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Unraveling Plant Nuclear Envelope Composition Using Proximity Labeling Proteomics.

The nuclear envelope (NE) defines the eukaryotic cell and functions in a myriad of fundamental cellular processes including but not limited to signal transduction, lipid metabolism, chromatin organization, and nucleocytoplasmic transportation. Although the general structure of the NE is well-conserved across eukaryotic kingdoms, its composition and functions vary substantially between species and remain largely unknown in plants. In this chapter, we describe a proximity-labeling-based proteomic approach to profile novel NE components in the model organism Arabidopsis. This method is generally suitable for the identification of protein components in subcellular compartments or protein complexes that are poorly accessible to traditional mass spectrometry approaches and can be easily applied to other plant species. In addition to giving a step-by-step detailed description of the proximity labeling proteomics procedure in plant samples, we also provide guidelines on the appropriate use of controls and statistical analysis to achieve a highly specific selection of probed candidates.

Proteomics

CRISPR-Enabled functional genomics in hPSCs-derived neural models for autism spectrum disorder.

Autism Spectrum Disorder (ASD) is a genetically heterogeneous neurodevelopmental condition in which hundreds of individually rare risk variants converge on a small number of shared biological pathways, including synaptic scaffolding, chromatin remodeling, excitation-inhibition balance, and cellular energy metabolism. Translating this genetic heterogeneity into mechanistic insight requires experimental systems capable of interrogating individual gene functions in human-relevant neural contexts at scale. CRISPR-enabled functional genomics in human pluripotent stem cell (hPSC)-derived neural models, spanning neural progenitors, cortical and inhibitory neurons, astrocytes, microglia, and brain organoids, provides precisely this capability. By integrating pooled perturbation screens with multimodal readouts including single-cell and spatial transcriptomics, chromatin accessibility profiling, proximity labeling proteomics, multi-electrode array electrophysiology, and metabolic flux analysis, these platforms enable systematic, causal mapping of ASD gene function at system resolution. Early applications have already revealed convergent mechanisms: BAF complex disruption expands the ventral progenitor pool and biases its fate toward oligodendrocyte and interneuron lineages; ADNP loss impairs microglial synaptic pruning through altered endocytic trafficking; and mTOR pathway dysregulation in PTEN- and TSC2-perturbed models links genetic risk directly to metabolic and mitochondrial dysfunction. Computational frameworks including MIMOSCA and SCEPTRE enable causal network reconstruction and pseudotime inference from these datasets, moving the field from gene lists toward pathway-level models of ASD pathobiology. Translational applications leverage isogenic iPSC panels and variant-level base and prime editing to stratify ASD variants by functional impact, informing gene therapy design for haploinsufficient targets such as CHD8 and SCN2A via AAV or antisense oligonucleotide delivery. Remaining challenges, including model developmental immaturity, batch variability, and the difficulty of modeling polygenic risk, are addressed by a roadmap integrating spatial perturbomics, AI-driven causal inference, and population-scale standardized biobanks. This review synthesizes the current state of CRISPR-based functional genomics in human stem cell neural models as a coherent experimental framework for converting ASD genetic associations into mechanistic understanding and therapeutic opportunity.

Humans

The critical role of PSAC channel in malaria parasite survival is driven home by phenotypic screening under relevant nutrient levels.

Spreading resistance to front-line treatments necessitate the search for new classes of antimalarials. Limitations of standard screening conditions lead us to develop an assay using culture media that more closely reflects nutrient levels in human serum to reveal new therapeutically relevant parasite pathways. Our approach was validated by testing 22k compounds followed by a full 750k compound screen and identified 29 chemotypes with higher activity in nutrient restricted media that were further characterized. Through a combination of chemo-genomics and innovative photocatalytic proximity labeling proteomics, we identified the target of two compounds as the CLAG3 component of the plasmodial surface anion channel (PSAC). Strikingly, every one of the other 29 chemotypes selected was also found to block PSAC activity, highlighting the importance of this nutrient channel for parasite survival under physiological conditions. The effect of PSAC inhibitors in the in vivo humanized mouse model was confirmed.

Animals

FGF13 is not secreted from mouse neurons.

FGF13, a noncanonical fibroblast growth factor (FGF) and member of the fibroblast growth factor homologous factor (FHF) subset, lacks a signal sequence and was previously reported to remain intracellular, where it regulates voltage-gated sodium channels (VGSCs) at least in part through direct interaction with the cytoplasmic C-terminus of VGSCs. Recent reports suggest FGF13 is secreted and regulates neuronal VGSCs through interactions with extracellular domains of integral plasma membrane proteins, yet supportive data are limited. Using rigorous positive and negative controls, we show that transfected FGF13 is not secreted from cultured cells in a heterologous expression system, nor is endogenous FGF13 secreted from cultured neurons. Furthermore, using multiple unbiased screens including proximity labeling proteomics, our results suggest FGF13 remains within membranes and is unavailable to interact directly with extracellular protein domains.

Animals

Differential assembly of RNP granules via activation of distinct dsRNA sensors by adenovirus mutants.

Recognition of double-stranded RNA (dsRNA) triggers antiviral defense mediated by PKR and OAS3/RNase L pathways through translational arrest and RNA decay. This is accompanied by assembly of distinct cytoplasmic ribonucleoprotein (RNP) condensates termed stress granules (SGs) and RNase L-dependent bodies (RLBs). Here we show that adenovirus mutants engage distinct RNA-sensing pathways and promote differential assembly of cytoplasmic RNP granules. Infection with splicing-defective ∆E4 mutant leads to dsRNA accumulation and activation of both PKR and OAS3/RNase L, promoting formation of RLB-like granules. In contrast, mutants lacking virus-associated (VA) RNAs trigger PKR activation and assembly of SGs despite absence of detectable dsRNA. Proximity labeling proteomic analysis revealed distinct protein compositions of canonical SGs and RLBs, which were reflected in virus-induced granules. While ∆VA-induced granules were PKR-dependent, ∆E4 mutants induced RLB-like granules independently of PKR and RNase L. In cells lacking these sensors, granule assembly during ∆E4 infection coincided with translational arrest independent of eIF2α phosphorylation, indicating additional pathways linking nuclear dsRNA sensing to translational control and RNP granule assembly during viral infection. These findings provide novel insights into how distinct dsRNA sensors modulate translation and RNP condensates in response to stress.

RNA, Double-Stranded

Proximity Proteomics to Profile Ebola Virus Protein Interactome in Its Functional Context.

Proximity labeling-based proteomics (proximity proteomics) has emerged as a popular and versatile approach to illuminate the molecular interactions between viruses and their hosts. In this approach, a proximity labeling enzyme tag is fused to a bait protein and labels neighboring proteins with a chemical handle such as biotin, allowing for downstream affinity purification. Compared to another widely used technique, affinity purification coupled mass spectrometry, proximity proteomics enables the detection of low affinity or transient interactors that might have important functions in the viral life cycle. Further, proximity proteomics can identify interactors of a labile bait protein, of which affinity purification is technically challenging. Here, we describe a proximity proteomic protocol to identify cellular interactors of the Ebola virus polymerase. A similar strategy is readily applicable to elucidate the virus-host interactions for Marburg virus.

Ebolavirus

Antibody-Based Proximity Labeling Reveals Bait-Proximal Proteomes in Paraffin-Embedded and Snap-Frozen Tissue Samples.

Proximity-based labeling approaches have proven highly valuable for uncovering protein-protein interactions, yet their application to primary patient material remains challenging. Here, we present a workflow enabling the use of the antibody-based ProtA-Turbo proximity labeling system in both formalin-fixed paraffin-embedded (FFPE) and snap-frozen tissue specimens. Our method efficiently directs biotinylation to diverse antibody baits across tissues of different origins. Downstream mass spectrometry-based proteomics analyses demonstrate the specificity of the method by profiling the proximal proteome of H3K27ac-marked chromatin, the nuclear lamina-associated protein EMD, and the Ser2-phosphorylated POLR2A subunit of RNA polymerase II. Using this method, we identified cell-type-specific factors and transcriptional regulators in salivary gland carcinoma, healthy testis, and testicular cancer tissue sections. The ability to detect disease-associated complexes directly within their native, spatially resolved cellular context using ProtA-Turbo can provide new insights into the molecular basis of human disease and may reveal novel, potentially actionable factors with translational relevance.

Humans

Spatiotemporally resolved GPCR interactome uncovers unique mediators of receptor agonism.

Cellular signaling by membrane G protein-coupled receptors (GPCRs) is governed by a complex and diverse array of mechanisms. The dynamics of a GPCR interactome, as it evolves over time and space in response to an agonist, provide a unique perspective on pleiotropic signaling decoding and functional selectivity at the cellular level. In this study, we utilized proximity-based APEX2 proteomics to investigate the interaction network of the luteinizing hormone receptor (LHR) on a minute-to-minute timescale. We developed an analytical approach that integrates quantitative multiplexed proteomics with temporal reference profiles, creating a platform to identify the proteomic environment of APEX2-tagged LHR at the nanometer scale. LHR activity is finely regulated spatially, leading to the identification of putative interactors, including the Ras-related GTPase RAP2B, which modulate both receptor signaling and post-endocytic trafficking. This work provides a valuable resource for spatiotemporal nanodomain mapping of LHR interactors across subcellular compartments.

Humans

From stem cells to somites: Revealing genetic and exogenous factors of human embryogenesis.

Stem-cell-based human embryo models offer an ethically tractable platform for studying early human development. This study employs somitoids, three-dimensional models of human somitogenesis, to investigate how transcriptional programs and culture conditions influence somite formation and segmentation. We show that pre-differentiation culture medium impacts the developmental potential of induced pluripotent stem cells (iPSCs), with StemFit medium and Matrigel embedding outperforming mTeSR Plus medium in generating robust somite-like structures. Strikingly, these differences arise despite only subtle changes in transcriptomic and time-resolved proteomic profiles. P300-based proximity labeling also reveals a largely overlapping set of chromatin-associated regulators across iPSC conditions. In somitoids, enhancer-associated profiling highlights factors linked to somitogenesis, including MESP2 and TBX6. Knockout of three identified regulators, BPTF, RBPJ, and CITED2, demonstrate their essential roles in somite formation. Together, these findings highlight how culture conditions and enhancer-associated networks influence early human development and demonstrate somitoids as a scalable system for functional genomics.

Humans

Dual proximity-based interactome mapping of FKBP51 and FKBP52 uncovers shared metabolic networks.

The 51 kDa FK506-binding protein (FKBP51) has been studied for its involvement in regulating multiple biological systems, particularly as a regulator of steroid hormone receptors, but roles in metabolism, pain response, cell survival, protein turnover, autophagy, immune response, and insulin signaling have also been described. Genetic variants of FKBP51 are associated with various stress-related mental disorders. While recent research has clarified aspects of these processes, the complete range of FKBP51 interactions remains undetermined. FKBP52, a closely related homolog, also affects similar pathways. Recent studies have identified new protein partners for FKBP51 and FKBP52, suggesting an even broader interactome with transient associations. To further characterize interactions, TurboID-based proximity labeling was performed in HeLa cells. Proteomic analysis confirmed known FKBP51 and FKBP52 interactions, while also identifying additional shared and unique binding partners with strong enrichment in metabolic pathways, amino acid biosynthesis, and carbon metabolism. Although FKBP51 and FKBP52 proximal proteins were primarily cytosolic, FKBP51 showed additional associations with exosomal proteins while FKBP52 engaged with additional nuclear proteins. These findings highlight the overlapping roles in metabolic signaling and differentiate pathway-specific partners.

Tacrolimus Binding Proteins

Spatial Proteomics Using BiFCPL Identifies Regulators of DMV Formation Involved in Coronavirus Replication.

β-Coronaviruses hijack host factors to remodel host endo-membranes to form double membrane vesicles (DMVs), which act as central hubs for the replication of viral genomes. Understanding the molecular mechanism underlying DMV formation is critical for developing effective antiviral strategies and has garnered significant attention. However, the host factors involved in DMV formation remain scanty. Here, we employed a bimolecular fluorescence complementation-based proximity labeling (BiFCPL) strategy to investigate the proteome of DMVs generated by co-expression of SARS-CoV-2 NSP3 and NSP4. Our analysis identified 62 proteins with high confidence, among which five proteins were localized in the endoplasmic reticulum (ER), and were further confirmed to be recruited to DMVs through interactions with NSP3/NSP4. Moreover, we demonstrated that the absence of GRAMD1B or TEX2 resulted in the formation of enlarged DMVs induced by either NSP3/NSP4 or coronaviruses infection, and impaired coronaviruses replication as well. Collectively, our study concerning host-virus interactions sheds light on novel host factors involved in DMV formation.

Virus Replication

Resolving cellular signaling in space and time: From organelle proteomics to spatial phosphoproteomics.

Cellular signaling is inherently organized in space and time, requiring coordinated control of protein localization, molecular interactions, and enzymatic activity across subcellular compartments. Recent advances in chemical biology, protein engineering, and quantitative proteomics have made it possible to interrogate these dimensions in an integrated manner. Here, we highlight emerging strategies to resolve signaling organization across three interconnected dimensions: organelle-resolved proteome mapping to define spatial context, proximity labeling to capture local protein interaction networks, and spatially resolved phosphoproteomics to quantify signaling outputs. Developments in proximity labeling, including split, conditionally activated and light-gated enzymes, enable temporally controlled, context-dependent profiling of transient protein assemblies in living cells. Advances in high-throughput and low-input phosphoproteomics, together with improved computational frameworks for kinase activity inference and subcellular enrichment strategies, are enabling spatially resolved measurement of signaling activity. Together, these approaches are shifting the field from static localization maps toward dynamic models of signaling networks.

Proteomics

Targeting STK17B kinase activates ferroptosis and suppresses drug resistance in multiple myeloma.

The progression of multiple myeloma (MM), an incurable malignancy of plasma cells, is often associated with the suppression of ferroptosis, a type of cell death driven by iron-dependent lipid peroxidation. The mechanisms underlying this suppression remain largely unknown. Here, we identified serine/threonine kinase 17b (STK17B) kinase as a critical suppressor of ferroptosis in MM. Elevated levels of STK17B are associated with poor overall survival in patients with MM, and STK17B expression is significantly higher in relapsed vs newly diagnosed MM cases. We found that inhibiting STK17B in MM cells increased the labile iron pool, enhanced lipid peroxidation, and sensitized cells to conventional anti-MM therapies. Notably, an orally available, in-house-generated STK17B inhibitor induced ferroptosis and significantly reduced tumor growth in MM xenograft mouse models. Mechanistically, proximity labeling assay combined with the phospho-proteomic analysis identified 2 major regulators of iron uptake and transport as direct targets of STK17B: iron-responsive element binding protein 2 (IREB2), and heat shock protein family B member 1 (HSPB1). We demonstrated that STK17B phosphorylates critical regulatory sites on IREB2 (S157) and HSPB1 (S15), thereby modulating the balance between IREB2 and HSPB1 downstream effectors, proferroptotic transferrin receptor, and antiferroptotic ferritin heavy chain proteins. Furthermore, we demonstrated that STK17B indirectly maintains activating phosphorylation of STAT3, a ferroptosis suppressor and a major driver of MM pathobiology. Our findings uncovered a clinically relevant and targetable STK17B-pIREB2S157/pHSPB1S15 signaling axis that suppresses ferroptosis and contributes to drug resistance in MM.

Ferroptosis

Photocatalytic Golgi Proteomics Reveals Palmitoylation-Regulated Golgiphagy.

The Golgi apparatus (GA) orchestrates protein modification, trafficking, and secretion through highly dynamic remodeling, yet its proteomic complexity remains difficult to resolve in living systems. Here, we report CAT-Golgi, a genetically independent and light-controlled photocatalytic proximity labeling strategy for in situ spatiotemporal mapping of the Golgi-associated proteome. Combining a cysteine-conjugated eosin photocatalyst (GolgiCat) with an aniline probe, CAT-Golgi enables rapid and precise protein labeling within minutes under mild green light, requiring no genetic manipulation and operating efficiently in hard-to-transfect and primary cells. Leveraging our extensive efforts in organelle-targeted photocatalytic systems, we extended this chemistry to the highly dynamic and reversible Golgi apparatus. CAT-Golgi achieved quantitative and comparative proteomics in HeLa, K562, Jurkat and primary HEKa cells, revealing both conserved and cell-type-specific profiles. Under Brefeldin A-induced Golgiphagy, CAT-Golgi captured large-scale proteome remodeling and identified palmitoyl-protein thioesterase 1 (PPT1) as a potential regulatory component. PPT1 downregulation enhanced ULK1 and TRPML1 palmitoylation, disrupted redox balance, and activated Golgiphagy. CAT-Golgi provides a broadly applicable chemical platform for decoding organelle dynamics, offering both conceptual and technical foundations for extending photocatalytic proteomics to other transient organelles and illuminating molecular mechanisms of organelle plasticity and disease progression.

Golgi Apparatus

Comprehensive proximity proteomics expand the known interactome of the oncoprotein β-catenin.

The oncoprotein β-catenin has critical roles in cell adhesion and cell signalling. β-catenin affects human physiology and pathology through numerous interaction partners, of which many have been discovered by standard affinity purification-based proteomics. However, the interaction landscape of β-catenin remains incompletely understood, highlighting a need for new experimental approaches for the exploration of β-catenin biology. Proximity proteomics, which facilitate the discovery of molecules vicinal to proteins-of-interest by mass spectrometry, have recently emerged as a powerful complementary tool for the study of protein-protein interactions, but have not been applied to β-catenin so far. We investigated the interactome of β-catenin in model cell lines by proximity proteomics using expression constructs with the biotin ligases BioID and TurboID. Mass spectrometry analyses following biotin labelling identified numerous candidate interactors of β-catenin, including many that had not been observed in earlier studies using standard proteomics. Enrichment analyses suggested that proximity proteomics capture proteins associated with the known biological functions of β-catenin, including cell adhesion, Wnt/β-catenin signalling, and transcription regulation. The molecular tools and data generated in this study provide new insights into β-catenin biology and highlight potential new regulators of β-catenin function that warrant further exploration.

beta Catenin

Mapping the FOXA1 Interactome in ER+ Breast Cancer Cells Using Proximity Labeling Reveals Novel Interactions with the Orphan Nuclear Receptor NR2C2.

UNLABELLED: FOXA1 is a pioneer transcription factor essential for chromatin accessibility and transcriptional regulation in hormone-driven cancers. In breast cancer, FOXA1 plays a central role in facilitating nuclear receptor binding, reprogramming enhancer landscapes, and promoting transcriptional changes associated with therapy resistance. Whereas FOXA1's function has been primarily studied in the context of estrogen receptor-α (ER), its broader protein interaction network remains incompletely defined. In this study, we systematically map FOXA1-interacting proteins in ER-positive breast cancer cells using proximity-dependent biotin labeling (miniTurbo) combined with quantitative LC-MS/MS proteomics. We engineered MCF-7 cell lines stably expressing miniTurbo-tagged FOXA1 at either the N-terminus or C-terminus to ensure comprehensive coverage of interaction interfaces. This approach recovered known FOXA1 partners, including AR, MLL3, YAP1, and GATA3, and identified 157 previously unreported FOXA1 interactors. Notably, 42 of these novel partners, including NR2C2, were significantly associated with poor relapse-free survival in patients with ER-positive breast cancer. To demonstrate the utility of this resource, we characterized the FOXA1-NR2C2 interaction in depth. Integrating chromatin immunoprecipitation sequencing and RNA sequencing, we show that FOXA1 and NR2C2 co-occupy a subset of genomic regions and drive co-regulated transcriptional programs involved in tumor progression. Our study reveals an expanded FOXA1 interactome and new insights into its functional network in breast cancer, providing candidate proteins for further exploration as biomarkers or therapeutic targets. IMPLICATIONS: These findings expand the FOXA1 interactome in breast cancer and uncover new candidate proteins with potential as biomarkers and therapeutic targets in hormone-driven tumors.

Humans

Proximity labeling puts ZFP36L1 as central hub for posttranscriptional regulation networks in T cells.

Effective T cell responses against pathogens require a rapid yet tightly controlled remodeling of the proteome, and RNA binding proteins (RBPs) are key in this process. For instance, the RBP ZFP36L1 prevents excessive protein production and thereby limits immunopathology. ZFP36L1 is primarily known to mediate mRNA decay, but it can also regulate other processes. How its mode of action relates to its interaction partners is, however, not well-understood. Here, we mapped the ZFP36L1 interactome in primary human T cells. Using proximity labeling, we identified known and new interactors that regulate 3'UTR-mediated RNA degradation, deadenylation, stress granule/p-body formation, as well as 5'UTR-mediated translation repression and mRNA decapping. Snapshot analysis uncovered the ZFP36L1 interactome dynamics and RNA (in)dependency throughout T cell activation. Intriguingly, proximity labeling also uncovered regulators of ZFP36L1 protein expression. This included the helicase UPF1, which not only interacts with ZFP36L1 protein but that may also promote its protein expression. Altogether, this comprehensive interactome map underlines the versatility of interactions with ZFP36L1 and their possible role in cellular function.

Humans

Integrative proximal-ubiquitomics profiling for deubiquitinase substrate discovery applied to USP30.

The growing interest in deubiquitinases (DUBs) as drug targets for modulating critical molecular pathways in disease is fueled by the discovery of their specific cellular roles. A crucial aspect of this fact is the identification of DUB substrates. While mass spectrometry-based proteomic methods can be used to study global changes in cellular ubiquitination following DUB activity perturbation, these datasets often include indirect and downstream ubiquitination events. To enrich for the direct substrates of DUB enzymes, we have developed a proximal-ubiquitome workflow that combines proximity labeling methodology (ascorbate peroxidase-2 [APEX2]) with subsequent ubiquitination enrichment based on the K-ε-GG motif. We applied this technology to identify altered ubiquitination events in the vicinity of the DUB ubiquitin-specific protease 30 (USP30) upon its inhibition. Our findings reveal ubiquitination events previously associated with USP30 on TOMM20 and FKBP8, as well as the candidate substrate LETM1, which is deubiquitinated in a USP30-dependent manner.

Humans