate-based soft materials with various functionalities for biological and biomedical applications.
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TL;DR: In this paper, multiple orthogonally translating organelles were designed that enable precise protein engineering inside living eukaryotic cells, and they were used to create mammalian cells with multiple expanded genetic codes.
17 citations
TL;DR: In this article, a methodology to form RNA-containing condensates in living cells with controlled RNA and protein composition is presented, based on physical constraints, provided by RNAs localized on condensate surface.
Abstract: Membrane-less organelles, by localizing and regulating complex biochemical reactions, are ubiquitous functional subunits of intracellular organization. They include a variety of nuclear and cytoplasmic ribonucleoprotein (RNP) condensates, such as nucleoli, P-bodies, germ granules and stress granules. While is it now recognized that specific RNA and protein families are critical for the biogenesis of RNP condensates, how these molecular constituents determine condensate size and morphology is unknown. To circumvent the biochemical complexity of endogenous RNP condensates, the use of programmable tools to reconstitute condensate formation with minimal constituents can be instrumental. Here we report a methodology to form RNA-containing condensates in living cells with controlled RNA and protein composition. Our bioengineered condensates are made of ArtiGranule scaffolds undergoing liquid-liquid phase separation in cells and programmed to specifically recruit a unique RNA species. We found that RNAs localized on condensate surface, either as isolated RNA molecules or as a homogenous corona of RNA molecules around the condensate. This simplified system allowed us to demonstrate that the size of the condensates scales with RNA surface density, the higher the RNA density is, the smaller and more frequent the condensates are. Our observations suggest a mechanism based on physical constraints, provided by RNAs localized on condensate surface, that limit condensate growth and coalescence.
17 citations
TL;DR: In this article , a methodology to form RNA-containing condensates in living cells programmed to specifically recruit a single RNA species is presented, which can be made of ArtiGranule scaffolds composed of an orthogonal protein that can bind to a specific heterologously expressed RNA.
15 citations
TL;DR: The potential impact of phase separation on drug discovery and RNA therapeutics, leveraging concrete examples, towards novel clinical opportunities was discussed in this paper . But, the authors did not consider the role of the condensates in the phase separation process.
13 citations
TL;DR: Li et al. as mentioned in this paper employed guanidinium perfunctionalized pillar[5]arene (GP5) for efficient delivery of proteins with different isoelectric points into different cell lines, and the bioactivities of the proteins were well maintained after intracellular delivery.
11 citations
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TL;DR: Fiji is a distribution of the popular open-source software ImageJ focused on biological-image analysis that facilitates the transformation of new algorithms into ImageJ plugins that can be shared with end users through an integrated update system.
Abstract: Fiji is a distribution of the popular open-source software ImageJ focused on biological-image analysis. Fiji uses modern software engineering practices to combine powerful software libraries with a broad range of scripting languages to enable rapid prototyping of image-processing algorithms. Fiji facilitates the transformation of new algorithms into ImageJ plugins that can be shared with end users through an integrated update system. We propose Fiji as a platform for productive collaboration between computer science and biology research communities.
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TL;DR: This work has shown that liquid–liquid phase separation driven by multivalent macromolecular interactions is an important organizing principle for biomolecular condensates and has proposed a physical framework for this organizing principle.
Abstract: In addition to membrane-bound organelles, eukaryotic cells feature various membraneless compartments, including the centrosome, the nucleolus and various granules. Many of these compartments form through liquid–liquid phase separation, and the principles, mechanisms and regulation of their assembly as well as their cellular functions are now beginning to emerge. Biomolecular condensates are micron-scale compartments in eukaryotic cells that lack surrounding membranes but function to concentrate proteins and nucleic acids. These condensates are involved in diverse processes, including RNA metabolism, ribosome biogenesis, the DNA damage response and signal transduction. Recent studies have shown that liquid–liquid phase separation driven by multivalent macromolecular interactions is an important organizing principle for biomolecular condensates. With this physical framework, it is now possible to explain how the assembly, composition, physical properties and biochemical and cellular functions of these important structures are regulated.
3,294 citations
TL;DR: The findings together suggest that several membrane-less organelles have been shown to exhibit a concentration threshold for assembly, a hallmark of phase separation, and represent liquid-phase condensates, which form via a biologically regulated (liquid-liquid) phase separation process.
Abstract: BACKGROUND Living cells contain distinct subcompartments to facilitate spatiotemporal regulation of biological reactions. In addition to canonical membrane-bound organelles such as secretory vesicles and endoplasmic reticulum, there are many organelles that do not have an enclosing membrane yet remain coherent structures that can compartmentalize and concentrate specific sets of molecules. Examples include assemblies in the nucleus such as the nucleolus, Cajal bodies, and nuclear speckles and also cytoplasmic structures such as stress granules, P-bodies, and germ granules. These structures play diverse roles in various biological processes and are also increasingly implicated in protein aggregation diseases. ADVANCES A number of studies have shown that membrane-less assemblies exhibit remarkable liquid-like features. As with conventional liquids, they typically adopt round morphologies and coalesce into a single droplet upon contact with one another and also wet intracellular surfaces such as the nuclear envelope. Moreover, component molecules exhibit dynamic exchange with the surrounding nucleoplasm and cytoplasm. These findings together suggest that these structures represent liquid-phase condensates, which form via a biologically regulated (liquid-liquid) phase separation process. Liquid phase condensation increasingly appears to be a fundamental mechanism for organizing intracellular space. Consistent with this concept, several membrane-less organelles have been shown to exhibit a concentration threshold for assembly, a hallmark of phase separation. At the molecular level, weak, transient interactions between molecules with multivalent domains or intrinsically disordered regions (IDRs) are a driving force for phase separation. In cells, condensation of liquid-phase assemblies can be regulated by active processes, including transcription and various posttranslational modifications. The simplest physical picture of a homogeneous liquid phase is often not enough to capture the full complexity of intracellular condensates, which frequently exhibit heterogeneous multilayered structures with partially solid-like characters. However, recent studies have shown that multiple distinct liquid phases can coexist and give rise to richly structured droplet architectures determined by the relative liquid surface tensions. Moreover, solid-like phases can emerge from metastable liquid condensates via multiple routes of potentially both kinetic and thermodynamic origins, which has important implications for the role of intracellular liquids in protein aggregation pathologies. OUTLOOK The list of intracellular assemblies driven by liquid phase condensation is growing rapidly, but our understanding of their sequence-encoded biological function and dysfunction lags behind. Moreover, unlike equilibrium phases of nonliving matter, living cells are far from equilibrium, with intracellular condensates subject to various posttranslational regulation and other adenosine triphosphate–dependent biological activity. Efforts using in vitro reconstitution, combined with traditional cell biology approaches and quantitative biophysical tools, are required to elucidate how such nonequilibrium features of living cells control intracellular phase behavior. The functional consequences of forming liquid condensates are likely multifaceted and may include facilitated reaction, sequestration of specific factors, and organization of associated intracellular structures. Liquid phase condensation is particularly interesting in the nucleus, given the growing interest in the impact of nuclear phase behavior on the flow of genetic information; nuclear condensates range from micrometer-sized bodies such as the nucleolus to submicrometer structures such as transcriptional assemblies, all of which directly interact with and regulate the genome. Deepening our understanding of these intracellular states of matter not only will shed light on the basic biology of cellular organization but also may enable therapeutic intervention in protein aggregation disease by targeting intracellular phase behavior.
2,432 citations
TL;DR: The basic physical concepts necessary to understand the consequences of liquid-like states for biological functions are discussed.
Abstract: Cells organize many of their biochemical reactions in non-membrane compartments. Recent evidence has shown that many of these compartments are liquids that form by phase separation from the cytoplasm. Here we discuss the basic physical concepts necessary to understand the consequences of liquid-like states for biological functions.
2,088 citations