The STX17-SNAP47-VAMP7/VAMP8 complex is the default SNARE complex mediating autophagosome-lysosome fusion

Autophagosome-lysosome fusion mediated by SNARE complexes is an essential step in autophagy. Two SNAP29-containing SNARE complexes have been extensively studied in starvation-induced bulk autophagy, while the relevant SNARE complexes in other types of autophagy occurring under non-starvation conditions have been overlooked. Here, we found that autophagosome-lysosome fusion in selective autophagy under non-starvation conditions does not require SNAP29-containing SNARE complexes, but requires the STX17-SNAP47-VAMP7/VAMP8 SNARE complex. Further, the STX17-SNAP47-VAMP7/VAMP8 SNARE complex also functions in starvation-induced autophagy. SNAP47 is recruited to autophagosomes following concurrent detection of ATG8s and PI(4,5)P2 via its Pleckstrin homology domain. By contrast, SNAP29-containing SNAREs are excluded from selective autophagy due to inactivation by O-GlcNAcylation under non-starvation conditions. These findings depict a previously unknown, default SNARE complex responsible for autophagosome-lysosome fusion in both selective and bulk autophagy, which could guide research and therapeutic development in autophagy-related diseases.

HDAC9-mediated calmodulin deacetylation induces memory impairment in Alzheimer's disease

AIMS

Alzheimer's disease (AD) is a neurodegenerative disease characterized by progressive cognitive dysfunction and memory impairment. AD pathology involves protein acetylation. Previous studies have mainly focused on histone acetylation in AD, however, the roles of nonhistone acetylation in AD are less explored.

METHODS

The protein acetylation and expression levels were detected by western blotting and co-immunoprecipitation. The stoichiometry of acetylation was measured by home-made and site-specific antibodies against acetylated-CaM (Ac-CaM) at K22, K95, and K116. Hippocampus-dependent learning and memory were evaluated by using the Morris water maze, novel object recognition, and contextual fear conditioning tests.

RESULTS

We showed that calmodulin (CaM) acetylation is reduced in plasma of AD patients and mice. CaM acetylation and its target Ca2+ /CaM-dependent kinase II α (CaMKIIα) activity were severely impaired in AD mouse brain. The stoichiometry showed that Ac-K22, K95-CaM acetylation were decreased in AD patients and mice. Moreover, we screened and identified that lysine deacetylase 9 (HDAC9) was the main deacetylase for CaM. In addition, HDAC9 inhibition increased CaM acetylation and CaMKIIα activity, and hippocampus-dependent memory in AD mice.

CONCLUSIONS

HDAC9-mediated CaM deacetylation induces memory impairment in AD, HDAC9, or CaM acetylation may become potential therapeutic targets for AD.

An Acetyl-Click Chemistry Assay to Measure Histone Acetyltransferase 1 Acetylation

HAT1, also known as Histone acetyltransferase 1, plays a crucial role in chromatin synthesis by stabilizing and acetylating nascent H4 before nucleosome assembly. It is required for tumor growth in various systems, making it a potential target for cancer treatment. To facilitate the identification of compounds that can inhibit HAT1 enzymatic activity, we have devised an acetyl-click assay for rapid screening. In this simple assay, we employ recombinant HAT1/Rbap46, which is purified from activated human cells. The method utilizes the acetyl-CoA analog 4-pentynoyl-CoA (4P) in a click-chemistry approach. This involves the enzymatic transfer of an alkyne handle through a HAT1-dependent acylation reaction to a biotinylated H4 N-terminal peptide. The captured peptide is then immobilized on neutravidin plates, followed by click-chemistry functionalization with biotin-azide. Subsequently, streptavidin-peroxidase recruitment is employed to oxidize amplex red, resulting in a quantitative fluorescent output. By introducing chemical inhibitors during the acylation reaction, we can quantify enzymatic inhibition based on a reduction of the fluorescence signal. Importantly, this reaction is scalable, allowing for high throughput screening of potential inhibitors for HAT1 enzymatic activity.

Endoplasmic reticulum stress caused by traumatic injury promotes cardiomyocyte apoptosis through acetylation modification of GRP78

Cardiomyocyte apoptosis is an important cause of trauma-induced secondary cardiac injury (TISCI), in which the endoplasmic reticulum stress (ERS)-mediated apoptosis signaling pathway is known to be first activated, but the mechanism remains unclear. In this study, rat models of traumatic injury are established by using the Noble-Collip trauma device. The expression of glucose-regulating protein 78 (GRP78, a molecular chaperone of the cardiomyocyte ER), acetylation modification of GRP78 and apoptosis of cardiomyocytes are determined. The results show that ERS-induced GRP78 elevation does not induce cardiomyocyte apoptosis in the early stage of trauma. However, with prolonged ERS, the GRP78 acetylation level is elevated, and the apoptosis of cardiomyocytes also increases significantly. In addition, in the early stage of trauma, the expression of histone acetyl-transferase (HAT) P300 is increased and that of histone deacetylase 6 (HDAC6) is decreased in cardiomyocytes. Inhibition of HDAC function could induce the apoptosis of traumatic cardiomyocytes by increasing the acetylation level of GRP78. Our present study demonstrates for the first time that post-traumatic protracted ERS can promote cardiomyocyte apoptosis by increasing the acetylation level of GRP78, which may provide an experimental basis for seeking early molecular events of TISCI.

Regulating Androgen Receptor Function in Prostate Cancer: Exploring the Diversity of Post-Translational Modifications

Androgen receptor (AR) transcriptional activity significantly influences prostate cancer (PCa) progression. In addition to ligand stimulation, AR transcriptional activity is also influenced by a variety of post-translational modifications (PTMs). A number of oncogenes and tumor suppressors have been observed leveraging PTMs to influence AR activity. Subjectively targeting these post-translational modifiers based on their impact on PCa cell proliferation is a rapidly developing area of research. This review elucidates the modifiers, contextualizes the effects of these PTMs on AR activity, and connects these cellular interactions to the progression of PCa.

Influenza A Virus and Acetylation: The Picture Is Becoming Clearer

Influenza A virus (IAV) is one of the most circulated human pathogens, and influenza disease, commonly known as the flu, remains one of the most recurring and prevalent infectious human diseases globally. IAV continues to challenge existing vaccines and antiviral drugs via its ability to evolve constantly. It is critical to identify the molecular determinants of IAV pathogenesis to understand the basis of flu severity in different populations and design improved antiviral strategies. In recent years, acetylation has been identified as one of the determinants of IAV pathogenesis. Acetylation was originally discovered as an epigenetic protein modification of histones. But, it is now known to be one of the ubiquitous protein modifications of both histones and non-histone proteins and a determinant of proteome complexity. Since our first observation in 2007, significant progress has been made in understanding the role of acetylation during IAV infection. Now, it is becoming clearer that acetylation plays a pro-IAV function via at least three mechanisms: (1) by reducing the host's sensing of IAV infection, (2) by dampening the host's innate antiviral response against IAV, and (3) by aiding the stability and function of viral and host proteins during IAV infection. In turn, IAV antagonizes the host deacetylases, which erase acetylation, to facilitate its replication. This review provides an overview of the research progress made on this subject so far and outlines research prospects for the significance of IAV-acetylation interplay.

Study of the acetylation-induced changes in the physicochemical and functional characteristics of insoluble dietary fiber from wheat bran

BACKGROUND

Wheat bran is rich in dietary fiber (DF), particularly insoluble dietary fiber (IDF). Although the benefits for human health following the consumption of these DFs have been documented, the lower water retention capacity (WRC) and other properties still limit the applications of DF. Therefore, the current research investigated the impact of acetylation on the changes in the corresponding physicochemical and functional properties of DF.

RESULTS

The current results indicated the acetylated group restricted the alignment of the molecular chains, which led to an increased amorphous phase in the fiber structure, followed by an enhanced thermal sensitivity and a reduced crystallinity as evidenced by X-ray diffraction (XRD). Moreover, the acetylation of the IDFs enhanced the cholesterol absorption capacity, but the corresponding antioxidant capacity and cation exchange capacity were reduced, which might be due to the partial loss of the phenolic compounds onto the polysaccharides during the modification. Interestingly, a lower degree of substitution (DS) of the IDF achieved from water-acetic anhydride modification led to a higher WRC and water swelling capacity (WSC). In contrast, a higher DS from acetic anhydride modification demonstrated a greatly improved in vitro hypoglycemic performance of the IDF, including α-amylase inhibitory activity and glucose dialysis retardation index (GDRI), compared to the other samples.

CONCLUSION

This study highlights a new approach to modify the functionality of IDFs via acetylation and the design of a novel IDF with hypoglycemic activity. © 2023 Society of Chemical Industry.

Posttranslational Acylations of the Rat Brain Transketolase Discriminate the Enzyme Responses to Inhibitors of ThDP-Dependent Enzymes or Thiamine Transport

Transketolase (TKT) is an essential thiamine diphosphate (ThDP)-dependent enzyme of the non-oxidative branch of the pentose phosphate pathway, with the glucose-6P flux through the pathway regulated in various medically important conditions. Here, we characterize the brain TKT regulation by acylation in rats with perturbed thiamine-dependent metabolism, known to occur in neurodegenerative diseases. The perturbations are modeled by the administration of oxythiamine inhibiting ThDP-dependent enzymes in vivo or by reduced thiamine availability in the presence of metformin and amprolium, inhibiting intracellular thiamine transporters. Compared to control rats, chronic administration of oxythiamine does not significantly change the modification level of the two detected TKT acetylation sites (K6 and K102) but doubles malonylation of TKT K499, concomitantly decreasing 1.7-fold the level of demalonylase sirtuin 5. The inhibitors of thiamine transporters do not change average levels of TKT acylation or sirtuin 5. TKT structures indicate that the acylated residues are distant from the active sites. The acylations-perturbed electrostatic interactions may be involved in conformational shifts and/or the formation of TKT complexes with other proteins or nucleic acids. Acetylation of K102 may affect the active site entrance/exit and subunit interactions. Correlation analysis reveals that the action of oxythiamine is characterized by significant negative correlations of K499 malonylation or K6 acetylation with TKT activity, not observed upon the action of the inhibitors of thiamine transport. However, the transport inhibitors induce significant negative correlations between the TKT activity and K102 acetylation or TKT expression, absent in the oxythiamine group. Thus, perturbations in the ThDP-dependent catalysis or thiamine transport manifest in the insult-specific patterns of the brain TKT malonylation and acetylations.

Post-translational modification and mitochondrial function in Parkinson's disease

Parkinson's disease (PD) is the second most common neurodegenerative disease with currently no cure. Most PD cases are sporadic, and about 5-10% of PD cases present a monogenic inheritance pattern. Mutations in more than 20 genes are associated with genetic forms of PD. Mitochondrial dysfunction is considered a prominent player in PD pathogenesis. Post-translational modifications (PTMs) allow rapid switching of protein functions and therefore impact various cellular functions including those related to mitochondria. Among the PD-associated genes, Parkin, PINK1, and LRRK2 encode enzymes that directly involved in catalyzing PTM modifications of target proteins, while others like α-synuclein, FBXO7, HTRA2, VPS35, CHCHD2, and DJ-1, undergo substantial PTM modification, subsequently altering mitochondrial functions. Here, we summarize recent findings on major PTMs associated with PD-related proteins, as enzymes or substrates, that are shown to regulate important mitochondrial functions and discuss their involvement in PD pathogenesis. We will further highlight the significance of PTM-regulated mitochondrial functions in understanding PD etiology. Furthermore, we emphasize the potential for developing important biomarkers for PD through extensive research into PTMs.

CLIC3 interacts with NAT10 to inhibit N4-acetylcytidine modification of p21 mRNA and promote bladder cancer progression

Chromatin accessibility plays important roles in revealing the regulatory networks of gene expression, while its application in bladder cancer is yet to be fully elucidated. Chloride intracellular channel 3 (CLIC3) protein has been reported to be associated with the progression of some tumors, whereas the specific mechanism of CLIC3 in tumor remains unclear. Here, we screened for key genes in bladder cancer through the identification of transcription factor binding site clustered region (TFCR) on the basis of chromatin accessibility and TF motif. CLIC3 was identified by joint profiling of chromatin accessibility data with TCGA database. Clinically, CLIC3 expression was significantly elevated in bladder cancer and was negatively correlated with patient survival. CLIC3 promoted the proliferation of bladder cancer cells by reducing p21 expression in vitro and in vivo. Mechanistically, CLIC3 interacted with NAT10 and inhibited the function of NAT10, resulting in the downregulation of ac4C modification and stability of p21 mRNA. Overall, these findings uncover an novel mechanism of mRNA ac4C modification and CLIC3 may act as a potential therapeutic target for bladder cancer.

The spatiotemporal control of ER membrane fragmentation during reticulophagy

Reticulophagy is an evolutionarily conserved mechanism essential to maintain the endoplasmic reticulum (ER) homeostasis. A series of studies identified a panel of reticulophagy receptors. However, it remains unclear how these receptors sense upstream signals for spatiotemporal control of reticulophagy and how ER is fragmented into small pieces for sequestration into phagophores. Recently, we and others showed that the oligomerization of RETREG1/FAM134B (reticulophagy regulator 1), an reticulophagy receptor, triggers the scission of ER membrane to facilitate reticulophagy. Furthermore, we demonstrated that upstream signals are transduced by sequential phosphorylation and acetylation of RETREG1, which stimulate its oligomerization, ER fragmentation and reticulophagy. Our work provides further mechanistic insights into how reticulophagy receptor conveys cellular signals to fine-tune of ER homeostasis.Abbreviations: ER, endoplasmic reticulum; MAP1LC3, microtubule-associated protein light chain 3; RETREG1, reticulophagy regulator 1; RHD, reticulon-homology domain.

Structure-Based Discovery of A Small Molecule Inhibitor of Histone Deacetylase 6 (HDAC6) that Significantly Reduces Alzheimer's Disease Neuropathology

Histone deacetylase 6 (HDAC6) is one of the key histone deacetylases (HDACs) that regulates various cellular functions including clearance of misfolded protein and immunological responses. Considerable evidence suggests that HDAC6 is closely related to amyloid and tau pathology, the two primary hallmarks of Alzheimer's disease (AD). It is still unclear whether HDAC6 expression changes with amyloid deposition in AD during disease progression or HDAC6 may be regulating amyloid phagocytosis or neuroinflammation or other neuropathological changes in AD. In this work, the pathological accumulation of HDAC6 in AD brains over age as well as the relationship of its regulatory activity - with amyloid pathogenesis and pathophysiological alterations is aimed to be enlightened using the newly developed HDAC6 inhibitor (HDAC6i) PB118 in microglia BV2 cell and 3D-AD human neural culture model. Results suggest that the structure-based rational design led to biologically compelling HDAC6i PB118 with multiple mechanisms that clear Aβ deposits by upregulating phagocytosis, improve tubulin/microtubule network by enhancing acetyl α-tubulin levels, regulate different cytokines and chemokines responsible for inflammation, and significantly reduce phospho-tau (p-tau) levels associated with AD. These findings indicate that HDAC6 plays key roles in the pathophysiology of AD and potentially serves as a suitable pharmacological target through chemical biology-based drug discovery in AD.

K64 acetylation of heat shock protein 90 suppresses nucleopolyhedrovirus replication in Bombyx mori

HSP90 is a highly conserved chaperone that facilitates the proliferation of many viruses, including silkworm (bombyx mori) nucleopolyhedrovirus (BmNPV), but the underlying regulatory mechanism was unclear. We found that suppression of HSP90 by 17-AAG, a HSP90-specific inhibitor, significantly reduced the expression of BmNPV capsid protein gp64 and viral genome replication, whereas overexpression of B. mori HSP90(BmHSP90) promoted BmNPV replication. Furthermore, in a recent study of the lysine acetylome of B. mori infected with BmNPV, we focused on the reduced viral proliferation due to changes of BmHSP90 lysine acetylation. Site-directed introduction of acetylated (K/Q) or deacetylated (K/R) mimic mutations into BmHSP90 revealed that lysine 64 (K64) acetylation activated the JAK/STAT pathway and reduced BmHSP90 ATPase activity, leading to diminished chaperone activity and ultimately inhibiting BmNPV proliferation. In this study, a single lysine 64 acetylation change of BmHSP90 was elucidated as a model of posttranslational modifications occurring in the wake of host-virus interactions, providing novel insights into potential antiviral strategies.

In vitro antiviral activity of favipiravir and its 6- and 3-O-substituted derivatives against coronavirus: Acetylation leads to improvement of antiviral activity

Favipiravir is currently approved for the treatment of the influenza virus and has shown encouraging results in terms of antiviral capacity in clinical studies against severe acute respiratory syndrome coronavirus 2. Favipiravir is a prodrug, where its favipiravir-ribofuranosyl-5B-triphosphate metabolite is capable of blocking RNA replication of the virus. However, the antiviral efficiency of favipiravir is limited by two factors: (i) low accumulation in plasma and rapid excretion/elimination post-administration and (ii) low conversion rate into the active metabolite. To tackle these problems, herein, we have designed new favipiravir analogues focusing on the replacement of the fluorine atom at the 6-position by halogen or hydrogen atoms and 3-O-functionalization with labile groups. The first type of functionalization seeks to increase the antiviral activity because of the better ability of the keto-tautomer as a function of the halogen, and it is hypothesized that the keto-tautomer tends to promote the formation of the ribofuranosyl-5B-triphosphate (RTP) metabolite. Meanwhile, the second type of functionalization seeks to promote lipophilicity and increase accumulation in cells. From the in vitro antiviral activity against two coronavirus models (bovine and human 229E), it was identified that the replacement did not improve the antiviral activity against both the models, which seems to be attributable to the low water solubility of these new 6-functionalized analogues. Meanwhile, with 3-O-functionalization, acetylation provided the most active compounds with higher half-maximal inhibitory concentration and selectivity than favipiravir, whereas benzylation/methanosulfonation yielded the least active compounds. In summary, acetylation is found to be a convenient functionalization to enhance the antiviral profile of favipiravir.

Acetylation of nuclear receptors in health and disease: an update

Lysine acetylation is a common reversible post-translational modification of proteins that plays a key role in regulating gene expression. Nuclear receptors (NRs) include ligand-inducible transcription factors and orphan receptors for which the ligand is undetermined, which together regulate the expression of genes involved in development, metabolism, homeostasis, reproduction and human diseases including cancer. Since the original finding that the ERα, AR and HNF4 are acetylated, we now understand that the vast majority of NRs are acetylated and that this modification has profound effects on NR function. Acetylation sites are often conserved and involve both ordered and disordered regions of NRs. The acetylated residues function as part of an intramolecular signalling platform intersecting phosphorylation, methylation and other modifications. Acetylation of NR has been shown to impact recruitment into chromatin, co-repressor and coactivator complex formation, sensitivity and specificity of regulation by ligand and ligand antagonists, DNA binding, subcellular distribution and transcriptional activity. A growing body of evidence in mice indicates a vital role for NR acetylation in metabolism. Additionally, mutations of the NR acetylation site occur in human disease. This review focuses on the role of NR acetylation in coordinating signalling in normal physiology and disease.

The SIRT3-ATAD3A axis regulates MAM dynamics and mitochondrial calcium homeostasis in cardiac hypertrophy

Mitochondria are energy-producing organelles that are mobile and harbor dynamic network structures. Although mitochondria and endoplasmic reticulum (ER) play distinct cellular roles, they are physically connected to maintain functional homeostasis. Abnormal changes in this interaction have been linked to pathological states, including cardiac hypertrophy. However, the exact regulatory molecules and mechanisms are yet to be elucidated. Here, we report that ATPase family AAA-domain containing protein 3A (ATAD3A) is an essential regulator of ER-mitochondria interplay within the mitochondria-associated membrane (MAM). ATAD3A prevents isoproterenol (ISO)-induced mitochondrial calcium accumulation, improving mitochondrial dysfunction and ER stress, which preserves cardiac function and attenuates cardiac hypertrophy. We also find that ATAD3A is a new substrate of NAD+-dependent deacetylase Sirtuin 3 (SIRT3). Notably, the heart mitochondria of SIRT3 knockout mice exhibited excessive formation of MAMs. Mechanistically, ATAD3A specifically undergoes acetylation, which reduces self-oligomerization and promotes cardiac hypertrophy. ATAD3A oligomerization is disrupted by acetylation at K134 site, and ATAD3A monomer closely interacts with the IP3R1-GRP75-VDAC1 complex, which leads to mitochondrial calcium overload and dysfunction. In summary, ATAD3A localizes to the MAMs, where it protects the homeostasis of ER-mitochondria contacts, quenching mitochondrial calcium overload and keeping mitochondrial bioenergetics unresponsive to ER stress. The SIRT3-ATAD3A axis represents a potential therapeutic target for cardiac hypertrophy.

Acetylation and Phosphorylation in the Regulation of Hypoxia-Inducible Factor Activities: Additional Options to Modulate Adaptations to Changes in Oxygen Levels

O2 is essential for the life of eukaryotic cells. The ability to sense oxygen availability and initiate a response to adapt the cell to changes in O2 levels is a fundamental achievement of evolution. The key switch for adaptation consists of the transcription factors HIF1A, HIF2A and HIF3A. Their levels are tightly controlled by O2 through the involvement of the oxygen-dependent prolyl hydroxylase domain-containing enzymes (PHDs/EGNLs), the von Hippel-Lindau tumour suppressor protein (pVHL) and the ubiquitin-proteasome system. Furthermore, HIF1A and HIF2A are also under the control of additional post-translational modifications (PTMs) that positively or negatively regulate the activities of these transcription factors. This review focuses mainly on two PTMs of HIF1A and HIF2A: phosphorylation and acetylation.

Sirtuin 2 promotes human cytomegalovirus replication by regulating cell cycle progression

IMPORTANCE

This study expands the growing understanding that protein acetylation is a highly regulated molecular toggle of protein function in both host anti-viral defense and viral replication. We describe a pro-viral role for the human enzyme SIRT2, showing that its deacetylase activity supports HCMV replication. By integrating quantitative proteomics, flow cytometry cell cycle assays, microscopy, and functional virology assays, we investigate the temporality of SIRT2 functions and substrates. We identify a pro-viral role for the SIRT2 deacetylase activity via regulation of CDK2 K6 acetylation and the G1-S cell cycle transition. These findings highlight a link between viral infection, protein acetylation, and cell cycle progression.

Genome-wide study reveals novel roles for formin-2 in axon regeneration as a microtubule dynamics regulator and therapeutic target for nerve repair

Peripheral nerves regenerate successfully; however, clinical outcome after injury is poor. We demonstrated that low-dose ionizing radiation (LDIR) promoted axon regeneration and function recovery after peripheral nerve injury (PNI). Genome-wide CpG methylation profiling identified LDIR-induced hypermethylation of the Fmn2 promoter, exhibiting injury-induced Fmn2 downregulation in dorsal root ganglia (DRGs). Constitutive knockout or neuronal Fmn2 knockdown accelerated nerve repair and function recovery. Mechanistically, increased microtubule dynamics at growth cones was observed in time-lapse imaging of Fmn2-deficient DRG neurons. Increased HDAC5 phosphorylation and rapid tubulin deacetylation were found in regenerating axons of neuronal Fmn2-knockdown mice after injury. Growth-promoting effect of neuronal Fmn2 knockdown was eliminated by pharmaceutical blockade of HDAC5 or neuronal Hdac5 knockdown, suggesting that Fmn2deletion promotes axon regeneration via microtubule post-translational modification. In silico screening of FDA-approved drugs identified metaxalone, administered either immediately or 24-h post-injury, accelerating function recovery. This work uncovers a novel axon regeneration function of Fmn2 and a small-molecule strategy for PNI.

Acetylation is required for full activation of the NLRP3 inflammasome

Full activation of the NLRP3 inflammasome needs two sequential signals: a priming signal, followed by a second, assembly signal. Several studies have shown that the two signals trigger post-translational modification (PTM) of NLRP3, affecting activity of the inflammasome, however, the PTMs induced by the second signal are less well characterized. Here, we show that the assembly signal involves acetylation of NLRP3 at lysine 24, which is important for the oligomerization and the actual assembly of NLRP3 without affecting its recruitment to dispersed trans-Golgi network (dTGN). Accordingly, NLRP3 inflammasome activation is impaired in NLRP3-K24R knock-in mice. We identify KAT5 as an acetyltransferase able to acetylate NLRP3. KAT5 deficiency in myeloid cells and pharmacological inhibition of KAT5 enzymatic activity reduce activation of the NLRP3 inflammasome, both in vitro and in vivo. Thus, our study reveals a key mechanism for the oligomerization and full activation of NLRP3 and lays down the proof of principle for therapeutic targeting of the KAT5-NLRP3 axis.

Effects of Wood Content and Modification on Properties of Wood Flour/Polybutylene Adipate Terephthalate Biocomposites

Biodegradable polymers have recently become attractive and have been increasingly used as matrix materials to replace fossil plastics due to concerns about the environmental issue. However, their application areas are limited due to their high costs and natural properties. In this study, we fabricated ecofriendly and economical polybutylene adipate terephthalate (PBAT) composites loaded with various concentrations of wood flour (WF) to investigate the effects on the PBAT and WF interfaces as well as the physical properties of the WF/PBAT biocomposites. Then, WF was acetylated with acetic anhydride, and the effect of WF acetylation on the mechanical and thermal properties of the biocomposites were investigated. The results showed that the tensile strength, tensile modulus, flexural strength and flexural modulus increased with WF loading in the composites, and acetylation could not only further increase these properties, but also increase the impact strength and elongation at break. The incorporation of WF would weaken the thermal stability of PBAT, but the thermal stability of the biocomposite could be improved after WF acetylation. The cold crystallization temperature and hydrophobicity of the WF/PBAT samples would be increased with the increasing load of the WF, while the melting enthalpy and the crystallinity of the samples reduced gradually. A morphological analysis of the modified composites revealed that the matrix exhibited greater interfacial interactions with the WF compared to the WF/PBAT. Considering the much lower cost of WF compared to PBAT, the improved properties of WF/PBAT biocomposites will make it economically competitive with other commercial polymers, and these biocomposites should have much wider application areas.

NAT10 Is Involved in Cardiac Remodeling Through ac4C-Mediated Transcriptomic Regulation

BACKGROUND

Heart failure, characterized by cardiac remodeling, is associated with abnormal epigenetic processes and aberrant gene expression. Here, we aimed to elucidate the effects and mechanisms of NAT10 (N-acetyltransferase 10)-mediated N4-acetylcytidine (ac4C) acetylation during cardiac remodeling.

METHODS

NAT10 and ac4C expression were detected in both human and mouse subjects with cardiac remodeling through multiple assays. Subsequently, acetylated RNA immunoprecipitation and sequencing, thiol-linked alkylation for the metabolic sequencing of RNA (SLAM-seq), and ribosome sequencing (Ribo-seq) were employed to elucidate the role of ac4C-modified posttranscriptional regulation in cardiac remodeling. Additionally, functional experiments involving the overexpression or knockdown of NAT10 were conducted in mice models challenged with Ang II (angiotensin II) and transverse aortic constriction.

RESULTS

NAT10 expression and RNA ac4C levels were increased in in vitro and in vivo cardiac remodeling models, as well as in patients with cardiac hypertrophy. Silencing and inhibiting NAT10 attenuated Ang II-induced cardiomyocyte hypertrophy and cardiofibroblast activation. Next-generation sequencing revealed ac4C changes in both mice and humans with cardiac hypertrophy were associated with changes in global mRNA abundance, stability, and translation efficiency. Mechanistically, NAT10 could enhance the stability and translation efficiency of CD47 and ROCK2 transcripts by upregulating their mRNA ac4C modification, thereby resulting in an increase in their protein expression during cardiac remodeling. Furthermore, the administration of Remodelin, a NAT10 inhibitor, has been shown to prevent cardiac functional impairments in mice subjected to transverse aortic constriction by suppressing cardiac fibrosis, hypertrophy, and inflammatory responses, while also regulating the expression levels of CD47 and ROCK2 (Rho associated coiled-coil containing protein kinase 2).

CONCLUSIONS

Therefore, our data suggest that modulating epitranscriptomic processes, such as ac4C acetylation through NAT10, may be a promising therapeutic target against cardiac remodeling.

SIRT2 negatively regulates the cGAS-STING pathway by deacetylating G3BP1

SIRT2, a cytoplasmic member of the Sirtuin family, has important roles in immunity and inflammation. However, its function in regulating the response to DNA virus infection remains elusive. Here, we find that SIRT2 is a unique regulator among the Sirtuin family that negatively modulates the cGAS-STING-signaling pathway. SIRT2 is down-regulated after Herpes simplex virus-1 (HSV-1) infection, and SIRT2 deficiency markedly elevates the expression levels of type I interferon (IFN). SIRT2 inhibits the DNA binding ability and droplet formation of cGAS by interacting with and deacetylating G3BP1 at K257, K276, and K376, leading to the disassembly of the cGAS-G3BP1 complex, which is critical for cGAS activation. Administration of AGK2, a selective SIRT2 inhibitor, protects mice from HSV-1 infection and increases the expression of IFN and IFN-stimulated genes. Our study shows that SIRT2 negatively regulates cGAS activation through G3BP1 deacetylation, suggesting a potential antiviral strategy by modulating SIRT2 activity.

Acetylation regulates the oligomerization state and activity of RNase J, the Helicobacter pylori major ribonuclease

In the gastric pathogen Helicobacter pylori, post-transcriptional regulation relies strongly on the activity of the essential ribonuclease RNase J. Here, we elucidated the crystal and cryo-EM structures of RNase J and determined that it assembles into dimers and tetramers in vitro. We found that RNase J extracted from H. pylori is acetylated on multiple lysine residues. Alanine substitution of several of these residues impacts on H. pylori morphology, and thus on RNase J function in vivo. Mutations of Lysine 649 modulates RNase J oligomerization in vitro, which in turn influences ribonuclease activity in vitro. Our structural analyses of RNase J reveal loops that gate access to the active site and rationalizes how acetylation state of K649 can influence activity. We propose acetylation as a regulatory level controlling the activity of RNase J and its potential cooperation with other enzymes of RNA metabolism in H. pylori.