Explore the vast range of titles available.

ObjectiveAutoantibodies against antigens carrying distinct post-translational modifications (PTMs), such as citrulline, homocitrulline or acetyllysine, are hallmarks of rheumatoid arthritis (RA). The relation between these anti-modified protein antibody (AMPA)-classes is poorly understood as is the ability of different PTM-antigens to activate B-cell receptors (BCRs) directed against citrullinated proteins (CP). Insights into the nature of PTMs able to activate such B cells are pivotal to understand the ‘evolution’ of the autoimmune response conceivable underlying the disease. Here, we investigated the cross-reactivity of monoclonal AMPA and the ability of different types of PTM-antigens to activate CP-reactive BCRs.MethodsBCR sequences from B cells isolated using citrullinated or acetylated antigens were used to produce monoclonal antibodies (mAb) followed by a detailed analysis of their cross-reactivity towards PTM-antigens. Ramos B-cell transfectants expressing CP-reactive IgG BCRs were generated and their activation on stimulation with PTM-antigens investigated.ResultsMost mAbs were highly cross-reactive towards multiple PTMs, while no reactivity was observed to the unmodified controls. B cells carrying CP-reactive BCRs showed activation on stimulation with various types of PTM-antigens.ConclusionsOur study illustrates that AMPA exhibit a high cross-reactivity towards at least two PTMs indicating that their recognition pattern is not confined to one type of modification. Furthermore, our data show that CP-reactive B cells are not only activated by citrullinated, but also by carbamylated and/or acetylated antigens. These data are vital for the understanding of the breach of B-cell tolerance against PTM-antigens and the possible contribution of these antigens to RA-pathogenesis.

Hypertension and kidney disease have been repeatedly associated with genomic variants and alterations of lysine metabolism. Here, we combined stable isotope labeling with untargeted metabolomics to investigate lysine’s metabolic fate in vivo. Dietary 13 C 6 labeled lysine was tracked to lysine metabolites across various organs. Globally, lysine reacts rapidly with molecules of the central carbon metabolism, but incorporates slowly into proteins and acylcarnitines. Lysine metabolism is accelerated in a rat model of hypertension and kidney damage, chiefly through N- alpha -mediated degradation. Lysine administration diminished development of hypertension and kidney injury. Protective mechanisms include diuresis, further acceleration of lysine conjugate formation, and inhibition of tubular albumin uptake. Lysine also conjugates with malonyl-CoA to form a novel metabolite Nε-malonyl-lysine to deplete malonyl-CoA from fatty acid synthesis. Through conjugate formation and excretion as fructoselysine, saccharopine, and Nε-acetyllysine, lysine lead to depletion of central carbon metabolites from the organism and kidney. Consistently, lysine administration to patients at risk for hypertension and kidney disease inhibited tubular albumin uptake, increased lysine conjugate formation, and reduced tricarboxylic acid (TCA) cycle metabolites, compared to kidney-healthy volunteers. In conclusion, lysine isotope tracing mapped an accelerated metabolism in hypertension, and lysine administration could protect kidneys in hypertensive kidney disease. Kidney metabolism in disease is important but not well understood. Here, using isotope-guided metabolomics, the authors show that lysine’s metabolic activity conveys kidney protection in hypertension through accelerated metabolism and physiological effects on tubular function.

Recognition of modified histones by “reader” proteins constitutes a key mechanism regulating diverse chromatin-associated processes important for normal and neoplastic development. We recently identified the YEATS domain as a novel acetyllysine-binding module; however, the functional importance of YEATS domain-containing proteins in human cancer remains largely unknown. Here, we show that the YEATS2 gene is highly amplified in human non-small cell lung cancer (NSCLC) and is required for cancer cell growth and survival. YEATS2 binds to acetylated histone H3 via its YEATS domain. The YEATS2-containing ATAC complex co-localizes with H3K27 acetylation (H3K27ac) on the promoters of actively transcribed genes. Depletion of YEATS2 or disruption of the interaction between its YEATS domain and acetylated histones reduces the ATAC complex-dependent promoter H3K9ac levels and deactivates the expression of essential genes. Taken together, our study identifies YEATS2 as a histone H3K27ac reader that regulates a transcriptional program essential for NSCLC tumorigenesis. Histone modification recognition is an important mechanism for gene expression regulation in cancer. Here, the authors identify YEATS2 as a histone H3K27ac reader, regulating a transcriptional program essential for tumorigenesis in human non-small cell lung cancer.

Background The impact of the gut microbiota on neuropsychiatric disorders has gained much attention in recent years; however, comprehensive data on the relationship between the gut microbiome and its metabolites and resistance to treatment for depression and anxiety is lacking. Here, we investigated intestinal metabolites in patients with depression and anxiety disorders, and their possible roles in treatment resistance. Results We analyzed fecal metabolites and microbiomes in 34 participants with depression and anxiety disorders. Fecal samples were obtained three times for each participant during the treatment. Propensity score matching led us to analyze data from nine treatment responders and nine non-responders, and the results were validated in the residual sample sets. Using elastic net regression analysis, we identified several metabolites, including N-ε-acetyllysine; baseline levels of the former were low in responders (AUC = 0.86; 95% confidence interval, 0.69–1). In addition, fecal levels of N-ε-acetyllysine were negatively associated with the abundance of Odoribacter . N-ε-acetyllysine levels increased as symptoms improved with treatment. Conclusion Fecal N-ε-acetyllysine levels before treatment may be a predictive biomarker of treatment-refractory depression and anxiety. Odoribacter may play a role in the homeostasis of intestinal L-lysine levels. More attention should be paid to the importance of L-lysine metabolism in those with depression and anxiety.

Cyclic peptide library screening technologies show immense promise for identifying drug leads and chemical probes for challenging targets. However, the structural and functional diversity encoded within such libraries is largely undefined. We have systematically profiled the affinity, selectivity, and structural features of library-derived cyclic peptides selected to recognize three closely related targets: the acetyllysine-binding bromodomain proteins BRD2, -3, and -4. We report affinities as low as 100 pM and specificities of up to 10⁶-fold. Crystal structures of 13 peptide–bromodomain complexes reveal remarkable diversity in both structure and binding mode, including both α-helical and β-sheet structures as well as bivalent binding modes. The peptides can also exhibit a high degree of structural preorganization. Our data demonstrate the enormous potential within these libraries to provide diverse binding modes against a single target, which underpins their capacity to yield highly potent and selective ligands.

Living animals rely extensively on post-translational modifications (PTMs) to regulate protein activity, stability, subcellular localization, and protein-protein interactions. These modifications are tightly controlled by the balance of “writer” and “eraser” enzymes, which add or remove PTMs on proteins. Current strategies to measure writer and eraser activities in living animals largely depend on invasive methods, such as single-cell sequencing, quantitative mass spectrometry, or activity-based probes, which often lack cell or tissue specificity. In this study, we report the development of autonomous cells—both prokaryotic and eukaryotic—with the ability to biosynthesize and genetically encode acetyllysine using the genetic code expansion technology. These engineered living sensors with a site-specific acetyllysine modification can be transplanted into living animals, enabling real-time monitoring of PTM dynamics in living cells and animals. We further demonstrate the utility of these cells in tracking deacetylase activity and assessing the effects of deacetylase inhibitors on PTM dynamics in living animals in real time. Hu and colleagues report the development of autonomous cells with the ability to biosynthesise and genetically encode acetyllysine using the genetic code expansion method. This approach enables functional studies and offers a powerful strategy for protein engineering and epigenetics research.

Human p300 is a transcriptional co-activator and a major acetyltransferase that acetylates histones and other proteins facilitating gene transcription. The activity of p300 relies on the fine-tuned interactome that involves a dozen p300 domains and hundreds of binding partners and links p300 to a wide range of vital signaling events. Here, we report a novel function of the ZZ-type zinc finger (ZZ) of p300 as a reader of histone H3. We show that the ZZ domain and acetyllysine-recognizing bromodomain of p300 play critical roles in modulating p300 enzymatic activity and its association with chromatin. The acetyllysine binding function of bromodomain is essential for acetylation of histones H3 and H4, whereas interaction of the ZZ domain with H3 promotes selective acetylation of the histone H3K27 and H3K18 sites.

Recently, it has become clear that ACPA can display cross-reactivity to other post-translational modifications (PTMs), more specifically homocitrulline and acetyllysine, as shown at both the monoclonal and polyclonal antibody level.2 3 B cell receptor analysis of ACPA-expressing B cells from patients with RA has shown that ACPAs have undergone extensive somatic hypermutation and that this can facilitate epitope spreading to multiple citrullinated epitopes.4 Given the association of ACPA epitope spreading with progression to disease, it is relevant to obtain more insights when cross-reactivity to other PTMs is introduced. Furthermore, insights in whether cross-reactivity is also present in ACPA-positive subjects without RA or confined to subjects that will—or have developed RA will also help to better understand the evolution of anti-modified protein antibody (AMPA) responses. [...]we analysed cross-reactivity of the ACPA response in pre-disease samples and ACPA-positive individuals without RA. Together, our data show that ACPA, anti-CarPA and AAPA already coexist before disease onset. [...]ACPA can be cross-reactive towards homocitrulline and acetyllysine in ACPA-positive individuals without RA.

Sirtuin 3 (SIRT3) modulates mitochondria-localized processes and is implicated in the metabolic reprogramming of cancer cells, especially fatty acid (FA) synthesis. However, the relationship between SIRT3 and aberrant lipid synthesis in cervical cancer remains unclear. Here, we investigated the clinical relevance of SIRT3 expression in cervical squamous cell carcinoma (CSCC), cervical intraepithelial neoplasia (CIN), and normal tissues. To analyze the role of SIRT3 in CCSC in vitro, endogenous SIRT3 levels were up- and down-regulated in SiHa and C33a cells, respectively, via lentiviral-based transfection. Levels were quantified using qRT-PCR. Acetylation levels for acetyl-coA carboxylase (ACC1) were measured with the anti-acetyllysine antibody. Knockdown of SIRT3 reduced levels of cellular lipid content in cells. To investigate the role of SIRT3 in cell proliferation, nude mice were xenografted with SIRT3-overexpressing or SIRT3-knockdown CCSC cells. Overall, the results demonstrate that SIRT3 significantly contributed to the reprogramming of FA synthesis in CCSC by up-regulating ACC1 to promote de novo lipogenesis by SIRT3 deacetylation. Moreover, the findings show that the SIRT3-mediated regulation of FA synthesis played a critical role in the proliferation and metastasis of CCSC cells, suggesting that SIRT3 has therapeutic potential in CCSC treatment.

Many autoimmune diseases (AIDs) are characterized by the persistence of autoreactive B cell responses, which have been directly implicated in disease pathogenesis. How and why these cells are generated or how they are maintained for years is largely unknown. Rheumatoid arthritis (RA) is among the most common AIDs and is characterized by autoantibodies recognizing proteins with posttranslational modifications (PTMs). This PTM-directed autoreactive B cell compartment is ill defined. Here, we visualized the B cell response against the three main types of PTM antigens implicated in RA by spectral flow cytometry. Our results showed extensive cross-reactivity of PTM-directed B cells against all three PTM antigens (citrulline, homocitrulline, and acetyllysine). Unsupervised clustering revealed several distinct memory B cell (mBC) populations. PTM-directed cells clustered with the most recently activated class-switched mBC phenotype, with high CD80, low CD24, and low CD21 expression. Notably, patients also harbored large fractions of PTM-directed plasmablasts (PBs). Both PTM-directed mBCs and PBs showed high expression of CXCR3, a receptor for chemokines present in abundance in arthritic joints. Together, our data provide detailed insight into the biology of B cell autoreactivity and its remarkable, seemingly exhaustless persistence in a prominent human AID.