Improving regulatory T cell-based therapy: insights into post-translational modification regulation.

Regulatory T (Treg) cells are pivotal for maintaining immune homeostasis and play essential roles in various diseases, such as autoimmune diseases, graft-versus-host disease (GVHD), tumors, and infectious diseases. Treg cells exert suppressive function via distinct mechanisms including inhibitory cytokines, granzyme or perforin-mediated cytolysis, metabolic disruption, and suppression of dendritic cells. Forkhead Box P3 (FOXP3), the characteristic transcription factor, is essential for Treg cell function and plasticity. Cumulative evidence has demonstrated that FOXP3 activity and Treg cell function are modulated by a variety of post-translational modifications (PTMs), including ubiquitination, acetylation, phosphorylation, methylation, glycosylation, poly(ADP-ribosyl)ation, and uncharacterized modifications. This review describes Treg cell suppressive mechanisms and summarizes the current evidence on PTM regulation of FOXP3 and Treg cell function. Understanding the regulatory role of PTMs in Treg cell plasticity and function will be helpful in designing therapeutic strategies for autoimmune diseases, GVHD, tumors, and infectious diseases.

Analysis and comparison of post-translational modifications of α-synuclein filaments in multiple system atrophy and dementia with Lewy bodies.

Our previous cryogenic electron microscopy (cryoEM) analysis showed that the core structures of α-synuclein filaments accumulated in brains of patients diagnosed with dementia with Lewy bodies (DLB) and multiple system atrophy (MSA) patients are different. We analyzed the post-translational modifications (PTMs) in these filaments , and examined their relationship with the core filament structures and pathological features. Besides the common PTMs in MSA and DLB filaments, acetylation, methylation, oxidation and phosphorylation were frequently detected in MSA filaments, but not in DLB filaments. Furthermore, in DLB filament cases, the processing occurred at the C-terminal side of Asp at 119 residue and Asn at 122 residue, while in MSA cases, the processing occurred at multiple sites between residues 109-123. We have previously reported that PTMs in tau filaments depend on the filament core structure. This was considered to apply to α-synuclein filaments as well. As an example, PTMs including processing sites detected in α-synuclein filaments in early-onset DLB (an atypical form, now named juvenile-onset α-synucleinopathy) brain also supported this idea. These suggests that PTMs appeared to be closely related to the specific filament core structures.

Cardiac tumour necrosis factor receptor-associated factor 7 mediates the ubiquitination of apoptosis signal-regulating kinase 1 and aggravates cardiac hypertrophy.

AIMS: Cardiac remodelling is a common pathophysiological process in the development of various cardiovascular diseases, but there is still a lack of effective interventions. Tumour necrosis receptor-associated factor 7 (TRAF7) belongs to the tumour necrosis factor receptor-associated factor family and plays an important role in biological processes. Previous studies have shown that TRAF7 mutations lead to congenital defects and malformations of the heart. However, the molecular mechanisms of TRAF7 in the underlying pathogenesis of pathological cardiac hypertrophy remain unknown. We aim to study the molecular mechanisms and effects of TRAF7 in cardiac remodelling and whether it has the potential to become a therapeutic target for cardiac remodelling. METHODS AND RESULTS: The pressure overload-induced cardiac hypertrophy model in mice was established via transverse aortic constriction (TAC) surgery, and cardiomyocytes were treated with phenylephrine (PE) to induce hypertrophic phenotype. Levels of cardiac dysfunction and remodelling were measured with echocardiography and tissue or cell staining. RNA sequencing, western blot, qRT-PCR, co-immunoprecipitation, and in vivo ubiquitination assays were used to explore the molecular mechanisms. The results showed that the expression of TRAF7 increased gradually during the development of hypertrophy. Accordingly, TRAF7 significantly exacerbated the PE-induced enlargement of primary neonatal Sprague-Dawley rat cardiomyocytes, whereas TRAF7 knockdown alleviated the hypertrophic phenotype in primary cardiomyocytes. Cardiac-specific overexpression of TRAF7 accelerated hypertrophic phenotype in mice and cardiac-specific Traf7 conditional knockout mice improved hypertrophic phenotype induced by TAC. Mechanistically, TRAF7 directly interacted with apoptosis signal-regulating kinase-1 (ASK1) and promoted ASK1 phosphorylation by mediating the K63-linked ubiquitination of ASK1 in response to PE stimulation, which then promoted ASK1 activation and downstream signalling during cardiac hypertrophy. Notably, the pro-hypertrophic effect of TRAF7 was largely blocked by GS4997 in vitro and cardiac-specific Ask1 conditional knockout in vivo. CONCLUSION: In summary, we identified TRAF7 as an essential regulator during cardiac hypertrophy, and modulation of the regulatory axis between TRAF7 and ASK1 could be a novel therapeutic strategy to prevent this pathological process.

Neddylation and Its Target Cullin 3 Are Essential for Adipocyte Differentiation.

The ongoing obesity epidemic has raised awareness of the complex physiology of adipose tissue. Abnormal adipocyte differentiation results in the development of systemic metabolic disorders such as insulin resistance and diabetes. The conjugation of NEDD8 (neural precursor cell expressed, developmentally downregulated 8) to target protein, termed neddylation, has been shown to mediate adipogenesis. However, much remains unknown about its role in adipogenesis. Here, we demonstrated that neddylation and its targets, the cullin (CUL) family members, are differentially regulated during mouse and human adipogenesis. Inhibition of neddylation by MLN4924 significantly reduced adipogenesis of 3T3-L1 and human stromal vascular cells. Deletion of NAE1, a subunit of the only NEDD8 E1 enzyme, suppressed neddylation and impaired adipogenesis. Neddylation deficiency did not affect mitotic cell expansion. Instead, it disrupted CREB/CEBPß/PPARγ signaling, essential for adipogenesis. Interestingly, among the neddylation-targeted CUL family members, deletion of CUL3, but not CUL1, CUL2, or CUL4A, largely replicated the adipogenic defects observed with neddylation deficiency. A PPARγ agonist minimally rescued the adipogenic defects caused by the deletion of NAE1 and CUL3. In conclusion, our study demonstrates that neddylation and its targeted CUL3 are crucial for adipogenesis. These findings provide potential targets for therapeutic intervention in obesity and metabolic disorders.

Cellular SUMO-specific proteases regulate HAdV-C5 E1B-55K SUMOylation and virus-induced cell transformation.

Various viral proteins are post-translationally modified by SUMO-conjugation during the human adenovirus (HAdV) replication cycle. This modification leads to diverse consequences for target proteins as it influences their intracellular localization or cell transformation capabilities. SUMOylated HAdV proteins include the multifunctional oncoprotein E1B-55K. Our previous research, along with that of others, has demonstrated a substantial influence of yet another adenoviral oncoprotein, E4orf6, on E1B-55K SUMOylation levels. Protein SUMOylation can be reversed by cellular sentrin/SUMO-specific proteases (SENPs). In this study, we investigated the interaction of E1B-55K with cellular SENPs to understand deSUMOylation activities and their consequences for cell transformation mediated by this adenoviral oncoprotein. We show that E1B-55K interacts with and is deSUMOylated by SENP 1, independently of E4orf6. Consistent with these results, we found that SENP 1 prevents E1A/E1B-dependent focus formation in rodent cells. We anticipate these findings to be the groundwork for future studies on adenovirus-host interactions, the mechanisms that underlie E1B-55K SUMOylation, as well as the role of this major adenoviral oncoprotein in HAdV-mediated cell transformation.

NAT10 resolves harmful nucleolar R-loops depending on its helicase domain and acetylation of DDX21.

BACKGROUND: Aberrant accumulation of R-loops leads to DNA damage, genome instability and even cell death. Therefore, the timely removal of harmful R-loops is essential for the maintenance of genome integrity. Nucleolar R-loops occupy up to 50% of cellular R-loops due to the frequent activation of Pol I transcription. However, the mechanisms involved in the nucleolar R-loop resolution remain elusive. The nucleolar acetyltransferase NAT10 harbors a putative RecD helicase domain (RHD), however, if NAT10 acts in the R-loop resolution is still unknown. METHODS: NAT10 knockdown cell lines were constructed using CRISPR/Cas9 technology and short hairpin RNA targeting NAT10 mRNA, respectively. The level of R-loops was detected by immunofluorescent staining combined with RNase H treatment. The helicase activity of NAT10 or DDX21 was determined by in vitro helicase experiment. The interaction between NAT10 and DDX21 was verified by co-immunoprecipitation, immunofluorescent staining and GST pull-down experiments. Acetylation sites of DDX21 by NAT10 were analyzed by mass spectrometry. NAT10 knockdown-induced DNA damage was evaluated by immunofluorescent staining and Western blot detecting γH2AX. RESULTS: Depletion of NAT10 led to the accumulation of nucleolar R-loops. NAT10 resolves R-loops through an RHD in vitro and in cells. However, Flag-NAT10 ∆RHD mutant still partially reduced R-loop levels in the NAT10-depleted cells, suggesting that NAT10 might resolve R-loops through additional pathways. Further, the acetyltransferase activity of NAT10 is required for the nucleolar R-loop resolution. NAT10 acetylates DDX21 at K236 and K573 to enhance the helicase activity of DDX21 to unwind nucleolar R-loops. The helicase activity of DDX21 significantly decreased by Flag-DDX21 2KR and increased by Flag-DDX21 2KQ in cells and in vitro. Consequently, NAT10 depletion-induced nucleolar R-loop accumulation led to DNA damage, which was rescued by co-expression of Flag-DDX21 2KQ and Flag-NAT10 G641E, demonstrating that NAT10 resolves nucleolar R-loops through bipartite pathways. CONCLUSION: We demonstrate that NAT10 is a novel R-loop resolvase and it resolves nucleolar R-loops depending on its helicase activity and acetylation of DDX21. The cooperation of NAT10 and DDX21 provides comprehensive insights into the nucleolar R-loop resolution for maintaining genome stability.

Flow Cytometry FRET Reveals Posttranslational Modifications Drive Protein Phosphatase-5 Conformational Changes in Mammalian Cells.

The serine/threonine protein phosphatase 5 (PP5) plays an essential role in regulating hormone and stress-induced signaling networks as well as extrinsic apoptotic pathways in cells. Unlike other protein phosphatases, PP5 possesses both regulatory and catalytic domains, and its function is further modulated through post-translational modifications (PTMs). PP5 contains a tetratricopeptide repeat (TPR) domain, which usually inhibits its phosphatase activity by blocking the active site (closed conformation). Certain activators bind to the PP5-TPR domain, alleviating this inhibition and allowing the catalytic domain to adopt an active (open) conformation. While this mechanism has been proposed based on structural and biophysical studies, PP5 conformational changes and activity has yet to be observed in cells. Here, we designed and developed a flow cytometry-based fluorescence resonance energy transfer (FC-FRET) method, enabling real-time observation of PP5 autoinhibition and activation within live mammalian cells. By quantifying FRET efficiency using sensitized emission, we established a standardized and adaptable data acquisition workflow. Our findings revealed that, in a cellular context, PP5 exists in multiple conformational states, none of which alone fully predict its activity. Additionally, we have demonstrated that PTMs such as phosphorylation and SUMOylation impact PP5 conformational changes, representing a significant advancement in our understanding of its regulatory mechanisms.

Palmitoylation regulates norepinephrine transporter uptake, surface localization, and total expression with pathogenic implications in postural orthostatic tachycardia syndrome.

Postural orthostatic tachycardia syndrome (POTS) is an adrenergic signaling disorder characterized by excessive plasma norepinephrine, postural tachycardia, and syncope. The norepinephrine transporter (NET) modulates adrenergic homeostasis via the reuptake of extracellular catecholamines and is implicated in the pathogenesis of adrenergic and neurological disorders. In this study, we reveal NET is palmitoylated in male Sprague-Dawley rats and Lilly Laboratory Cell Porcine Kidney (LLC-PK1) cells. S-palmitoylation, or the addition of a 16-carbon saturated fatty acid, is a reversible post-translational modification responsible for the regulation of numerous biological mechanisms. We found that LLC-PK1 NET is dynamically palmitoylated, and that inhibition with the palmitoyl acyltransferase (DHHC) inhibitor, 2-bromopalmitate (2BP) results in decreased NET palmitoylation within 90 min of treatment. This result was followed closely by a reduction in transport capacity, cell surface, and total cellular NET expression after 120 min of treatment. Increasing 2BP concentrations and treatment time revealed a nearly complete loss of total NET protein. Co-expression with individual DHHCs revealed a single DHHC enzyme, DHHC1, promoted wild-type (WT) hNET palmitoylation and elevated NET protein levels. The POTS-associated NET mutant, A457P, exhibits dramatically decreased transport capacity and cell surface levels which we have confirmed in the current study. In an attempt to recover A457P NET expression, we co-expressed the A457P variant with DHHC1 to drive expression as seen with the WT protein but instead saw an increase in NET N-terminal immuno-detectable forms and fragments. Elimination of a potential palmitoylation site at cysteine 44 in the N-terminal tail of hNET resulted in a low expression phenotype mimicking the A457P hNET variant. Further investigation of A457P NET palmitoylation and surface expression is necessary, but our preliminary novel findings reveal palmitoylation as a mechanism of NET regulation and suggest that dysregulation of this process may contribute to the pathogenesis of adrenergic disorders like POTS.

Nphos: Database and Predictor of Protein N-phosphorylation.

Protein N-phosphorylation is widely present in nature and participates in various biological processes. However, current knowledge on N-phosphorylation is extremely limited compared to that on O-phosphorylation. In this study, we collected 11,710 experimentally verified N-phosphosites of 7344 proteins from 39 species and subsequently constructed the database Nphos to share up-to-date information on protein N-phosphorylation. Upon these substantial data, we characterized the sequential and structural features of protein N-phosphorylation. Moreover, after comparing hundreds of learning models, we chose and optimized gradient boosting decision tree (GBDT) models to predict three types of human N-phosphorylation, achieving mean area under the receiver operating characteristic curve (AUC) values of 90.56%, 91.24%, and 92.01% for pHis, pLys, and pArg, respectively. Meanwhile, we discovered 488,825 distinct N-phosphosites in the human proteome. The models were also deployed in Nphos for interactive N-phosphosite prediction. In summary, this work provides new insights and points for both flexible and focused investigations of N-phosphorylation. It will also facilitate a deeper and more systematic understanding of protein N-phosphorylation modification by providing a data and technical foundation. Nphos is freely available at http://www.bio-add.org/Nphos/ and http://ppodd.org.cn/Nphos/.

MEK1/2 promote ROS production and deubiquitinate NLRP3 independent of ERK1/2 during NLRP3 inflammasome activation.

Inflammasomes are cytosolic supramolecular complexes that play a key role in the innate immune response. Overactivation of NLR family pyrin domain containing 3 (NLRP3) inflammasome leads to multiple diseases. Post-translational modifications (PTMs) are essential modulators of inflammasomes especially in activation phase. Here we found that MEK1/2 kinase activity was indispensable in NLRP3 inflammasome activation both in vitro and in vivo. Inhibition of MEK1/2 resulted in reactive oxygen species (ROS) scavenging and ubiquitination of NLRP3, which further blocked NLRP3 inflammasome activation. These effects were independent of ERK1/2, which were classic downstream of MEK1/2. These investigations proposed a mechanism that MEK1/2 regulated inflammation via non-transcriptional regulation of NLRP3 inflammasome and might help better understanding the effects and side-effects of MEK inhibitors in clinical use.

Chemokine Receptor N-Terminus Charge Dictates Reliance on Post-Translational Modifications for Effective Ligand Capture and Following Boosting by Defense Peptides.

The chemokine receptors CCR1 and CCR5 display overlapping expression patterns and ligand dependency. Here we find that ligand activation of CCR5, not CCR1, is dependent on N-terminal receptor O-glycosylation. Release from O-glycosylation dependency is obtained by increasing CCR5 N-terminus acidity to the level of CCR1. Ligand activation of CCR5, not CCR1, drastically improves in the absence of glycosaminoglycans (GAGs). Ligand activity at both CCR1 and CCR5 is boosted by positively charged/basic peptides shown to interact with acidic chemokine receptor N-termini. We propose that receptors with an inherent low N-terminus acidity rely on post-translational modifications (PTMs) to efficiently compete with acidic entities in the local environment for ligand capture. Although crucial for initial ligand binding, strong electrostatic interactions between the ligand and the receptor N-terminus may counteract following insertion of the ligand into the receptor binding pocket and activation, a process that seems to be aided in the presence of basic peptides. Basic peptides bind to the naked CCR1 N-terminus, not the CCR5 N-terminus, explaining the loss of boosting of ligand-induced signaling via CCR5 in cells incapable of glycosylation.

Histone post-translational modification and heterochromatin alterations in neurodegeneration: revealing novel disease pathways and potential therapeutics.

Alzheimer's disease (AD), Parkinson's disease (PD), Frontotemporal Dementia (FTD), and Amyotrophic lateral sclerosis (ALS) are complex and fatal neurodegenerative diseases. While current treatments for these diseases do alleviate some symptoms, there is an imperative need for novel treatments able to stop their progression. For all of these ailments, most cases occur sporadically and have no known genetic cause. Only a small percentage of patients bear known mutations which occur in a multitude of genes. Hence, it is clear that genetic factors alone do not explain disease occurrence. Chromatin, a DNA-histone complex whose basic unit is the nucleosome, is divided into euchromatin, an open form accessible to the transcriptional machinery, and heterochromatin, which is closed and transcriptionally inactive. Protruding out of the nucleosome, histone tails undergo post-translational modifications (PTMs) including methylation, acetylation, and phosphorylation which occur at specific residues and are connected to different chromatin structural states and regulate access to transcriptional machinery. Epigenetic mechanisms, including histone PTMs and changes in chromatin structure, could help explain neurodegenerative disease processes and illuminate novel treatment targets. Recent research has revealed that changes in histone PTMs and heterochromatin loss or gain are connected to neurodegeneration. Here, we review evidence for epigenetic changes occurring in AD, PD, and FTD/ALS. We focus specifically on alterations in the histone PTMs landscape, changes in the expression of histone modifying enzymes and chromatin remodelers as well as the consequences of these changes in heterochromatin structure. We also highlight the potential for epigenetic therapies in neurodegenerative disease treatment. Given their reversibility and pharmacological accessibility, epigenetic mechanisms provide a promising avenue for novel treatments. Altogether, these findings underscore the need for thorough characterization of epigenetic mechanisms and chromatin structure in neurodegeneration.

Advances in understanding the roles of plant HAT and HDAC in non-histone protein acetylation and deacetylation.

MAIN CONCLUSION: This review focuses on HATs and HDACs that modify non-histone proteins, summarizes functional mechanisms of non-histone acetylation as well as the roles of HATs and HDACs in rice and Arabidopsis. The growth and development of plants, as well as their responses to biotic and abiotic stresses, are governed by intricate gene and protein regulatory networks, in which epigenetic modifying enzymes play a crucial role. Histone lysine acetylation levels, modulated by histone acetyltransferases (HATs) and histone deacetylases (HDACs), are well-studied in the realm of transcriptional regulation. However, the advent of advanced proteomics has unveiled that non-histone proteins also undergo acetylation, with its underlying mechanisms now being clarified. Indeed, non-histone acetylation influences protein functionality through diverse pathways, such as modulating protein stability, adjusting enzymatic activity, steering subcellular localization, influencing interactions with other post-translational modifications, and managing protein-protein and protein-DNA interactions. This review delves into the recent insights into the functional mechanisms of non-histone acetylation in plants. We also provide a summary of the roles of HATs and HDACs in rice and Arabidopsis, and explore their potential involvement in the regulation of non-histone proteins.

PTMoreR-enabled cross-species PTM mapping and comparative phosphoproteomics across mammals.

To support PTM proteomic analysis and annotation in different species, we developed PTMoreR, a user-friendly tool that considers the surrounding amino acid sequences of PTM sites during BLAST, enabling a motif-centric analysis across species. By controlling sequence window similarity, PTMoreR can map phosphoproteomic results between any two species, perform site-level functional enrichment analysis, and generate kinase-substrate networks. We demonstrate that the majority of real P-sites in mice can be inferred from experimentally derived human P-sites with PTMoreR mapping. Furthermore, the compositions of 129 mammalian phosphoproteomes can also be predicted using PTMoreR. The method also identifies cross-species phosphorylation events that occur on proteins with an increased tendency to respond to the environmental factors. Moreover, the classic kinase motifs can be extracted across mammalian species, offering an evolutionary angle for refining current motifs. PTMoreR supports PTM proteomics in non-human species and facilitates quantitative phosphoproteomic analysis.

O-GlcNAcylation: Crosstalk between Hemostasis, Inflammation, and Cancer.

O-linked ß-N-acetylglucosamine (O-GlcNAc, O-GlcNAcylation) is a post-translational modification of serine/threonine residues of proteins. Alterations in O-GlcNAcylation have been implicated in several types of cancer, regulation of tumor progression, inflammation, and thrombosis through its interaction with signaling pathways. We aim to explore the relationship between O-GlcNAcylation and hemostasis, inflammation, and cancer, which could serve as potential prognostic tools or clinical predictions for cancer patients' healthcare and as an approach to combat cancer. We found that cancer is characterized by high glucose demand and consumption, a chronic inflammatory state, a state of hypercoagulability, and platelet hyperaggregability that favors thrombosis; the latter is a major cause of death in these patients. Furthermore, we review transcription factors and pathways associated with O-GlcNAcylation, thrombosis, inflammation, and cancer, such as the PI3K/Akt/c-Myc pathway, the nuclear factor kappa B pathway, and the PI3K/AKT/mTOR pathway. We also review infectious agents associated with cancer and chronic inflammation and potential inhibitors of cancer cell development. We conclude that it is necessary to approach both the diagnosis and treatment of cancer as a network in which multiple signaling pathways are integrated, and to search for a combination of potential drugs that regulate this signaling network.

Post-Translational Modifications to Cysteine Residues in Plant Proteins and Their Impact on the Regulation of Metabolism and Signal Transduction.

Cys is one of the least abundant amino acids in proteins. However, it is often highly conserved and is usually found in important structural and functional regions of proteins. Its unique chemical properties allow it to undergo several post-translational modifications, many of which are mediated by reactive oxygen, nitrogen, sulfur, or carbonyl species. Thus, in addition to their role in catalysis, protein stability, and metal binding, Cys residues are crucial for the redox regulation of metabolism and signal transduction. In this review, we discuss Cys post-translational modifications (PTMs) and their role in plant metabolism and signal transduction. These modifications include the oxidation of the thiol group (S-sulfenylation, S-sulfinylation and S-sulfonylation), the formation of disulfide bridges, S-glutathionylation, persulfidation, S-cyanylation S-nitrosation, S-carbonylation, S-acylation, prenylation, CoAlation, and the formation of thiohemiacetal. For each of these PTMs, we discuss the origin of the modifier, the mechanisms involved in PTM, and their reversibility. Examples of the involvement of Cys PTMs in the modulation of protein structure, function, stability, and localization are presented to highlight their importance in the regulation of plant metabolic and signaling pathways.

Exploring Protein Post-Translational Modifications of Breast Cancer Cells Using a Novel Combinatorial Search Algorithm.

Post-translational modification of proteins plays an important role in cancer cell biology. Proteins encoded by oncogenes may be activated by phosphorylation, products of tumour suppressors might be inactivated by phosphorylation or ubiquitinylation, which marks them for degradation; chromatin-binding proteins are often methylated and/or acetylated. These are just a few of the many hundreds of post-translational modifications discovered by years of painstaking experimentation and the chemical analysis of purified proteins. In recent years, mass spectrometry-based proteomics emerged as the principal technique for identifying such modifications in samples from cultured cells and tumour tissue. Here, we used a recently developed combinatorial search algorithm implemented in the MGVB toolset to identify novel modifications in samples from breast cancer cell lines. Our results provide a rich resource of coupled protein abundance and post-translational modification data seen in the context of an important biological function-the response of cells to interferon gamma treatment-which can serve as a starting point for future investigations to validate promising modifications and explore the utility of the underlying molecular mechanisms as potential diagnostic or therapeutic targets.

Functions of Coenzyme A and Acyl-CoA in Post-Translational Modification and Human Disease.

Coenzyme A (CoA) is synthesized from pantothenate, L-cysteine and adenosine triphosphate (ATP), and plays a vital role in diverse physiological processes. Protein acylation is a common post-translational modification (PTM) that modifies protein structure, function and interactions. It occurs via the transfer of acyl groups from acyl-CoAs to various amino acids by acyltransferase. The characteristics and effects of acylation vary according to the origin, structure, and location of the acyl group. Acetyl-CoA, formyl-CoA, lactoyl-CoA, and malonyl-CoA are typical acyl group donors. The major acyl donor, acyl-CoA, enables modifications that impart distinct biological functions to both histone and non-histone proteins. These modifications are crucial for regulating gene expression, organizing chromatin, managing metabolism, and modulating the immune response. Moreover, CoA and acyl-CoA play significant roles in the development and progression of neurodegenerative diseases, cancer, cardiovascular diseases, and other health conditions. The goal of this review was to systematically describe the types of commonly utilized acyl-CoAs, their functions in protein PTM, and their roles in the progression of human diseases.

A Novel C-Terminal Truncated Bacteriocin Found by Comparison between Leuconostoc mesenteroides 406 and 213M0 Isolated from Mongolian Traditional Fermented Milk, Airag.

Bacteriocins produced by lactic acid bacteria are known to be useful tools for food biopreservation and fermentation control. Leuconostoc mesenteroides subsp. mesenteroides 406 and 213M0 isolated from different samples of Mongolian traditional fermented milk, airag, had been reported to produce listericidal bacteriocin-like inhibitory substances with similar but slightly different properties. In this study, the antibacterial properties and the related gene sequences of both strains were compared, and then their bacteriocins were purified and identified. Strain 406 was superior to strain 213M0 in cell growth and antibacterial activity against many strains. However, the activity of 213M0 was stronger than that of 406 against a few strains. DNA sequencing revealed two and three plasmids in 406 and 213M0, respectively, and each one of them harbored an almost identical mesentericin Y105-B105 gene cluster. Removal of these plasmids resulted in a complete loss of activity, indicating that the antibacterial activity of both strains was generated by bacteriocins encoded on the plasmids. Mesentericins Y105 and B105 were purified from both cultures, and another novel bacteriocin, named mesentericin M, was identified from the 213M0 culture only. Its structural gene was coded on a 213M0 plasmid and, surprisingly, its C-terminal three amino acid residues were post-translationally cleaved. To our knowledge, this is the first report of a C-terminal truncated bacteriocin. In conclusion, the novel bacteriocin should be mainly responsible for the difference in antibacterial properties between the two strains.

Interaction with IP6K1 supports pyrophosphorylation of substrate proteins by the inositol pyrophosphate 5-InsP7.

Inositol pyrophosphates (PP-InsPs) are a sub-family of water soluble inositol phosphates that possess one or more diphosphate groups. PP-InsPs can transfer their ß-phosphate group to a phosphorylated Ser residue to generate pyrophosphorylated Ser. This unique post-translational modification occurs on Ser residues that lie in acidic stretches within an intrinsically disordered protein sequence. Serine pyrophosphorylation is dependent on the presence of Mg2+ ions, but does not require an enzyme for catalysis. The mechanisms by which cells regulate PP-InsP-mediated pyrophosphorylation are still unknown. We performed mass spectrometry to identify interactors of IP6K1, an enzyme responsible for the synthesis of the PP-InsP 5-InsP7. Interestingly, IP6K1 interacted with several proteins that are known to undergo 5-InsP7-mediated pyrophosphorylation, including the nucleolar proteins NOLC1, TCOF and UBF1, and AP3B1, the ß subunit of the AP3 adaptor protein complex. The IP6K1 interactome also included CK2, a protein kinase that phosphorylates Ser residues prior to pyrophosphorylation. We observe the formation of a protein complex between IP6K1, AP3B1, and the catalytic α-subunit of CK2, and show that disrupting IP6K1 binding to AP3B1 lowers its in vivo pyrophosphorylation. We propose that assembly of a substrate-CK2-IP6K complex would allow for coordinated pre-phosphorylation and pyrophosphorylation of the target serine residue, and provide a mechanism to regulate this enzyme-independent modification.