Review, evaluation, and discussion of the challenges of missing value imputation for mass spectrometry-based label-free global proteomics.

In this review, we apply selected imputation strategies to label-free liquid chromatography-mass spectrometry (LC-MS) proteomics datasets to evaluate the accuracy with respect to metrics of variance and classification. We evaluate several commonly used imputation approaches for individual merits and discuss the caveats of each approach with respect to the example LC-MS proteomics data. In general, local similarity-based approaches, such as the regularized expectation maximization and least-squares adaptive algorithms, yield the best overall performances with respect to metrics of accuracy and robustness.

Changes in protein expression across laboratory and field experiments in Geobacter bemidjiensis.

Bacterial extracellular metal respiration, as carried out by members of the genus Geobacter, is of interest for applications including microbial fuel cells and bioremediation. Geobacter bemidjiensis is the major species whose growth is stimulated during groundwater amendment with acetate. We have carried out label-free proteomics studies of G.

Protein and microRNA biomarkers from lavage, urine, and serum in military personnel evaluated for dyspnea.

Background: We have identified candidate protein and microRNA (miRNA) biomarkers for dyspnea by studying serum, lavage fluid, and urine from military personnel who reported serious respiratory symptoms after they were deployed to Iraq or Afghanistan.

Methods: Forty-seven soldiers with the complaint of dyspnea who enrolled in the STudy of Active Duty Military Personnel for Environmental Dust Exposure (STAMPEDE) underwent comprehensive pulmonary evaluations at the San Antonio Military Medical Center. The evaluation included fiber-optic bronchoscopy with bronchoalveolar lavage.

Expediting SRM assay development for large-scale targeted proteomics experiments.

Because of its high sensitivity and specificity, selected reaction monitoring (SRM)-based targeted proteomics has become increasingly popular for biological and translational applications. Selection of optimal transitions and optimization of collision energy (CE) are important assay development steps for achieving sensitive detection and accurate quantification; however, these steps can be labor-intensive, especially for large-scale applications. Herein, we explored several options for accelerating SRM assay development evaluated in the context of a relatively large set of 215 synthetic peptide targets.

Proteomic analysis of saliva in HIV-positive heroin addicts reveals proteins correlated with cognition.

The prevalence of HIV-associated neurocognitive disorders (HAND) remains high despite effective antiretroviral therapies. Multiple etiologies have been proposed over the last several years to account for this phenomenon, including the neurotoxic effects of antiretrovirals and co-morbid substance abuse; however, no underlying molecular mechanism has been identified. Emerging evidence in several fields has linked the gut to brain diseases, but the effect of the gut on the brain during HIV infection has not been explored.

Quantitative analysis of human salivary gland-derived intact proteome using top-down mass spectrometry.

There are several notable challenges inherent for fully characterizing the entirety of the human saliva proteome using bottom-up approaches, including polymorphic isoforms, PTMs, unique splice variants, deletions, and truncations. To address these challenges, we have developed a top-down based LC-MS/MS approach, which cataloged 20 major human salivary proteins with a total of 83 proteoforms, containing a broad range of PTMs. Among these proteins, several previously reported disease biomarker proteins were identified at the intact protein level, such as beta-2 microglobulin.

A semiautomated framework for integrating expert knowledge into disease marker identification.

Background: The availability of large complex data sets generated by high throughput technologies has enabled the recent proliferation of disease biomarker studies. However, a recurring problem in deriving biological information from large data sets is how to best incorporate expert knowledge into the biomarker selection process.

Objective: To develop a generalizable framework that can incorporate expert knowledge into data-driven processes in a semiautomated way while providing a metric for optimization in a biomarker selection scheme.

Approach to cerebrospinal fluid (CSF) biomarker discovery and evaluation in HIV infection.

Central nervous system (CNS) infection is a nearly universal facet of systemic HIV infection that varies in character and neurological consequences. While clinical staging and neuropsychological test performance have been helpful in evaluating patients, cerebrospinal fluid (CSF) biomarkers present a valuable and objective approach to more accurate diagnosis, assessment of treatment effects and understanding of evolving pathobiology. We review some lessons from our recent experience with CSF biomarker studies.

A Multi-Omic View of Host-Pathogen-Commensal Interplay in Salmonella-Mediated Intestinal Infection.

The potential for commensal microorganisms indigenous to a host (the 'microbiome' or 'microbiota') to alter infection outcome by influencing host-pathogen interplay is largely unknown. We used a multi-omics "systems" approach, incorporating proteomics, metabolomics, glycomics, and metagenomics, to explore the molecular interplay between the murine host, the pathogen Salmonella enterica serovar Typhimurium (S. Typhimurium), and commensal gut microorganisms during intestinal infection with S.

Evaluation of selected binding domains for the analysis of ubiquitinated proteomes.

Ubiquitination is an abundant post-translational modification that consists of covalent attachment of ubiquitin to lysine residues or the N-terminus of proteins. Mono- and polyubiquitination have been shown to be involved in many critical eukaryotic cellular functions and are often disrupted by intracellular bacterial pathogens. Affinity enrichment of ubiquitinated proteins enables global analysis of this key modification.

Trauma-associated human neutrophil alterations revealed by comparative proteomics profiling.

Purpose: Polymorphonuclear neutrophils (PMNs) play an important role in mediating the innate immune response after severe traumatic injury; however, the cellular proteome response to traumatic condition is still largely unknown.

Experimental Design: We applied 2D-LC-MS/MS-based shotgun proteomics to perform comparative proteome profiling of human PMNs from severe trauma patients and healthy controls.

Results: A total of 197 out of ~2500 proteins (being identified with at least two peptides) were observed with significant abundance changes following the injury.

Suite of activity-based probes for cellulose-degrading enzymes.

Microbial glycoside hydrolases play a dominant role in the biochemical conversion of cellulosic biomass to high-value biofuels. Anaerobic cellulolytic bacteria are capable of producing multicomplex catalytic subunits containing cell-adherent cellulases, hemicellulases, xylanases, and other glycoside hydrolases to facilitate the degradation of highly recalcitrant cellulose and other related plant cell wall polysaccharides. Clostridium thermocellum is a cellulosome-producing bacterium that couples rapid reproduction rates to highly efficient degradation of crystalline cellulose.

A comparative analysis of computational approaches to relative protein quantification using peptide peak intensities in label-free LC-MS proteomics experiments.

Liquid chromatography coupled with mass spectrometry (LC-MS) is widely used to identify and quantify peptides in complex biological samples. In particular, label-free shotgun proteomics is highly effective for the identification of peptides and subsequently obtaining a global protein profile of a sample. As a result, this approach is widely used for discovery studies.

DanteR: an extensible R-based tool for quantitative analysis of -omics data.

Motivation: The size and complex nature of mass spectrometry-based proteomics datasets motivate development of specialized software for statistical data analysis and exploration. We present DanteR, a graphical R package that features extensive statistical and diagnostic functions for quantitative proteomics data analysis, including normalization, imputation, hypothesis testing, interactive visualization and peptide-to-protein rollup. More importantly, users can easily extend the existing functionality by including their own algorithms under the Add-On tab.

Morphine produces immunosuppressive effects in nonhuman primates at the proteomic and cellular levels.

Morphine has long been known to have immunosuppressive properties in vivo, but the molecular and immunologic changes induced by it are incompletely understood. To explore how these changes interact with lentiviral infections in vivo, animals from two nonhuman primate species (African green monkeys and pigtailed macaques) were provided morphine and studied using a systems biology approach. Biological specimens were obtained from multiple sources (e.

Macaque proteome response to highly pathogenic avian influenza and 1918 reassortant influenza virus infections.

The host proteome response and molecular mechanisms that drive disease in vivo during infection by a human isolate of the highly pathogenic avian influenza virus (HPAI) and 1918 pandemic influenza virus remain poorly understood. This study presents a comprehensive characterization of the proteome response in cynomolgus macaque (Macaca fascicularis) lung tissue over 7 days of infection with HPAI (the most virulent), a reassortant virus containing 1918 hemagglutinin and neuraminidase surface proteins (intermediate virulence), or a human seasonal strain (least virulent). A high-sensitivity two-dimensional liquid chromatography-tandem mass spectroscopy strategy and functional network analysis were implemented to gain insight into response pathways activated in macaques during influenza virus infection.

Characterization of macaque pulmonary fluid proteome during monkeypox infection: dynamics of host response.

Understanding viral pathogenesis is challenging because of confounding factors, including nonabrasive access to infected tissues and high abundance of inflammatory mediators that may mask mechanistic details. In diseases such as influenza and smallpox where the primary cause of mortality results from complications in the lung, the characterization of lung fluid offers a unique opportunity to study host-pathogen interactions with minimal effect on infected animals. This investigation characterizes the global proteome response in the pulmonary fluid, bronchoalveolar lavage fluid, of macaques during upper respiratory infection by monkeypox virus (MPXV), a close relative of the causative agent of smallpox, variola virus.

Extensive HIV-1 intra-host recombination is common in tissues with abnormal histopathology.

There is evidence that immune-activated macrophages infected with the Human Immunodeficiency Virus (HIV) are associated with tissue damage and serve as a long-lived viral reservoir during therapy. In this study, we analyzed 780 HIV genetic sequences generated from 53 tissues displaying normal and abnormal histopathology. We found up to 50% of the sequences from abnormal lymphoid and macrophage rich non-lymphoid tissues were intra-host viral recombinants.

HIV-1 activates macrophages independent of Toll-like receptors.

Background: Macrophages provide an interface between innate and adaptive immunity and are important long-lived reservoirs for Human Immunodeficiency Virus Type-1 (HIV-1). Multiple genetic networks involved in regulating signal transduction cascades and immune responses in macrophages are coordinately modulated by HIV-1 infection.

Methodology/principal Findings: To evaluate complex interrelated processes and to assemble an integrated view of activated signaling networks, a systems biology strategy was applied to genomic and proteomic responses by primary human macrophages over the course of HIV-1 infection.

Impact on genetic networks in human macrophages by a CCR5 strain of human immunodeficiency virus type 1.

Human immunodeficiency virus type 1 (HIV-1) impacts multiple lineages of hematopoietic cells, including lymphocytes and macrophages, either by direct infection or indirectly by perturbations of cell networks, leading to generalized immune deficiency. We designed a study to discover, in primary human macrophages, sentinel genetic targets that are impacted during replication over the course of 7 days by a CCR5-using virus. Expression of mRNA and proteins in virus- or mock-treated macrophages from multiple donors was evaluated.