Biology subjects

Ivarsson, Y.

Publications and source records attributed to Ivarsson, Y..

At least 19 recordsLinked to original sources

bioRxiv2026

An Atlas of Short Linear Motif-Mediated Human Protein-Protein Interactions

Short linear motifs (SLiMs) within intrinsically disordered protein regions mediate transient interactions crucial for cell physiology1. However, the global interaction landscape of human SLiMs remains largely uncharted. Here we present the Atlas of SLiM-mediated Human protein-protein Interactions (ASHI), which maps more than 20,000 interactions by screening over 800 human protein domains against a library of one million peptides tiling the human disordered proteome. ASHI expands the SLiM interactome, uncovers novel binding modes for known peptide-binding domains, and reveals unexpected peptide-binding activities in enzymes, chaperones, RNA-binding proteins, and modification-reader domains. Furthermore, intrinsically disordered regions emerge as densely encoded interaction platforms where interaction specificity is governed by diverse mechanisms, including key motif determinants, flanking residues, competition, and multivalency. These data provide an unprecedented foundation for modeling dynamic interaction networks, interpreting disease-associated variants, and decoding the dark proteome.

biochemistry↗

bioRxiv2025

Systematic Discovery of Motif-based Interactions of the Auxiliary Domains of USP Family Deubiquitinases

The ubiquitin-specific proteases (USPs) family is the largest family of human deubiquitinating enzymes (DUBs). While most USPs are agnostic to polyubiquitin linkage-type, their substrate specificity is thought to be mediated by the recognition of the ubiquitylated protein itself. In addition to their catalytic domain, USPs have one or more auxiliary domains (ADs) with key functions in regulating DUB activity and subcellular localization. We hypothesize that some ADs bind short linear motifs (SLiMs) typically found in intrinsically disordered regions of proteins to achieve targeting to substrates and multiprotein complexes. To test this hypothesis, we systematically assessed the potential of 29 USP-ADs and two full-length USPs for SLiM binding using a combination of proteomic-peptide phage display, peptide arrays and affinity measurements. We discovered SLiM-based interactions for 14 ADs from 9 USP-DUBs, including CYLD, USP11, USP19, USP20, USP22 and USP33, and define the consensus motif and properties of the SLiM-AD binding. Interestingly, we established that the zf-UBP and DUSP2 domains of USP20 and USP33 are SLiM binding ADs with similar binding profiles, explaining the functional redundancy between the two DUBs. Our work reveals unique motifs recognized by the auxiliary domains CAP-Gly, UBL, zf-UBP and DUSP, with potential functional implications for substrate recognition and complex assemblies.

biochemistry↗

bioRxiv2025

AlphaFold models of host-pathogen interactions elucidate the prevalence and structural modes of molecular mimicry

Pathogens exploit host cellular machinery through protein-protein interactions (PPIs), often using molecular mimicry to hijack host cellular processes. While there have been thousands of host-pathogen PPIs determined to date, the lack of structural information for these impedes the study of the prevalence of molecular mimicry and convergent evolution of protein interaction interfaces. To address this, we benchmarked AlphaFold2 and 3 for prediction of structures of host-pathogen interactions observing that accurate models can be retrieved when ranking by modelling confidence, despite an overall low performance. We predicted structures for 6,782 pathogen-human PPIs yielding 803 models of higher confidence. Most pathogen proteins interacting with a common human protein are predicted to do so via the same interface, suggesting a high degree of convergent evolution of protein interaction interfaces. When comparing structural models from host-pathogen and host-host interactions, we observe that a majority of pathogen proteins are predicted to target existing human PPI interfaces. We categorized instances of mimicry into different modes, occurring at different frequencies: 1) via the same domain family (least common); 2) via a similar structural motif; and 3) via a similar linear motif (most common). We selected examples of linear motif interactions for binding assay testing, confirming 8 out of 12 predicted interfaces, including 3 viral linear motif interactions. This validates AlphaFolds ability to model some host-pathogen interactions and the mechanisms underlying molecular mimicry. This work showcases the value of large-scale structural modelling to study convergent evolution of host-pathogen interactions and how molecular mimicry may contribute to infection or host defense.

bioinformatics↗

bioRxiv2024

High-throughput discovery and deep characterization of cyclin-CDK docking motifs

Cyclin-CDKs are master regulators of cell division. In addition to directly activating the CDK, the cyclin subunit regulates CDK specificity by binding short peptide "docking" motifs in CDK substrates. Here, we measure the relative binding strength of [~]100,000 peptides to 11 human cyclins from five cyclin families (D, E, A, B and F). Using a quantitative intracellular binding assay and large-scale tiled peptide screening, we identified a range of non-canonical binders that unveil a broader than anticipated repertoire of cyclin docking motif types. Structural and saturation mutagenesis studies revealed distinct binding modes and sequence features that govern motif recognition, binding strength, and cyclin preference. Docking motifs vary from highly selective to pan-cyclin, thereby fine-tuning the timing of CDK phosphorylation during cell cycle progression. Overall, these findings provide an unprecedented depth of understanding about the rules encoding specificity and affinity within a group of related but distinct protein domains.

molecular biology↗

bioRxiv2024

Defining short linear motif binding determinants by phage-based multiplexed deep mutational scanning

Deep mutational scanning (DMS) has emerged as a powerful approach for evaluating the effects of mutations on binding or function. Here, we developed a multiplexed DMS by phage display protocol to define the binding determinants of short linear motifs (SLiMs) binding to peptide binding domains. We first designed a benchmarking DMS library to evaluate the performance of the approach on well-known ligands for eleven different peptide binding domains, including the talin-1 PTB domain. Systematic benchmarking against a gold-standard set of motifs from the eukaryotic linear motif (ELM) database confirmed that the DMS by phage analysis correctly identifies known motif binding determinants. The DMS analysis further defined a non-canonical PTB binding motif, with a putative extended conformation. A second DMS library was designed aiming to provide information on the binding determinants for 19 SLiM-based interactions between human and SARS-CoV-2 proteins. The analysis confirmed the affinity determining residues of viral peptides binding to host proteins, and refined the consensus motifs in human peptides binding to five domains from SARS-CoV-2 proteins, including the non-structural protein (NSP) 9. The DMS analysis further pinpointed mutations that increased the affinity of ligands for NSP3 and NSP9. An affinity improved cell-permeable NSP9-binding peptide was found to exert stronger antiviral effects as compared to the initial wild-type peptide. Our study demonstrates that DMS by phage display can efficiently be multiplexed and applied to refine binding determinants, and shows how DMS by phage display can guide peptide-engineering efforts.

biochemistry↗

bioRxiv2024

Benchmarking computational tools for de novo motif discovery

BackgroundOver the past twenty years, numerous motif discovery bioinformatic tools have been developed for discovering short linear motifs (SLiMs) from high-throughput experimental data on domain-peptide interactions. However, these tools are generally evaluated individually and mostly using synthetic data that do not accurately capture the motif context observed within proteomic data. Consequently, it is unclear how these tools perform in real-world use cases and how they perform compared to each other. ResultsHere, we benchmarked five motif discovery tools and seven general sequence alignment tools on their capacity to find SLiMs. For this purpose we have built MEP-Bench, a benchmarking dataset of peptides of varying complexity from curated SLiM instances from the Eukaryotic Linear Motif database. MEP-Bench allows tools to be tested for the effect of dataset size, peptide length, background noise level and motif complexity on motif discovery. The main metric used to compare all tools was the percentage of correctly aligned SLiM containing peptides. Two motif discovery tools (DEME and SLiMFinder) and a sequence alignment tool (Opal) outperformed the rest of the tools when benchmarked with this metric, averaging over 70% correctly aligned motif-containing peptides. The performance of the motif discovery tools and Opal were not affected by the sizes of the datasets. However, increasing peptide lengths and noise levels decreased all tools performances. While all tools performed well for N-/C-terminal motifs, for low-complexity motifs only DEME and SLiMFinder returned correctly aligned motifs for 50% or more of the datasets. ConclusionsThis study highlights DEME, SLiMFinder and Opal as the best performing tools for finding motifs in short peptides, and it indicates experimental parameters that should be considered given the limitations of the available tools. However, there is room for improvement, as no tool was able to identify all motif types. We propose that MEP-Bench can serve as a valuable resource for the SLiM community to compare new motif discovery methods with those benchmarked here.

bioinformatics↗

bioRxiv2023

Proteome-scale characterisation of protein motif interactome rewiring by disease mutations

Whole genome and exome sequencing are reporting on hundreds of thousands of missense mutations. Taking a pan-disease approach, we explored how mutations in the intrinsically disordered regions (IDRs) break or generate protein interactions mediated by short linear motifs. We created a peptide-phage display library tiling [~]57,000 peptides from the IDRs of the human proteome overlapping 12,301 single nucleotide variant associated with diverse phenotypes including cancer, metabolic diseases and neurological diseases. By screening 80 human proteins, we identified 366 mutation-modulated interactions, with half of the mutations diminishing binding, and half enhancing binding or creating novel interaction interfaces. The effects of the mutations were confirmed by affinity measurements. In cellular assays, the effects of motif-disruptive mutations were validated, including loss of a nuclear localisation signal in the cell division control protein CDC45 by a mutation associated with Meier-Gorlin syndrome. The study provides insights into how disease-associated mutations may perturb and rewire the motif-based interactome.

biochemistry↗

bioRxiv2022

Evaluation of affinity-purification coupled to mass spectrometry approaches for capture of short linear motif-based interactions

Low affinity and transient protein-protein interactions, such as short linear motif (SLiM)-based interactions, require dedicated experimental tools for discovery and validation. Here, we evaluated and compared biotinylated peptide pulldown and protein interaction screen on peptide matrix (PRISMA) coupled to mass-spectrometry (MS) using a set of peptides containing interaction motifs. Eight different peptide sequences that engage in interactions with three distinct protein domains (KEAP1 Kelch, MDM2 SWIB, and TSG101 UEV) with a wide range of affinities were tested. We found that peptide pulldown can be an effective approach for SLiM validation, however, parameters such as protein abundance and competitive interactions can prevent the capture of known interactors. The use of tandem peptide repeats improved the capture and preservation of some interactions. When testing PRISMA, it failed to provide comparable results for a model peptide that successfully pulled down a known interactor using biotinylated peptide pulldown. Overall, in our hands, we find that albeit more laborious, biotin-peptide pulldown was more successful in terms of validation of known interactions. Our results highlight that the tested affinity-capture MS-based methods for validation of SLiM-based interactions from cell lysates are suboptimal, and we identified parameters for consideration for method development.

biochemistry↗

bioRxiv2022

Identification of motif-based interactions between SARS-CoV-2 protein domains and human peptide ligands pinpoint antiviral targets.

The infection and replication cycle of all viruses depend on interactions between viral and host proteins. Each of these protein-protein interactions is therefore a potential drug target. These host-virus interactions often involve a disordered protein region on one side of the interface and a folded protein domain on the other. Here, we used proteomic peptide phage display (ProP-PD) to identify peptides from the intrinsically disordered regions of the human proteome that bind to folded protein domains encoded by the SARS-CoV-2 genome. Eleven folded domains of SARS-CoV-2 proteins were found to bind peptides from human proteins. Of 281 high/medium confidence peptides, 23 interactions involving eight SARS-CoV-2 protein domains were tested by fluorescence polarization, and binding was observed with affinities spanning the whole micromolar range. The key specificity determinants were established for six of these domains, two based on ProP-PD and four by alanine scanning SPOT arrays. Finally, two cell-penetrating peptides, targeting Nsp9 and Nsp16, respectively, were shown to function as inhibitors of viral replication. Our findings demonstrate how high-throughput peptide binding screens simultaneously provide information on potential host-virus interactions and identify ligands with antiviral properties.

molecular biology↗

bioRxiv2022

A syntenin inhibitor blocks endosomal entry of SARS-CoV-2 and a panel of RNA viruses

Viruses are dependent on interactions with host factors in order to efficiently establish an infection and replicate. Targeting such interactions provides an attractive strategy to develop novel antivirals. Syntenin is a protein known to regulate the architecture of cellular membranes by its involvement in protein trafficking, and has previously been shown to be important for HPV infection. Here we show that a highly potent and metabolically stable peptide inhibitor that binds to the PDZ1 domain of syntenin inhibits SARS-CoV-2 infection by blocking the endosomal entry of the virus. Furthermore, we found that the inhibitor also hampered chikungunya infection, and strongly reduced flavivirus infection, which are completely dependent on receptor mediated endocytosis for their entry. In conclusion, we have identified a novel pan-viral inhibitor that efficiently target a broad range of RNA viruses.

biochemistry↗

bioRxiv2022

Coupling to short linear motifs creates versatile PME-1 activities in PP2A holoenzyme demethylation and inhibition

Protein phosphatase 2A (PP2A) holoenzymes target broad substrates by recognizing short motifs via regulatory subunits. PP2A methylesterase 1 (PME-1) is a cancer-promoting enzyme and undergoes methylesterase activation upon binding to the PP2A core enzyme. Here we showed that PME-1 readily demethylates different families of PP2A holoenzymes and blocks substrate recognition in vitro. The high-resolution cryo-EM structure of a PP2A-B56 holoenzyme-PME-1 complex reveals that PME-1 disordered regions, including a substrate-mimicking motif, tether to the B56 regulatory subunit at remote sites. They occupy the holoenzyme substrate-binding groove and allow large structural shifts in both holoenzyme and PME-1 to enable multi-partite contacts at structured cores to activate the methylesterase. B56-interface mutations selectively block PME-1 activity toward PP2A-B56 holoenzymes and affect the methylation of a fraction of total cellular PP2A. The B56-interface mutations allow us to uncover B56-specific PME-1 functions in p53 signaling. Our studies reveal multiple mechanisms of PME-1 in suppressing holoenzyme functions and versatile PME-1 activities derived from coupling substrate-mimicking motifs to dynamic structured cores.

biochemistry↗

bioRxiv2022

Large-scale phage-based screening reveals extensive pan-viral mimicry of host short linear motifs

Viruses mimic host short linear motifs (SLiMs) to hijack and deregulate cellular functions. Studies of motif-mediated interactions therefore provide insight into virus-host dependencies, and reveal targets for therapeutic intervention. Here, we describe the pan-viral discovery of 1,712 SLiM-based virus-host interactions using a phage peptidome tiling the intrinsically disordered protein regions of 229 RNA viruses. We find mimicry of host SLiMs to be a ubiquitous viral strategy, reveal novel host proteins hijacked by viruses, and identify cellular pathways frequently deregulated by viral motif mimicry. Using structural and biophysical analyses, we show that viral mimicry-based interactions have similar binding strength and bound conformations as endogenous interactions. Finally, we establish polyadenylate-binding protein 1 as a potential target for broad-spectrum antiviral agent development. Our platform enables rapid discovery of mechanisms of viral interference and the identification of potential therapeutic targets which can aid in combating future epidemics and pandemics.

biochemistry↗

bioRxiv2022

Large-scale identification of phospho-modulated motif-based protein-protein interactions

Phosphorylation is an extensively studied post-translation modification that regulates protein function by promoting, inhibiting or modulating protein-protein interactions. Deciphering which of the hundreds of thousands of phosphosites in the proteome that regulate interactions remains challenging. We generated a proteomic peptide-phage display (ProP-PD) library to screen for phosphosites that regulate short linear motif-based interactions. The phage peptidome covers 13,500 phospho-serine/threonine sites found in the intrinsically disordered regions of the human proteome, each phosphosite being represented as a wildtype and a phosphomimetic variant. We screened 73 modular domains and identified 252 putative phospho-modulated interactions. Affinity measurements confirmed the phosphomodulation of 16 out of 21 tested interactions. We discovered a novel phospho-dependent interaction between clathrin and the mitotic spindle protein hepatoma-upregulated protein (HURP). We validated the phospho-dependent clathrin interaction in a cellular context and found it to be essential for the mitotic function of HURP. Structural characterisation elucidated the molecular basis for the phospho-dependency of the clathrin-HURP interaction. Collectively, our work showcases the power of phosphomimetic ProP-PD to discover novel phospho-modulated SLiM-based interactions required for cellular function.

biochemistry↗

bioRxiv2021

Large scale discovery of coronavirus-host factor protein interaction motifs reveals SARS-CoV-2 specific mechanisms and vulnerabilities

Viral proteins make extensive use of short peptide interaction motifs to hijack cellular host factors. However, current methods do not identify this important class of protein-protein interactions. Uncovering peptide mediated interactions provides both a molecular understanding of viral interactions with their host and the foundation for developing novel antiviral reagents. Here we describe a scalable viral peptide discovery approach covering 229 RNA viruses that provides high resolution information on direct virus-host interactions. We identify 269 peptide-based interactions for 18 coronaviruses including a specific interaction between the human G3BP1/2 proteins and an {Phi}xFG peptide motif in the SARS-CoV-2 nucleocapsid (N) protein. This interaction supports viral replication and through its {Phi}xFG motif N rewires the G3BP1/2 interactome to disrupt stress granules. A peptide-based inhibitor disrupting the G3BP1/2-N interaction blocks SARS-CoV-2 infection showing that our results can be directly translated into novel specific antiviral reagents.

biochemistry↗

bioRxiv2021

Proteome-scale amino-acid resolution footprinting of protein-binding sites in the intrinsically disordered regions of the human proteome

Specific protein-protein interactions are central to all processes that underlie cell physiology. Numerous studies using a wide range of experimental approaches have identified tens of thousands of human protein-protein interactions. However, many interactions remain to be discovered, and low affinity, conditional and cell type-specific interactions are likely to be disproportionately under-represented. Moreover, for most known protein-protein interactions the binding regions remain uncharacterized. We previously developed proteomic peptide phage display (ProP-PD), a method for simultaneous proteome-scale identification of short linear motif (SLiM)-mediated interactions and footprinting of the binding region with amino acid resolution. Here, we describe the second-generation human disorderome (HD2), an optimized ProP-PD library that tiles all disordered regions of the human proteome and allows the screening of ~1,000,000 overlapping peptides in a single binding assay. We define guidelines for how to process, filter and rank the results and provide PepTools, a toolkit for annotation and analysis of identified hits. We uncovered 2,161 interaction pairs for 35 known SLiM-binding domains and confirmed a subset of 38 interactions by biophysical or cell-based assays. Finally, we show how the amino acid resolution binding site information can be used to pinpoint functionally important disease mutations and phosphorylation events in intrinsically disordered regions of the human proteome. The HD2 ProP-PD library paired with PepTools represents a powerful pipeline for unbiased proteome-wide discovery of SLiM-based interactions.

biochemistry↗

bioRxiv2020

Defining binding motifs and dynamics of the multi-pocket FERM domain from ezrin, radixin, moesin and merlin

The ERM (ezrin, radixin and moesin) family of proteins and the related protein merlin participate in signaling events at the cell cortex. The proteins share an N-terminal FERM (band Four-point-one (4.1) ERM) domain comprised of three subdomains (F1, F2, and F3) that hold multiple binding sites for short linear peptide motifs. By screening the FERM domains of the ERMs and merlin against a phage library that display peptides representing the intrinsically disordered regions of the human proteome we identified more than 220 FERM binding peptides. The majority of the peptides contained an apparent Yx[FILV] motif, but ligands with alternative motifs were also found. Interactions with thirteen peptides were validated using a fluorescence polarization assay, and interactions with seven full-length proteins were validated through pull-down experiments. We investigated the energy landscapes of interactions between the moesin FERM domain and representative set of ligands using Rosetta FlexPepDock computational peptide docking protocols, which provide a detailed molecular understanding of the binding of peptides with distinct motifs (YxV and E[Y/F]xDFYDF) to different sites on the F3 subdomain. A third motif (FY[D/E]L(4-5x)PLxxx[L/V]) was proposed to bind more diffusely. By combining competition and modeling experiments, we further uncovered interdependencies between different types of ligands. The study expands the motif-based interactomes of the ERMs and merlin, and suggests that the FERM domain acts as a switchable interaction hub where one class of ligands to the F3 subdomain allosterically regulates binding of other F3 ligands.

biochemistry↗

bioRxiv2020

Cytoplasmic short linear motifs in ACE2 and integrin beta3 link SARS-CoV-2 host cell receptors to endocytosis and autophagy

The spike protein of the SARS-CoV-2 interacts with angiotensin converting enzyme 2 (ACE2) and enters the host cell by receptor-mediated endocytosis. Concomitantly, evidence is pointing to the involvement of additional host cell receptors, such as integrins. The cytoplasmic tails of ACE2 and integrin {beta}3 contain a plethora of predicted binding motifs. Here, we confirm the functionality of some of these motifs through affinity measurements. The class I PDZ binding motif in the ACE2 cytoplasmic tail binds the first PDZ domain of the scaffold protein NHERF3. The clathrin-adaptor subunit AP2 2 interacts with an endocytic motif in the ACE2 with low affinity and the interaction is abolished by phosphorylation of Tyr781. Furthermore, the C-terminal region of integrin b3 contains a LC3-interacting region, and its interaction with ATG8 domains is enhanced by phosphorylation. Together, our data provides possible molecular links between host cell receptors and endocytosis and autophagy. One sentence summaryAffinity measurements confirmed binding of short linear motifs in the cytoplasmic tails of ACE2 and integrin {beta}3, thereby linking the receptors to endocytosis and autophagy.

biochemistry↗

bioRxiv2019

Systematic discovery of Short Linear Motifs decodes calcineurin phosphatase signaling

Short linear motifs (SLiMs) drive dynamic protein-protein interactions essential for signaling, but sequence degeneracy and low binding affinities make them difficult to identify. We harnessed unbiased systematic approaches for SLiM discovery to elucidate the regulatory network of calcineurin (CN)/PP2B, the Ca2+-activated phosphatase that recognizes LxVP and PxIxIT motifs. In vitro proteome-wide detection of CN-binding peptides, in vivo SLiM-dependent proximity labeling, and in silico modeling of motif determinants uncovered unanticipated CN interactors, including NOTCH1, which we establish as a CN substrate. Unexpectedly, CN shows SLiM-dependent proximity to centrosomal and nuclear pore complex (NPC) proteins - structures where Ca2+ signaling is largely uncharacterized. CN dephosphorylates human and yeast NPC proteins and promotes accumulation of a nuclear transport reporter, suggesting conserved NPC regulation by CN. The CN network assembled here provides a resource to investigate Ca2+ and CN signaling and demonstrates synergy between experimental and computational methods, establishing a blueprint for examining SLiM-based networks.

cell biology↗