RESUMEN
Defects in organellar acidification indicate compromised or infected compartments. Recruitment of the autophagy-related ATG16L1 complex to pathologically neutralized organelles targets ubiquitin-like ATG8 molecules to perturbed membranes. How this process is coupled to proton gradient disruption is unclear. Here, we reveal that the V1H subunit of the vacuolar ATPase (V-ATPase) proton pump binds directly to ATG16L1. The V1H/ATG16L1 interaction only occurs within fully assembled V-ATPases, allowing ATG16L1 recruitment to be coupled to increased V-ATPase assembly following organelle neutralization. Cells lacking V1H fail to target ATG8s during influenza infection or after activation of the immune receptor stimulator of interferon genes (STING). We identify a loop within V1H that mediates ATG16L1 binding. A neuronal V1H isoform lacks this loop and is associated with attenuated ATG8 targeting in response to ionophores in primary murine and human iPSC-derived neurons. Thus, V1H controls ATG16L1 recruitment following proton gradient dissipation, suggesting that the V-ATPase acts as a cell-intrinsic damage sensor.
Asunto(s)
Proteínas Relacionadas con la Autofagia , ATPasas de Translocación de Protón Vacuolares , ATPasas de Translocación de Protón Vacuolares/metabolismo , ATPasas de Translocación de Protón Vacuolares/genética , Humanos , Proteínas Relacionadas con la Autofagia/metabolismo , Proteínas Relacionadas con la Autofagia/genética , Animales , Ratones , Unión Proteica , Neuronas/metabolismo , Familia de las Proteínas 8 Relacionadas con la Autofagia/metabolismo , Familia de las Proteínas 8 Relacionadas con la Autofagia/genética , Autofagia , Células HEK293 , Células Madre Pluripotentes Inducidas/metabolismo , Gripe Humana/virología , Gripe Humana/metabolismo , Gripe Humana/genética , Ratones Endogámicos C57BL , Transducción de Señal , Proteínas Portadoras/metabolismo , Proteínas Portadoras/genética , Ratones NoqueadosRESUMEN
BACKGROUND: The malaria parasite Plasmodium falciparum replicates within red blood cells, then ruptures the cell in a process called egress in order to continue its life cycle. Egress is regulated by a proteolytic cascade involving an essential parasite subtilisin-like serine protease called SUB1. Maturation of SUB1 initiates in the parasite endoplasmic reticulum with autocatalytic cleavage of an N-terminal prodomain (p31), which initially remains non-covalently bound to the catalytic domain, p54. Further trafficking of the p31-p54 complex results in formation of a terminal p47 form of the SUB1 catalytic domain. Recent work has implicated a parasite aspartic protease, plasmepsin X (PMX), in maturation of the SUB1 p31-p54 complex through controlled cleavage of the prodomain p31. METHODS: Here we use biochemical and enzymatic analysis to examine the activation of SUB1 by PMX. RESULTS: We show that both p31 and p31-p54 are largely dimeric under the relatively acidic conditions to which they are likely exposed to PMX in the parasite. We confirm the sites within p31 that are cleaved by PMX and determine the order of cleavage. We find that cleavage by PMX results in rapid loss of the capacity of p31 to act as an inhibitor of SUB1 catalytic activity and we directly demonstrate that exposure to PMX of recombinant p31-p54 complex activates SUB1 activity. CONCLUSIONS: Our results confirm that precise, PMX-mediated cleavage of the SUB1 prodomain activates SUB1 enzyme activity. GENERAL SIGNIFICANCE: Our findings elucidate the role of PMX in activation of SUB1, a key effector of malaria parasite egress.
Asunto(s)
Ácido Aspártico Endopeptidasas , Plasmodium falciparum , Proteínas Protozoarias , Plasmodium falciparum/enzimología , Plasmodium falciparum/metabolismo , Ácido Aspártico Endopeptidasas/metabolismo , Ácido Aspártico Endopeptidasas/genética , Proteínas Protozoarias/metabolismo , Proteínas Protozoarias/genética , Proteínas Protozoarias/química , Proteolisis , Humanos , Subtilisinas/metabolismo , Dominio Catalítico , Dominios Proteicos , Malaria Falciparum/parasitología , Malaria Falciparum/metabolismo , Eritrocitos/parasitología , Eritrocitos/metabolismoRESUMEN
Protein folding is assisted by molecular chaperones that bind nascent polypeptides during mRNA translation. Several structurally distinct classes of chaperones promote de novo folding, suggesting that their activities are coordinated at the ribosome. We used biochemical reconstitution and structural proteomics to explore the molecular basis for cotranslational chaperone action in bacteria. We found that chaperone binding is disfavored close to the ribosome, allowing folding to precede chaperone recruitment. Trigger factor recognizes compact folding intermediates that expose an extensive unfolded surface, and dictates DnaJ access to nascent chains. DnaJ uses a large surface to bind structurally diverse intermediates and recruits DnaK to sequence-diverse solvent-accessible sites. Neither Trigger factor, DnaJ, nor DnaK destabilize cotranslational folding intermediates. Instead, the chaperones collaborate to protect incipient structure in the nascent polypeptide well beyond the ribosome exit tunnel. Our findings show how the chaperone network selects and modulates cotranslational folding intermediates.
Asunto(s)
Proteínas de Escherichia coli , Escherichia coli , Proteínas del Choque Térmico HSP40 , Proteínas HSP70 de Choque Térmico , Biosíntesis de Proteínas , Pliegue de Proteína , Ribosomas , Ribosomas/metabolismo , Ribosomas/genética , Proteínas de Escherichia coli/metabolismo , Proteínas de Escherichia coli/genética , Proteínas de Escherichia coli/química , Proteínas HSP70 de Choque Térmico/metabolismo , Proteínas HSP70 de Choque Térmico/genética , Proteínas del Choque Térmico HSP40/metabolismo , Proteínas del Choque Térmico HSP40/genética , Escherichia coli/metabolismo , Escherichia coli/genética , Unión Proteica , Chaperonas Moleculares/metabolismo , Chaperonas Moleculares/genética , Modelos Moleculares , Conformación Proteica , Isomerasa de PeptidilprolilRESUMEN
RAD52 is important for the repair of DNA double-stranded breaks1,2, mitotic DNA synthesis3-5 and alternative telomere length maintenance6,7. Central to these functions, RAD52 promotes the annealing of complementary single-stranded DNA (ssDNA)8,9 and provides an alternative to BRCA2/RAD51-dependent homologous recombination repair10. Inactivation of RAD52 in homologous-recombination-deficient BRCA1- or BRCA2-defective cells is synthetically lethal11,12, and aberrant expression of RAD52 is associated with poor cancer prognosis13,14. As a consequence, RAD52 is an attractive therapeutic target against homologous-recombination-deficient breast, ovarian and prostate cancers15-17. Here we describe the structure of RAD52 and define the mechanism of annealing. As reported previously18-20, RAD52 forms undecameric (11-subunit) ring structures, but these rings do not represent the active form of the enzyme. Instead, cryo-electron microscopy and biochemical analyses revealed that ssDNA annealing is driven by RAD52 open rings in association with replication protein-A (RPA). Atomic models of the RAD52-ssDNA complex show that ssDNA sits in a positively charged channel around the ring. Annealing is driven by the RAD52 N-terminal domains, whereas the C-terminal regions modulate the open-ring conformation and RPA interaction. RPA associates with RAD52 at the site of ring opening with critical interactions occurring between the RPA-interacting domain of RAD52 and the winged helix domain of RPA2. Our studies provide structural snapshots throughout the annealing process and define the molecular mechanism of ssDNA annealing by the RAD52-RPA complex.
Asunto(s)
Microscopía por Crioelectrón , ADN de Cadena Simple , Complejos Multiproteicos , Proteína Recombinante y Reparadora de ADN Rad52 , Proteína de Replicación A , Humanos , ADN de Cadena Simple/química , ADN de Cadena Simple/metabolismo , ADN de Cadena Simple/ultraestructura , Modelos Moleculares , Unión Proteica , Proteína Recombinante y Reparadora de ADN Rad52/química , Proteína Recombinante y Reparadora de ADN Rad52/metabolismo , Proteína Recombinante y Reparadora de ADN Rad52/ultraestructura , Proteína de Replicación A/química , Proteína de Replicación A/metabolismo , Proteína de Replicación A/ultraestructura , Complejos Multiproteicos/química , Complejos Multiproteicos/metabolismo , Complejos Multiproteicos/ultraestructura , Dominios Proteicos , Sitios de UniónRESUMEN
Regulated protein phosphorylation controls most cellular processes. The protein phosphatase PP1 is the catalytic subunit of many holoenzymes that dephosphorylate serine/threonine residues. How these enzymes recruit their substrates is largely unknown. Here, we integrated diverse approaches to elucidate how the PP1 non-catalytic subunit PPP1R15B (R15B) captures its full trimeric eIF2 substrate. We found that the substrate-recruitment module of R15B is largely disordered with three short helical elements, H1, H2, and H3. H1 and H2 form a clamp that grasps the substrate in a region remote from the phosphorylated residue. A homozygous N423D variant, adjacent to H1, reducing substrate binding and dephosphorylation was discovered in a rare syndrome with microcephaly, developmental delay, and intellectual disability. These findings explain how R15B captures its 125 kDa substrate by binding the far end of the complex relative to the phosphosite to present it for dephosphorylation by PP1, a paradigm of broad relevance.
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Dominio Catalítico , Factor 2 Eucariótico de Iniciación , Proteína Fosfatasa 1 , Humanos , Fosforilación , Proteína Fosfatasa 1/genética , Proteína Fosfatasa 1/metabolismoRESUMEN
Homologous recombination is a fundamental process of life. It is required for the protection and restart of broken replication forks, the repair of chromosome breaks and the exchange of genetic material during meiosis. Individuals with mutations in key recombination genes, such as BRCA2 (also known as FANCD1), or the RAD51 paralogues RAD51B, RAD51C (also known as FANCO), RAD51D, XRCC2 (also known as FANCU) and XRCC3, are predisposed to breast, ovarian and prostate cancers1-10 and the cancer-prone syndrome Fanconi anaemia11-13. The BRCA2 tumour suppressor protein-the product of BRCA2-is well characterized, but the cellular functions of the RAD51 paralogues remain unclear. Genetic knockouts display growth defects, reduced RAD51 focus formation, spontaneous chromosome abnormalities, sensitivity to PARP inhibitors and replication fork defects14,15, but the precise molecular roles of RAD51 paralogues in fork stability, DNA repair and cancer avoidance remain unknown. Here we used cryo-electron microscopy, AlphaFold2 modelling and structural proteomics to determine the structure of the RAD51B-RAD51C-RAD51D-XRCC2 complex (BCDX2), revealing that RAD51C-RAD51D-XRCC2 mimics three RAD51 protomers aligned within a nucleoprotein filament, whereas RAD51B is highly dynamic. Biochemical and single-molecule analyses showed that BCDX2 stimulates the nucleation and extension of RAD51 filaments-which are essential for recombinational DNA repair-in reactions that depend on the coupled ATPase activities of RAD51B and RAD51C. Our studies demonstrate that BCDX2 orchestrates RAD51 assembly on single stranded DNA for replication fork protection and double strand break repair, in reactions that are critical for tumour avoidance.
Asunto(s)
Microscopía por Crioelectrón , Proteínas de Unión al ADN , Complejos Multiproteicos , Recombinasa Rad51 , Proteínas Supresoras de Tumor , Humanos , Reparación del ADN , Replicación del ADN , Proteínas de Unión al ADN/química , Proteínas de Unión al ADN/metabolismo , Proteínas de Unión al ADN/ultraestructura , Recombinación Homóloga , Recombinasa Rad51/química , Recombinasa Rad51/metabolismo , Recombinasa Rad51/ultraestructura , Proteínas Supresoras de Tumor/química , Proteínas Supresoras de Tumor/metabolismo , Proteínas Supresoras de Tumor/ultraestructura , Inhibidores de Poli(ADP-Ribosa) Polimerasas , Neoplasias/genética , Neoplasias/prevención & control , Proteómica , Simulación por Computador , Complejos Multiproteicos/química , Complejos Multiproteicos/metabolismo , Complejos Multiproteicos/ultraestructura , Roturas del ADN de Doble CadenaRESUMEN
Modular SCF (SKP1-CUL1-Fbox) ubiquitin E3 ligases orchestrate multiple cellular pathways in eukaryotes. Their variable SKP1-Fbox substrate receptor (SR) modules enable regulated substrate recruitment and subsequent proteasomal degradation. CAND proteins are essential for the efficient and timely exchange of SRs. To gain structural understanding of the underlying molecular mechanism, we reconstituted a human CAND1-driven exchange reaction of substrate-bound SCF alongside its co-E3 ligase DCNL1 and visualized it by cryo-EM. We describe high-resolution structural intermediates, including a ternary CAND1-SCF complex, as well as conformational and compositional intermediates representing SR- or CAND1-dissociation. We describe in molecular detail how CAND1-induced conformational changes in CUL1/RBX1 provide an optimized DCNL1-binding site and reveal an unexpected dual role for DCNL1 in CAND1-SCF dynamics. Moreover, a partially dissociated CAND1-SCF conformation accommodates cullin neddylation, leading to CAND1 displacement. Our structural findings, together with functional biochemical assays, help formulate a detailed model for CAND-SCF regulation.
Asunto(s)
Proteínas Cullin , Proteínas Ligasas SKP Cullina F-box , Humanos , Proteínas Ligasas SKP Cullina F-box/genética , Proteínas Ligasas SKP Cullina F-box/metabolismo , Proteínas Cullin/metabolismo , Factores de Transcripción/metabolismo , Proteínas Portadoras/metabolismoRESUMEN
Photoaffinity labelling is a promising method for studying protein-ligand interactions. However, obtaining a specific, efficient crosslinker can require significant optimisation. We report a modified mRNA display strategy, photocrosslinking-RaPID (XL-RaPID), and exploit its ability to accelerate the discovery of cyclic peptides that photocrosslink to a target of interest. As a proof of concept, we generated a benzophenone-containing library and applied XL-RaPID screening against a model target, the second bromodomain of BRD3. This crosslinking screening gave two optimal candidates that selectively labelled the target protein in cell lysate. Overall, this work introduces direct photocrosslinking screening as a versatile technique for identifying covalent peptide ligands from mRNA display libraries incorporating reactive warheads.
RESUMEN
TRIM proteins are the largest family of E3 ligases in mammals. They include the intracellular antibody receptor TRIM21, which is responsible for mediating targeted protein degradation during Trim-Away. Despite their importance, the ubiquitination mechanism of TRIM ligases has remained elusive. Here we show that while Trim-Away activation results in ubiquitination of both ligase and substrate, ligase ubiquitination is not required for substrate degradation. N-terminal TRIM21 RING ubiquitination by the E2 Ube2W can be inhibited by N-terminal acetylation, but this doesn't prevent substrate ubiquitination nor degradation. Instead, uncoupling ligase and substrate degradation prevents ligase recycling and extends functional persistence in cells. Further, Trim-Away degrades substrates irrespective of whether they contain lysines or are N-terminally acetylated, which may explain the ability of TRIM21 to counteract fast-evolving pathogens and degrade diverse substrates.
Asunto(s)
Lisina , Ubiquitina-Proteína Ligasas , Animales , Lisina/metabolismo , Ubiquitinación , Ubiquitina-Proteína Ligasas/genética , Ubiquitina-Proteína Ligasas/metabolismo , Procesamiento Proteico-Postraduccional , Proteolisis , Mamíferos/metabolismoRESUMEN
ATG9A and ATG2A are essential core members of the autophagy machinery. ATG9A is a lipid scramblase that allows equilibration of lipids across a membrane bilayer, whereas ATG2A facilitates lipid flow between tethered membranes. Although both have been functionally linked during the formation of autophagosomes, the molecular details and consequences of their interaction remain unclear. By combining data from peptide arrays, crosslinking, and hydrogen-deuterium exchange mass spectrometry together with cryoelectron microscopy, we propose a molecular model of the ATG9A-2A complex. Using this integrative structure modeling approach, we identify several interfaces mediating ATG9A-2A interaction that would allow a direct transfer of lipids from ATG2A into the lipid-binding perpendicular branch of ATG9A. Mutational analyses combined with functional activity assays demonstrate their importance for autophagy, thereby shedding light on this protein complex at the heart of autophagy.
Asunto(s)
Autofagosomas , Autofagia , Microscopía por Crioelectrón , Bioensayo , LípidosRESUMEN
In response to improper kinetochore-microtubule attachments in mitosis, the spindle assembly checkpoint (SAC) assembles the mitotic checkpoint complex (MCC) to inhibit the anaphase-promoting complex/cyclosome, thereby delaying entry into anaphase. The MCC comprises Mad2:Cdc20:BubR1:Bub3. Its assembly is catalysed by unattached kinetochores on a Mad1:Mad2 platform. Mad1-bound closed-Mad2 (C-Mad2) recruits open-Mad2 (O-Mad2) through self-dimerization. This interaction, combined with Mps1 kinase-mediated phosphorylation of Bub1 and Mad1, accelerates MCC assembly, in a process that requires O-Mad2 to C-Mad2 conversion and concomitant binding of Cdc20. How Mad1 phosphorylation catalyses MCC assembly is poorly understood. Here, we characterized Mps1 phosphorylation of Mad1 and obtained structural insights into a phosphorylation-specific Mad1:Cdc20 interaction. This interaction, together with the Mps1-phosphorylation dependent association of Bub1 and Mad1, generates a tripartite assembly of Bub1 and Cdc20 onto the C-terminal domain of Mad1 (Mad1CTD). We additionally identify flexibility of Mad1:Mad2 that suggests how the Cdc20:Mad1CTD interaction brings the Mad2-interacting motif (MIM) of Cdc20 near O-Mad2. Thus, Mps1-dependent formation of the MCC-assembly scaffold functions to position and orient Cdc20 MIM near O-Mad2, thereby catalysing formation of C-Mad2:Cdc20.
Asunto(s)
Proteínas de Ciclo Celular , Puntos de Control de la Fase M del Ciclo Celular , Proteínas de Ciclo Celular/metabolismo , Cinetocoros/metabolismo , Mitosis , Catálisis , Proteínas Mad2/metabolismo , Huso Acromático/metabolismo , Proteínas Cdc20/metabolismoRESUMEN
This paper examines the relationship between conceptual and embodied reasoning in engineering work. In the last decade across multiple research projects on pipeline engineering, we have observed only a few times when engineers have expressed embodied or sensory aspects of their practice, as if the activity itself is disembodied. Yet, they also often speak about the importance of field experience. In this paper, we look at engineers' accounts of the value of field experience showing how it works on their sense of what the technology that they are designing looks, feels, and sounds like in practice, and so what this means for construction and operation, and the management of risk. We show how office-based pipeline engineering work is an exercise in embodied imagination that humanizes the socio-technical system as it manifests in the technical artifacts that they work with. Engineers take the role of the other to reason through the practicability of their designs and risk acceptability.
RESUMEN
During bacterial cell division, filaments of tubulin-like FtsZ form the Z-ring, which is the cytoplasmic scaffold for divisome assembly. In Escherichia coli, the actin homologue FtsA anchors the Z-ring to the membrane and recruits divisome components, including bitopic FtsN. FtsN regulates the periplasmic peptidoglycan synthase FtsWI. To characterize how FtsA regulates FtsN, we applied electron microscopy to show that E. coli FtsA forms antiparallel double filaments on lipid monolayers when bound to the cytoplasmic tail of FtsN. Using X-ray crystallography, we demonstrate that Vibrio maritimus FtsA crystallizes as an equivalent double filament. We identified an FtsA-FtsN interaction site in the IA-IC interdomain cleft of FtsA using X-ray crystallography and confirmed that FtsA forms double filaments in vivo by site-specific cysteine cross-linking. FtsA-FtsN double filaments reconstituted in or on liposomes prefer negative Gaussian curvature, like those of MreB, the actin-like protein of the elongasome. We propose that curved antiparallel FtsA double filaments together with treadmilling FtsZ filaments organize septal peptidoglycan synthesis in the division plane.
Asunto(s)
Proteínas de Escherichia coli , Escherichia coli , Actinas/metabolismo , Proteínas Bacterianas/genética , Proteínas Bacterianas/metabolismo , Cisteína/metabolismo , Escherichia coli/metabolismo , Proteínas de Escherichia coli/metabolismo , Lípidos , Liposomas , Proteínas de la Membrana/metabolismo , Peptidoglicano/metabolismo , Tubulina (Proteína)/metabolismoRESUMEN
Most eukaryotic messenger RNAs (mRNAs) are processed at their 3' end by the cleavage and polyadenylation specificity factor (CPF/CPSF). CPF mediates the endonucleolytic cleavage of the pre-mRNA and addition of a polyadenosine (poly(A)) tail, which together define the 3' end of the mature transcript. The activation of CPF is highly regulated to maintain the fidelity of RNA processing. Here, using cryo-EM of yeast CPF, we show that the Mpe1 subunit directly contacts the polyadenylation signal sequence in nascent pre-mRNA. The region of Mpe1 that contacts RNA also promotes the activation of CPF endonuclease activity and controls polyadenylation. The Cft2 subunit of CPF antagonizes the RNA-stabilized configuration of Mpe1. In vivo, the depletion or mutation of Mpe1 leads to widespread defects in transcription termination by RNA polymerase II, resulting in transcription interference on neighboring genes. Together, our data suggest that Mpe1 plays a major role in accurate 3' end processing, activating CPF, and ensuring timely transcription termination.
Asunto(s)
Precursores del ARN , Proteínas de Saccharomyces cerevisiae , Saccharomyces cerevisiae , Factores de Escisión y Poliadenilación de ARNm , Secuencia de Aminoácidos , Microscopía por Crioelectrón , Poliadenilación , Unión Proteica , Estructura Terciaria de Proteína , Precursores del ARN/genética , ARN Mensajero/genética , Saccharomyces cerevisiae/genética , Saccharomyces cerevisiae/metabolismo , Proteínas de Saccharomyces cerevisiae/genética , Proteínas de Saccharomyces cerevisiae/metabolismo , Factores de Escisión y Poliadenilación de ARNm/genética , Factores de Escisión y Poliadenilación de ARNm/metabolismoRESUMEN
The amount of any given protein in the brain is determined by the rates of its synthesis and destruction, which are regulated by different cellular mechanisms. Here, we combine metabolic labeling in live mice with global proteomic profiling to simultaneously quantify both the flux and amount of proteins in mouse models of neurodegeneration. In multiple models, protein turnover increases were associated with increasing pathology. This method distinguishes changes in protein expression mediated by synthesis from those mediated by degradation. In the AppNL-F knockin mouse model of Alzheimer's disease, increased turnover resulted from imbalances in both synthesis and degradation, converging on proteins associated with synaptic vesicle recycling (Dnm1, Cltc, Rims1) and mitochondria (Fis1, Ndufv1). In contrast to disease models, aging in wild-type mice caused a widespread decrease in protein recycling associated with a decrease in autophagic flux. Overall, this simple multidimensional approach enables a comprehensive mapping of proteome dynamics and identifies affected proteins in mouse models of disease and other live animal test settings.
Asunto(s)
Enfermedad de Alzheimer , Proteoma , Envejecimiento , Enfermedad de Alzheimer/metabolismo , Animales , Encéfalo/metabolismo , Modelos Animales de Enfermedad , Mamíferos/metabolismo , Ratones , Ratones Transgénicos , Proteoma/metabolismo , Proteómica/métodosRESUMEN
Cross-talk between distinct protein post-translational modifications is critical for an effective DNA damage response. Arginine methylation plays an important role in maintaining genome stability, but how this modification integrates with other enzymatic activities is largely unknown. Here, we identify the deubiquitylating enzyme USP11 as a previously uncharacterised PRMT1 substrate, and demonstrate that the methylation of USP11 promotes DNA end-resection and the repair of DNA double strand breaks (DSB) by homologous recombination (HR), an event that is independent from another USP11-HR activity, the deubiquitylation of PALB2. We also show that PRMT1 is a ubiquitylated protein that it is targeted for deubiquitylation by USP11, which regulates the ability of PRMT1 to bind to and methylate MRE11. Taken together, our findings reveal a specific role for USP11 during the early stages of DSB repair, which is mediated through its ability to regulate the activity of the PRMT1-MRE11 pathway.
Asunto(s)
Arginina/metabolismo , Proteína Homóloga de MRE11/metabolismo , Proteína-Arginina N-Metiltransferasas/metabolismo , Recombinasa Rad51/metabolismo , Reparación del ADN por Recombinación , Proteínas Represoras/metabolismo , Tioléster Hidrolasas/metabolismo , Ubiquitinación , Arginina/química , Línea Celular , Daño del ADN , Inestabilidad Genómica , Humanos , MetilaciónRESUMEN
Non-degradative ubiquitin chains and phosphorylation events govern signaling responses by innate immune receptors. The deubiquitinase CYLD in complex with SPATA2 is recruited to receptor signaling complexes by the ubiquitin ligase LUBAC and regulates Met1- and Lys63-linked polyubiquitin and receptor signaling outcomes. Here, we investigate the molecular determinants of CYLD activity. We reveal that two CAP-Gly domains in CYLD are ubiquitin-binding domains and demonstrate a requirement of CAP-Gly3 for CYLD activity and regulation of immune receptor signaling. Moreover, we identify a phosphorylation switch outside of the catalytic USP domain, which activates CYLD toward Lys63-linked polyubiquitin. The phosphorylated residue Ser568 is a novel tumor necrosis factor (TNF)-regulated phosphorylation site in CYLD and works in concert with Ser418 to enable CYLD-mediated deubiquitination and immune receptor signaling. We propose that phosphorylated CYLD, together with SPATA2 and LUBAC, functions as a ubiquitin-editing complex that balances Lys63- and Met1-linked polyubiquitin at receptor signaling complexes to promote LUBAC signaling.
Asunto(s)
Enzima Desubiquitinante CYLD/metabolismo , Línea Celular Tumoral , Cristalografía por Rayos X , Enzima Desubiquitinante CYLD/antagonistas & inhibidores , Enzima Desubiquitinante CYLD/genética , Endopeptidasas/química , Endopeptidasas/genética , Endopeptidasas/metabolismo , Humanos , Proteína Adaptadora de Señalización NOD2/genética , Proteína Adaptadora de Señalización NOD2/metabolismo , Fosforilación , Poliubiquitina/metabolismo , Unión Proteica , Dominios Proteicos , Estructura Terciaria de Proteína , Interferencia de ARN , ARN Interferente Pequeño/metabolismo , Transducción de Señal , Factor de Necrosis Tumoral alfa/metabolismo , Ubiquitina/metabolismoRESUMEN
The mTORC1 kinase complex regulates cell growth, proliferation, and survival. Because mis-regulation of DEPTOR, an endogenous mTORC1 inhibitor, is associated with some cancers, we reconstituted mTORC1 with DEPTOR to understand its function. We find that DEPTOR is a unique partial mTORC1 inhibitor that may have evolved to preserve feedback inhibition of PI3K. Counterintuitively, mTORC1 activated by RHEB or oncogenic mutation is much more potently inhibited by DEPTOR. Although DEPTOR partially inhibits mTORC1, mTORC1 prevents this inhibition by phosphorylating DEPTOR, a mutual antagonism that requires no exogenous factors. Structural analyses of the mTORC1/DEPTOR complex showed DEPTOR's PDZ domain interacting with the mTOR FAT region, and the unstructured linker preceding the PDZ binding to the mTOR FRB domain. The linker and PDZ form the minimal inhibitory unit, but the N-terminal tandem DEP domains also significantly contribute to inhibition.
Asunto(s)
Péptidos y Proteínas de Señalización Intracelular/metabolismo , Diana Mecanicista del Complejo 1 de la Rapamicina/metabolismo , Serina-Treonina Quinasas TOR/metabolismo , Sitios de Unión , Microscopía por Crioelectrón , Escherichia coli , Regulación de la Expresión Génica , Humanos , Procesamiento de Imagen Asistido por Computador , Péptidos y Proteínas de Señalización Intracelular/genética , Diana Mecanicista del Complejo 1 de la Rapamicina/genética , Modelos Moleculares , Dominios PDZ , Unión Proteica , Conformación Proteica , Proteínas Recombinantes , Serina-Treonina Quinasas TOR/genéticaRESUMEN
The Spike (S) protein of SARS-CoV-2 binds ACE2 to direct fusion with host cells. S comprises a large external domain, a transmembrane domain, and a short cytoplasmic tail. Understanding the intracellular trafficking of S is relevant to SARS-CoV-2 infection, and to vaccines expressing full-length S from mRNA or adenovirus vectors. Here we report a proteomic screen for cellular factors that interact with the cytoplasmic tail of S. We confirm interactions with the COPI and COPII vesicle coats, ERM family actin regulators, and the WIPI3 autophagy component. The COPII binding site promotes exit from the endoplasmic reticulum, and although binding to COPI should retain S in the early Golgi where viral budding occurs, there is a suboptimal histidine residue in the recognition motif. As a result, S leaks to the surface where it accumulates and can direct the formation of multinucleate syncytia. Thus, the trafficking signals in the tail of S indicate that syncytia play a role in the SARS-CoV-2 lifecycle.
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COVID-19/metabolismo , Membrana Celular/metabolismo , Células Gigantes/metabolismo , SARS-CoV-2/metabolismo , Glicoproteína de la Espiga del Coronavirus/metabolismo , Enzima Convertidora de Angiotensina 2/metabolismo , Animales , Vesículas Cubiertas por Proteínas de Revestimiento/metabolismo , Chlorocebus aethiops , Retículo Endoplásmico/metabolismo , Aparato de Golgi/metabolismo , Células HEK293 , Humanos , Unión Proteica , Dominios Proteicos , Proteómica , Células Vero , Ensamble de Virus/genéticaRESUMEN
Situated in critiques of the "moral muteness" of technical rationality, we examine concepts of ethics and the avoidance of ethical language among Australian gas pipeline engineers. We identify the domains in which they saw ethics as operating, including public safety, environmental protection, sustainability, commercial probity, and modern slavery. Particularly with respect to ethical matters that bear on public safety, in the course of design and operational activities, engineers principally advocated for action using technical language, avoiding reference to potential consequences such as death or destruction of property. Within their organizations, they saw themselves as occupying a technical "line of defense". We argue that this focus on technical language is action-oriented. Ethics tells practitioners of unacceptable outcomes, but it does not guide them in what they need to do to avoid that outcome in practice. We observed some cases where engineers had not made the connection between their role and ethics in the sense of public safety. We argue that muteness on ethical matters can obscure the nature of the risk where technical advice is being taken on by non-technical actors, and where technical actors themselves do not have a clear sense of their public safety obligations.