Enrichment Of Posttranslational Modifications Research Articles

The Plant PTM Viewer 2.0: in-depth exploration of plant protein modification landscapes.

Post-translational modifications (PTMs) greatly increase protein diversity and functionality. To help the plant research community interpret the ever-increasing number of reported PTMs, the Plant PTM Viewer (https://www.psb.ugent.be/PlantPTMViewer) provides an intuitive overview of plant protein PTMs and the tools to assess it. This update includes 62 novel PTM profiling studies, adding a total of 112 000 modified peptides reporting plant PTMs, including 14 additional PTM types and three species (moss, tomato, and soybean). Furthermore, an open modification re-analysis of a large-scale Arabidopsis thaliana mass spectrometry tissue atlas identified previously uncharted landscapes of lysine acylations predominant in seed and flower tissues and 3-phosphoglycerylation on glycolytic enzymes in plants. An extra 'Protein list analysis' tool was developed for retrieval and assessing the enrichment of PTMs in a protein list of interest. We conducted a protein list analysis on nuclear proteins, revealing a substantial number of redox modifications in the nucleus, confirming previous assumptions regarding the redox regulation of transcription. We encourage the plant research community to use PTM Viewer 2.0 for hypothesis testing and new target discovery, and also to submit new data to expand the coverage of conditions, plant species, and PTM types, thereby enriching our understanding of plant biology.

The Impacts of Osmotic Stress During the Critical Window of Development on Protein and Histone PTM Alterations in California grunion

The California Grunion, Leuresthes tenuis, can experience a broad range of salinities during their early life stages, with their nursery grounds measuring salinities of 21 to 42ppt under normal conditions. Due to the unique subterrestrial incubation of their eggs within the sand of California beaches, it is not unlikely for this marine fish to hatch in non-seawater conditions, whereafter the larvae may transition to relatively diluted estuaries or concentrated harbors to develop as juveniles for several months. Consequently, they are an ideal system to study the impacts of ecologically relevant salinity stress on the alteration of proteins and histone post-translational modifications (PTMs) during early development. The study of the relationship between the critical window of development (CWD), in which sexual bipotential is lost, and the longevity of protein landscape and histone PTM changes has not been widely explored. The CWD is of interest as this is when the gametes of this species become set. Therefore, we hypothesize that histone PTM changes that occur during this time may thus be a form of heritable epigenetics. Thus, hypo-and-hyperosmotic exposures of L. tenuis hatchlings during this window, and past it, attempt to identify if the CWD is relevant to the presence and persistence of protein and histone PTM changes under salinity stress. We hypothesize that exposure to osmotic stress during the CWD will result in induced compensatory mechanisms in the protein landscape of the California grunion larvae, as well as persistent alterations in the histone PTMs in the larvae. To elucidate the relationship between these factors, California grunion larvae were exposed in replicate to one of three chronic salinity treatments (16ppt, 32ppt, or 40ppt) for the duration of their CWD (68dph), with 16ppt and 40ppt inducing hypoosmotic and hyperosmotic stress respectively. Chronic post-CWD exposures and recovery times until 98dph were used to determine whether the CWD or prolonged salinity exposures were key to alterations in the histone PTM and protein landscape of the larvae. After each timepoint, L. tenuis were culled and processed for histone PTM enrichment and proteomic analysis. At the time of culling, there were no significant differences in survivorship between replicates and experimental groups, with statistically significant different deaths between groups occurring only shortly after hatching. Skyline and MSstats were used in the analysis of the statistical significance of differential regulation of proteins and histone PTMs under stress conditions versus the controls. Of special interest is the osmoregulatory mechanisms involved in the myo-inositol biosynthesis pathway, with analysis focusing on the abundance of histone acetylation, amidation, ubiquitylation, and 4-hydroxynonelation in histone PTMs, as the accumulations of these have been found to be correlated with osmotic stress in some fish tissues. Funding provided by NSF IOS-2209383 and NSF GRFP. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Uncommon posttranslational modifications in proteomics: ADP-ribosylation, tyrosine nitration, and tyrosine sulfation.

Posttranslational modifications (PTMs) are covalent modifications of proteins that modulate the structure and functions of proteins and regulate biological processes. The development of various mass spectrometry-based proteomics workflows has facilitated the identification of hundreds of PTMs and aided the understanding of biological significance in a high throughput manner. Improvements in sample preparation and PTM enrichment techniques, instrumentation for liquid chromatography-tandem mass spectrometry (LC-MS/MS), and advanced data analysis tools enhance the specificity and sensitivity of PTM identification. Highly prevalent PTMs like phosphorylation, glycosylation, acetylation, ubiquitinylation, and methylation are extensively studied. However, the functions and impact of less abundant PTMs are not as well understood and underscore the need for analytical methods that aim to characterize these PTMs. This review focuses on the advancement and analytical challenges associated with the characterization of three less common but biologically relevant PTMs, specifically, adenosine diphosphate-ribosylation, tyrosine sulfation, and tyrosine nitration. The advantages and disadvantages of various enrichment, separation, and MS/MS techniques utilized to identify and localize these PTMs are described.

Comprehensive Protocol to Simultaneously Study Protein Phosphorylation, Acetylation, and N-Linked Sialylated Glycosylation.

Posttranslational modifications (PTMs) such as phosphorylation, acetylation, and glycosylation are an essential regulatory mechanism of protein function and interaction, and they are associated with a wide range of biological processes. Since most PTMs alter the molecular mass of a protein, mass spectrometry (MS) is the ideal analytical tool for studying various PTMs. However, PTMs are often present in substoichiometric levels, and therefore their unmodified counterpart often suppresses their signal in MS. Consequently, PTM analysis by MS is a challenging task, requiring highly specialized and sensitive PTM-specific enrichment methods. Currently, several methods have been implemented for PTM enrichment, and each of them has its drawbacks and advantages as they differ in selectivity and specificity toward specific protein modifications. Unfortunately, for the vast majority of more than 400 known modifications, we have no or poor tools for selective enrichment.Here, we describe a comprehensive workflow to simultaneously study phosphorylation, acetylation, and N-linked sialylated glycosylation from the same biological sample. The protocol involves an initial titanium dioxide (TiO2) step to enrich for phosphopeptides and sialylated N-linked glycopeptides followed by glycan release and post-fractionation using sequential elution from immobilized metal affinity chromatography (SIMAC) to separate mono-phosphorylated and deglycosylated peptides from multi-phosphorylated ones. The IMAC flow-through and acidic elution are subsequently subjected to a next round of TiO2 enrichment for further separation of mono-phosphopeptides from deglycosylated peptides. Furthermore, the lysine-acetylated peptides present in the first TiO2 flow-through fraction are enriched by immunoprecipitation (IP) after peptide cleanup. Finally, the samples are fractionated by high pH reversed phase chromatography (HpH) or hydrophilic interaction liquid chromatography (HILIC ) to reduce sample complexity and increase the coverage in the subsequent LC-MS /MS analysis. This allows the analysis of multiple types of modifications from the same highly complex biological sample without decreasing the quality of each individual PTM study.

Abstract 1308: Post translational crosstalk networks identify strategies to overcome EMT-mediated resistance to EGFR inhibitors

Abstract Epithelial-mesenchymal transition (EMT) mediates intrinsic and acquired resistance to epidermal growth factor receptor (EGFR) inhibitors. This becomes a major hurdle in lung cancer treatment due to the lack of effective therapeutic strategies. We hypothesized that decoding the EMT signaling network could provide insights into the specific combinatorial logic associated with EMT signaling and identify new therapeutic strategies to combat EGFRi resistance. To test this hypothesis, we applied sequential enrichment of post-translational modifications (SEPTM) proteomics to analyze proteomes of expressed proteins and multiple post-translational modifications (PTM) including phosphorylation, ubiquitination, and acetylation in erlotinib sensitive cells (HCC4006) and matched erlotinib resistant cells after EMT (HCC4006ER). We conducted integrative informatics to characterize EMT associated proteins, PTMs, pathways, cross-talk among PTMs and signaling networks from our data. We used siRNA and small molecules to functionally interrogate our results by assaying cell viability and migration. We identified 6,641 proteins, 2,418 unique pSTY sites, 784 unique UbK-sites and 713 unique AcK-sites respectively. We found 377 proteins increased and 1377 proteins decreased (p<0.05, fold>2) in HCC4006ER cells compared to parent HCC4006 cells. We constructed an EMT signaling network, composed of 206 proteins with PTM changes including pSTY-sites (141 increase, 191 decrease), UbK-sites (29 increase, 32 decrease) and AcK-sites (14 increase, 46 decrease). Of 206 differentially modified proteins, 88 proteins are reported to be associated with EMT. Pathway analysis enriched 284 pathways from this EMT signaling network. We identified small molecule inhibitors associated with various pathways and tested for their effects on resistant cells. Inhibitors targeting 17 pathways and 3 major transcription factors were found to have effects on H4006ER viability, with inhibitors targeting DDR1, WNT and CDK signaling pathways demonstrating the most impact. Using RNAi, we found that that loss-of-function of 8 of 88 EMT-associated proteins (TAGLN2, STMN1, FYN, HNRNPA2B1, DDR1, INPPL1, OSMR and PRKAR2A) decreased HCC4006ER cell viability. Finally, integrative informatics revealed cross-talk among PTMs within EMT signaling network. From this analysis, we found that inhibiting GLI induced transcription sensitizes H4006ER cells to both EGFR inhibitor and Casein Kinase inhibitor. Collectively, SEPTM proteomics allows decoding the complex interplay in PTM modulation associated with EMT-mediated resistance. Our results suggest DDR1 as a potential actionable target for EMT driven resistance, which can serve as an example for combinatorial targeting of EMT proteins and signaling pathways as a strategy for overcoming EMT-mediated drug resistance. Citation Format: Guolin Zhang, Karen Ross, Bin Fang, Jun-Min Zhou, Paul A. Stewart, Emma Adhikari, Eric A. Welsh, Xuefeng Wang, John M. Koomen, Cathy H. Wu, Eric B. Haura. Post translational crosstalk networks identify strategies to overcome EMT-mediated resistance to EGFR inhibitors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 1308.

Utilizing a Comprehensive Immunoprecipitation Enrichment System to Identify an Endogenous Post-translational Modification Profile for Target Proteins

It is now well-appreciated that post-translational modifications (PTMs) play an integral role in regulating a protein's structure and function, which may be essential for a given protein's role both physiologically and pathologically. Enrichment of PTMs is often necessary when investigating the PTM status of a target protein, because PTMs are often transient and relatively low in abundance. Many pitfalls are encountered when enriching for a PTM of a target protein, such as buffer incompatibility, the target protein antibody is not IP-compatible, loss of PTM signal, and others. The degree of difficulty is magnified when investigating multiple PTMs like acetylation, ubiquitination, SUMOylation 2/3, and tyrosine phosphorylation for a given target protein. Studying a combination of these PTMs may be necessary, as crosstalk between PTMs is prevalent and critical for protein regulation. Often, these PTMs are studied in different lysis buffers and with unique inhibitor compositions. To simplify the process, a unique denaturing lysis system was developed that effectively isolates and preserves these four PTMs; thus, enabling investigation of potential crosstalk in a single lysis system. A unique filter system was engineered to remove contaminating genomic DNA from the lysate, which is a problematic by-product of denaturing buffers. Robust affinity matrices targeting each of the four PTMs were developed in concert with the buffer system to maximize the enrichment and detection of the endogenous states of these four PTMs. This comprehensive PTM detection toolset streamlines the process of obtaining critical information about whether a protein is modified by one or more of these PTMs.

Utilizing a Comprehensive Immunoprecipitation Enrichment System to Identify an Endogenous Post-translational Modification Profile for Target Proteins.

It is now well-appreciated that post-translational modifications (PTMs) play an integral role in regulating a protein's structure and function, which may be essential for a given protein's role both physiologically and pathologically. Enrichment of PTMs is often necessary when investigating the PTM status of a target protein, because PTMs are often transient and relatively low in abundance. Many pitfalls are encountered when enriching for a PTM of a target protein, such as buffer incompatibility, the target protein antibody is not IP-compatible, loss of PTM signal, and others. The degree of difficulty is magnified when investigating multiple PTMs like acetylation, ubiquitination, SUMOylation 2/3, and tyrosine phosphorylation for a given target protein. Studying a combination of these PTMs may be necessary, as crosstalk between PTMs is prevalent and critical for protein regulation. Often, these PTMs are studied in different lysis buffers and with unique inhibitor compositions. To simplify the process, a unique denaturing lysis system was developed that effectively isolates and preserves these four PTMs; thus, enabling investigation of potential crosstalk in a single lysis system. A unique filter system was engineered to remove contaminating genomic DNA from the lysate, which is a problematic by-product of denaturing buffers. Robust affinity matrices targeting each of the four PTMs were developed in concert with the buffer system to maximize the enrichment and detection of the endogenous states of these four PTMs. This comprehensive PTM detection toolset streamlines the process of obtaining critical information about whether a protein is modified by one or more of these PTMs.

Body Fluid Degradomics and Characterization of Basic N-Terminome.

Rapid improvements in instrumentation and data analysis make mass spectrometry-based proteomics the method of choice for global characterization of proteomes and discovery of protein-based biomarkers. On the contrary to tissue biopsies, body fluids-e.g., blood, wound fluid, urine, and saliva-are noninvasive and easy to collect and process. However, they are very complex and present high dynamic ranges of protein concentrations, rendering direct shotgun proteomics analysis as inefficient for identification of low-abundance proteins in these specimens. Sample prefractionation, immunoaffinity depletion of highly abundant proteins, and enrichment of posttranslational modifications (PTM) are common strategies for proteome simplification of body fluids. Combinatorial peptide ligand libraries (CPLL) relatively deplete high-abundance proteins by binding equimolar amounts of protein species in the sample and provide an elegant species-independent alternative to immunoaffinity-based approaches. By cleaving target proteins, proteases catalyze an irreversible PTM, whereby uncontrolled proteolysis is associated with many diseases. Thus, proteolytic events represent powerful indicators for disease progression and their specific identification in body fluids holds great promises for establishment of novel biomarkers. Quantitative N-terminal enrichment strategies, such as terminal amine isotopic labeling of substrates (TAILS) detect protease-generated neo-N-termini with high specificity and increase coverage of low-abundance proteins by inherent proteome simplification. In this chapter, we describe a protocol that combines the CPLL technology with iTRAQ-based TAILS to systematically characterize the basic N-terminome of body fluid proteomes and its alterations in disease conditions that we have successfully applied to explore the wound fluid degradome at multiple time points after skin injury.

Identification, Quantification, and Site Localization of Protein Posttranslational Modifications via Mass Spectrometry-Based Proteomics.

Posttranslational modifications (PTMs) are important biochemical processes for regulating various signaling pathways and determining specific cell fate. Mass spectrometry (MS)-based proteomics has been developed extensively in the past decade and is becoming the standard approach for systematic characterization of different PTMs on a global scale. In this chapter, we will explain the biological importance of various PTMs, summarize key innovations in PTMs enrichment strategies, high-performance liquid chromatography (HPLC)-based fractionation approaches, mass spectrometry detection methods, and lastly bioinformatic tools for PTMs related data analysis. With great effort in recent years by the proteomics community, highly efficient enriching methods and comprehensive resources have been developed. This chapter will specifically focus on five major types of PTMs; phosphorylation, glycosylation, ubiquitination/sumosylation, acetylation, and methylation.

Progress and Application of LC-MS Technologies for Characterizing Protein Post Translational Modifications

Abstract Post translational modifications (PTMs) are the utmost important molecular processes for regulating various signaling pathways and determining specific cell fate. At molecular level, PTMs related “writing”, “erasing” and “reading” processes are the most critical processes for realizing their dynamic regulation and all belong to the research areas of biological analytical chemistry. Liquid chromatography-mass spectrometry (LC-MS)-based proteomics have been developed extensively in the past decade and becoming the standard approach for characterizing different PTMs on a global scale. Here, we will explain the biological importance of various PTMs, summarize key innovation for developing PTMs enrichment strategies, high-performance liquid chromatography-based fractionation approaches, and mass spectrometry detection methods and highlight some new research directions. With recent great effort from the proteomics society for developing highly efficient enriching methods and building comprehensive resources, we will specifically focus our discussion on five major types of PTMs, including phosphorylation, glycosylation, ubiquitination, acetylation, and methylation. With the development of novel enrichment methods, liquid chromatography separation approaches, and biological mass spectrometry techniques, we expect the methodology and technology innovation in bioanalytical chemistry field will greatly facilitate the protein PTMs research at system level.

Characterization of human neural differentiation from pluripotent stem cells using proteomics/PTMomics--current state-of-the-art and challenges.

Stem cells are unspecialized cells capable of self-renewal and to differentiate into the large variety of cells in the body. The possibility to differentiate these cells into neural precursors and neural cells in vitro provides the opportunity to study neural development, nerve cell biology, neurological disease as well as contributing to clinical research. The neural differentiation process is associated with changes at protein and their post-translational modifications (PTMs). PTMs are important regulators of proteins physicochemical properties, function, activity, and interaction with other proteins, DNA/RNA, and complexes. Moreover, the interplay between PTMs is essential to regulate a range of cellular processes that abnormalities in PTM signaling are associated with several diseases. Altogether, this makes PTMs very relevant to study in order to uncover disease pathogenesis and increase the understanding of molecular processes in cells. Substantial advances in PTM enrichment methods and mass spectrometry has allowed the characterization of a subset of PTMs in large-scale studies. This review focuses on the current state-of-the-art of proteomic, as well as PTMomic studies related to human neural differentiation from pluripotent stem cells. Moreover, some of the challenges in stem cell biology, differentiation, and proteomics/PTMomics that are not exclusive to neural development will be discussed.

Comprehensive protocol to simultaneously study protein phosphorylation, acetylation, and N-linked sialylated glycosylation.

Post-translational modifications (PTMs) such as phosphorylation, acetylation, and glycosylation are an essential regulatory mechanism of protein function and they are associated with a range of biological processes. Since most PTMs alter the molecular mass of a protein, mass spectrometry (MS) is the ideal analytical tool for studying various PTMs. However, PTMs are generally present in substoichiometric levels and therefore their unmodified counterpart often suppresses their signal in MS. Consequently, PTM analysis by MS is a challenging task requiring highly specialized and sensitive enrichment methods. Currently, several methods have been implemented for PTM enrichment and each of them has its drawbacks and advantages as they differ in selectivity and specificity toward specific protein modifications. Unfortunately, for most of the more than 300 known modifications we have none or poor tools for selective enrichment.Here, we describe a comprehensive workflow to simultaneously study phosphorylation, acetylation, and N-linked sialylated glycosylation from the same biological sample. The protocol involves an initial titanium dioxide (TiO2) step to enrich for phosphopeptides and sialylated N-linked glycopeptides followed by glycan release and post-fractionation using sequential elution from immobilized metal affinity chromatography (SIMAC) to separate mono-phosphorylated and deglycosylated peptides from multi-phosphorylated ones. The IMAC flow-through and acidic elution is subsequently subjected to a next round of TiO2 enrichment for further separation of mono-phosphopeptides from deglycosylated peptides. In addition, the acetylated peptides present in the first TiO2 flow-through are enriched by immunoprecipitation (IP). Finally, the samples are fractionated by hydrophilic interaction liquid chromatography (HILIC) to reduce sample complexity and increase the coverage during LC-MS/MS analysis. This allows the analysis of multiple types of modifications from the same highly complex biological sample without decreasing the quality of each individual PTM study.

Comparison at the peptide level with post‐translational modification consideration reveals more differences between two unenriched samples (778.1)

In shotgun strategy, peptide sequences are first identified from MS/MS spectra, and the existence and abundance of the proteins are then inferred from the peptide information. However, the protein inference step can produce errors and a loss of information. To identify the information that is lost using the traditional approaches, this study compared the proteomic data of two leukemia cell lines (Jurkat and K562) at peptide level with consideration of post‐translational modifications (PTMs). After database search, the observed modification name was matched with the modification classification on the Unimod website. Only the peptides with ‘post‐translational’ modifications were compared between the two cell lines. As a result, a total of 44887 non‐redundant peptides were identified in both the Jurkat and K562 cell lines. Of these peptides, even without specific PTM enrichment, 11.43% of them (with at least two spectra in one cell line) existed in different PTM forms between the two cell lines, and 1.89% of the peptides were modified in both cell lines, but with different modifications or on different sites. The sensitivity of PTM identification will become greater and more differences will be found if PTMs are enriched or if the peptides can be compared in a quantitative manner. Therefore, comparing proteomic data at the peptide level with consideration of PTMs can reveal differences between two unenriched samples.Grant Funding Source: Supported by National Basic Research Program of China (2012CB517606, 2013CB530805, 2011CB964901).

RegulatING chromatin regulators: post-translational modification of the ING family of epigenetic regulators

The five human ING genes encode at least 15 splicing isoforms, most of which affect cell growth, differentiation and apoptosis through their ability to alter gene expression by epigenetic mechanisms. Since their discovery in 1996, ING proteins have been classified as type II tumour suppressors on the basis of reports describing their down-regulation and mislocalization in a variety of cancer types. In addition to their regulation by transcriptional mechanisms, understanding the range of PTMs (post-translational modifications) of INGs is important in understanding how ING functions are fine-tuned in the physiological setting and how they add to the repertoire of activities affected by the INGs. In the present paper we review the different PTMs that have been reported to occur on INGs. We discuss the PTMs that modulate ING function under normal conditions and in response to a variety of stresses. We also describe the ING PTMs that have been identified by several unbiased MS-based PTM enrichment techniques and subsequent proteomic analysis. Among the ING PTMs identified to date, a subset has been characterized for their biological significance and have been shown to affect processes including subcellular localization, interaction with enzymatic complexes and ING protein half-life. The present review aims to highlight the emerging role of PTMs in regulating ING function and to suggest additional pathways and functions where PTMs may effect ING function.