Curated Optogenetic Publication Database

Abstract: G protein-coupled receptors (GPCRs) are the largest class of receptors in the genome and control many signaling cascades essential for survival. GPCR signaling is regulated by β-arrestins, multifunctional adapter proteins that direct receptor desensitization, internalization, and signaling. While at many GPCRs, β-arrestins interact with a wide array of signaling effectors, it is unclear how β-arrestins promote such varied functions. Here we show that β-arrestins undergo liquid-liquid phase separation (LLPS) to form condensates that regulate GPCR function. We demonstrate that β-arrestin oligomerization occurs in proximity to the GPCR and regulates GPCR functions such as internalization and signaling. This model is supported by a cryoEM structure of the adhesion receptor ADGRE1 in a 2:2 complex with β-arrestin 1, with a β-arrestin orientation that can promote oligomerization. Our work provides a paradigm for β-arrestin condensates as regulators of GPCR function, with LLPS serving as an important promoter of signaling compartmentalization at GPCRs.

Abstract: Pyroptosis, an inflammatory form of cell death, is associated with large cell swelling and plasma membrane rupture. Recently, such swelling has been shown to occur in a two steps fashion, but the precise molecular and biophysic mechanisms driving the process remain elusive. We demonstrate through advanced quantitative microscopy that, between the two swelling phases, cell volume stabilizes, while plasma membrane permeability to ions and small molecules is markedly elevated due to the formation of pores. From a biophysical perspective, how such a volume plateau exists is puzzling as ion pumps should not regulate the cell volume in these conditions. To address this, we developed a physical model based on an ions pump-and-leak framework, incorporating the dynamics of non-selective pore formation. We experimentally identify two distinct pore permeability dynamics, associated to an increase in the water filtration coefficient and to an ion selectivity decrease due to pore opening. Altogether our results suggest the existence of two mechanistically different pore types, likely driven by separate molecular players. Our findings provide fundamental insights into the biophysics of cell death and may have broader implications for understanding membrane rupture in other pathological contexts. Significance Statement: Among various programmed lytic cell death, pyropytosis is marked by dramatic changes in cell shape and large fluctuations in volume, fundamentally altering the cell’s physical properties. These biophysical changes are not mere byproducts but integral components of the death process, closely interacting with molecular events. By combining optogenetics, quantitative microscopy, and modeling, we show that a progressive increase in plasma membrane permeability alone drives cell swelling and membrane lysis. We therefore demonstrate that a deeper understanding of these dynamic cell modifications and their consequences will shed light on the molecular and biophysical mechanisms driving different forms of cell death.

Abstract: While optogenetic tools have recently opened new avenues for controlling and understanding cellular behavior, Suh et al.1 present an effective strategy to regulate tissue densification and outgrowth through optogenetic control of EGFR. Their work ultimately uncovers fundamental principles that pave the way for improved tissue engineering approaches.

Abstract: Lipids are a major class of biological molecules, the primary components of cellular membranes, and critical signaling molecules that regulate cell biology and physiology. Due to their dynamic behavior within membranes, rapid transport between organelles, and complex and often redundant metabolic pathways, lipids have traditionally been considered among the most challenging biological molecules to study. In recent years, a plethora of tools bridging the chemistry-biology interface has emerged for studying different aspects of lipid biology. Here, we provide an overview of these approaches. We discuss methods for lipid detection, including genetically encoded biosensors, synthetic lipid analogs, and metabolic labeling probes. For targeted manipulation of lipids, we describe pharmacological agents and controllable enzymes, termed membrane editors, that harness optogenetics and chemogenetics. To conclude, we survey techniques for elucidating lipid-protein interactions, including photoaffinity labeling and proximity labeling. Collectively, these strategies are revealing new insights into the regulation, dynamics, and functions of lipids in cell biology.

Abstract: Optogenetics has substantially enhanced our understanding of biological processes by enabling high-precision tracking and manipulation of individual cells. It relies on photosensitive proteins to monitor and control cellular activities, thereby paving the way for significant advancements in complex system research. Photosensitive proteins play a vital role in the development of optogenetics, facilitating the establishment of cutting-edge methods. Recent breakthroughs in protein design have opened up opportunities to develop protein-based tools that can precisely manipulate and monitor cellular activities. These advancements will significantly accelerate the development and application of optogenetic tools. This article emphasizes the pivotal role of protein design in the development of optogenetic tools, offering insights into potential future directions. We begin by providing an introduction to the historical development and fundamental principles of optogenetics, followed by an exploration of the operational mechanisms of key photosensitive domains, which includes clarifying the conformational changes they undergo in response to light, such as allosteric modulation and dimerization processes. Building on this foundation, we reveal the development of protein design tools that will enable the creation of even more sophisticated optogenetic techniques.

Abstract: In cancer cells, ATR signaling is crucial to tolerate the intrinsically high damage levels that normally block replication fork progression. Assembly of TopBP1, a multifunctional scaffolding protein, into condensates is required to amplify ATR kinase activity to the levels needed to coordinate the DNA damage response and manage DNA replication stress. Many ATR inhibitors are tested for cancer treatment in clinical trials, but their overall effectiveness is oven compromised by the emergence of resistance and toxicities. In this proof-of-concept study, we propose to disrupt the ATR pathway by targeting TopBP1 condensation. First, we screened a molecule-based library using a previously developed optogenetic approach and identified several TopBP1 condensation inhibitors. Amongst them, AZD2858 disrupted TopBP1 assembly induced by the clinically relevant topoisomerase I inhibitor SN-38, thereby inhibiting the ATR/Chk1 signaling pathway. We found that AZD2858 exerted its effects by disrupting TopBP1 self-interaction and binding to ATR in mammalian cells, and by increasing its chromatin recruitment n cell-free Xenopus laevis egg extracts. Moreover, AZD2858 prevented S-phase checkpoint induction by SN-38, leading to increased DNA damage and apoptosis in a colorectal cancer cell line. Lastly, AZD2858 showed synergistic effect in combination with the FOLFIRI chemotherapy regimen in a spheroid model of colorectal cancer.

Abstract: Cells process dynamic signaling inputs to regulate fate decisions during development. While oscillations or waves in key developmental pathways, such as Wnt, have been widely observed the principles governing how cells decode these signals remain unclear. By leveraging optogenetic control of the Wnt signaling pathway in both HEK293T cells and H9 human embryonic stem cells, we systematically map the relationship between signal frequency and downstream pathway activation. We find that cells exhibit a minimal response to Wnt at certain frequencies, a behavior we term anti-resonance. We developed both detailed biochemical and simplified hidden variable models that explain how anti-resonance emerges from the interplay between fast and slow pathway dynamics. Remarkably, we find that frequency directly influences cell fate decisions involved in human gastrulation; signals delivered at anti-resonant frequencies result in dramatically reduced mesoderm differentiation. Our work reveals a previously unknown mechanism of how cells decode dynamic signals and how anti-resonance may filter against spurious activation. These findings establish new insights into how cells decode dynamic signals with implications for tissue engineering, regenerative medicine, and cancer biology.

Abstract: Optogenetics is an emerging technology that uses the light-responsive effects of photosensitive proteins to regulate the function of specific cells. This technique combines genetics with optics, allowing for the precise inhibition or activation of cell functions through the introduction of photosensitive proteins into target cells and subsequent light stimulation to activate these proteins. In recent years, numerous basic and clinical studies have demonstrated the unique advantages of this approach in the research and treatment of neurological disorders. This review aims to introduce the fundamental principles and techniques of optogenetics, as well as its applications in the research and treatment of neurological diseases.

Abstract: Necroptosis plays a crucial role in the progression of various diseases and has gained substantial attention for its potential to activate antitumor immunity. However, the complex signaling networks that regulate necroptosis have made it challenging to fully understand its mechanisms and translate this knowledge into therapeutic applications. To address these challenges, an optogenetically activatable necroptosis system is developed that allows for precise spatiotemporal control of key necroptosis regulators, bypassing complex upstream signaling processes. The system, specifically featuring optoMLKL, demonstrates that it can rapidly assemble into functional higher-order "hotspots" within cellular membrane compartments, independent of RIPK3-mediated phosphorylation. Moreover, the functional module of optoMLKL significantly enhances innate immune responses by promoting the release of iDAMPs and cDAMPs, which are critical for initiating antitumor immunity. Furthermore, optoMLKL exhibits antitumor effects when activated in patient-derived pancreatic cancer organoids, highlighting its potential for clinical application. These findings will pave the way for innovative cancer therapies by leveraging optogenetic approaches to precisely control and enhance necroptosis.

Abstract: The regulation of PKC epsilon (PKCε) and its downstream effects is still not fully understood, making it challenging to develop targeted therapies or interventions. A more precise tool that enables spatiotemporal control of PKCε activity is thus required. Here, we describe a photo-activatable optogenetic PKCε probe (Opto-PKCε) consisting of an engineered PKCε catalytic domain and a blue-light inducible dimerization domain. Molecular dynamics and AlphaFold simulations enable rationalization of the dark-light activity of the optogenetic probe. We first characterize the binding partners of Opto-PKCε, which are similar to those of PKCε. Subsequent validation of the Opto-PKCε tool is performed with phosphoproteome analysis, which reveals that only PKCε substrates are phosphorylated upon light activation. Opto-PKCε could be engineered for recruitment to specific subcellular locations. Activation of Opto-PKCε in isolated hepatocytes reveals its sustained activation at the plasma membrane is required for its phosphorylation of the insulin receptor at Thr1160. In addition, Opto-PKCε recruitment to the mitochondria results in its lowering of the spare respiratory capacity through phosphorylation of complex I NDUFS4. These results demonstrate that Opto-PKCε may have broad applications for the studies of PKCε signaling with high specificity and spatiotemporal resolution.

Abstract: Cells under high confinement form highly polarized hydrostatic pressure-driven, stable leader blebs that enable efficient migration in low adhesion, environments. Here we investigated the basis of the polarized bleb morphology of metastatic melanoma cells migrating in non-adhesive confinement. Using high-resolution time-lapse imaging and specific molecular perturbations, we found that EGF signaling via PI3K stabilizes and maintains a polarized leader bleb. Protein activity biosensors revealed a unique EGFR/PI3K activity gradient decreasing from rear-to-front, promoting PIP3 and Rac1-GTP accumulation at the bleb rear, with its antagonists PIP2 and RhoA-GTP concentrated at the bleb tip, opposite to the front-to-rear organization of these signaling modules in integrin-mediated mesenchymal migration. Optogenetic experiments showed that disrupting this gradient caused bleb retraction, underscoring the role of this signaling gradient in bleb stability. Mathematical modeling and experiments identified a mechanism where, as the bleb initiates, CD44 and ERM proteins restrict EGFR mobility in a membrane-apposed cortical actin meshwork in the bleb rear, establishing a rear-to-front EGFR-PI3K-Rac activity gradient. Thus, our study reveals the biophysical and molecular underpinnings of cell polarity in bleb-based migration of metastatic cells in non-adhesive confinement, and underscores how alternative spatial arrangements of migration signaling modules can mediate different migration modes according to the local microenvironment.

Abstract: Collective cell migration and tissue morphogenesis play a variety of important roles in the development of many species. Tissue morphogenesis often generates mechanical forces that alter cell shapes and arrangements, resembling collective cell migration-like behaviors. Genetic methods have been widely used to study collective cell migration and its like behavior, advancing our understanding of these processes during development. However, a growing body of research shows that collective cell migration during development is not a simple behavior but is often combined with other cellular and tissue processes. In addition, different surrounding environments can also influence migrating cells, further complicating collective cell migration during development. Due to the complexity of developmental processes and tissues, traditional genetic approaches often encounter challenges and limitations. Thus, some methods with spatiotemporal control become urgent in dissecting collective cell migration and tissue morphogenesis during development. Optogenetics is a method that combines optics and genetics, providing a perfect strategy for spatiotemporally controlling corresponding protein activity in subcellular, cellular or tissue levels. In this review, we introduce the basic mechanisms underlying different optogenetic tools. Then, we demonstrate how optogenetic methods have been applied in vivo to dissect collective cell migration and tissue morphogenesis during development. Additionally, we describe some promising optogenetic approaches for advancing this field. Together, this review will guide and facilitate future studies of collective cell migration in vivo and tissue morphogenesis by optogenetics.

Abstract: Immunotherapy, the medicinal modulation of a host's immune response to better combat a pathogen or disease, has transformed cancer treatments in recent decades. T-cells, an important component of the adaptive immune system, are further paramount for therapy success. Recent immunotherapeutic modalities have therefore more frequently targeted T-cells for cancer treatments and other pathologies and are termed adoptive T-cell (ATC) therapies. ATC therapies characterize various types of immunotherapies but predominantly fall into three established techniques: tumour-infiltrating lymphocyte, chimeric antigen receptor T-cell, and engineered T-cell receptor therapies. Despite promising clinical results, all ATC therapy types fall short in providing long-term sustained tumour clearance while being particularly ineffective against solid tumours, with substantial developments aiming to understand and prevent the typical drawbacks of ATC therapy. Optogenetics is a relatively recent development, incorporating light-sensitive protein domains into cells or tissues of interest to optically tune specific biological processes. Optogenetic manipulation of immunological functions is rapidly becoming an investigative tool in immunology, with light-sensitive systems now being used to optimize many cellular therapeutic modalities and ATC therapies. This review focuses on how optogenetic approaches are currently utilized to improve ATC therapy in clinical settings by deepening our understanding of the molecular rationale behind therapy success. Moreover, this review further critiques current immuno-optogenetic systems and speculates on the expansion of recent developments, enhancing current ATC-based therapeutic modalities to pave the way for clinical progress.

Abstract: Research for biopharmaceutical production processes with mammalian cells steadily aims to enhance the cell-specific productivity as a means for optimizing total productivities of bioreactors. Whereas current technologies such as pH, temperature, and osmolality shift require modifications of the cultivation medium, the use of optogenetic switches in recombinant producer cells might be a promising contact-free alternative. However, the proper application of optogenetically engineered cells requires a detailed understanding of basic cellular responses of cells that do not yet contain the optogenetic switches. The knowhow of ideal light exposure to enable the optimum use of related approaches is missing so far. Consequently, the current study set out to find optimum conditions for IgG1 producing Chinese hamster ovary (CHO) cells which were exposed to blue LED light. Growth characteristics, cell-specific productivity using enzyme-linked immunosorbent assay, as well as cell cycle distribution using flow cytometry were analyzed. Whereas too harsh light exposure causes detrimental growth effects that could be compensated with antioxidants, a surprising boost of cell-specific productivity by 57% occurred at optimum high light doses. The increase coincided with an increased number of cells in the G1 phase of the cell cycle after 72 h of illumination. The results present a promising new approach to boost biopharmaceutical productivity of mammalian cells simply by proper light exposure without any further optogenetic engineering. KEY POINTS: • Blue LED light hinders growth in CHO DP-12 cells • Antioxidants protect to a certain degree from blue light effects • Illumination with blue LED light raises cell-specific productivity.

Abstract: Mutations of the cyclin-dependent kinase-like 5 (CDKL5) gene, which encodes a serine/threonine protein kinase, can cause the CDKL5 deficiency disorder (CDD), a severe neurodevelopmental disease characterized by epileptic encephalopathy and neurocognitive impairment. The CDKL5 kinase consists of a catalytic N-terminal domain (NTD) and a less characterized C-terminal domain (CTD). Numerous disease-related mutations truncate CDKL5, leaving the NTD intact while variably shortening the CTD, which highlights the importance of the CTD for CDKL5 function. By systematically analyzing CDKL5 compositional features and evolutionary dynamics, we found that the CTD is a low-complexity region (LCR) highly enriched in serine residues and with a high propensity to undergo liquid-liquid phase separation (LLPS), a biophysical process of condensation controlling protein localization and function. Using a combination of super-resolution imaging, electron microscopy, and molecular and cellular approaches, including optogenetic LLPS induction, we discovered that CDKL5 undergoes LLPS, predominantly driven by its CTD, forming membraneless condensates in neuronal and non-neuronal cells. A CTD internal fragment (CTIF) plays a pivotal LLPS-promoting role, along with the distal portion of the protein. Indeed, two disease-related truncating mutations (S726X and R781X), eliding variable portions of the CTIF, significantly impair LLPS. This impairment is paralleled at the functional level by a reduction in the CDKL5-dependent phosphorylation of EB2, a known CDKL5 target. These findings demonstrate that CDKL5 undergoes LLPS, driven by a CTD region elided by most disease-related truncating mutations. Its loss––through the impairment of CDKL5 LLPS and functional activity––may play a key role in the molecular pathogenesis of CDD.

Abstract: The post-translational modification of intracellular proteins through O-linked β-N-acetylglucosamine (O-GlcNAc) is a conserved regulatory mechanism in multicellular organisms. Catalyzed by O-GlcNAc transferase (OGT), this dynamic modification has an essential role in signal transduction, gene expression, organelle function and systemic physiology. Here, we present Opto-OGT, an optogenetic probe that allows for precise spatiotemporal control of OGT activity through light stimulation. By fusing a photosensitive cryptochrome protein to OGT, Opto-OGT can be robustly and reversibly activated with high temporal resolution by blue light and exhibits minimal background activity without illumination. Transient activation of Opto-OGT results in mTORC activation and AMPK suppression, which recapitulate nutrient-sensing signaling. Furthermore, Opto-OGT can be customized to localize to specific subcellular sites. By targeting OGT to the plasma membrane, we demonstrate the downregulation of site-specific AKT phosphorylation and signaling outputs in response to insulin stimulation. Thus, Opto-OGT is a powerful tool for defining the role of O-GlcNAcylation in cell signaling and physiology.

Abstract: Dysfunction of the RNA binding protein heterogeneous nuclear ribonucleoprotein A1 (hnRNP A1) contributes to neurodegeneration, the primary cause of permanent disability in multiple sclerosis (MS). To better understand the role of hnRNP A1 dysfunction in the pathogenesis of neurodegeneration, we utilized optogenetics-driven hnRNP A1 clustering to model its dysfunction in neuron-like differentiated Neuro-2A cells. hnRNP A1 clustering activates the integrated stress response (ISR) and results in a neurodegenerative phenotype marked by decreased neuronal protein translation and neurite loss. Small molecule inhibition of the ISR with either PERKi (GSK2606414) or ISRIB (integrated stress response inhibitor) attenuated both the decrease in neuronal translation and neurite loss, without affecting hnRNP A1 clustering. We then confirmed a strong association between hnRNP A1 clustering and ISR activation in neurons from MS brains. These data illustrate that hnRNP A1 dysfunction promotes neurodegeneration by activation of the ISR in vitro and in vivo, thus revealing a novel therapeutic target to reduce neurodegeneration and subsequent disability in MS.

Abstract: Alternative splicing is a fundamental process that contributes to the functional diversity and complexity of proteins. The regulation of each alternative splicing event involves the coordinated action of multiple RNA-binding proteins, creating a diverse array of alternatively spliced products. Dysregulation of alternative splicing is associated with various diseases, including neurodegeneration. Here we demonstrate that CELF2, a splicing regulator and a GWAS-identified risk factor for Alzheimer’s disease, binds to mRNAs associated with neurodegenerative diseases, with a specific interaction observed in the intron adjacent to exon 10 on Tau mRNA. Loss of CELF2 in the mouse brain results in a decreased inclusion of Tau exon 10, leading to a reduced 4R:3R ratio. Further exploration shows that the hinge domain of CELF2 possesses an intrinsically disordered region (IDR), which mediates CELF2 condensation and function. The functionality of IDR in regulating CELF2 function is underscored by its substitutability with IDRs from FUS and TAF15. Using TurboID we identified proteins that interact with CELF2 through its IDR. We revealed that CELF2 co-condensate with NOVA2 and SFPQ, which coordinate with CELF2 to regulate the alternative splicing of Tau exon 10. A negatively charged residue within the IDR (D388), which is conserved among CELF proteins, is critical for CELF2 condensate formation, interactions with NOVA2 and SFPQ, and function in regulating tau exon 10 splicing. Our data allow us to propose that CELF2 regulates Tau alternative splicing by forming condensates through its IDR with other splicing factors, and that the composition of the proteins within the condensates determines the outcomes of alternative splicing events.

Abstract: Cells use signalling pathways as windows into the environment to gather information, transduce it into their interior, and use it to drive behaviours. MAPK (ERK) is a highly conserved signalling pathway in eukaryotes, directing multiple fundamental cellular behaviours such as proliferation, migration, and differentiation, making it of few central hubs in the signalling circuitry of cells. Despite this versatility of behaviors, population-level measurements have reported low information content (< 1 bit) relayed through the ERK pathway, rendering the population barely able to distinguish the presence or absence of stimuli. Here, we contrast the information transmitted by a single cell and a population of cells. Using a combination of optogenetic experiments, data analysis based on information theory framework, and numerical simulations we quantify the amount of information transduced from the receptor to ERK, from responses to singular, brief and sparse input pulses. We show that single cells are indeed able to resolve between graded stimuli, yielding over 2 bit of information, however showing a large population heterogeneity

Abstract: Biomolecular condensates appear throughout cell physiology and pathology, but the specific role of condensation or its dynamics is often difficult to determine. Optogenetics offers an expanding toolset to address these challenges, providing tools to directly control condensation of arbitrary proteins with precision over their formation, dissolution, and patterning in space and time. In this review, we describe the current state of the field for optogenetic control of condensation. We survey the proteins and their derivatives that form the foundation of this toolset, and we discuss the factors that distinguish them to enable appropriate selection for a given application. We also describe recent examples of the ways in which optogenetic condensation has been used in both basic and applied studies. Finally, we discuss important design considerations when engineering new proteins for optogenetic condensation, and we preview future innovations that will further empower this toolset in the coming years.

Abstract: When mammalian cells are exposed to extracellular stress, they coordinate the condensation of stress granules (SGs) through the action of key nucleating proteins G3BP1 and G3BP2 (G3BPs) and, simultaneously, undergo a massive reduction in translation.1-5 Although SGs and G3BPs have been linked to this translation response, their overall impact has been unclear. Here, we investigate the longstanding question of how, and indeed whether, G3BPs and SGs shape the stress translation response. We find that SGs are enriched for mRNAs that are resistant to the stress-induced translation shutdown. Although the accurate recruitment of these stress-resistant mRNAs does require the context of stress, a combination of optogenetic tools and spike-normalized ribosome profiling demonstrates that G3BPs and SGs are necessary and sufficient to both help prioritize the translation of their enriched mRNAs and help suppress cytosolic translation. Together these results support a model in which G3BPs and SGs reinforce the stress translation program by prioritizing the translation of their resident mRNAs.

Abstract: Immediately after fertilization the genome is transcriptionally quiescent. Maternally encoded pioneer transcription factors reprogram the chromatin state and facilitate the transcription of the zygotic genome. In Drosophila, transcription is initiated by the pioneer factor Zelda. While Zelda-occupied sites are enriched with histone acetylation, a post-translational mark associated with active cis-regulatory regions, the functional relationship between Zelda and histone acetylation in zygotic genome activation remained unclear. We show that Zelda-mediated recruitment of the histone acetyltransferase CBP is essential for zygotic transcription. CBP catalytic activity is necessary for release of RNA Polymerase II (Pol II) into transcription elongation and for embryonic development. However, CBP also activates zygotic transcription independent of acetylation through Pol II recruitment. Neither acetylation nor CBP are required for the pioneering function of Zelda. Our data suggest that pioneer factor-mediated recruitment of CBP is a conserved mechanism required to activate zygotic transcription but that this role is separable from the function of pioneer factors in restructuring chromatin accessibility.

Abstract: RNA molecules play a vital role in linking genetic information with various cellular processes. In recent years, a variety of optogenetic tools have been engineered for regulating cellular RNA metabolism and functions. These highly desirable tools can offer non-intrusive control with spatial precision, remote operation, and biocompatibility. Here, we would like to review these currently available approaches that can regulate RNAs with light: from non-genetically encodable chemically modified oligonucleotides to genetically encoded RNA aptamers that recognize photosensitive small-molecule or protein ligands. Some key applications of these optogenetic tools will also be highlighted to illustrate how they have been used for regulating all aspects of the RNA life cycle: from RNA synthesis, maturation, modification, and translation to their degradation, localization, and phase separation control. Some current challenges and potential practical utilizations of these RNA optogenetic tools will also be discussed.

Abstract: Proteinaceous inclusions formed by C9orf72-derived dipeptide-repeat (DPR) proteins are a histopathological hallmark in ∼50% of familial amyotrophic lateral sclerosis/frontotemporal dementia (ALS/FTD) cases. However, DPR aggregation/inclusion formation could not be efficiently recapitulated in cell models for four out of five DPRs. In this study, using optogenetics, we achieved chemical-free poly-PR condensation/aggregation in cultured cells including human motor neurons, with spatial and temporal control. Strikingly, nuclear poly-PR condensates had anisotropic, hollow-center appearance, resembling TDP-43 anisosomes, and their growth was limited by RNA. These condensates induced abnormal TDP-43 granulation in the nucleus without stress response activation. Cytoplasmic poly-PR aggregates forming under prolonged opto-stimulation were more persistent than its nuclear condensates, selectively sequestered TDP-43 in a demixed state and surrounded spontaneous stress granules. Thus, poly-PR condensation accompanied by nuclear TDP-43 dysfunction may constitute an early pathological event in C9-ALS/FTD. Anisosome-type condensates of disease-linked proteins may represent a common molecular species in neurodegenerative disease.

Abstract: Actin homeostasis is fundamental for cell structure and consumes a large portion of cellular ATP. It has been documented in the literature that certain glycolytic enzymes can interact with actin, indicating an intricate interplay between the cytoskeleton and cellular metabolism. Here we report that hyperosmotic stress triggers actin severing and subsequent phase separation of the actin-binding protein TPM4. TPM4 condensates glycolytic enzymes such as HK2, PFKM, and PKM2, and adhere to and wrap around actin filaments. Notably, the condensates of TPM4 and glycolytic enzymes are enriched of NADH and ATP, suggestive of their functional importance in cell metabolism. At cellular level, actin filaments assembly is enhanced upon hyperosmotic stress and TPM4 condensation, while depletion of TPM4 impaired osmolarity-induced actin reorganization. At tissue level, co-localized condensates of TPM4 and glycolytic enzymes are observed in renal tissues subjected to hyperosmotic stress. Together, our findings suggest that stress-induced actin perturbation may act on TPM4 to organize glycolytic hubs that tether energy production to cytoskeletal reorganization.