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Search indexed bioRxiv preprints in genomics, neuroscience, cell biology and bioinformatics. Read source abstracts and check manuscript versions; preprints are not peer reviewed.

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bioRxiv2019

In-depth and 3-Dimensional Exploration of the Budding Yeast Phosphoproteome

Phosphorylation is one of the most dynamic and widespread post-translational modifications regulating virtually every aspect of eukaryotic cell biology. Here we present a comprehensive phosphoproteomic dataset for budding yeast, comprised of over 30,000 high confidence phosphorylation sites identified by mass spectrometry. This single dataset nearly doubles the size of the known phosphoproteome in budding yeast and defines a set of cell cycle-regulated phosphorylation events. With the goal of enhancing the identification of functional phosphorylation events, we performed computational positioning of phosphorylation sites on available 3D protein structures and systematically identified events predicted to regulate protein complex architecture. Results reveal a large number of phosphorylation sites mapping to or near protein interaction interfaces, many of which result in steric or electrostatic \"clashes\" predicted to disrupt the interaction. Phosphorylation site mutants experimentally validate our predictions and support a role for phosphorylation in negatively regulating protein-protein interactions. With the advancement of Cryo-EM and the increasing number of available structures, our approach should help drive the functional and spatial exploration of the phosphoproteome.

biochemistry↗

bioRxiv2019

Generation of Recombinant Mammalian Selenoproteins through Genetic Code Expansion with Photocaged Selenocysteine

Selenoproteins contain the amino acid selenocysteine and are found in all domains of life. The functions of many selenoproteins are poorly understood, partly due to difficulties in producing recombinant selenoproteins for cell-biological evaluation. Endogenous mammalian selenoproteins are produced through a non-canonical translation mechanism requiring suppression of the UGA stop codon, and a selenocysteine insertion sequence (SECIS) element in the 3 untranslated region of the mRNA. Here, recombinant selenoproteins are generated in mammalian cells through genetic code expansion, circumventing the requirement for the SECIS element, and selenium availability. An engineered orthogonal E. coli leucyl-tRNA synthetase/tRNA pair is used to incorporate a photocaged selenocysteine (DMNB-Sec) at the UAG amber stop codon. Recombinantly expressed selenoproteins can be photoactivated in living cells with spatial and temporal control. Using this approach, the native selenoprotein methionine-R-sulfoxide reductase 1 is generated and activated in mammalian cells. The ability to site-specifically introduce selenocysteine directly in mammalian cells, and temporally modulate selenoprotein activity, will aid in the characterization of mammalian selenoprotein function.

biochemistry↗

bioRxiv2026

MinJ is a conserved nine-pass transmembrane protein that contains a putative transmembrane β-sheet

The Min system disassembles FtsZ-rings after septation in Bacillus subtilis and is localized to the nascent division plane and cell poles by the protein MinJ. The N-terminal region of MinJ contains transmembrane segments while the C-terminal region of MinJ contains a PDZ domain but its topology and functional domains are poorly understood. Here we empirically test MinJ topology based on a variety of transmembrane prediction models and find that the data is most consistent with Alphafold3, which predicts a 9-pass transmembrane protein with an external N-terminus and internal C-terminus. Deletion analysis indicates that all regions of the protein tested are required for function but deletion of the PDZ domain alone preserves polar localization and interaction with both MinD and DivIVA. Moreover, Alphafold predicts that transmembrane segments 6 and 7 comprise staves of an unusual transmembrane {beta}-sheet and deletion of the putative {beta}-sheet in the absence of MinD results in a minicell frequency that exceeds mutation of MinD alone. Bioinformatic analysis indicates that MinJ is highly conserved within Firmicutes and is co-conserved with MinD and DivIVA with which it interacts. Our data clarify the structure of MinJ and support models in which MinJ has functions in addition to restricting the activity of the Min system. IMPORTANCEFaithful positioning of the bacterial division site is important for cell growth and is coordinated by the conserved Min system. Although the Min system of Bacillus subtilis has been extensively studied, MinJ, the membrane protein that links the division inhibitor MinCD to the polar determinant DivIVA, remains the least well-understood. Here we experimentally define the membrane topology of MinJ and show that our data are most consistent with a nine-pass transmembrane architecture predicted by AlphaFold3. We further provide genetic, cell biological, and evolutionary evidence supporting that two of the staves form a highly conserved putative transmembrane {beta}-sheet, a structure normally excluded from the plasma membrane. Our findings refine MinJ structural organization and provide a framework for understanding its conserved functions in bacterial cell division.

microbiology↗

bioRxiv2023

Development and utilization of new O2-independent bioreporters

Fluorescent proteins have revolutionized science since their discovery in 1962. They have enabled imaging experiments to decipher the function of proteins, cells and organisms, as well as gene regulation. GFP and all its derivatives are now standard tools in cell biology, immunology, molecular biology and microbiology laboratories around the world. A common feature of these proteins is their O2-dependent maturation allowing fluorescence, which precludes their use in anoxic contexts. In this work, we report the development and in cellulo characterization of genetic circuits encoding the O2-independent KOFP-7 protein, a flavin-binding fluorescent protein. We have optimized the genetic circuit for high bacterial fluorescence at population and single-cell level, implemented this circuit in various plasmids differing in host range, and quantified their fluorescence under both aerobic and anaerobic conditions. Finally, we showed that KOFP-7 based constructions can be used to produce fluorescing cells of V. diazotrophicus, a facultative anaerobe, demonstrating the usefulness of the genetic circuits for various anaerobic bacteria. These genetic circuits can thus be modified at will, both to solve basic and applied research questions, opening a highway to shed light on the obscure anaerobic world. ImportanceFluorescent proteins are used since decades, and have allowed major discoveries in biology in a wide variety of fields, and are used in environmental as well as clinical contexts. GFP and all its derivatives share a common feature: they rely on the presence of O2 for protein maturation and fluorescence. This dependency precludes their use in anoxic environments. Here, we constructed a series of genetic circuits allowing production of KOFP-7, an O2-independant Flavin-Binding Fluorescent Protein. We demonstrated that Escherichia coli cells producing KOFP-7 are fluorescent, both at the population and single-cell levels. Importantly, we showed that, unlike cells producing GFP, cells producing KOFP-7 are fluorescent in anoxia. Finally, we demonstrated that Vibrio diazotrophicus NS1, a facultative anaerobe, is fluorescent in the absence of O2 when KOFP-7 is produced. Altogether, the development of new genetic circuits allowing O2-independent fluorescence will open new perspective to study anaerobic processes.

molecular biology↗

bioRxiv2021

Comprehensive Benchmarking of CITE-seq versus DOGMA-seq Single Cell Multimodal Omics

The recently developed transcription, epitopes, and chromatin accessibility by sequencing (TEA-seq) and similar DOGMA-seq single-cell trimodal omics assays provide unprecedented opportunities for understanding cell biology, but independent optimization, benchmarking and evaluation are lacking. We explored the utility, pros and cons of DOGMA-seq compared to the bimodal cellular indexing of transcriptomes and epitopes by sequencing (CITE-seq) assay in activated and stimulated human peripheral blood T cells. We identified an optimal incubation time and concentration of digitonin (DIG) for cell permeabilization and found that single-cell trimodal omics measurements after DIG permeabilization were generally better than after an alternative "low-loss lysis" (LLL) permeabilization condition. Next, we found that DOGMA-seq with optimized DIG permeabilization and its ATAC library provides more information, even though its mRNA and cell surface protein antibody-derived tag (ADT) libraries have slightly inferior quality, compared to CITE-seq. Finally, we recognized the additional value of DOGMA-seq for studying lineage-specific T helper cells.

genomics↗

bioRxiv2023

Automatic Detection of Cell-cycle Stages using Recurrent Neural Networks

Mitosis is the process by which eukaryotic cells divide to produce two similar daughter cells with identical genetic material. Research into the process of mitosis is therefore of critical importance both for the basic understanding of cell biology and for the clinical approach to manifold pathologies resulting from its malfunctioning, including cancer. In this paper, we propose an approach to study mitotic progression automatically using deep learning. We used neural networks to predict different mitosis stages. We extracted video sequences of cells undergoing division and trained a Recurrent Neural Network (RNN) to extract image features. The use of RNN enabled better extraction of features. The RNN-based approach gave better performance compared to classifier based feature extraction methods which do not use time information. Evaluation of precision, recall, and F-score indicates the superiority of the proposed model compared to the baseline. To study the loss in performance due to confusion between adjacent classes, we plotted the confusion matrix as well, to quantify the amount of misclassification. In addition, we visualized the feature space to understand why RNNs are better at classifying the mitosis stages than other classifier models, which indicated the formation of strong clusters for the different classes, clearly confirming the advantage of the proposed RNN-based approach.

bioinformatics↗

bioRxiv2023

Trifunctional sphinganine: a new tool to dissect sphingolipid function

Functions of the sphingolipids sphingosine and sphinganine in cells are not well established. While some signaling roles for sphingosine have been elucidated, the closely related sphinganine has been described only insofar as it does not elicit many of the same signaling responses. The underlying mechanisms behind the cell biological differences between these lipids are not well understood. Here, we prepared multifunctionalized derivatives of the two lipid species that only differ in a single double bond of the carbon backbone. Using these novel probes, we were able to define their spatiotemporal distribution within cells. Furthermore, we used these tools to systematically map the protein interactomes of both lipids. The lipid-protein conjugates, prepared through photo-crosslinking in live cells and extraction via click chemistry to azide beads, revealed significant differences in the captured proteins, highlighting their distinct roles in various cellular processes. This work elucidates mechanistic differences between these critical lipids and sets the foundation for further studies on the functions of sphingosine and sphinganine.

biochemistry↗

bioRxiv2025

Generating cognate epitope sequences of T-cell receptors with a generative transformer

Single-cell TCR sequencing enables high-resolution analysis of T Cell Receptor (TCR) diversity and clonality, offering valuable insights into immune responses and disease mechanisms. However, identifying cognate epitopes for individual TCRs requires complex and costly functional assays. We address this challenge with EpitopeGen, a largescale transformer model based on the GPT-2 architecture that generates potential cognate epitope sequences directly from TCR sequences. To overcome the scarcity of TCR-epitope binding pairs ({approx} 100, 000), EpitopeGen uses a semi-supervised learning method, termed BINDSEARCH, which searches over 70 billion potential pairs and incorporates high binding affinity predictions as pseudo-labels. To incorporate CD8+ T cell biology into the model as an inductive bias, EpitopeGen employs a novel data balancing method, termed Antigen Category Filter, that carefully controls antigen category ratios in its training dataset. EpitopeGen significantly outperforms baseline approaches, generating epitopes with high binding affinity, diversity, naturalness, and biophysical stability. Notably, the epitopes generated by EpitopeGen follow biologically plausible antigen category distributions, a crucial feature not achieved by other models. Using EpitopeGen, we directly identify subsets of clonally expanded tumorinfiltrating lymphocytes that recognize tumor-associated antigens, exhibiting elevated cytotoxicity and reduced exhaustion markers. From COVID-19 patients, EpitopeGen detects T cells that recognize COVID-19 spike proteins and non-structural proteins with distinct transcriptomic characteristics. In conclusion, EpitopeGen represents the first computational method that enables direct inference of antigen recognition profiles of CD8+ T cells from plain TCR repertoires.

immunology↗

bioRxiv2025

Zinc deficiency induces spatially distinct responses in roots and impacts ZIP12-dependent zinc homeostasis in Arabidopsis

How zinc (Zn) deficiency shapes root development remains unclear, with conflicting reports on its effect on primary root growth in Arabidopsis thaliana (Arabidopsis). The impact of Zn shortage on the root apical meristem (RAM) in particular has not been systematically explored. Using an integrative approach combining cell biology, transcriptomics, and ionomics, we dissected how Zn deficiency alters root zonation and function. We showed that Zn deficiency triggers a striking reorganization of the root tip (RT): the RAM size is reduced, yet meristematic activity and local Zn levels are preserved. This is accompanied by promoted cell elongation and differentiation. Transcriptome profiling revealed a distinct Zn deficiency response in the RAM-enriched RT compared to mature root tissues, with ZIP12 emerging as the most strongly induced gene in the RT. Functional analysis of zip12 mutants uncovered major defects in root growth, RAM structure, expression of Zn-responsive genes, and metal partitioning. Our work unveiled a new layer of root developmental plasticity under Zn deficiency and identified ZIP12 as a central player in maintaining Zn homeostasis and root meristem function in Arabidopsis. These findings provide a framework to better understand how plants adapt root growth to fluctuating micronutrient availability.

plant biology↗

bioRxiv2025

Endothelial decorin is increased by ageing and, induces inflammation and diastolic dysfunction in the heart

AimsCardiovascular disease is the leading cause of death in the European Union and aging is one of its major risk factors resulting in the progressive deterioration of the cardiac structures and function. Here, we have combined single-nucleus-RNA-sequencing, imaging, and molecular and cell biology approaches to explore the maladaptive signals that drive cardiac ageing. Methods and resultsSingle-nucleus-RNA-sequencing analysis of young (3 months) and old (18 months) murine hearts revealed that the expression of decorin, a secreted proteoglycan expressed in the extracellular matrix of endothelial cells, is induced by ageing. Decorin treatment via osmotic mini-pump induced diastolic dysfunction and a pro-inflammatory environment in the myocardium characterized by increased infiltration of immune cells, increased expression of IL- 1{beta} in endothelial cells and microvascular leakage in 3 months old mice. In vitro, decorin treatment induces cardiomyocyte hypertrophy, the expression of different pro-inflammatory cytokines like IL1B in endothelial cells, and compromises the endothelial barrier function. ConclusionsTogether, our results identify decorin as a novel player contributing to cardiac aging and disease. Decorin contributes to the age-related structural and functional dysfunction of the heart by inducing a pro-inflammatory environment in the myocardial microvasculature, a hallmark of cardiac ageing. Translational perspectiveAgeing is a major risk factor of cardiovascular disease and the molecular and cellular mechanisms that drive this process have not been completely described. The data presented here identifies decorin as a novel player contributing to systemic inflammation and microvascular dysfunction, two hallmarks of ageing. Although, because of its role regulating TGF-{beta} signalling, decorin has been proposed for anti-fibrotic therapies, the pro-inflammatory effects observed on the cardiac microvasculature should be taken into account for the employment of decorin as an antifibrotic agent to treat disease associated cardiac fibrosis.

physiology↗

bioRxiv2025

rapunzel5 is necessary for normal hematopoietic development in zebrafish

The molecular mechanisms regulating the highly complex process of hematopoiesis in vertebrates is still enigmatic. This system begins with the controlled differentiation of adult hematopoietic stem and progenitor cells (HSPCs), which can proliferate and generate all types of mature blood cells. Identifying the underlying factors and mechanisms that allow HSPCs to differentiate and proliferate is an essential issue in stem cell biology and tissue homeostasis; disruptions in these processes can cause severe diseases. A transcriptomic screen of hematopoietic-supportive zebrafish stromal tissues identified rapunzel5 (rpz5) was likely involved in vertebrate hematopoiesis. We performed loss-of-function experiments in zebrafish embryos at the one-cell-stage with morpholinos to determine if blood cell production was affected by rpz5. rpz5 knockdown resulted in reduced amounts of red blood cells, myeloid cells, and thrombocytes, and adding back exogenous rpz5 rescued these deficiencies. Further analysis with methylcellulose assays indicated that there was also a significant reduction in HSPCs following rpz5 reduction. Together, these findings suggest that zebrafish rpz5 is essential for normal formation, differentiation, and proliferation of HSPCs, specifically down the erythroid and myeloid pathway. Fully understanding the roles of novel genes such as rpz5 is essential for understanding the evolution of vertebrate hematopoiesis and for treating hematological diseases in the future.

genetics↗

bioRxiv2020

Formation of flavone-based wooly fibres by glandular trichomes of Dionysia tapetodes.

Dionysia tapetodes, a small cushion-forming mountainous evergreen in the Primulaceae, possesses a vast surface-covering of long silky fibres forming the characteristic "wooly" farina. This contrasts with some related Primula which instead possess a powdery farina. Using a combination of cell biology and analytical chemical techniques, we provide a detailed insight of wooly farina formation by glandular trichomes that produce a mixture of flavone and substituted flavone derivatives, including hydroxyflavones. Conversely, our analysis show that the powdery form consist almost entirely of flavone. The wooly farina in D. tapetodes is extruded through specific sites at the surface of the glandular head cell, characterised by a small complete gap in the plasma membrane, cell wall and cuticle. The data is consistent with formation and thread elongation occurring from within the cell. The putative mechanism of wool thread formation and its stability is discussed.

plant biology↗

bioRxiv2015

In planta expression screens of candidate effector proteins from the wheat yellow rust fungus reveal processing bodies as a pathogen-targeted plant cell compartment

Rust fungal pathogens of wheat (Triticum spp.) affect crop yields worldwide. The molecular mechanisms underlying the virulence of these pathogens remain elusive, due to the limited availability of suitable molecular genetic research tools. Notably, the inability to perform high-throughput analyses of candidate virulence proteins (also known as effectors) impairs progress. We previously established a pipeline for the fast-forward screens of rust fungal effectors in the model plant Nicotiana benthamiana. This pipeline involves selecting candidate effectors in silico and performing cell biology and protein-protein interaction assays in planta to gain insight into the putative functions of candidate effectors. In this study, we used this pipeline to identify and characterize sixteen candidate effectors from the wheat yellow rust fungal pathogen Puccinia striiformis f sp tritici. Nine candidate effectors targeted a specific plant subcellular compartment or protein complex, providing valuable information on their putative functions in plant cells. One candidate effector, PST02549, accumulated in processing bodies (P-bodies), protein complexes involved in mRNA decapping, degradation, and storage. PST02549 also associates with the P-body-resident ENHANCER OF mRNA DECAPPING PROTEIN 4 (EDC4) from N. benthamiana and wheat. Our work identifies P-bodies as a novel plant cell compartment targeted by pathogen effectors.

Plant Biology↗

bioRxiv2020

BrainPhys neuronal medium optimized for imaging and optogenetics in vitro

The capabilities of imaging technologies, fluorescent sensors, and optogenetics tools for cell biology have improved exponentially in the last ten years. At the same time, advances in cellular reprogramming and organoid engineering have quickly expanded the use of human neuronal models in vitro. Altogether this creates an increasing need for tissue culture conditions better adapted to live-cell imaging. Here, we identified multiple caveats of traditional media when used for live imaging and functional assays on neuronal cultures (e.g., phototoxicity, suboptimal fluorescence signals, and unphysiological neuronal activity). To overcome these issues, we developed a new neuromedium, "BrainPhys Imaging", in which we adjusted fluorescent and phototoxic compounds. The new medium is based on the formulation of the original BrainPhys medium, which we designed to better support the neuronal activity of human neurons in vitro 1. We tested the new imaging-optimized formulation on human neurons cultured in monolayers or organoids, and rat primary neurons. BrainPhys Imaging enhanced fluorescence signals and reduced phototoxicity throughout the entire light spectrum. Importantly, consistent with standard BrainPhys, we showed that the new imaging medium optimally supports the electrical and synaptic activity of midbrain and human cortical neurons in culture. We also benchmarked the capacity of the new medium for functional calcium imaging and optogenetic control of human neurons. Altogether, our study shows that the new BrainPhys Imaging improves the quality of a wide range of fluorescence imaging applications with live neurons in vitro while supporting cell viability and neuronal functions.

neuroscience↗

bioRxiv2022

Linking cells across single-cell modalities by synergistic matching of neighborhood structure

A wide variety of experimental methods are available to characterize different properties of single cells in a complex biosample. However, because these measurement techniques are typically destructive, researchers are often presented with complementary measurements from disjoint subsets of cells, providing a fragmented view of the cells biological processes. This creates a need for computational tools capable of integrating disjoint multi-omics data. Because different measurements typically do not share any features, the problem requires the integration to be done in unsupervised fashion. Recently, several methods have been proposed that project the cell measurements into a common latent space and attempt to align the corresponding low-dimensional manifolds. In this study we present an approach, Synmatch, which produces a direct matching of the cells between modalities by exploiting information about neighborhood structure in each modality. Synmatch relies on the intuition that cells which are close in one measurement space should be close in the other as well. This allows us to formulate the matching problem as a constrained supermodular optimization problem over neighborhood structures that can be solved efficiently. We show that our approach successfully matches cells in small real multi-omics datasets and performs favorably when compared to recently published state-of-the-art methods. Further, we demonstrate that Synmatch is capable of scaling to large datasets of thousands of cells. The Synmatch code and data used in this manuscript are available at https://github.com/orgs/Noble-Lab/synmatch

genomics↗

bioRxiv2026

Objective method to estimate the duration of the DNAreplication cycle without perturbation in Escherichia coli.

All cells, including unicellular organisms such as Escherichia coli, depend on the robustness of their cell cycle for proliferation. The cell cycle is central to the organisms highly resilient proliferation program and is thus a key focus in many areas of cell biology. However, studying the DNA replication cycle in bacteria remains challenging due to technical limitations. The durations of the replicative and post-replicative phases (known as the C and D periods, respectively) are inferred from the analysis of cellular DNA content distributions, obtained through microscopy or flow cytometry. This analysis typically requires pharmacological treatments to conduct replication run-off experiments, which help distinguish between cells that have or have not yet initiated DNA replication. Four decades ago, Skarstad, Steen and Boye showed that flow cytometry profiles measuring DNA amount per cell from exponentially growing cells could provide sufficient information to infer the durations of cell cycle periods at low growth rates. In this study, we propose an objective and automated approach that implements this idea to estimate cell cycle parameters for any growth conditions. Specifically, we validate a Nested Sampling method to estimate cell cycle parameters directly from flow cytometry data, eliminating the dependence on bacterial strain sensitivity to drugs. This tool, available as a Python package, allows for the accurate and minimally biased estimation of the C+D period under any biologically relevant conditions. Given its independence from pharmacological treatments, we anticipate broad adoption of this tool, especially as we show that most natural isolates of E. coli are not amenable to the state of the art replication run-off experiments.

microbiology↗

bioRxiv2024

Ionizable networks mediate pH-dependent allosteryin SH2 signaling proteins

Intracellular pH dynamics regulate normal cell biology, but most molecular drivers remain unknown. We developed a computational pipeline to identify pH-sensitive proteins and their mechanisms. We applied the pipeline to SHP2, a pH-sensitive signaling protein, with unknown mechanism. We found that SHP2 phosphatase activity is pH-sensitive in vitro and in cells, and mutation of identified His116 and Glu252 abolishes pH-sensitive function. We also discovered that Src is an unrecognized pH-dependent kinase and mutation of the identified ionizable network abolishes pH-sensitive activity. Importantly, we found that Src kinase activity was pH sensitive even in the presence of EGF and with a phosphomimetic (Src-Y527E) mutant required for auto-inhibitory SH2 domain binding. Thus, the identified pH-sensitive regulation of Src kinase activity functions in concert with established mechanisms of Src regulation by phosphorylation. Constant pH molecular dynamics simulations performed on both SHP2 and Src support allosteric regulation mediated by pH-dependent binding of inhibitory SH2 domains to the respective catalytic domains. Finally, we show that evolutionarily conserved putative pH-sensing networks were identified across SH2 domain-containing signaling proteins. Taken together, our computational, biophysical, and cellular analyses reveal a role for pHi dynamics in allosterically regulating activity of modular SH2 signaling proteins to control biology. One-sentence summaryThis paper investigates the role of pH in the allosteric regulation of signaling proteins with SH2 domains, specifically focusing on SHP2 and Src

biochemistry↗

bioRxiv2024

A proximity ligation screen identifies SNAT2 as a novel target of the MARCH1 E3 ubiquitin ligase

E3 ubiquitin ligases are part of various families of proteins and include hundreds of members, which play key roles in all aspects of cell biology. They generally regulate the half-life of other proteins but can also modulate their cellular localization and functions. The MARCH family of ubiquitin ligases is composed of 11 members and two closely related proteins, MARCH1 and MARCH8, share similar targets, while being active in different cell types. Although they appear to target principally immune cell components, such as MHC class II molecules and the co-stimulatory molecule CD86, the repertory of their targets remains to be fully documented. Here, to further define the MARCH1s interactome, we adapted a proximity-dependent biotin identification (BioID)-based screening approach in live HEK293 cells. We transfected a fusion protein consisting of mouse MARCH1 linked to YFP at its N-terminus and to the biotin ligase of Aquifex aeolicus at its C-terminus. Upon transient overexpression of this construct in the presence of exogenous biotin, we could recover biotinylated proteins that are presumably found within 10nm of MARCH1. To help in the identification of bona fide down-regulated specific targets, we compared MARCH1s interactome with the one obtained using a ubiquitination-deficient MARCH1 mutant (MARCH1W104A). CD98 and CD71, two previously described targets of MARCH1, were identified in this screen. Of 16 other biotinylated proteins identified by semi-quantitative mass spectrometry, 10 were tested directly by flow cytometry to monitor their expression in the presence or absence of transfected MARCH1. The protein levels of five of these endogenous targets, CD29, CD112, NKCC1, CD147 and SNAT2, confirmed their negative regulation by MARCH1 in this system. SNAT2 was particularly sensitive to the presence of MARCH1 and was found to be ubiquitinated on Western blots following immunoprecipitation. Thus, BioID2 is an effective mean of characterizing the interactome of MARCH1 and the identification of SNAT2 suggests a role of this ubiquitin ligase in cellular metabolism.

immunology↗