Legionella pneumophila-mediated host posttranslational modifications

Legionella pneumophila is a Gram-negative bacterium ubiquitously present in freshwater environments and causes a serious type of pneumonia called Legionnaires’disease.During infections,L.pneumophila releases over 300 effector proteins into host cells through an Icm/Dot type IV secretion system to manipulate the host defense system for survival within the host.Notably,certain effector proteins mediate posttranslational modifications(PTMs),serving as useful approaches exploited by L.pneumophila to modify host proteins.Some effectors catalyze the addition of host protein PTMs,while others mediate the removal of PTMs from host proteins.In this review,we summarize L.pneumophila effector-mediated PTMs of host proteins,including phosphorylation,ubiquitination,glycosylation,AMPylation,phosphocholination,methylation,and ADP-ribosylation,as well as dephosphorylation,deubiquitination,deAMPylation,deADP-ribosylation,dephosphocholination,and delipidation.We describe their molecular mechanisms and biological functions in the regulation of bacterial growth and Legionella-containing vacuole biosynthesis and in the disruption of host immune and defense machinery.

LncRNA-mediated posttranslational modifications and reprogramming of energy metabolism in cancer

Altered metabolism is a hallmark of cancer,and the reprogramming of energy metabolism has historically been considered a general phenomenon of tumors.It is well recognized that long noncoding RNAs(lncRNAs)regulate energy metabolism in cancer.However,lncRNA-mediated posttranslational modifications and metabolic reprogramming are unclear at present.In this review,we summarized the current understanding of the interactions between the alterations in cancer-associated energy metabolism and the lncRNA-mediated posttranslational modifications of metabolic enzymes,transcription factors,and other proteins involved in metabolic pathways.In addition,we discuss the mechanisms through which these interactions contribute to tumor initiation and progression,and the key roles and clinical significance of functional lncRNAs.We believe that an in-depth understanding of lncRNA-mediated cancer metabolic reprogramming can help to identify cellular vulnerabilities that can be exploited for cancer diagnosis and therapy.

Posttranslational regulation of androgen dependent and independent androgen receptor activities in prostate cancer

Prostate cancer(PCa)is the most commonly diagnosed cancer among men in western countries.Androgen receptor(AR)signaling plays key roles in the development of PCa.Androgen deprivation therapy(ADT)remains the standard therapy for advanced PCa.In addition to its ligand androgen,accumulating evidence indicates that posttranscriptional modification is another important mechanism to regulate AR activities during the progression of PCa,especially in castration resistant prostate cancer(CRPC).To date,a number of posttranscriptional modifications of AR have been identified,including phosphorylation(e.g.by CDK1),acetylation(e.g.by p300 and recognized by BRD4),methylation(e.g.by EZH2),ubiquitination(e.g.by SPOP),and SUMOylation(e.g.by PIAS1).These modifications are essential for the maintenance of protein stability,nuclear localization and transcriptional activity of AR.This review summarizes posttranslational modifications that influence androgen-dependent and-independent activities of AR,PCa progression and therapy resistance.We further emphasize that in addition to androgen,posttranslational modification is another important way to regulate AR activity,suggesting that targeting AR posttranslational modifications,such as proteolysis targeting chimeras(PROTACs)of AR,represents a potential and promising alternate for effective treatment of CRPC.Potential areas to be investigated in the future in the field of AR posttranslational modifications are also discussed.

Global characterization of modifications to the charge isomers of IgG antibody

Posttranslational modifications of antibody products affect their stability,charge distribution,and drug activity and are thus a critical quality attribute.The comprehensive mapping of antibody modifications and different charge isomers(CIs)is of utmost importance,but is challenging.We intended to quantitatively characterize the posttranslational modification status of CIs of antibody drugs and explore the impact of posttranslational modifications on charge heterogeneity.The CIs of antibodies were fractionated by strong cation exchange chromatography and verified by capillary isoelectric focusing-whole column imaging detection,followed by stepwise structural characterization at three levels.First,the differences between CIs were explored at the intact protein level using a top-down mass spectrometry approach;this showed differences in glycoforms and deamidation status.Second,at the peptide level,common modifications of oxidation,deamidation,and glycosylation were identified.Peptide mapping showed nonuniform deamidation and glycoform distribution among CIs.In total,10 N-glycoforms were detected by peptide mapping.Finally,an in-depth analysis of glycan variants of CIs was performed through the detection of enriched glycopeptides.Qualitative and quantitative analyses demonstrated the dynamics of 24 N-glycoforms.The results revealed that sialic acid modification is a critical factor accounting for charge heterogeneity,which is otherwise missed in peptide mapping and intact molecular weight analyses.This study demonstrated the importance of the comprehensive analyses of antibody CIs and provides a reference method for the quality control of biopharmaceutical analysis.

Alexander disease:the road ahead

Alexander disease is a rare neurodegenerative disorder caused by mutations in the glial fibrillary acidic protein,a type III intermediate filament protein expressed in astrocytes.Both early(infantile or juvenile)and adult onsets of the disease are known and,in both cases,astrocytes present characteristic aggregates,named Rosenthal fibers.Mutations are spread along the glial fibrillary acidic protein sequence disrupting the typical filament network in a dominant manner.Although the presence of aggregates suggests a proteostasis problem of the mutant forms,this behavior is also observed when the expression of wild-type glial fibrillary acidic protein is increased.Additionally,several isoforms of glial fibrillary acidic protein have been described to date,while the impact of the mutations on their expression and proportion has not been exhaustively studied.Moreover,the posttranslational modification patterns and/or the protein-protein interaction networks of the glial fibrillary acidic protein mutants may be altered,leading to functional changes that may modify the morphology,positioning,and/or the function of several organelles,in turn,impairing astrocyte normal function and subsequently affecting neurons.In particular,mitochondrial function,redox balance and susceptibility to oxidative stress may contribute to the derangement of glial fibrillary acidic protein mutant-expressing astrocytes.To study the disease and to develop putative therapeutic strategies,several experimental models have been developed,a collection that is in constant growth.The fact that most cases of Alexander disease can be related to glial fibrillary acidic protein mutations,together with the availability of new and more relevant experimental models,holds promise for the design and assay of novel therapeutic strategies.

Protein arginine methyltransferase 6 is a novel substrate of protein arginine methyltransferase 1

BACKGROUND Post-translational modifications play key roles in various biological processes.Protein arginine methyltransferases(PRMTs)transfer the methyl group to specific arginine residues.Both PRMT1 and PRMT6 have emerges as crucial factors in the development and progression of multiple cancer types.We posit that PRMT1 and PRMT6 might interplay directly or in-directly in multiple ways accounting for shared disease phenotypes.AIM To investigate the mechanism of the interaction between PRMT1 and PRMT6.METHODS Gel electrophoresis autoradiography was performed to test the methyltranferase activity of PRMTs and characterize the kinetics parameters of PRMTs.Liquid chromatography-tandem mass spectrometryanalysis was performed to detect the PRMT6 methylation sites.RESULTS In this study we investigated the interaction between PRMT1 and PRMT6,and PRMT6 was shown to be a novel substrate of PRMT1.We identified specific arginine residues of PRMT6 that are methylated by PRMT1,with R106 being the major methylation site.Combined biochemical and cellular data showed that PRMT1 downregulates the enzymatic activity of PRMT6 in histone H3 methylation.CONCLUSION PRMT6 is methylated by PRMT1 and R106 is a major methylation site induced by PRMT1.PRMT1 methylation suppresses the activity of PRMT6.

The complexity of nitric oxide generation and function in plants

Plants are exposed to environmental stress,in natural and agricultural conditions.Nitric oxide(NO),a small gaseous molecule which plays important roles in plants,has been involved in many physiological processes,and emerged as an important endogenous signaling molecule in the adaptation of plants to biotic and abiotic stress.NO is produced from a variety of enzymatic and non enzymatic sources,which are not yet fully understood.Also,NO and reactive nitrogen species(RNS)can produce posttranslational modifications affecting protein function.Nitrate reductase,a key enzyme in the nitrogen metabolism,is a proposed source of NO in plants which could be affected by posttranslational modifications.Thus,different pathways seem to be involved and can also regulate NO synthesis in the plant cell under physiological or stress conditions.However,how the levels of NO are reached in such time and place to fulfill its functions,are still puzzles to elucidate.

PTMD: A Database of Human Disease-associated Post-translational Modifications

Various posttranslational modifications （PTMs） participate in nearly all aspects of biological processes by regulating protein functions, and aberrant states of PTMs are frequently implicated in human diseases. Therefore, an integral resource of PTM–disease associations （PDAs）would be a great help for both academic research and clinical use. In this work, we reported PTMD,a well-curated database containing PTMs that are associated with human diseases. We manually collected 1950 known PDAs in 749 proteins for 23 types of PTMs and 275 types of diseases from the literature. Database analyses show that phosphorylation has the largest number of disease associations, whereas neurologic diseases have the largest number of PTM associations. We classified all known PDAs into six classes according to the PTM status in diseases and demonstrated that the upregulation and presence of PTM events account for a predominant proportion of diseaseassociated PTM events. By reconstructing a disease–gene network, we observed that breast cancers have the largest number of associated PTMs and AKT1 has the largest number of PTMs connected to diseases. Finally, the PTMD database was developed with detailed annotations and can be a useful resource for further analyzing the relations between PTMs and human diseases. PTMD is freely accessible at http：//ptmd.biocuckoo.org.

Proteomics of protein post-translational modifications implicated in neurodegeneration

Mass spectrometry(MS)-based proteomics has developed into a battery of approaches that is exceedingly adept at identifying with high mass accuracy and precision any of the following:oxidative damage to proteins(redox proteomics),phosphorylation(phosphoproteomics),ubiquitination(diglycine remnant proteomics),protein fragmentation(degradomics),and other posttranslational modifications(PTMs).Many studies have linked these PTMs to pathogenic mechanisms of neurodegeneration.To date,identifying PTMs on specific pathology-associated proteins has proven to be a valuable step in the evaluation of functional alteration of proteins and also elucidates biochemical and structural explanations for possible pathophysiological mechanisms of neurodegenerative diseases.This review provides an overview of methods applicable to the identification and quantification of PTMs on proteins and enumerates historic,recent,and potential future research endeavours in the field of proteomics furthering the understanding of PTM roles in the pathogenesis of neurodegeneration.

Protein lysine crotonylation in cellular processions and disease associations

Protein lysine crotonylation(Kcr)is one conserved form of posttranslational modifications of proteins,which plays an important role in a series of cellular physiological and pathological processes.Lysine e-amino groups are the primary sites of such modification,resulting in four-carbon planar lysine crotonylation that is structurally and functionally distinct from the acetylation of these residues.High levels of Kcr modifications have been identified on both histone and non-histone proteins.The present review offers an update on the research progression regarding protein Kcr modifications in biomedical contexts and provides a discussion of the mechanisms whereby Kcr modification governs a range of biological processes.In addition,given the importance of protein Kcr modification in disease onset and progression,the potential viability of Kcr regulators as therapeutic targets is elucidated.

Targeting the PD-L1 cytoplasmic domain and its regulatory pathways to enhance cancer immunotherapy

As a significant member of the immune checkpoint,programmed cell death 1 ligand 1(PD-L1)plays a critical role in cancer immune escape and has become an important target for cancer immunotherapy.Clinically approved drugs mainly target the extracellular domain of PD-L1.Recently,the small cytoplasmic domain of PD-L1 has been reported to regulate PD-L1 stability and function through multiple pathways.Therefore,the intracellular domain of PD-L1 and its regulatory pathways could be promising targets for cancer therapy,expanding available strategies for combined immunotherapy.Here,we summarize the emerging roles of the PD-L1 cytoplasmic domain and its regulatory pathways.The conserved motifs,homodimerization,and posttranslational modifications ofthe PD-L1 cytoplasmic domain have been reported to regulate the membrane anchoring,degradation,nucleartranslocation,and glycosylation of PD-L1.This summary provides a comprehensive understanding of the functions of the PD-L1 cytoplasmic domain and evaluates the broad prospects for targeted therapy.

Th17 Cells in autoimmune diseases

Th17 cells are a new subset of CD4^＋ T cells fungi. Accumulating evidence suggests that Tb17 cells involved in the clearance of extracellular pathogens and and their signature cytokines have a pivotal role in the pathogenesis of multiple autoimmune-mediated inflammatory diseases. Here, we summarize recent research progress on Th17 function in the development and pathogenesis of autoimmune diseases. We also propose to identify new small molecule compounds to manipulate Th17 function for potential therapeutic application to treat human autoimmune diseases, including rheumatoid arthritis, systemic lupus erythematosus, Sjogren＇s syndrome, inflammatory bowel disease, and multiple sclerosis.

Tumor suppressor p53 cross-talks with TRIM family proteins

p53 is a key tumor suppressor.As a transcription factor,p53 accumulates in cells in response to various stress signals and selectively transcribes its target genes to regulate a wide variety of cellular stress responses to exert its function in tumor suppression.In addition to tumor suppression,p53 is also involved in many other physiological and pathological processes,e.g.anti-infection,immune response,development,reproduction,neurodegeneration and aging.To maintain its proper function,p53 is under tight and delicate regulation through different mechanisms,particularly the posttranslational modifications.The tripartite motif(TRIM)family proteins are a large group of proteins characterized by the RING,B-Box and coiled-coil(RBCC)domains at the N-terminus.TRIM proteins play important roles in regulation of many fundamental biological processes,including cell proliferation and death,DNA repair,transcription,and immune response.Alterations of TRIM proteins have been linked to many diseases including cancer,infectious diseases,developmental disorders,and neurodegenera-tion.Interestingly,recent studies have revealed that many TRIM proteins are involved in the regulation of p53,and at the same time,many TRIM proteins are also regulated by p53.Here,we review the cross-talk between p53 and TRIM proteins,and its impact upon cellular biological processes as well as cancer and other diseases.

Deciphering the PTM codes of the tumor suppressor p53

The genome guardian p53 functions as a transcription factor that senses numerous cellular stresses and orchestrates the corresponding transcriptional events involved in determining various cellular outcomes,including cell cycle arrest,apoptosis,senescence,DNA repair,and metabolic regulation.In response to diverse stresses,p53 undergoes multiple posttranslational modifications(PTMs)that coordinate with intimate interdependencies to precisely modulate its diverse properties in given biological contexts.Notably,PTMs can recruit‘reader’proteins that exclusively recognize specific modifications and facilitate the functional readout of p53.Targeting PTM–reader interplay has been developing into a promising cancer therapeutic strategy.In this review,we summarize the advances in deciphering the‘PTM codes’of p53,focusing particularly on the mechanisms by which the specific reader proteins functionally decipher the information harbored within these PTMs of p53.We also highlight the potential applications of intervention with p53 PTM–reader interactions in cancer therapy and discuss perspectives on the‘PTMomic’study of p53 and other proteins.

Regulation of the urea cycle by CPS1 O-GlcNAcylation in response to dietary restriction and aging

O-linked N-acetyl-glucosamine glycosylation(O-GlcNAcylation)of intracellular proteins is a dynamic process broadly implicated in age-related disease,yet it remains uncharacterized whether and how O-GlcNAcylation contributes to the natural aging process.O-GlcNAc transferase(OGT)and the opposing enzyme O-GlcNAcase(OGA)control this nutrient-sensing protein modification in cells.Here,we show that global O-GlcNAc levels are increased in multiple tissues of aged mice.In aged liver,carbamoyl phosphate synthetase 1(CPS1)is among the most heavilyO-GlcNAcylated proteins.CPS1O-GlcNAcylation is reversed by calorie restriction and is sensitive to genetic and pharmacological manipulations of theO-GlcNAc pathway.High glucose stimulates CPS1O-GlcNAcylation and inhibits CPS1 activity.Liver-specific deletion of OGT potentiates CPS1 activity and renders CPS1 irresponsive to further stimulation by a prolonged fasting.Our results identify CPS1 O-GlcNAcylation as a key nutrient-sensing regulatory step in the urea cycle during aging and dietary restriction,implying a role for mitochondrial O-GlcNAcylation in nutritional regulation of longevity.

Chaperone-mediated autophagy: roles in neurodegeneration

Chaperone-mediated autophagy(CMA)selectively delivers cytosolic proteins with an exposed CMA-targeting motif to lysosomes for degradation and plays an important role in protein quality control and cellular homeostasis.A growing body of evidence supports the hypothesis that CMA dysfunction may be involved in the pathogenic process of neurodegenerative diseases.Both down-regulation and compensatory up-regulation in CMA activities have been observed in association with neurodegenerative conditions.Recent studies have revealed several new mechanisms by which CMA function may be involved in the regulation of factors critical for neuronal viability and homeostasis.Here,we summarize these recent advances in the understanding of the relationship between CMA dysfunction and neurodegeneration and discuss the therapeutic potential of targeting CMA in the treatment of neurodegenerative diseases.

Regulation of Torpor in the Gray Mouse Lemur:Transcriptional and Translational Controls and Role of AMPK Signaling

The gray mouse lemur（Microcebus murinus） is one of few primate species that is able to enter daily torpor or prolonged hibernation in response to environmental stresses. With an emerging significance to human health research, lemurs present an optimal model for exploring molecular adaptations that regulate primate hypometabolism. A fundamental challenge is how to effectively regulate energy expensive cellular processes（e.g., transcription and translation） during transitionsto/from torpor without disrupting cellular homeostasis. One such regulatory mechanism is reversible posttranslational modification of selected protein targets that offers fine cellular control without the energetic burden. This study investigates the role of phosphorylation and/or acetylation in regulating key factors involved in energy homeostasis（AMP-activated protein kinase, or AMPK, signaling pathway）, m RNA translation（eukaryotic initiation factor 2a or e IF2 a, eukaryotic initiation factor 4E or e IF4 E, and initiation factor 4E binding protein or 4EBP）, and gene transcription（histone H3） in six tissues of torpid and aroused gray mouse lemurs. Our results indicated selective tissue-specific changes of these regulatory proteins. The relative level of Thr172-phosphorylated AMPKa was significantly elevated in the heart but reduced in brown adipose tissue during daily torpor, as compared to the aroused lemurs, implicating the regulation of AMPK activity during daily torpor in these tissues. Interestingly, the levels of the phosphorylated e IFs were largely unaltered between aroused and torpid animals. Phosphorylation and acetylation of histone H3 were examined as a marker for transcriptional regulation. Compared to the aroused lemurs, level of Ser10-phosphorylated histone H3 decreased significantly in white adipose tissue during torpor, suggesting global suppression of gene transcription. However, a significant increase in acetyl-histone H3 in the heart of torpid lemurs indicated a possible stimulation of transcriptional activity of this tissue. Overall, our study demonstrates that AMPK signaling and posttranslational regulation of selected proteins may play crucial roles in the control of transcription/translation during daily torpor in mouse lemurs.

Total synthesis of TRADD death domain with arginine N-GlcNAcylation by hydrazide-based native chemical ligation

TNFR1-associated death domain protein(TRADD)with arginine N-GlcNAcylation is a novel and structurally unique posttranslational modification(PTM)glycoprotein that blocks the formation of death-inducing signaling complex(DISC),orchestrating host nuclear factorκB(NF-κB)signaling in entero-pathogenic Escherichia coli(EPEC)-infected cells.This particular glycosylated modification plays an extremely vital role for the effective colonization and pathogenesis of pathogens in the gut.Herein we describe the total synthesis of TRADD death domain(residues 195-312)with arginine235 NGlcNAcylation(Arg-GIcNAc TRADD(195-312)).Two longish peptidyl fragments of the wild-type primary sequence were obtained by robust,microwave-assisted,highly efficient,solid-phase peptide synthesis(SPPS),the N-GlcNAcylated sector was built by total synthesis and attached specifically to resinbound peptide with an unprotected ornithine residue via silver-promoted on-resin guanidinylation,ArgGlcNAc TRADD(195-312)was constructed by hydrazide-based native chemical ligation(NCL).The facile synthetic strategy is expected to be generally applicable for the rapid synthesis of other proteins with Arg-GIcNAc modification and to pave the way for the related chemically biological study.

Multifunctions of Histone H1 Proteins

Among various histones, histone H1 proteins have been appreciated for their multiple functions in diverse biological processes. In addition to being a structural protein in chromatin, H1 proteins also play critical roles in cell cycle, gene expression, and development. Recent studies reveal the possible effects of H1 in some diseases, such as cancer and neurodegenerative diseases. Here, we review different variants of HI, the functions, and post translational modifications of ill variants are also discussed.

Pan-Specific Antibodies as Novel Tools to Detect Valyllysine

Objective:Amino acyl modification of lysine residues is an essential mechanism of nutrient sensing that regulates various biological functions including reproduction.At present,the lack of pan-specific antibodies for a recently identified lysine valylation hinders the characterization and detection of this modification.The objective of this study is to raise pan-specific antibodies that may facilitate the identification of novel expression patterns of lysine valylation.Methods:Chicken ovalbumin was valylated as an immunogen to raise polyclonal antibodies(PcAbs)in rabbits.The population of the pan-specific antibodies recognizing valylated lysine was purified using the chemically synthesized valylated peptides consisting of random amino acids.The specificity of the antibodies was evaluated using ELISA,dot blots,Western blots,and immunohistochemistry(IHC)staining in human epididymis as well.Results:A preliminary and simple strategy to make an anti-valylated lysine PcAb was developed.The recognition of the antibodies to valyllysine was evaluated as pan specific.This was useful for the detection of the newly identified valyl modification using ELISA,dot blots,and Western blots.The antibodies were also successfully utilized in IHC assays,which revealed novel valyllysine modification patterns in epididymis tissues of human.Conclusions:A new antibody tool was provided for the study of lysine valylation.The novel expression patterns of valyllysine in the epididymis suggest that this modification may be involved in sperm maturation.