In JoVE (2)

Other Publications (11)

Articles by Sebastian Wagner in JoVE

Other articles by Sebastian Wagner on PubMed

Regulation of Ubiquitin-binding Proteins by Monoubiquitination

Nature Cell Biology. Feb, 2006  |  Pubmed ID: 16429130

Proteins containing ubiquitin-binding domains (UBDs) interact with ubiquitinated targets and regulate diverse biological processes, including endocytosis, signal transduction, transcription and DNA repair. Many of the UBD-containing proteins are also themselves monoubiquitinated, but the functional role and the mechanisms that underlie this modification are less well understood. Here, we demonstrate that monoubiquitination of the endocytic proteins Sts1, Sts2, Eps15 and Hrs results in intramolecular interactions between ubiquitin and their UBDs, thereby preventing them from binding in trans to ubiquitinated targets. Permanent monoubiquitination of these proteins, mimicked by the fusion of ubiquitin to their carboxyl termini, impairs their ability to regulate trafficking of ubiquitinated receptors. Moreover, we mapped the in vivo monoubiquitination site in Sts2 and demonstrated that its mutation enhances the Sts2-mediated effects of epidermal-growth-factor-receptor downregulation. We propose that monoubiquitination of ubiquitin-binding proteins inhibits their capacity to bind to and control the functions of ubiquitinated targets in vivo.

Sternal Fractures Occur Most Often in Old Cars to Seat-belted Drivers Without Any Airbag Often with Concomitant Spinal Injuries: Clinical Findings and Technical Collision Variables Among 42,055 Crash Victims

The Annals of Thoracic Surgery. Aug, 2006  |  Pubmed ID: 16863741

The incidence and treatment of sternal fractures caused by traffic accidents is of increasing importance to ensure best possible outcomes.

E3-independent Monoubiquitination of Ubiquitin-binding Proteins

Molecular Cell. Jun, 2007  |  Pubmed ID: 17588522

Ubiquitin (Ub)-binding domains (UBDs) are key elements in conveying Ub-based cellular signals. UBD-containing proteins interact with ubiquitinated targets and control numerous biological processes. They themselves undergo UBD-dependent monoubiquitination, which promotes intramolecular binding of the UBD to the attached Ub and leads to their inactivation. Here, we report that, in contrast to the established ubiquitination pathway, the presence of UBDs allows the ubiquitination of host proteins independently of E3 ligases. UBDs of different types, including UBA, UIM, UBM, NFZ, and UBZ, can directly cooperate with Ub-charged E2 enzymes to promote monoubiquitination. Using FRET and siRNA technologies, we verify that Ub-loaded E2 and substrates interact in cells and that E2 enzymes are essential for their monoubiquitination in vivo. This modification is mechanistically and functionally distinct from E3-mediated and growth factor-dependent monoubiquitination.

Suppressor of T-cell Receptor Signalling 1 and 2 Differentially Regulate Endocytosis and Signalling of Receptor Tyrosine Kinases

FEBS Letters. Oct, 2007  |  Pubmed ID: 17880946

Suppressor of T-cell receptor signalling 1 and 2 (Sts-1 and 2) negatively regulate the endocytosis of receptor tyrosine kinases. The UBA domain of Sts-2 and SH3-dependent Cbl-binding are required for this function. Sts-1 and -2 also possess a PGM domain, which was recently reported to exhibit tyrosine phosphatase activity. Here, we demonstrate that the PGM of Sts-1, but not of Sts-2, dephosphorylates the EGFR at multiple tyrosines thereby terminating its signalling and endocytosis. In contrast to Sts-2 the UBA of Sts-1 did not contribute significantly to receptor stabilization. Thus, although Sts-1 and Sts-2 are structurally highly homologous and both inhibit ligand-induced EGFR degradation, their mechanisms of action differ significantly. As a consequence, Sts-1-containing receptor complexes are inactive, whereas Sts-2-containing complexes are signalling competent.

Signal Processing by Its Coil Zipper Domain Activates IKK Gamma

Proceedings of the National Academy of Sciences of the United States of America. Jan, 2008  |  Pubmed ID: 18216269

NF-kappaB activation occurs upon degradation of its inhibitor I-kappaB and requires prior phosphorylation of the inhibitor by I-kappaB kinase (IKK). Activity of IKK is governed by its noncatalytic subunit IKKgamma. Signaling defects due to missense mutations in IKKgamma have been correlated to its inability to either become ubiquitylated or bind ubiquitin noncovalently. Because the relative contribution of these events to signaling had remained unknown, we have studied mutations in the coil-zipper (CoZi) domain of IKKgamma that either impair signaling or cause constitutive NF-kappaB activity. Certain signaling-deficient alleles neither bound ubiquitin nor were they ubiquitylated by TRAF6. Introducing an activating mutation into those signaling-impaired alleles restored their ubiquitylation and created mutants constitutively activating NF-kappaB without repairing the ubiquitin-binding defect. Constitutive activity therefore arises downstream of ubiquitin binding but upstream of ubiquitylation. Such constitutive activity reveals a signal-processing function for IKKgamma beyond that of a mere ubiquitin-binding adaptor. We propose that this signal processing may involve homophilic CoZi interactions as suggested by the enhanced affinity of CoZi domains from constitutively active IKKgamma.

[Agreement Between Clinical Evaluation and Structured Clinical Interviews (SCID for DSM-IV) in Morbidly Obese Pre-bariatric Surgery Patients]

Psychotherapie, Psychosomatik, Medizinische Psychologie. Dec, 2010  |  Pubmed ID: 20401825

The goal of the study was to determine the concordance between mental disorder assessed during clinical evaluation and those independently obtained by a SCID interview in morbidly obese patients prior to bariatric surgery. In 116 patients a SCID interview was conducted. The agreement was moderate for any current diagnosis (kappa 0.43) current affective disorder (kappa 0.41) and current eating disorders (kappa 0.47). For current anxiety disorders agreement was poor wit a kappa of 0.11. For anxiety disorders and eating disorders the use of SCID resulted in more diagnoses than did standard clinical evaluation. Generally, the SCID produced more current axis 1 diagnoses than the clinical evaluation. When conducting a clinical evaluation prior to bariatric surgery a structured clinical interview should be used to assess mental co-mobidity.

Anxiety and Depression in Bariatric Surgery Patients: a Prospective, Follow-up Study Using Structured Clinical Interviews

Journal of Affective Disorders. Sep, 2011  |  Pubmed ID: 21501874

Candidates for bariatric surgery frequently have co-morbid psychiatric problems.

Phosphorylation of the Autophagy Receptor Optineurin Restricts Salmonella Growth

Science (New York, N.Y.). Jul, 2011  |  Pubmed ID: 21617041

Selective autophagy can be mediated via receptor molecules that link specific cargoes to the autophagosomal membranes decorated by ubiquitin-like microtubule-associated protein light chain 3 (LC3) modifiers. Although several autophagy receptors have been identified, little is known about mechanisms controlling their functions in vivo. In this work, we found that phosphorylation of an autophagy receptor, optineurin, promoted selective autophagy of ubiquitin-coated cytosolic Salmonella enterica. The protein kinase TANK binding kinase 1 (TBK1) phosphorylated optineurin on serine-177, enhancing LC3 binding affinity and autophagic clearance of cytosolic Salmonella. Conversely, ubiquitin- or LC3-binding optineurin mutants and silencing of optineurin or TBK1 impaired Salmonella autophagy, resulting in increased intracellular bacterial proliferation. We propose that phosphorylation of autophagy receptors might be a general mechanism for regulation of cargo-selective autophagy.

Proteome-wide Mapping of the Drosophila Acetylome Demonstrates a High Degree of Conservation of Lysine Acetylation

Science Signaling. 2011  |  Pubmed ID: 21791702

Posttranslational modification of proteins by acetylation and phosphorylation regulates most cellular processes in living organisms. Surprisingly, the evolutionary conservation of phosphorylated serine and threonine residues is only marginally higher than that of unmodified serines and threonines. With high-resolution mass spectrometry, we identified 1981 lysine acetylation sites in the proteome of Drosophila melanogaster. We used data sets of experimentally identified acetylation and phosphorylation sites in Drosophila and humans to analyze the evolutionary conservation of these modification sites between flies and humans. Site-level conservation analysis revealed that acetylation sites are highly conserved, significantly more so than phosphorylation sites. Furthermore, comparison of lysine conservation in Drosophila and humans with that in nematodes and zebrafish revealed that acetylated lysines were significantly more conserved than were nonacetylated lysines. Bioinformatics analysis using Gene Ontology terms suggested that the proteins with conserved acetylation control cellular processes such as protein translation, protein folding, DNA packaging, and mitochondrial metabolism. We found that acetylation of ubiquitin-conjugating E2 enzymes was evolutionarily conserved, and mutation of a conserved acetylation site impaired the function of the human E2 enzyme UBE2D3. This systems-level analysis of comparative posttranslational modification showed that acetylation is an anciently conserved modification and suggests that phosphorylation sites may have evolved faster than acetylation sites.

A Phospho-proteomic Screen Identifies Substrates of the Checkpoint Kinase Chk1

Genome Biology. 2011  |  Pubmed ID: 21851590

The cell-cycle checkpoint kinase Chk1 is essential in mammalian cells due to its roles in controlling processes such as DNA replication, mitosis and DNA-damage responses. Despite its paramount importance, how Chk1 controls these functions remains unclear, mainly because very few Chk1 substrates have hitherto been identified.

A Proteome-wide, Quantitative Survey of in Vivo Ubiquitylation Sites Reveals Widespread Regulatory Roles

Molecular & Cellular Proteomics : MCP. Oct, 2011  |  Pubmed ID: 21890473

Post-translational modification of proteins by ubiquitin is a fundamentally important regulatory mechanism. However, proteome-wide analysis of endogenous ubiquitylation remains a challenging task, and almost always has relied on cells expressing affinity tagged ubiquitin. Here we combine single-step immunoenrichment of ubiquitylated peptides with peptide fractionation and high-resolution mass spectrometry to investigate endogenous ubiquitylation sites. We precisely map 11,054 endogenous putative ubiquitylation sites (diglycine-modified lysines) on 4,273 human proteins. The presented data set covers 67% of the known ubiquitylation sites and contains 10,254 novel sites on proteins with diverse cellular functions including cell signaling, receptor endocytosis, DNA replication, DNA damage repair, and cell cycle progression. Our method enables site-specific quantification of ubiquitylation in response to cellular perturbations and is applicable to any cell type or tissue. Global quantification of ubiquitylation in cells treated with the proteasome inhibitor MG-132 discovers sites that are involved in proteasomal degradation, and suggests a nonproteasomal function for almost half of all sites. Surprisingly, ubiquitylation of about 15% of sites decreased more than twofold within four hours of MG-132 treatment, showing that inhibition of proteasomal function can dramatically reduce ubiquitylation on many sites with non-proteasomal functions. Comparison of ubiquitylation sites with acetylation sites reveals an extensive overlap between the lysine residues targeted by these two modifications. However, the crosstalk between these two post-translational modifications is significantly less frequent on sites that show increased ubiquitylation upon proteasome inhibition. Taken together, we report the largest site-specific ubiquitylation dataset in human cells, and for the first time demonstrate proteome-wide, site-specific quantification of endogenous putative ubiquitylation sites.

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