Reviews & Perspectives
New Views of Old Proteins: Clarifying the Enigmatic Proteome
In Brief Capturing the biology of proteins will require improved technologies to readout their composition in space and time. Developing these improved technologies presents a major opportunity for biomedical research. How might we proceed in the decades ahead?MHC Class I Immunopeptidome: Past, Present, and Future
In Brief A pioneer in studying CD8+ T-cell immunosurveillance of viruses and tumors reviews the critical contributions of MS-based studies to early, current, and future understanding of how cells generate the MHC class I immunopeptidome: the repertoire of foreign and self-peptides presented by MHC class I molecules for T-cell recognition.Scaling Up Single-Cell Proteomics
In Brief Single-cell proteomics will drive the next wave of single-cell biology. This requires broad adoption of existing methods, the application of rigorous quality control standards, and the continuous advancement of the technology. The advancement will be driven by numerous innovations, including highly parallelized analysis, and will increase the throughput, quantitative accuracy, and the accessibility of the single-cell proteomics.Ethical Principles, Constraints, and Opportunities in Clinical Proteomics
In Brief We introduce bioethical principles and use these as operational definitions to carry out a systematic review of the literature on ethical issues in clinical proteomics. We identify 10 ethical themes across 16 studies, many of which are familiar from other fields. We therefore survey how genomics has dealt with ethical issues and regulation. We also add our own perspectives on the ethical aspects of study design and sample treatment as well as the ethical potential of preventive proteomics profiling.Reflections on the HUPO Human Proteome Project, the Flagship Project of the Human Proteome Organization, at 10 Years
In Brief Starting from several organ-oriented projects, HUPO in 2010 launched the Human Proteome Project to identify and characterize the protein parts list and integrate proteomics into multiomics research. Key steps were partnerships with neXtProt, PRIDE, PeptideAtlas, Human Protein Atlas, and instrument makers; global engagement of researchers; creation of ProteomeXchange; adoption of HPP Guidelines for Interpretation of MS Data and SRMAtlas for proteotypic peptides; annual metrics of finding “missing proteins” and functionally annotating proteins; and initiatives for early career scientists.Data Management of Sensitive Human Proteomics Data: Current Practices, Recommendations, and Perspectives for the Future
In Brief Availability of proteomics data in the public domain has become the norm, as it has been the case in genomics and transcriptomics for many years. Analogously to sequencing data, there are increasing ethical issues and legal requirements related to sensitive human clinical proteomics data. We review the current state of the art and make concrete recommendations to address these issues in the proteomics field, which are summarized in four different areas.Are There Indeed Spliced Peptides in the Immunopeptidome?
In Brief Peptide splicing was suggested to significantly contribute ligands to the immunopeptidome. This article argues that peptide splicing is at most very rare, even if it happens at all. Considerations against peptide splicing are based on bioinformatics calculations related to the analysis of the LC-MS/MS data, and on the abundance of water in the cells, which should compete effectively with the transpeptidation reaction, needed for peptide splicing.Low Mass Blood Peptides Discriminative of Inflammatory Bowel Disease (IBD) Severity: A Quantitative Proteomic Perspective
Breakdown of the protective gut barrier releases effector molecules and degradation products into the blood stream making serum and plasma ideal as a diagnostic medium. The enriched low mass proteome is unexplored as a source of differentiators for diagnosing and monitoring inflammatory bowel disease (IBD) activity, that is less invasive than colonoscopy. Differences in the enriched low mass plasma proteome (<25 kDa) were assessed by label-free quantitative mass-spectrometry. A panel of marker candidates were progressed to validation phase and “Tier-2” FDA-level validated quantitative assay.A Proteome-wide Domain-centric Perspective on Protein Phosphorylation
Phosphorylation is a widespread post-translational modification that modulates the function of a large number of proteins. Here we show that a significant proportion of all the domains in the human proteome is significantly enriched or depleted in phosphorylation events. A substantial improvement in phosphosites prediction is achieved by leveraging this observation, which has not been tapped by existing methods. Phosphorylation sites are often not shared between multiple occurrences of the same domain in the proteome, even when the phosphoacceptor residue is conserved.A Proteomic Perspective of Sirtuin 6 (SIRT6) Phosphorylation and Interactions and Their Dependence on Its Catalytic Activity
Sirtuin 6 (SIRT6), a member of the mammalian sirtuin family, is a nuclear deacetylase with substrate-specific NAD+-dependent activity. SIRT6 has emerged as a critical regulator of diverse processes, including DNA repair, gene expression, telomere maintenance, and metabolism. However, our knowledge regarding its interactions and regulation remains limited. Here, we present a comprehensive proteomics-based analysis of SIRT6 protein interactions and their dependence on SIRT6 catalytic activity. We also identify evolutionarily conserved SIRT6 phosphorylations, including four within a proline-rich disordered region, and show that the conserved S338 phosphorylation can modulate selected SIRT6 interactions.A Proteomic Perspective of Inbuilt Viral Protein Regulation: pUL46 Tegument Protein is Targeted for Degradation by ICP0 during Herpes Simplex Virus Type 1 Infection
Much like the host cells they infect, viruses must also regulate their life cycles. Herpes simples virus type 1 (HSV-1), a prominent human pathogen, uses a promoter-rich genome in conjunction with multiple viral trans-activating factors. Following entry into host cells, the virion-associated outer tegument proteins pUL46 and pUL47 act to increase expression of viral immediate–early (α) genes, thereby helping initiate the infection life cycle. Because pUL46 has gone largely unstudied, we employed a hybrid mass spectrometry-based approach to determine how pUL46 exerts its functions during early stages of infection.Putting the Pieces Together: High-performance LC-MS/MS Provides Network-, Pathway-, and Protein-level Perspectives in Populus
High-performance mass spectrometry (MS)-based proteomics enabled the construction of a detailed proteome atlas for Populus, a woody perennial plant model organism. Optimization of experimental procedures and implementation of current state-of-the-art instrumentation afforded the most detailed look into the predicted proteome space of Populus, offering varying proteome perspectives: (1) network-wide, (2) pathway-specific, and (3) protein-level viewpoints. Together, enhanced protein retrieval through a detergent-based lysis approach and maximized peptide sampling via the dual-pressure linear ion trap mass spectrometer (LTQ Velos), have resulted in the identification of 63,056 tryptic peptides.Proteome Dynamics: Revisiting Turnover with a Global Perspective
Although bulk protein turnover has been measured with the use of stable isotope labeled tracers for over half a century, it is only recently that the same approach has become applicable to the level of the proteome, permitting analysis of the turnover of many proteins instead of single proteins or an aggregated protein pool. The optimal experimental design for turnover studies is dependent on the nature of the biological system under study, which dictates the choice of precursor label, protein pool sampling strategy, and treatment of data.Dehydration-responsive Nuclear Proteome of Rice (Oryza sativa L.) Illustrates Protein Network, Novel Regulators of Cellular Adaptation, and Evolutionary Perspective
Water deficit or dehydration is the most crucial environmental constraint on plant growth and development and crop productivity. It has been postulated that plants respond and adapt to dehydration by altering their cellular metabolism and by activating various defense machineries. The nucleus, the regulatory hub of the eukaryotic cell, is a dynamic system and a repository of various macromolecules that serve as modulators of cell signaling dictating the cell fate decision. To better understand the molecular mechanisms of dehydration-responsive adaptation in plants, we developed a comprehensive nuclear proteome of rice.
