Aberrant post-translational protein modifications in the pathogenesis of alcohol-induced liver injury

It is likely that the majority of proteins will undergo post-translational modification, be it enzymatic or non-enzymatic. These modified protein(s) regulate activity, localization and interaction with other cellular molecules thereby maintaining cellular hemostasis. Alcohol exposure significantly alters several of these post-translational modifications leading to impairments of many essential physiological processes. Here, we present new insights into novel modifications following ethanol exposure and their role in the initiation and progression of liver injury. This critical review condenses the proceedings of a symposium at the European Society for the Biomedical Research on Alcoholism Meeting held September 12-15, 2015, in Valencia, Spain.

Systematic Analysis of Post-Translational Modifications for Increased Longevity of Biotherapeutic Proteins

Protein-based therapeutics (PPTs) are drugs used to treat a variety of different conditions in the human body by alleviating enzymatic deficiencies, augmenting other proteins and drugs, modulating signal pathways, and more. However, many PPTs struggle from a short half-life due to degradation caused by irreversible protein aggregation in the bloodstream. Currently, the most researched strategies for improving the efficiency and longevity of PPTs are post-translational modifications (PTMs). The goal of our research was to determine which type of PTM increases longevity the most for each of three commonly-used therapeutic proteins by comparing the docking scores (DS) and binding free energies (BFE) from protein aggregation and reception simulations. DS and BFE values were used to create a quantitative index that outputs a relative number from −1 to 1 to show reduced performance, no change, or increased performance. Results showed that methylation was the most beneficial for insulin (p < 0.1) and human growth hormone (p < 0.0001), and both phosphorylation and methylation were somewhat optimal for erythropoietin (p < 0.1 and p < 0.0001, respectively). Acetylation consistently provided the worst benefits with the most negative indices, while methylation had the most positive indices throughout. However, PTM efficacy varied between PPTs, supporting previous studies regarding how each PTM can confer different benefits based on the unique structures of recipient proteins.

Comprehensive analysis of the gut microbiome and posttranslational modifications elucidates the route involved in microbiota-host interactions

The gut microbiome interacts with the host to maintain body homeostasis,with gut microbial dysbiosis implicated in many diseases.However,the underlying mechanisms of gut microbe regulation of host behavior and brain functions remain unclear.This study aimed to elucidate the influence of gut microbiota on brain functions via post-translational modification mechanisms in the presence or absence of bacteria without any stimulation.We conducted succinylome analysis of hippocampal proteins in germ-free(GF)and specific pathogen-free(SPF)mice and metagenomic analysis of feces from SPF mice.These results were integrated with previously reported hippocampal acetylome and phosphorylome data from the same batch of mice.Subsequent bioinformatics analyses revealed 584 succinylation sites on 455 proteins,including 54 up-regulated succinylation sites on 91 proteins and 99 down-regulated sites on 51 proteins in the GF mice compared to the SPF mice.We constructed a panoramic map of gut microbiota-regulated succinylation,acetylation,and phosphorylation,and identified cross-talk and relative independence between the different types of post-translational modifications in modulating complicated intracellular pathways.Pearson correlation analysis indicated that 13 taxa,predominantly belonging to the Bacteroidetes phylum,were correlated with the biological functions of post-translational modifications.Positive correlations between these taxa and succinylation and negative correlations between these taxa and acetylation were identified in the modulation of intracellular pathways.This study highlights the hippocampal physiological changes induced by the absence of gut microbiota,and proteomic quantification of succinylation,phosphorylation,and acetylation,contributing to our understanding of the role of the gut microbiome in brain function and behavioral phenotypes.

Post-translational modifications of hepatitis C viral proteins and their biological significance

Replication of hepatitis C virus(HCV)depends on the interaction of viral proteins with various host cellular proteins and signalling pathways.Similar to cellular proteins,post-translational modifications(PTMs)of HCV proteins are essential for proper protein function and regulation,thus,directly affecting viral life cycle and the generation of infectious virus particles.Cleavage of the HCV polyprotein by cellular and viral proteases into more than 10 proteins represents an early protein modification step after translation of the HCV positivestranded RNA genome.The key modifications include the regulated intramembranous proteolytic cleavage of core protein,disulfide bond formation of core,glycosylation of HCV envelope proteins E1 and E2,methylation of nonstructural protein 3(NS3),biotinylation of NS4A,ubiquitination of NS5B and phosphorylation of core and NS5B.Other modifications like ubiquitination of core and palmitoylation of core and NS4B proteins have been reported as well.For some modifications such as phosphorylation of NS3 and NS5A and acetylation of NS3,we have limited understanding of their effects on HCV replication and pathogenesis while the impact of other modifications is far from clear.In this review,we summarize the available information on PTMs of HCV proteins and discuss their relevance to HCV replication and pathogenesis.

Complex interactomes and post-translational modifications of the regulatory proteins HABP4 and SERBP1 suggest pleiotropic cellular functions

The 57 kDa antigen recognized by the Ki-1 antibody,is also known as intracellular hyaluronic acid binding protein 4 and shares 40.7%identity and 67.4%similarity with serpin mRNA binding protein 1,which is also named CGI-55,or plasminogen activator inhibitor type-1-RNA binding protein-1,indicating that they might be paralog proteins,possibly with similar or redundant functions in human cells.Through the identification of their protein interactomes,both regulatory proteins have been functionally implicated in transcriptional regulation,mRNA metabolism,specifically RNA splicing,the regulation of mRNA stability,especially,in the context of the progesterone hormone response,and the DNA damage response.Both proteins also show a complex pattern of post-translational modifications,involving Ser/Thr phosphorylation,mainly through protein kinase C,arginine methylation and SUMOylation,suggesting that their functions and locations are highly regulated.Furthermore,they show a highly dynamic cellular localization pattern with localizations in both the cytoplasm and nucleus as well as punctuated localizations in both granular cytoplasmic protein bodies,upon stress,and nuclear splicing speckles.Several reports in the literature show altered expressions of both regulatory proteins in a series of cancers as well as mutations in their genes that may contribute to tumorigenesis.This review highlights important aspects of the structure,interactome,post-translational modifications,sub-cellular localization and function of both regulatory proteins and further discusses their possible functions and their potential as tumor markers in different cancer settings.

Human T-lymphotropic virus proteins and post-translational modification pathways

Cell life from the cell cycle to the signaling transduction and response to stimuli is finely tuned by protein post-translational modifications(PTMs).PTMs alter the conformation,the stability,the localization,and hence the pattern of interactions of the targeted protein.Cell pathways involve the activation of enzymes,like kinases,ligases and transferases,that,once activated,act on many proteins simultaneously,altering the state of the cell and triggering the processes they are involved in.Viruses enter a balanced system and hijack the cell,exploiting the potential of PTMs either to activate viral encoded proteins or to alter cellular pathways,with the ultimate consequence to perpetuate through their replication.Human T-lymphotropic virus type 1(HTLV-1)is known to be highly oncogenic and associates with adult T-cell leukemia/lymphoma,HTLV-1-associated myelopathy/tropical spastic paraparesis and other inflammatory pathological conditions.HTLV-1 protein activity is controlled by PTMs and,in turn,viral activity is associated with the modulation of cellular pathways based on PTMs.More knowledge is acquired about the PTMs involved in the activation of its proteins,like Tax,Rex,p12,p13,p30,HTLV-I basic leucine zipper factorand Gag.However,more has to be understood at the biochemical level in order to counteract the associated fatal outcomes.This review will focus on known PTMs that directly modify HTLV-1 components and on enzymes whose activity is modulated by viral proteins.

Computer-Assisted analysis of subcellular localization signals and post-translational modifications of human prion proteins

In the present work, computational analyses were applied to study the subcellular localiza-tion and posttranslational modifications of hu-man prion proteins (PrPs). The tentative location of prion protein was determined to be in the nu-cleolus inside the nucleus by the following bio-informatics tools: Hum-PLoc, Euk-PLoc and Nuc-PLoc. Based on our results signal peptides with average of 22 base pairs in N-terminal were identified in human PrPs. This theoretical study demonstrates that PrP is post-translationally modified by: 1) attachment of two N-linked complex carbohydrate moieties (N181 and N197), 2) attachmet of glycosylphosphatidylinositol (GPI) at serine 230 and 3) formation of two di-sulfide bonds between “6–22” and “179–214” cysteines. Furthermore, ten protein kinase phosphorylation sites were predicted in human PrP. The above-noted phosphorylation was car-ried out by PKC and CK2. By using bioinfor-matics tools, we have shown that computation-ally human PrPs locate particularly into the nu-cleolus.

Protein post-translational modifications in auxin signaling

Protein post-translational modifications(PTMs),such as ubiquitination,phosphorylation,and small ubiquitin-like modifier(SUMO)ylation,are crucial for regulating protein stability,activity,subcellular localization,and binding with cofactors.Such modifications remarkably increase the variety and complexity of proteomes,which are essential for regulating numerous cellular and physiological processes.The regulation of auxin signaling is finely tuned in time and space to guide various plant growth and development.Accumulating evidence indicates that PTMs play critical roles in auxin signaling regulations.Thus,a thorough and systematic review of the functions of PTMs in auxin signal transduction will improve our profound comprehension of the regulation mechanism of auxin signaling and auxin-mediated various processes.This review discusses the progress of protein ubiquitination,phosphorylation,histone acetylation and methylation,SUMOylation,and S-nitrosylation in the regulation of auxin signaling.

Does mRNA structure contain genetic information for regulating co-translational protein folding？

Currently many facets of genetic information are illdefined. In particular, how protein folding is genetically regulated has been a long-standing issue for genetics and protein biology. And a generic mechanistic model with supports of genomic data is still lacking. Recent technological advances have enabled much needed genome-wide experiments. While putting the effect of codon optimality on debate, these studies have supplied mounting evidence suggesting a role of m RNA structure in the regulation of protein folding by modulating translational elongation rate. In conjunctions with previous theories, this mechanistic model of protein folding guided by m RNA structure shall expand our understandings of genetic information and offer new insights into various biomedical puzzles.

Lipid accumulation and protein modifications of Bruch’s membrane in age-related macular degeneration

Age-related macular degeneration(AMD)is a progressive retinal disease,which is the leading cause of blindness in western countries.There is an urgency to establish new therapeutic strategies that could prevent or delay the progression of AMD more efficiently.Until now,the pathogenesis of AMD has remained unclear,limiting the development of the novel therapy.Bruch’s membrane(BM)goes through remarkable changes in AMD,playing a significant role during the disease course.The main aim of this review is to present the crucial processes that occur at the level of BM,with special consideration of the lipid accumulation and protein modifications.Besides,some therapies targeted at these molecules and the construction of BM in tissue engineering of retinal pigment epithelium(RPE)cells transplantation were listed.Hopefully,this review may provide a reference for researchers engaged in pathogenesis or management on AMD.

Post-translational modifications of prostaglandin-endoperoxide synthase 2 in colorectal cancer:An update

The biosynthesis of prostanoids is involved in both physiological and pathological processes. The expression of prostaglandin-endoperoxide synthase 2(PTGS2; also known as COX-2) has been traditionally associated to the onset of several pathologies, from inflammation to cardiovascular, gastrointestinal and oncologic events. For this reason, the search of selective PTGS2 inhibitors has been a focus for therapeutic interventions. In addition to the classic non-steroidal anti-inflammatory drugs, selective and specific PTGS2 inhibitors, termed coxibs, have been generated and widely used. PTGS2 activity is less restrictive in terms of substrate specificity than the homeostatic counterpart PTGS1, and it accounts for the elevated prostanoid synthesis that accompanies several pathologies. The main regulation of PTGS2 occurs at the transcription level. In addition to this, the stability of the mRNA is finely regulated through the interaction with several cytoplasmic elements, ranging from specificmicroR NAs to proteins that control mR NA degradation. Moreover, the protein has been recognized to be the substrate for several post-translational modifications that affect both the enzyme activity and the targeting for degradation via proteasomal and non-proteasomal mechanisms. Among these modifications, phosphorylation, glycosylation and covalent modifications by reactive lipidic intermediates and by free radicals associated to the proinflammatory condition appear to be the main changes. Identification of these post-translational modifications is relevant to better understand the role of PTGS2 in several pathologies and to establish a correct analysis of the potential function of this protein in diseases progress. Finally, these modifications can be used as biomarkers to establish correlations with other parameters, including the immunomodulation dependent on molecular pathological epidemiology determinants, which may provide a better frame for potential therapeutic interventions.

2007 International Symposium on Protein Modification and Degradation in Beijing(SPMDB2007)

Presidents of Symposium Depei Liu,President of Chinese Academy of Medical Sciences Zhu Chen,Vice President of Chinese Academy ofSciences.

Evaluation of laboratory and environmental exposure systems for protein modification upon gas pollutants and environmental factors

Chemical modifications of proteins induced by ambient ozone(O_(3))and nitrogen oxides(NOx)are of public health concerns due to their potential to trigger respiratory diseases.The laboratory and environmental exposure systems have been widely used to investigate their relevant mechanism in the atmosphere.Using bovine serum albumin(BSA)as a model protein,we evaluated the two systems and aimed to reduce the uncertainties of both the reactants and products in the corresponding kinetic study.In the laboratory simulation system,the generated gaseous pollutants showed negligible losses.Ten layers of BSA were coated on the flow tube with protein extraction recovery of 87.4%.For environmental exposure experiment,quartz fiber filter was selected as the upper filter with low gaseous O_(3)(8.0%)and NO_(2)(1.7%)losses,and cellulose acetate filter was appropriate for the lower filter with protein extraction efficiency of 95.2%.The protein degradation process was observed without the exposure to atmospheric oxidants and contributed to the loss of protein monomer mass fractions,while environmental factors(e.g.,molecular oxygen and ultraviolet)may cause greater protein monomer losses.Based on the evaluation,the study exemplarily applied the two systems to protein modification and both showed that O_(3) promotes the protein oligomerization and nitration,while increased temperature can accelerate the oligomerization and increased relative humidity can inhibit the nitration in the environmental exposure samples.The developed laboratory and environmental systems are suitable for studying protein modifications formed under different atmospheric conditions.A combination of the two will further reveal the actual mechanism of protein modifications.

Protein post-translational modification by lysine succinylation:Biochemistry,biological implications,and therapeutic opportunities

Lysine succinylation(Ksuc)is a novel protein post-translational modification(PTM)wherein a succinyl group modifies a lysine residue.Ksuc leads to significant chemical and struc-tural changes to the modified protein.Recent studies have shown that Ksuc might play an important role in organism physiology and some pathophysiological processes,such as tumor-igenesis and metabolic diseases.To provide an understanding of the molecular mechanism and functions of Ksuc in different organisms,we reviewed the current literature about Ksuc,mainly summarizing the research advances in eukaryotes and prokaryotes based on both traditional study methods and site prediction tools.We also discussed inhibitors or activators associated with Ksuc that may contribute to proteomic studies and could be useful in future clinical prac-tice.A deeper understanding of Ksuc may shed new light on life science at the protein level and could lead to novel therapeutic strategies for various diseases.

Role of 3'-untranslated region translational control in cancer development, diagnostics and treatment

The messenger RNA 3'-untranslated region(3'UTR)plays an important role in regulation of gene expres-sion on the posttranscriptional level. The 3'UTR con-trols gene expression via orchestrated interactionbetween the structural components of mRNAs(cis-ele-ment) and the specific trans-acting factors(RNA bind-ing proteins and non-coding RNAs). The crosstalk ofthese factors is based on the binding sequences and/or direct protein-protein interaction, or just functionalinteraction. Much new evidence that has accumulatedsupports the idea that several RNA binding factors canbind to common mRNA targets: to the non-overlappingbinding sites or to common sites in a competitive fash-ion. Various factors capable of binding to the sameRNA can cooperate or be antagonistic in their actions.The outcome of the collective function of all factorsbound to the same mRNA 3'UTR depends on manycircumstances, such as their expression levels, affinity to the binding sites, and localization in the cell, which can be controlled by various physiological conditions. Moreover, the functional and/or physical interactions of the factors binding to 3'UTR can change the character of their actions. These interactions vary during the cell cycle and in response to changing physiological condi-tions. Abnormal functioning of the factors can lead to disease. In this review we will discuss how alterations of these factors or their interaction can affect cancer development and promote or enhance the malignant phenotype of cancer cells. Understanding these altera-tions and their impact on 3'UTR-directed posttran-scriptional gene regulation will uncover promising new targets for therapeutic intervention and diagnostics. We will also discuss emerging new tools in cancer di-agnostics and therapy based on 3'UTR binding factors and approaches to improve them.

mRNA-specific translational regulation in yeast

The expression of a gene is governed at various levels,from transcriptional to translational level.The translational control is widely used to regulate gene expression,especially when a rapid,local,and selective control over protein synthesis is required.The present review describes instructive examples of translational regulation in yeast,together with regulatory elements within mRNAs.The review also outlines the important contributions of mRNA-binding proteins that act in harmony with several translational elements to generate appropriate translational signals and responses.

Electron transfer in protein modifications:from detection to imaging

Signal pathways participate in vital biological processes and regulate complex life activities through protein modifications.Protein modifications in signal pathways are accompanied by electron transfer.The study of electronic behavior helps to explore the physical and chemical processes in signal pathways,receiving extensive attention.There are some excellent reviews that have summarized methods for signal pathway detection,while few discussions are from an electron transfer perspective.This review describes the relationship between signal pathways and electron transfer in protein modification.Subsequently,we summarize the electron transfer-based detection methods,such as electrochemical,photoelectrochemical and electrochemiluminescence methods.Additionally,the applications of signal pathway detection in mechanism study and imaging are also reviewed.Finally,a comprehensive discussion of the summary and outlooks in this field is presented,aiming to provide valuable guidance for the molecular mechanism of life processes and the development of new analytical techniques.

Analysis of the Arabidopsis Floral Proteome:Detection of over 2000 Proteins and Evidence for Posttranslational Modifications

The proteome of the Arabidopsis flower has not been extensively studied previously. Here, we report a proteomic analysis of the wild type Arabidopsis flower. Using both two-dimensional electrophoresis/mass spectrometry （2-DGEIMS） and multi-dimensional protein identification technology （MudPIT） approaches, we identified 2 446 proteins. Although a single experiment or analysis uncovered only a subset of the proteins we identified, a combination of multiple experiments and analyses facilitated the detection of a greater number of proteins. When proteins are grouped according to RNA expression levels revealed by microarray experiments, we found that proteins encoded by genes with relatively high levels of expression were detected with greater frequencies. On the other hand, at the level of the individual gene/protein, there was not a good correlation between protein spot intensity and microarray values. We also obtained strong evidence for post-translational modification from 2-DGE and MudPIT data. We detected proteins that are annotated to function in protein synthesis, folding, modification, and degradation, as well as the presence of regulatory proteins such as transcription factors and protein kinases. Finally, sequence and evolutionary analysis of genes for active methyl group metabolisms suggests that these genes are highly conserved. Our results allow the formulation of hypotheses regarding post-translational regulation of proteins in the flower, providing new understanding about Arabidopsis flower development and physiology.

Multi-omics Data Reveal the Effect of Sodium Butyrate on Gene Expression and Protein Modification in Streptomyces

Streptomycetes possess numerous gene clusters and the potential to produce a large amount of natural products.Histone deacetylase(HDAC)inhibitors play an important role in the regulation of histone modifications in fungi,but their roles in prokaryotes remain poorly understood.Here,we investigated the global effects of the HDAC inhibitor,sodium butyrate(SB),on marine-derived Streptomyces olivaceus FXJ 8.021,particularly focusing on the activation of secondary metabolite biosynthesis.The antiSMASH analysis revealed 33 secondary metabolite biosynthetic gene clusters(BGCs)in strain FXJ 8.021,among which the silent lobophorin BGC was activated by SB.Transcriptomic data showed that the expression of genes involved in lobophorin biosynthesis(ge00097–ge00139)and CoA-ester formation(e.g.,ge02824),as well as the glycolysis/gluconeogenesis pathway(e.g.,ge01661),was significantly up-regulated in the presence of SB.Intracellular CoA-ester analysis confirmed that SB triggered the biosynthesis of CoA-ester,thereby increasing the precursor supply for lobophorin biosynthesis.Further acetylomic analysis revealed that the acetylation levels on 218 sites of 190 proteins were up-regulated and those on 411 sites of 310 proteins were down-regulated.These acetylated proteins were particularly enriched in transcriptional and translational machinery components(e.g.,elongation factor GE04399),and their correlations with the proteins involved in lobophorin biosynthesis were established by protein–protein interaction network analysis,suggesting that SB might function via a complex hierarchical.

The pathogenic mechanism of TAR DNA-binding protein 43(TDP-43)in amyotrophic lateral sclerosis

The onset of amyotrophic lateral sclerosis is usually characterized by focal death of both upper and/or lower motor neurons occurring in the motor cortex,basal ganglia,brainstem,and spinal cord,and commonly involves the muscles of the upper and/or lower extremities,and the muscles of the bulbar and/or respiratory regions.However,as the disease progresses,it affects the adjacent body regions,leading to generalized muscle weakness,occasionally along with memory,cognitive,behavioral,and language impairments;respiratory dysfunction occurs at the final stage of the disease.The disease has a complicated pathophysiology and currently,only riluzole,edaravone,and phenylbutyrate/taurursodiol are licensed to treat amyotrophic lateral sclerosis in many industrialized countries.The TAR DNA-binding protein 43 inclusions are observed in 97%of those diagnosed with amyotrophic lateral sclerosis.This review provides a preliminary overview of the potential effects of TAR DNAbinding protein 43 in the pathogenesis of amyotrophic lateral sclerosis,including the abnormalities in nucleoplasmic transport,RNA function,post-translational modification,liquid-liquid phase separation,stress granules,mitochondrial dysfunction,oxidative stress,axonal transport,protein quality control system,and non-cellular autonomous functions(e.g.,glial cell functions and prion-like propagation).