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Cross-link assisted spatial proteomics to map sub-organelle proteomes and membrane protein topology

ABSTRACT: The specific functions of cellular organelles and sub-compartments depend on their protein content, which can be characterized by spatial proteomics approaches. However, many spatial proteomics methods are limited in their ability to resolve organellar sub-compartments, profile multiple sub-compartments in parallel, and/or characterize membrane-associated proteomes. Here, we develop a cross-linking assisted spatial proteomics (CLASP) strategy that addresses these shortcomings. Using human mitochondria as a model system, we show that CLASP can elucidate spatial proteomes of all mitochondrial sub-compartments and provide topological insight into the mitochondrial membrane proteome in a single experiment. Biochemical and imaging-based follow-up studies demonstrate that CLASP allows discovering mitochondria-associated proteins and revising previous protein sub-compartment localization and membrane topology data. This study extends the scope of cross-linking mass spectrometry beyond protein structure and interaction analysis towards spatial proteomics, establishes a method for concomitant profiling of sub-organelle and membrane proteomes, and provides a resource for mitochondrial spatial biology

INSTRUMENT(S): Orbitrap Fusion Lumos

ORGANISM(S): Homo Sapiens (human)

TISSUE(S): Cell Culture

SUBMITTER: Kerem Akkaya

LAB HEAD: Fan Liu

PROVIDER: PXD046382 | Pride | 2024-02-21

REPOSITORIES: Pride

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Cross-link assisted spatial proteomics to map sub-organelle proteomes and membrane protein topology

Project description:The specific functions of cellular organelles and sub-compartments depend on their protein content, which can be characterized by spatial proteomics approaches. However, many spatial proteomics methods are limited in their ability to resolve organellar sub-compartments, profile multiple sub-compartments in parallel, and/or characterize membrane-associated proteomes. Here, we develop a cross-linking assisted spatial proteomics (CLASP) strategy that addresses these shortcomings. Using human mitochondria as a model system, we show that CLASP can elucidate spatial proteomes of all mitochondrial sub-compartments and provide topological insight into the mitochondrial membrane proteome in a single experiment. Biochemical and imaging-based follow-up studies demonstrate that CLASP allows discovering mitochondria-associated proteins and revising previous protein sub-compartment localization and membrane topology data. This study extends the scope of cross-linking mass spectrometry beyond protein structure and interaction analysis towards spatial proteomics, establishes a method for concomitant profiling of sub-organelle and membrane proteomes, and provides a resource for mitochondrial spatial biology.

2024-02-21 | PXD032132 | Pride

Yeast TLDc domain-containing proteins control assembly and subcellular localization of the V-ATPase

Project description:Yeast vacuoles, equivalent to lysosomes in other eukaryotes, are important acidic degradative organelles as well as storage compartments and signaling hubs. To perform these functions, they rely on important protein complexes, including the V-ATPase, responsible for organelle acidification. In this study, we used cross-linking mass spectrometry to characterize the protein complexes of isolated vacuoles. We were able to detect many known protein-protein interactions, including known protein complexes, as well as undescribed ones. Among these, we identified the uncharacterized TLDc domain-containing protein Rtc5 as a novel interactor of the V-ATPase. We show that Rtc5 localizes to the vacuole membrane depending on N-myristoylation and on its interactions with the V-ATPase. We further analyzed the influence of this protein, and the second yeast TLDc domain-containing protein, Oxr1, on V-ATPase function. We find that both Rtc5 and Oxr1 promote the disassembly of the vacuolar V-ATPase in vivo, counteracting the role of the assembly chaperone, the RAVE complex. Finally, Oxr1 is necessary for the retention in the late Golgi complex of an organelle-specific subunit of the V-ATPase. Collectively, our results shed light on the in vivo roles of yeast TLDc domain-containing proteins in relation to the V-ATPase, highlighting the multifaceted regulation of this crucial protein complex.

2024-03-11 | PXD046792 | Pride

Mass Spectrometry Uncovers Protein Interactions and Stoichiometry of Intermediates and Sub-complexes for SNARE Complex Assembly

Project description:The neuronal SNARE complex assembles from vesicular Synaptobrevin-2 as well as Syntaxin-1 and SNAP25 anchored to the presynaptic membrane. It mediates fusion of synaptic vesicles with the presynaptic plasma membrane resulting in exocytosis of neurotransmitters into the synaptic cleft. While the general sequence of SNARE complex formation is well-established, our knowledge on possible intermediates is still incomplete. We, therefore, follow the step-wise assembly of the SNARE complex and target individual SNAREs, binary sub-complexes, the ternary SNARE complex as well as interactions with Complexin-1. Using native mass spectrometry, we identify the stoichiometry of preferred sub-complexes and monitor oligomerisation of various assemblies. Importantly, we find that interactions with Complexin-1 reduce self-association of the ternary SNARE complex. Chemical cross-linking provides detailed insights into these interactions suggesting a role during membrane fusion. Taken together, we unravel possible intermediates and preferred sub-complexes and compile a road map of SNARE complex assembly including regulation by Complexin-1.

2023-01-25 | PXD030619 | Pride

Spatial, Quantitative and Functional Deconstruction of Virus and Host Protein Interactions Inside Intact Cytomegalovirus Particles

Project description:Viral infections involve packaging of the viral genome and proteins into virions. Knowing virion composition and structure is critical to understand viral pathogenesis. However, an integrated picture of virion proteome organization of large viruses, such as Herpesviruses, is lacking. Here we use cross-linking mass spectrometry to derive a spatially resolved structural interactome of intact human cytomegalovirus virions. We capture interactions of 82 host and 33 viral proteins, allowing us to de novo allocate them into distinct virion-layers and identify several host proteins as constitutive virion components recruited via specific protein interactions. The abundant viral protein pp150 forms domain-specific interactions with all virion layers and scaffolds numerous viral and host proteins such as PP1 phosphatase and 14-3-3 proteins, which are incorporated via nearby short linear motifs in pp150’s C-terminus. PP1 recruitment antagonizes 14-3-3 proteins and is pivotal during early and late viral replication steps. Collectively, this study gives a spatial and quantitative inventory of the system-wide organization and functional relevance of protein interactions inside native herpesvirus particles.

2023-06-14 | PXD031911 | Pride

Molecular characterization of a complex of Apoptosis Inducing Factor 1 (AIFM1) with cytochrome c oxidase of the mitochondrial respiratory chain

Project description:Combining mass spectrometry based chemical cross-linking and complexome profiling, we analyzed the interactome of heart mitochondria. We focused on complexes of oxidative phosphorylation and found that dimeric apoptosis inducing factor 1 (AIFM1) forms a defined complex with ~10% of monomeric cytochrome c oxidase (COX), but hardly interacts with respiratory chain supercomplexes. Multiple AIFM1 inter-crosslinks engaging six different COX subunits provided structural restraints to build a detailed atomic model of the COX-AIFM12 complex. Application of two complementary proteomic approaches thus provided unexpected insight into the macromolecular organization of the mitochondrial complexome. Our structural model excludes direct electron transfer between AIFM1 and COX. Notably however, the binding site of cytochrome c remains accessible allowing formation of a ternary complex. The discovery of the previously overlooked COX-AIFM12 complex and clues provided by the structural model hint at a role of AIFM1 in OXPHOS biogenesis and in programmed cell death.

2021-09-09 | PXD025102 | Pride

Normal respiratory chain capacity and physiology in mice with severely reduced levels of mitochondrial respirasomes; Cross-linking of intact mitochondria

Project description:The mammalian oxidative phosphorylation (OXPHOS) system in the inner mitochondrial membrane comprises respiratory chain complexes I-IV (CI-CIV) and ATP synthase. Together, these protein complexes harvest metabolic energy to generate ATP, the cellular energy currency. The inner mitochondrial membrane is abundant in OXPHOS complexes and CI, CIII and CIV exhibit specific protein-protein interactions to form stable supercomplex assemblies, exemplified by the respirasome (CI-CIII2-CIV). Respirasomes are conserved in evolution, and as well documented by biochemical and structural methods. However, their physiological roles are much debated, despite a substantial literature suggesting their importance in facilitating catalysis and regulating turnover in response to metabolic demand. To investigate the in vivo role of respirasomes, we deleted a short conserved, charged loop in the UQCRC1 subunit of CIII that contacts CI. The resulting homozygous knock-in mice show profoundly decreased levels of respirasomes on blue native polyacrylamide gel electrophoresis (BN-PAGE) and complexome profiling proteomics analyses of different tissues, although the individual complexes appear unaffected. In vivo The spatial organization of respirasomes in vivo was altered in knock-in mice as shown by cross-linking experiments on intact mitochondria. Surprisingly, the mutant mice are healthy, with normal respiratory chain capacity and normal exercise tolerance. Therefore, respirasomes are dispensable for OXPHOS function in vivo.

2023-03-11 | PXD031345 | Pride

MRPS36 provides a missing link in the eukaryotic 2-oxoglutarate dehydrogenase complex for recruitment of E3 to the E2 core - Phospoproteomics data

Project description:The tricarboxylic acid (TCA) cycle, or Krebs cycle, is the central pathway of energy production in eukaryotic cells and plays a key part in aerobic respiration throughout all kingdoms of life. The enzymes involved in this cycle generate the reducing equivalents NADH and FADH2 by a series of enzymatic reactions, which are utilized by the electron transport chain to produce ATP. One of the key enzymes in this cycle is 2-oxoglutarate dehydrogenase (OGDHC), which generates NADH by oxidative decarboxylation of 2-oxoglutarate to succinyl-CoA. Notably, this enzyme consists of multiple subunits as a megadalton protein complex. Thus far, it was thought that OGDHC consists of solely three catalytically active subunits (E1, E2, E3). However in fungi and animals, the small protein MRPS36 has been proposed as a putative additional component. Based on extensive XL-MS data obtained from measurements in both, mice and bovine heart mitochondria, and from phylogenetic analyses, we provide structural evidence that MRPS36 is an exclusive and crucial member of eukaryotic OGDHC. Comparative genomics analysis and computational structure predictions reveal that in eukaryotic OGDHC, E2o does not contain a peripheral subunit-binding (PSBD) domain. Instead, our data provide compelling evidence that in eukaryotes, MRPS36 evolved as E3 adaptor protein, functionally replacing the PSBD domain. Based on our data we provide a refined structural model of the complete eukaryotic OGDHC assembly containing all its 58 subunits (~ 3.4 MDa). The model provides new insights into the protein-protein interactions within the OGDH complex and highlights putative mechanistic implications.

2023-03-10 | PXD036896 | Pride

Mapping protein interactions in the active TOM-TIM23 supercomplex

Project description:Nuclear-encoded mitochondrial proteins destined for the matrix have to be transported across two membranes. The TOM and TIM23 complexes facilitate the transport of precursor proteins with N-terminal targeting signals into the matrix. During transport, precursors are recognized by the TIM23 complex in the inner membrane for handover from the TOM complex. However, we have little knowledge on the organisation of the TOM-TIM23 transition zone and on how precursor transfer between the translocases occurs. Here, we designed a precursor protein that is stalled during matrix transport in a TOM-TIM23-spanning manner and enables purification of the translocation intermediate. Combining chemical cross-linking with mass spectrometric analyses and structural modelling allowed us to map the molecular environment of the intermembrane space interface of TOM and TIM23 as well as the import motor interactions with amino acid resolution. Our analyses provide a framework for understanding presequence handover and translocation during matrix protein transport.

2021-12-13 | PXD028002 | Pride

Cause and consequence of tethering a sub-TAD to different nuclear compartments

Project description:Detailed genomic contact maps have revealed that chromosomes are composed of developmentally stable topologically associated domains (TADs) and more flexible sub-TADs. These domains reside in active and inactive nuclear compartments, but cause and consequence of compartmentalization are largely unknown. Here, we combined lacO/lacR binding platforms with allele-specific 4C technologies to track their precise position in the three-dimensional genome upon recruitment of NANOG, SUV39H1 or EZH2. We observed locked genomic loci resistant to spatial repositioning and unlocked loci that could be repositioned to different nuclear sub-compartments with distinct chromatin signatures. Focal protein recruitment caused the entire sub- TAD, but not surrounding regions, to engage in new genomic contacts. Compartment switching was uncoupled from gene expression changes and enzymatically modifying histones per se was insufficient for repositioning. Collectively this suggests that transassociated factors determine three-dimensional compartmentalization independent of their cis-effect on local chromatin composition and activity. 4C-seq was performed on a range of viewpoints in 129/Sv;C57BL/6 embryonic stem cells carying a lacO array in chromosome 8 and 11.

2015-12-19 | E-GEOD-76174 | biostudies-arrayexpress

In vivo protein interaction network analysis reveals porin-localized toxin inactivation in antibiotic resistant bacteria

Project description:The nosocomial pathogen Acinetobacter baumannii is a frequent cause of hospital acquired infections worldwide, and a challenge for treatment due to its evolved resistance to antibiotics, including carbapenems. To gain insight on A. baumannii antibiotic resistance mechanisms, we analyzed the protein interaction network of a multidrug-resistant A. baumannii clinical strain Ab5075. Using in vivo chemical cross-linking and mass spectrometry, we identified 2,068 non-redundant cross-linked peptide pairs containing 245 intra- and 398 inter- molecular interactions. Outer membrane proteins OmpA and YiaD, and carbapenemase Oxa-23 are hubs of the identified interaction network. Eighteen novel interactors of Oxa-23 were identified. Interactions of Oxa-23 with outer membrane porins OmpA and CarO were verified with co-immunoprecipitation analysis. Furthermore, transposon mutagenesis of oxa-23 or interactors of Oxa-23 demonstrated changes in meropenem or imipenem sensitivity in Ab5075. These results provide the first view of a porin-localized toxin inactivation model and increase understanding of bacterial antibiotic resistance mechanisms.

2016-12-22 | PXD004236 | Pride

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