ARD1-mediated Hsp70 acetylation balances stress-induced protein refolding and degradation

Transcriptome analysis indicates the mechanisms of BmNPV resistance in Bombyx mori midgut

Bombyx mori nucleopolyhedrovirus (BmNPV) caused serious economic losses in sericulture. Analyzing the molecular mechanism of silkworms (B. mori) resistance to BmNPV is of great significance for the prevention and control of silkworm virus diseases and the biological control of agricultural lepidopteran pests. In order to clarify the defense mechanisms of silkworms against BmNPV, we constructed a near isogenic line BC8 with high resistance to BmNPV through the highly BmNPV-resistant strain NB and the highly BmNPV-susceptible strain 306. In this study, RNA-Seq technique was used to analyze the transcriptome level differences in the midgut of BC8 and 306 following BmNPV infection. A total of 1350 DEGs were identified. Clustering analysis showed that these genes could be divided into 8 clusters with different expression patterns. Functional annotations based on GO and KEGG analysis indicated that they were involved in various metabolism pathways. Finally, 32 BmNPV defense responsive genes were screened. They were involved in metabolism, reactive oxygen species (ROS), signal transduction and immune response, and insect hormones. The further verification shows that HSP70 should participate in resistance responses of anti-BmNPV. These findings have paved the way in further functional characterization of candidate genes and subsequently can be used in breeding of BmNPV resistance dominant silkworms.

Developing an SNP dataset for efficiently evaluating soybean germplasm resources using the genome sequencing data of 3,661 soybean accessions

BACKGROUND

Single nucleotide polymorphism (SNP) markers play significant roles in accelerating breeding and basic crop research. Several soybean SNP panels have been developed. However, there is still a lack of SNP panels for differentiating between wild and cultivated populations, as well as for detecting polymorphisms within both wild and cultivated populations.

RESULTS

This study utilized publicly available resequencing data from over 3,000 soybean accessions to identify differentiating and highly conserved SNP and insertion/deletion (InDel) markers between wild and cultivated soybean populations. Additionally, a naturally occurring mutant gene library was constructed by analyzing large-effect SNPs and InDels in the population.

CONCLUSION

The markers obtained in this study are associated with numerous genes governing agronomic traits, thus facilitating the evaluation of soybean germplasms and the efficient differentiation between wild and cultivated soybeans. The natural mutant gene library permits the quick identification of individuals with natural mutations in functional genes, providing convenience for accelerating soybean breeding using reverse genetics.

Protein Quality Control of NKCC2 in Bartter Syndrome and Blood Pressure Regulation

Mutations in NKCC2 generate antenatal Bartter syndrome type 1 (type 1 BS), a life-threatening salt-losing nephropathy characterized by arterial hypotension, as well as electrolyte abnormalities. In contrast to the genetic inactivation of NKCC2, inappropriate increased NKCC2 activity has been associated with salt-sensitive hypertension. Given the importance of NKCC2 in salt-sensitive hypertension and the pathophysiology of prenatal BS, studying the molecular regulation of this Na-K-2Cl cotransporter has attracted great interest. Therefore, several studies have addressed various aspects of NKCC2 regulation, such as phosphorylation and post-Golgi trafficking. However, the regulation of this cotransporter at the pre-Golgi level remained unknown for years. Similar to several transmembrane proteins, export from the ER appears to be the rate-limiting step in the cotransporter's maturation and trafficking to the plasma membrane. The most compelling evidence comes from patients with type 5 BS, the most severe form of prenatal BS, in whom NKCC2 is not detectable in the apical membrane of thick ascending limb (TAL) cells due to ER retention and ER-associated degradation (ERAD) mechanisms. In addition, type 1 BS is one of the diseases linked to ERAD pathways. In recent years, several molecular determinants of NKCC2 export from the ER and protein quality control have been identified. The aim of this review is therefore to summarize recent data regarding the protein quality control of NKCC2 and to discuss their potential implications in BS and blood pressure regulation.

Biomarker-Based Risk Stratification Tool in Pediatric Acute Respiratory Distress Syndrome: Single-Center, Longitudinal Validation in a 2014-2019 Cohort

OBJECTIVES

The Pediatric Acute Respiratory Distress Syndrome Biomarker Risk Model (PARDSEVERE) used age and three plasma biomarkers measured within 24 hours of pediatric acute respiratory distress syndrome (ARDS) onset to predict mortality in a pilot cohort of 152 patients. However, longitudinal performance of PARDSEVERE has not been evaluated, and it is unclear whether the risk model can be used to prognosticate after day 0. We, therefore, sought to determine the test characteristics of PARDSEVERE model and population over the first 7 days after ARDS onset.

DESIGN

Secondary unplanned post hoc analysis of data from a prospective observational cohort study carried out 2014-2019.

SETTING

University-affiliated PICU.

PATIENTS

Mechanically ventilated children with ARDS.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Between July 2014 and December 2019, 279 patients with ARDS had plasma collected at day 0, 266 at day 3 (11 nonsurvivors, two discharged between days 0 and 3), and 207 at day 7 (27 nonsurvivors, 45 discharged between days 3 and 7). The actual prevalence of mortality on days 0, 3, and 7, was 23% (64/279), 14% (38/266), and 13% (27/207), respectively. The PARDSEVERE risk model for mortality on days 0, 3, and 7 had area under the receiver operating characteristic curve (AUROC [95% CI]) of 0.76 (0.69-0.82), 0.68 (0.60-0.76), and 0.74 (0.65-0.83), respectively. The AUROC data translate into prevalence thresholds for the PARDSEVERE model for mortality (i.e., using the sensitivity and specificity values) of 37%, 27%, and 24% on days 0, 3, and 7, respectively. Negative predictive value (NPV) was high throughout (0.87-0.90 for all three-time points).

CONCLUSIONS

In this exploratory analysis of the PARDSEVERE model of mortality risk prediction in a population longitudinal series of data from days 0, 3, and 7 after ARDS diagnosis, the diagnostic performance is in the "acceptable" category. NPV was good. A major limitation is that actual mortality is far below the prevalence threshold for such testing. The model may, therefore, be more useful in cohorts with higher mortality rates (e.g., immunocompromised, other countries), and future enhancements to the model should be explored.

NAA10 gene expression is associated with mesenchymal transition, dedifferentiation, and progression of clear cell renal cell carcinoma

INTRODUCTION

We aimed to investigate the expression and prognostic role of NAA10 in clear cell renal cell carcinoma (ccRCC).

MATERIAL AND METHODS

We performed a gene expression and survival analysis based on the human cancer genome atlas database of ccRCC patients (TCGA-KIRC).

RESULTS

The patients in the TCGA-KIRC (n = 537) were divided into two subgroups: NAA10-low and NAA10-high expression groups. NAA10-high ccRCC exhibited higher T stages (p = 0.002), a higher frequency of distant metastasis (p = 0.018), more advanced AJCC stages (p < 0.001), a lower overall survival time (p = 0.036), and a lower survival rate (p < 0.001). NAA10-high ccRCC was associated with increased activity of non-specific oncogenic pathways, including oxidative phosphorylation (p < 0.001) and cell cycle progression [G2 to M phase transition (p = 0.045) and E2F targets (p < 0.001)]. Additionally, the NAA10-high tumors showed reduced apoptosis via TRIAL pathways (p < 0.001) and increased levels of activity that promoted epithelial-mesenchymal transition (p = 0.026) or undifferentiation (p = 0.01). In ccRCC, NAA10 expression was found to be a negative prognostic factor in both non-metastatic (p < 0.001) and metastatic tumors (p = 0.032).

CONCLUSIONS

In ccRCC, NAA10 expression was shown to be a negative prognostic factor related to tumor progression rather than tumor initiation, and high NAA10 expression promoted epithelial-mesenchymal transition and undifferentiation.

Modulation of cAMP/cGMP signaling as prevention of congenital heart defects in Pde2A deficient embryos: a matter of oxidative stress

Phosphodiesterase 2A (Pde2A) is a dual-specific PDE that breaks down both cAMP and cGMP cyclic nucleotides. We recently highlighted a direct relationship between Pde2A impairment, a consequent increase of cAMP, and the appearance of mouse congenital heart defects (CHDs). Here we aimed to characterize the pathways involved in the development of CHDs and in their prevention by pharmacological approaches targeting cAMP and cGMP signaling. Transcriptome analysis revealed a modulation of more than 500 genes affecting biological processes involved in the immune system, cardiomyocyte development and contractility, angiogenesis, transcription, and oxidative stress in hearts from Pde2A-/- embryos. Metoprolol and H89 pharmacological administration prevented heart dilatation and hypertabeculation in Pde2A-/- embryos. Metoprolol was also able to partially impede heart septum defect and oxidative stress at tissue and molecular levels. Amelioration of cardiac defects was also observed by using the antioxidant NAC, indicating oxidative stress as one of the molecular mechanisms underpinning the CHDs. In addition, Sildenafil treatment recovered cardiac defects suggesting the requirement of cAMP/cGMP nucleotides balance for the correct heart development.

The Inhibition of the Membrane-Bound Transcription Factor Site-1 Protease (MBTP1) Alleviates the p.Phe508del-Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) Defects in Cystic Fibrosis Cells

Cystic Fibrosis (CF) is present due to mutations in the Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) gene, the most frequent variant being p.phe508del. The CFTR protein is a chloride (Cl-) channel which is defective and almost absent of cell membranes when the p.Phe508del mutation is present. The p.Phe508del-CFTR protein is retained in the endoplasmic reticulum (ER) and together with inflammation and infection triggers the Unfolded Protein Response (UPR). During the UPR, the Activating Transcription Factor 6 (ATF6) is activated with cleavage and then decreases the expression of p.Phe508del-CFTR. We have previously shown that the inhibition of the activation of ATF6 alleviates the p.Phe508del-CFTR defects in cells overexpressing the mutated protein. In the present paper, our aim was to inhibit the cleavage of ATF6, and thus its activation in a human bronchial cell line with endogenous p.Phe508del-CFTR expression and in bronchial cells from patients, to be more relevant to CF. This was achieved by inhibiting the protease MBTP1 which is responsible for the cleavage of ATF6. We show here that this inhibition leads to increased mRNA and p.Phe508del-CFTR expression and, consequently, to increased Cl-efflux. We also explain the mechanisms linked to these increases with the modulation of genes when MBTP1 is inhibited. Indeed, RT-qPCR assays show that genes such as HSPA1B, CEBPB, VIMP, PFND2, MAPK8, XBP1, INSIG1, and CALR are modulated. In conclusion, we show that the inhibition of MBTP1 has a beneficial effect in relevant models to CF and that this is due to the modulation of genes involved in the disease.

Multiple impacts of Naa10p on cancer progression: Molecular functions and clinical prospects

Nα-acetyltransferase 10 protein (Naa10p) is known as the catalytic subunit of N-terminal acetyltransferases A (NatA) complex, associating with Naa15p to acetylate N-termini of the human proteome. Recent investigations have unveiled additional functions for Naa10p, encompassing lysine ε-acetylation and acetyltransferase-independent activities. Its pleiotropic roles have been implicated in diverse physiological and pathological contexts. Emerging evidence has implicated Naa10p in cancer progression, demonstrating dual attributes as an oncogene or a tumor suppressor contingent on the cancer type and acetyltransferase activity context. In this comprehensive review, we present a pan-cancer analysis aimed at elucidating the intricacies underlying Naa10p dysregulation in cancer. Our findings propose the potential involvement of c-Myc as a modulatory factor influencing Naa10p expression. Moreover, we provide a consolidated summary of recent advancements in understanding the intricate molecular underpinnings through which Naa10p contributes to cancer cell proliferation and metastasis. Furthermore, we delve into the multifaceted nature of Naa10p's roles in regulating cancer behaviors, potentially attributed to its interactions with a repertoire of partner proteins. Through an exhaustive exploration of Naa10p's functions, spanning its acetylation activity and acetyltransferase-independent functionalities, this review offers novel insights with implications for targeted therapeutic strategies involving this pivotal protein in the realm of cancer therapeutics.

Extremely low-frequency electromagnetic field induces acetylation of heat shock proteins and enhances protein folding

The pervasive weak electromagnetic fields (EMF) inundate the industrialized society, but the biological effects of EMF as weak as 10 µT have been scarcely analyzed. Heat shock proteins (HSPs) are molecular chaperones that mediate a sequential stress response. HSP70 and HSP90 provide cells under undesirable situations with either assisting covalent folding of proteins or degrading improperly folded proteins in an ATP-dependent manner. Here we examined the effect of extremely low-frequency (ELF)-EMF on AML12 and HEK293 cells. Although the protein expression levels of HSP70 and HSP90 were reduced after an exposure to ELF-EMF for 3 h, acetylations of HSP70 and HSP90 were increased, which was followed by an enhanced binding affinities of HSP70 and HSP90 for HSP70/HSP90-organizing protein (HOP/STIP1). After 3 h exposure to ELF-EMF, the amount of mitochondria was reduced but the ATP level and the maximal mitochondrial oxygen consumption were increased, which was followed by the reduced protein aggregates and the increased cell viability. Thus, ELF-EMF exposure for 3 h activated acetylation of HSPs to enhance protein folding, which was returned to the basal level at 12 h. The proteostatic effects of ELF-EMF will be able to be applied to treat pathological states in humans.

The fine-tuned crosstalk between lysine acetylation and the circadian rhythm

Circadian rhythm is a roughly 24-h wake and sleep cycle that almost all of the organisms on the earth follow when they execute their biological functions and physiological activities. The circadian clock is mainly regulated by the transcription-translation feedback loop (TTFL), consisting of the core clock proteins, including BMAL1, CLOCK, PERs, CRYs, and a series of accessory factors. The circadian clock and the downstream gene expression are not only controlled at the transcriptional and translational levels but also precisely regulated at the post-translational modification level. Recently, it has been discovered that CLOCK exhibits lysine acetyltransferase activities and could acetylate protein substrates. Core clock proteins are also acetylated, thereby altering their biological functions in the regulation of the expression of downstream genes. Studies have revealed that many protein acetylation events exhibit oscillation behavior. However, the biological function of acetylation on circadian rhythm has only begun to explore. This review will briefly introduce the acetylation and deacetylation of the core clock proteins and summarize the proteins whose acetylation is regulated by CLOCK and circadian rhythm. Then, we will also discuss the crosstalk between lysine acetylation and the circadian clock or other post-translational modifications. Finally, we will briefly describe the possible future perspectives in the field.

RNAseq analysis of the drug jian-yan-ling (JYL) using both in vivo and in vitro models

Ethnopharmacological relevance

Jian-yan-ling (JYL) is a drug used in traditional Chinese medicine (TCM) prescriptions for the treatment of tumors after radiotherapy and chemotherapy, to effectively alleviate leukocytopenia. However, the genetic mechanisms underlying the function of JYL remain unclear.

Aim of the study

This study aimed to explore the RNA changes and potential biological processes related to the anti-aging or life-extending effects of JYL treatments.

Materials and methods

In vivo treatments were performed using Canton-S Drosophila corresponding to three groups: control, low-concentration (low-conc.), and high-concentration (high-conc.) groups. The low-conc. And the high-conc. Groups were treated with 4 mg/mL JYL and 8 mg/mL JYL, respectively. Thirty Drosophila eggs were placed in each vial, and the third instar larvae and adults 7 and 21 days post-eclosion were collected for RNA sequencing, irrespective of the gender.In vitro treatments were conducted using humanized immune cell lines HL60 and Jurkat, which were divided into 3 groups: control (0 μg/mL JYL), low-concentration (40 μg/mL JYL), and high-concentration (80 μg/mL JYL). The cells were collected after 48 h of each JYL drug treatment. Both the Drosophila and cell samples were analyzed using RNA sequencing.

Results

The in vivo experiments revealed 74 upregulated genes in the low-concentration group, and CG13078 was a commonly downregulated differential gene, which is involved in ascorbate iron reductase activity. Further analysis of the co-expression map identified the key genes: regulatory particle non-ATPase (RPN), regulatory particle triple-A ATPase (RPT), and tripeptidyl-peptidase II (TPP II). For the in vitro experiments, 19 co-differential genes were compared between different concentrations of the HL 60 cell line, of which three genes were upregulated: LOC107987457 (phostensin-like gene), HSPA1A (heat shock protein family A member 1 A), and H2AC19 (H2A clustered histone 19). In the HL 60 cell line, JYL activated proteasome-related functions. In the Jurkat cell line, there were no common differential genes despite the presence of a dosage-dependent trend.

Conclusions

The RNA-seq results showed that the traditional Chinese medicine JYL has longevity and anti-aging effects, indicating that further investigation is required.

Profiling the Hsp70 Chaperone Network in Heat-Induced Proteotoxic Stress Models of Human Neurons

Heat stroke is among the most hazardous hyperthermia-related illnesses and an emerging threat to humans from climate change. Acute brain injury and long-lasting brain damage are the hallmarks of this condition. Hyperthermic neurological manifestations are remarkable for their damage correlation with stress amplitude and long-term persistence. Hyperthermia-induced protein unfolding, and nonspecific aggregation accumulation have neurotoxic effects and contribute to the pathogenesis of brain damage in heat stroke. Therefore, we generated heat-induced, dose-responsive extreme and mild proteotoxic stress models in medulloblastoma [Daoy] and neuroblastoma [SH-SY5Y] and differentiated SH-SY5Y neuronal cells. We show that heat-induced protein aggregation is associated with reduced cell proliferation and viability. Higher protein aggregation in differentiated neurons than in neuroblastoma precursors suggests a differential neuronal vulnerability to heat. We characterized the neuronal heat shock response through RT-PCR array analysis of eighty-four genes involved in protein folding and protein quality control (PQC). We identify seventeen significantly expressed genes, five of which are Hsp70 chaperones, and four of their known complementing function proteins. Protein expression analysis determined the individual differential contribution of the five Hsp70 chaperones to the proteotoxic stress response and the significance of only two members under mild conditions. The co-expression analysis reveals significantly high co-expression between the Hsp70 chaperones and their interacting partners. The findings of this study lend support to the hypothesis that hyperthermia-induced proteotoxicity may underlie the brain injury of heat stroke. Additionally, this study presents a comprehensive map of the Hsp70 network in these models with potential clinical and translational implications.

Efficient biodegradation of tris-(2-chloroisopropyl) phosphate by a novel strain Amycolatopsis sp. FT-1: Process optimization, mechanism studies and toxicity changes

In this study, a newly isolated strain Amycolatopsis sp. FT-1 was confirmed to be an efficient tris-(2-chloroisopropyl) phosphate (TCPP) degrader. The maximum degradation efficiency of 100 % was achieved when glucose concentration was 6.0 g/L, TCPP concentration was 1.1 mg/L, pH was 6.3 and temperature was 35 °C. Proteome analysis indicated that TCPP was transformed into diester, monoester and ketone product through hydrolysis by phosphoesterase and oxidation mediated by proteins involved in bio-Fenton reaction. The increased expression of proteins serving as organic hydroperoxides scavenger and two subunits of xanthine dehydrogenase enabled Amycolatopsis sp. FT-1 to defend against TCPP-induced oxidative damage. Meanwhile, proteins involved in the resistance to proteotoxic stress were found to be up-regulated, including Hsp70 protein, ATP-dependent Clp protease proteolytic subunit, elongation factor G and trehalose synthesis-related enzymes. The overexpression of TetR/AcrR family transcriptional regulator and multidrug efflux transporter also benefited the survival of Amycolatopsis sp. FT-1 under TCPP stress. Luminescent bacteria test showed that biotoxicity of TCPP was remarkably decreased after biodegradation by Amycolatopsis sp. FT-1. To the best of our knowledge, this is the first study to report the biotransformation of TCPP by pure strain and to offer important insights into the proteomic mechanisms of TCPP microbial degradation.

ARD1 stabilizes NRF2 through direct interaction and promotes colon cancer progression

AIMS

Aberrant overactivation/overexpression of NRF2 is implicated as a driving event in tumor progression, which has been attributed to its mutation or inactivation of the inhibitory protein, KEAP1. However, alternative mechanisms responsible for sustained activation of NRF2 are less understood.

MAIN METHODS

Human colon cancer cell lines and tissues obtained from colorectal cancer (CRC) patients were used. To examine the expression levels of ARD1 and NRF2, Western blot and immunofluorescence analyses were performed. To investigate the potential relevance of NRF2 and ARD1 to human CRC, NRF2 and ARD1 were individually silenced in human colon cancer cells (HCT-116) by transfection with their specific small interfering RNA (siRNA). To determine the functional role of ARD1 in NRF2 regulation, in situ proximate ligation, co-immunoprecipitation, nano-LC-ESI MS/MS, and in vitro acetylation assays were performed.

KEY FINDINGS

ARD1 knockdown in human colon cancer cell lines significantly reduced the protein levels of NRF2 without affecting its mRNA expression; however, silencing of NRF2 did not alter ARD1 protein expression. In addition, these two proteins were co-localized and physically interacted with each other both in human colon cancer cells (HCT-116) and human colon tumor tissues. Mechanistically, ARD1 overexpression increased the acetylation levels of NRF2. Moreover, an in vitro acetylation assay and mass spectrometric analysis demonstrated that ARD1 could directly acetylate NRF2. Ectopic expression of mutant forms of ARD1 with defective acetyltransferase activity reduced the stability of NRF2.

SIGNIFICANCE

In conclusion, ARD1 may potentiate the oncogenic function of NRF2 in human colon cancer by stabilizing this transcription factor.

Protein homeostasis in aging and cancer

Aging is a major risk factor for cancer development. As dysfunction in protein homeostasis, or proteostasis, is a universal hallmark of both the aging process and cancer, a comprehensive understanding of the proteostasis system and its roles in aging and cancer will shed new light on how we can improve health and quality of life for older individuals. In this review, we summarize the regulatory mechanisms of proteostasis and discuss the relationship between proteostasis and aging and age-related diseases, including cancer. Furthermore, we highlight the clinical application value of proteostasis maintenance in delaying the aging process and promoting long-term health.

Heat-Induced Proteotoxic Stress Response in Placenta-Derived Stem Cells (PDSCs) Is Mediated through HSPA1A and HSPA1B with a Potential Higher Role for HSPA1B

Placenta-derived stem cells (PDSCs), due to unique traits such as mesenchymal and embryonic characteristics and the absence of ethical constraints, are in a clinically and therapeutically advantageous position. To aid in stemness maintenance, counter pathophysiological stresses, and withstand post-differentiation challenges, stem cells require elevated protein synthesis and consequently augmented proteostasis. Stem cells exhibit source-specific proteostasis traits, making it imperative to study them individually from different sources. These studies have implications for understanding stem cell biology and exploitation in the augmentation of therapeutic applications. Here, we aim to identify the primary determinants of proteotoxic stress response in PDSCs. We generated heat-induced dose-responsive proteotoxic stress models of three stem cell types: placental origin cells, the placenta-derived mesenchymal stem cells (pMSCs), maternal origin cells, the decidua parietalis mesenchymal stem cells (DPMSCs), and the maternal–fetal interface cells, decidua basalis mesenchymal stem cells (DBMSCs), and measured stress induction through biochemical and cell proliferation assays. RT-PCR array analysis of 84 genes involved in protein folding and protein quality control led to the identification of Hsp70 members HSPA1A and HSPA1B as the prominent ones among 17 significantly expressed genes and with further analysis at the protein level through Western blotting. A kinetic analysis of HSPA1A and HSPA1B gene and protein expression allowed a time series evaluation of stress response. As identified by protein expression, an active stress response is in play even at 24 h. More prominent differences in expression between the two homologs are detected at the translational level, alluding to a potential higher requirement for HSPA1B during proteotoxic stress response in PDSCs.

HDAC4 Inhibitors as Antivascular Senescence Therapeutics

Aging is an inevitable consequence of life, and during this process, the epigenetic landscape changes and reactive oxygen species (ROS) accumulation increases. Inevitably, these changes are common in many age-related diseases, including neurodegeneration, hypertension, and cardiovascular diseases. In the current research, histone deacetylation 4 (HDAC4) was studied as a potential therapeutic target in vascular senescence. HDAC4 is a specific class II histone deacetylation protein that participates in epigenetic modifications and deacetylation of heat shock proteins and various transcription factors. There is increasing evidence to support that HDAC4 is a potential therapeutic target, and developments in the synthesis and testing of HDAC4 inhibitors are now gaining interest from academia and the pharmaceutical industry.

Quantitative Proteomic Analysis Reveals Important Roles of the Acetylation of ER-Resident Molecular Chaperones for Conidiation in Fusarium oxysporum

Fusarium oxysporum is one of the most abundant and diverse fungal species found in soils and includes nonpathogenic, endophytic, and pathogenic strains affecting a broad range of plant and animal hosts. Conidiation is the major mode of reproduction in many filamentous fungi, but the regulation of this process is largely unknown. Lysine acetylation (Kac) is an evolutionarily conserved and widespread posttranslational modification implicated in regulation of multiple metabolic processes. A total of 62 upregulated and 49 downregulated Kac proteins were identified in sporulating mycelia versus nonsporulating mycelia of F. oxysporum. Diverse cellular proteins, including glycolytic enzymes, ribosomal proteins, and endoplasmic reticulum–resident molecular chaperones, were differentially acetylated in the sporulation process. Altered Kac levels of three endoplasmic reticulum–resident molecular chaperones, PDI^K70, HSP70^K604, and HSP40^K32 were identified that with important roles in F. oxysporum conidiation. Specifically, K70 acetylation (K70ac) was found to be crucial for maintaining stability and activity of protein disulphide isomerase and the K604ac of HSP70 and K32ac of HSP40 suppressed the detoxification ability of these heat shock proteins, resulting in higher levels of protein aggregation. During conidial formation, an increased level of PDI^K70ac and decreased levels of HSP70^K604ac and HSP40^K32ac contributed to the proper processing of unfolded proteins and eliminated protein aggregation, which is beneficial for dramatic cell biological remodeling during conidiation in F. oxysporum.

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Importance and levels of acetylation in conidiation of Fusarium oxysporum.

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Protein folding was regulated by acetylation during conidiation.

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Acetylation modulates activities of ER-resident molecular chaperones.

N-α-Acetyltransferase 10 inhibits invasion and metastasis of oral squamous cell carcinoma via regulating Pirh2-p53 signalling pathway

N‐α‐Acetyltransferase 10 (NAA10) was reported to be involved in tumour invasion and metastasis in several of tumours. However, the role and mechanism of NAA10‐mediated invasion and metastasis in oral squamous cell carcinoma (OSCC) remains undetermined. Herein, our study showed that NAA10 inhibits cell migration and invasion in vitro and attenuates the xenograft tumorigenesis in nude mice. Mechanistically, we demonstrated that there is a physical interaction between NAA10 and RelA/p65 in OSCC cells, thereby preventing RelA/p65‐mediated transcriptional activation of Pirh2. Consequently, inhibition of Pirh2 increased p53 level and suppressed the expression of p53 downstream targets, matrix metalloprotein‐2 (MMP‐2) and MMP‐9. Therefore, NAA10 may function as a tumour metastasis suppressor in the progression of OSCC by targeting Pirh2‐p53 axis and might be a prognostic marker as well as a therapeutic target for OSCC.

Hypoglycemia Impairs the Heat Shock Protein Response: A Risk for Heat Shock in Cattle?

Background

Heat stress (HS) in cattle is a major debilitating problem, affecting health and milk yield. Physiologically, HS has been shown to lower blood glucose levels to 2.5 mmol/l (45 mg/dl) and results in upregulation of heat shock proteins (HSPs), eliciting the heat shock response (HSR) of which HSP90, 70 and 27 have been shown to be protective. However, it is unclear if the HSP response is blunted by decreased glucose, thereby preventing adaptive mechanisms. To address this question, this exploratory reverse translational study on the effects of hypoglycemia on the HSP pathway was undertaken.

Methods

A human prospective, study in healthy control individuals (n = 23) was undertaken. Subjects underwent hyperinsulinemic-induced hypoglycemia [≤2.0 mmol/L (36 mg/dl)] with blood sampling at baseline, at hypoglycemia and for a 24-h post-hypoglycemia follow-up period. Proteomic analysis of the heat shock-related protein pathway, the pathway associated with HS in cattle, was performed.

Results

In response to hypoglycemia, HS pathway proteins were significantly decreased (p &lt; 0.05): HSP70 and HSP27 (at hypoglycemia); DnaJ homolog subfamily B member 1 (DNAJB1), Stress-induced-phosphoprotein 1 (STIP1) and the ubiquitin pathway proteins, Ubiquitin-conjugating enzyme (UBE2L3) and Ubiquitin-conjugating enzyme E2 N (UBE2N) (at 30-min post-hypoglycemia); HSP90 (at 2-h post-hypoglycemia). STIP1, UBE2L3, and UBE2N remained suppressed at 24-h.

Conclusion

Heat stress in cattle reduces blood glucose that, in turn, may blunt the HS pathway protective response, including HSP 90, 70, 27 and the ubiquitin proteins, leading to adverse outcomes. Monitoring of blood glucose in susceptible cattle may allow for earlier intervention and may also identify those animals at greatest risk to ensure that milk yield is not compromised.

The Role of Tea Tree Oil in Alleviating Palmitic Acid-Induced Lipid Accumulation in Bovine Hepatocytes

Tea tree oil (TTO) plays an important role in lipid metabolism, alleviating the inflammatory responses. Fatty liver is associated with lipid accumulation in hepatocytes, leading to inflammation. However, there is very limited information on the effects of TTO on lipid accumulation, and inflammation in bovine hepatocytes. This study aimed to evaluate whether TTO alleviates palmitic acid (PA)-induced lipid accumulation in bovine hepatocytes. Hepatocytes isolated from mid-lactating Holstein cows were pretreated with 100 μM PA for 72 h. Cells were either pretreated with PA alone (PA group) or with PA followed by 0.00625% TTO treatment for 12 h (PT group). Expression of fatty acid oxidant genes increased (P < 0.05) while fatty acid synthesis genes decreased (P < 0.05) in the PT group compared with the PA group. PA treatment resulted in increased (P < 0.05) expression of tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6), but these increases were less in the PT group (P < 0.05). Compared to the PA group, expression of phosphorylated (p)-p65 and p-inhibitor κBα (p-IκBα) was suppressed (P < 0.05) by TTO treatment. TTO treatment limited (P < 0.05) the increase in intracellular reactive oxygen species (ROS) and prevented (P < 0.05) a reduction in mitochondrial membrane potential observed in response to PA treatment. Expression of endoplasmic reticulum (ER) stress genes was reduced (P < 0.05) in the PT group compared with the PA group. Our results suggest that TTO treatment attenuates the effects of PA in hepatocytes, leading to fatty acid oxidation, decreased fatty acid synthesis, suppressed inflammatory response, and reduced ER stress. Taken together, the results of this study suggest that TTO treatment may be a promising therapeutic approach to imbalanced lipid homeostasis, inflammation and ER stress in dairy cows shortly before and after calving.

Biochemical analysis of novel NAA10 variants suggests distinct pathogenic mechanisms involving impaired protein N-terminal acetylation

NAA10 is the catalytic subunit of the N-terminal acetyltransferase complex, NatA, which is responsible for N-terminal acetylation of nearly half the human proteome. Since 2011, at least 21 different NAA10 missense variants have been reported as pathogenic in humans. The clinical features associated with this X-linked condition vary, but commonly described features include developmental delay, intellectual disability, cardiac anomalies, brain abnormalities, facial dysmorphism and/or visual impairment. Here, we present eight individuals from five families with five different de novo or inherited NAA10 variants. In order to determine their pathogenicity, we have performed biochemical characterisation of the four novel variants c.16G>C p.(A6P), c.235C>T p.(R79C), c.386A>C p.(Q129P) and c.469G>A p.(E157K). Additionally, we clinically describe one new case with a previously identified pathogenic variant, c.384T>G p.(F128L). Our study provides important insight into how different NAA10 missense variants impact distinct biochemical functions of NAA10 involving the ability of NAA10 to perform N-terminal acetylation. These investigations may partially explain the phenotypic variability in affected individuals and emphasise the complexity of the cellular pathways downstream of NAA10.

OUP accepted manuscript

Reactive oxygen species (ROS) are constantly produced in cells, an excess of which causes oxidative stress. ROS has been linked to regulation of the Hippo pathway; however, the underlying detailed mechanisms remain unclear. Here, we report that MOB1, a substrate of MST1/2 and co-activator of LATS1/2 in the canonical Hippo pathway, interacts with and is acetylated at lysine 11 by acetyltransferase CBP and deacetylated by HDAC6. MOB1-K11 acetylation stabilizes itself by reducing its binding capacity with E3 ligase Praja2 and subsequent ubiquitination. MOB1-K11 acetylation increases its phosphorylation and activates LATS1. Importantly, upstream oxidative stress signals promote MOB1 acetylation by suppressing CBP degradation, independent of MST1/2 kinase activity and HDAC6 deacetylation effect, thereby linking oxidative stress to activation of the Hippo pathway. Functionally, the acetylation-deficient mutant MOB1-K11R promotes lung cancer cell proliferation, migration and invasion in vitro and accelerates tumor growth in vivo, compared to the wild-type MOB1. Clinically, acetylated MOB1 corresponds to better prediction of overall survival in patients with non-small cell lung cancer. Therefore, as demonstrated, an oxidative stress-CBP regulatory axis controls MOB1-K11 acetylation and activates LATS1, thereby activating the Hippo pathway and suppressing YAP/TAZ nuclear translocation and tumor progression.

With or without You: Co-Chaperones Mediate Health and Disease by Modifying Chaperone Function and Protein Triage

Heat shock proteins (HSPs) are a family of molecular chaperones that regulate essential protein refolding and triage decisions to maintain protein homeostasis. Numerous co-chaperone proteins directly interact and modify the function of HSPs, and these interactions impact the outcome of protein triage, impacting everything from structural proteins to cell signaling mediators. The chaperone/co-chaperone machinery protects against various stressors to ensure cellular function in the face of stress. However, coding mutations, expression changes, and post-translational modifications of the chaperone/co-chaperone machinery can alter the cellular stress response. Importantly, these dysfunctions appear to contribute to numerous human diseases. Therapeutic targeting of chaperones is an attractive but challenging approach due to the vast functions of HSPs, likely contributing to the off-target effects of these therapies. Current efforts focus on targeting co-chaperones to develop precise treatments for numerous diseases caused by defects in protein quality control. This review focuses on the recent developments regarding selected HSP70/HSP90 co-chaperones, with a concentration on cardioprotection, neuroprotection, cancer, and autoimmune diseases. We also discuss therapeutic approaches that highlight both the utility and challenges of targeting co-chaperones.

Hydroxylation of the Acetyltransferase NAA10 Trp38 Is Not an Enzyme-Switch in Human Cells

NAA10 is a major N-terminal acetyltransferase (NAT) that catalyzes the cotranslational N-terminal (Nt-) acetylation of 40% of the human proteome. Several reports of lysine acetyltransferase (KAT) activity by NAA10 exist, but others have not been able to find any NAA10-derived KAT activity, the latter of which is supported by structural studies. The KAT activity of NAA10 towards hypoxia-inducible factor 1α (HIF-1α) was recently found to depend on the hydroxylation at Trp38 of NAA10 by factor inhibiting HIF-1α (FIH). In contrast, we could not detect hydroxylation of Trp38 of NAA10 in several human cell lines and found no evidence that NAA10 interacts with or is regulated by FIH. Our data suggest that NAA10 Trp38 hydroxylation is not a switch in human cells and that it alters its catalytic activity from a NAT to a KAT.

Prenatal exposure to endocrine disrupting chemicals is associated with altered DNA methylation in cord blood

Prenatal exposure to endocrine disrupting chemicals can interfere with development, and has been associated with social-cognitive functioning and adverse health outcomes later in life. Exposure-associated changes of DNA methylation (DNAm) patterns have been suggested as a possible mediator of this relationship. This study investigated whether prenatal low-dose exposure to polychlorinated biphenyls (PCBs) and polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) is associated with altered DNAm patterns across the genome in a Western urban-industrial population. In 142 mother-infant pairs from the Duisburg Birth Cohort Study, PCBs and PCDD/Fs levels were quantified from maternal blood during late pregnancy and associated with DNAm levels in cord blood using the Illumina EPIC beadchip. The epigenome-wide association studies (EWAS) identified 32 significantly differentially methylated positions (DMPs) and eight differentially methylated regions (DMRs) associated with six congeners of PCB and PCDD in females or males (FDRs < 0.05). DMPs and DMRs mapped to genes involved in neurodevelopment, gene regulation, and immune functioning. Weighted gene correlation network analysis (WGCNA) showed 31 co-methylated modules (FDRs < 0.05) associated with one congener of PCDF levels in females. Results of both analytical strategies indicate that prenatal exposure to PCBs and PCDD/Fs is associated with altered DNAm of genes involved in neurodevelopment, gene expression and immune functioning. DNAm and gene expression levels of several of these genes were previously associated with EDC exposure in rodent models. Follow-up studies will clarify whether these epigenetic changes might contribute to the origin for adverse mental and health outcomes.

Plasma heat shock protein response to euglycemia in type 2 diabetes

INTRODUCTION

Glucose variability is associated with mortality and macrovascular diabetes complications. The mechanisms through which glucose variability mediates tissue damage are not well understood, although cellular oxidative stress is likely involved. As heat shock proteins (HSPs) play a role in the pathogenesis of type 2 diabetes (T2D) complications and are rapidly responsive, we hypothesized that HSP-related proteins (HSPRPs) would differ in diabetes and may respond to glucose normalization.

RESEARCH DESIGN AND METHODS

A prospective, parallel study in T2D (n=23) and controls (n=23) was undertaken. T2D subjects underwent insulin-induced blood glucose normalization from baseline 7.6±0.4 mmol/L (136.8±7.2 mg/dL) to 4.5±0.07 mmol/L (81±1.2 mg/dL) for 1 hour. Control subjects were maintained at 4.9±0.1 mmol/L (88.2±1.8 mg/dL). Slow Off-rate Modified Aptamer-scan plasma protein measurement determined a panel of HSPRPs.

RESULTS

At baseline, E3-ubiquitin-protein ligase (carboxyl-terminus of Hsc70 interacting protein (CHIP) or HSPABP2) was lower (p=0.03) and ubiquitin-conjugating enzyme E2G2 higher (p=0.003) in T2D versus controls. Following glucose normalization, DnaJ homolog subfamily B member 1 (DNAJB1 or HSP40) was reduced (p=0.02) in T2D, with HSP beta-1 (HSPB1) and HSP-70-1A (HSP70-1A) (p=0.07 and p=0.09, respectively) also approaching significance relative to T2D baseline levels.

CONCLUSIONS

Key HSPRPs involved in critical protein interactions, CHIP and UBE2G2, were altered in diabetes at baseline. DNAJB1 fell in response to euglycemia, suggesting that HSPs are reacting to basal stress that could be mitigated by tight glucose control with reduction of glucose variability.

Hypoxia-Induced Cancer Cell Responses Driving Radioresistance of Hypoxic Tumors: Approaches to Targeting and Radiosensitizing

Simple Summary

Some regions of aggressive malignancies experience hypoxia due to inadequate blood supply. Cancer cells adapting to hypoxic conditions somehow become more resistant to radiation exposure and this decreases the efficacy of radiotherapy toward hypoxic tumors. The present review article helps clarify two intriguing points: why hypoxia-adapted cancer cells turn out radioresistant and how they can be rendered more radiosensitive. The critical molecular targets associated with intratumoral hypoxia and various approaches are here discussed which may be used for sensitizing hypoxic tumors to radiotherapy.

Abstract

Within aggressive malignancies, there usually are the “hypoxic zones”—poorly vascularized regions where tumor cells undergo oxygen deficiency through inadequate blood supply. Besides, hypoxia may arise in tumors as a result of antiangiogenic therapy or transarterial embolization. Adapting to hypoxia, tumor cells acquire a hypoxia-resistant phenotype with the characteristic alterations in signaling, gene expression and metabolism. Both the lack of oxygen by itself and the hypoxia-responsive phenotypic modulations render tumor cells more radioresistant, so that hypoxic tumors are a serious challenge for radiotherapy. An understanding of causes of the radioresistance of hypoxic tumors would help to develop novel ways for overcoming this challenge. Molecular targets for and various approaches to radiosensitizing hypoxic tumors are considered in the present review. It is here analyzed how the hypoxia-induced cellular responses involving hypoxia-inducible factor-1, heat shock transcription factor 1, heat shock proteins, glucose-regulated proteins, epigenetic regulators, autophagy, energy metabolism reprogramming, epithelial–mesenchymal transition and exosome generation contribute to the radioresistance of hypoxic tumors or may be inhibited for attenuating this radioresistance. The pretreatments with a multitarget inhibition of the cancer cell adaptation to hypoxia seem to be a promising approach to sensitizing hypoxic carcinomas, gliomas, lymphomas, sarcomas to radiotherapy and, also, liver tumors to radioembolization.

Differential Effects of STCH and Stress-Inducible Hsp70 on the Stability and Maturation of NKCC2

Mutations in the Na-K-2Cl co-transporter NKCC2 lead to type I Bartter syndrome, a life-threatening kidney disease. We previously showed that export from the ER constitutes the limiting step in NKCC2 maturation and cell surface expression. Yet, the molecular mechanisms involved in this process remain obscure. Here, we report the identification of chaperone stress 70 protein (STCH) and the stress-inducible heat shock protein 70 (Hsp70), as two novel binding partners of the ER-resident form of NKCC2. STCH knock-down increased total NKCC2 expression whereas Hsp70 knock-down or its inhibition by YM-01 had the opposite effect. Accordingly, overexpressing of STCH and Hsp70 exerted opposite actions on total protein abundance of NKCC2 and its folding mutants. Cycloheximide chase assay showed that in cells over-expressing STCH, NKCC2 stability and maturation are heavily impaired. In contrast to STCH, Hsp70 co-expression increased NKCC2 maturation. Interestingly, treatment by protein degradation inhibitors revealed that in addition to the proteasome, the ER associated degradation (ERAD) of NKCC2 mediated by STCH, involves also the ER-to-lysosome-associated degradation pathway. In summary, our data are consistent with STCH and Hsp70 having differential and antagonistic effects with regard to NKCC2 biogenesis. These findings may have an impact on our understanding and potential treatment of diseases related to aberrant NKCC2 trafficking and expression.

Differential Effects of STCH and Stress-Inducible Hsp70 on the Stability and Maturation of NKCC2

Mutations in the Na-K-2Cl co-transporter NKCC2 lead to type I Bartter syndrome, a life-threatening kidney disease. We previously showed that export from the ER constitutes the limiting step in NKCC2 maturation and cell surface expression. Yet, the molecular mechanisms involved in this process remain obscure. Here, we report the identification of chaperone stress 70 protein (STCH) and the stress-inducible heat shock protein 70 (Hsp70), as two novel binding partners of the ER-resident form of NKCC2. STCH knock-down increased total NKCC2 expression whereas Hsp70 knock-down or its inhibition by YM-01 had the opposite effect. Accordingly, overexpressing of STCH and Hsp70 exerted opposite actions on total protein abundance of NKCC2 and its folding mutants. Cycloheximide chase assay showed that in cells over-expressing STCH, NKCC2 stability and maturation are heavily impaired. In contrast to STCH, Hsp70 co-expression increased NKCC2 maturation. Interestingly, treatment by protein degradation inhibitors revealed that in addition to the proteasome, the ER associated degradation (ERAD) of NKCC2 mediated by STCH, involves also the ER-to-lysosome-associated degradation pathway. In summary, our data are consistent with STCH and Hsp70 having differential and antagonistic effects with regard to NKCC2 biogenesis. These findings may have an impact on our understanding and potential treatment of diseases related to aberrant NKCC2 trafficking and expression.

Deacetylation of HSC70-4 Promotes Bombyx mori Nucleopolyhedrovirus Proliferation via Proteasome-Mediated Nuclear Import

Silkworm (Bombyx mori) is a model organism with great agricultural economic value that plays a crucial role in biological studies. B. mori nucleopolyhedrovirus (BmNPV) is a major viral pathogen found in silkworms, which leads to huge silk loss annually. In a recent lysine acetylome of silkworm infected with BmNPV, we focused on the heat shock cognate protein 70-4 (HSC70-4) lysine acetylation change due to the consequent nuclear accumulation and viral structure assembly. In this study, the genome replication, proliferation, and production of budded viruses (BVs) were arrested by HSP/HSC70 inhibitor treatment. However, HSC70-4 overexpression enhanced BmNPV reproduction. Furthermore, site-direct mutagenesis for acetylated mimic (K/Q) or deacetylated mimic (K/R) mutants of HSC70-4 demonstrated that lysine 77 (K77) deacetylation promotes HSC70-4 stability, viral DNA duplication, and HSC70-4 nuclear entry upon BmNPV challenge, and the nuclear propulsion of HSC70-4 after viral stimulus might be dependent on the interaction with the carboxyl terminus of HSC70-interacting protein (CHIP, an E3 ubiquitin ligase), followed by ubiquitin-proteasome system assistance. In this study, single lysine 77 deacetylation of HSC70-4 was deemed a part of the locomotive pathway for facilitating BmNPV proliferation and provided novel insights into the antiviral strategic development.

NAA10 p.(N101K) disrupts N-terminal acetyltransferase complex NatA and is associated with developmental delay and hemihypertrophy

Nearly half of all human proteins are acetylated at their N-termini by the NatA N-terminal acetyltransferase complex. NAA10 is evolutionarily conserved as the catalytic subunit of NatA in complex with NAA15, but may also have NatA-independent functions. Several NAA10 variants are associated with genetic disorders. The phenotypic spectrum includes developmental delay, intellectual disability, and cardiac abnormalities. Here, we have identified the previously undescribed NAA10 c.303C>A and c.303C>G p.(N101K) variants in two unrelated girls. These girls have developmental delay, but they both also display hemihypertrophy a feature normally not observed or registered among these cases. Functional studies revealed that NAA10 p.(N101K) is completely impaired in its ability to bind NAA15 and to form an enzymatically active NatA complex. In contrast, the integrity of NAA10 p.(N101K) as a monomeric acetyltransferase is intact. Thus, this NAA10 variant may represent the best example of the impact of NatA mediated N-terminal acetylation, isolated from other potential NAA10-mediated cellular functions and may provide important insights into the phenotypes observed in individuals expressing pathogenic NAA10 variants.

Identification of metastasis-related genes by genomic and transcriptomic studies in murine melanoma

AIMS

We systematically characterized metastatic murine B16-F10 melanoma, a sub-line derived from murine melanoma B16-F1 cells.

MATERIALS AND METHODS

RNA-sequencing and network analyses (Ingenuity Pathway Analysis) were performed to identify novel potential metastasis mechanisms. Chromosomal aberrations were identified by multicolor fluorescence in situ hybridization (mFISH) using all 21 murine whole chromosome painting probes.

KEY FINDINGS

Numerous genes were overexpressed in B16-F10 cells, some of which have been already described as being metastasis-linked. Nr5a1/sf1, a known prognostic marker for adrenal tumors, was 177-fold upregulated in B16-F10 cells compared to B16-F1 cells. Hoxb8 was 75-fold upregulated, which was previously associated with gastric cancer progression and metastasis. Ptk7, which is linked with tumorigenesis and metastasis of esophageal squamous carcinoma, was 67-fold upregulated. B16-F10 cells acquired additional chromosomal aberrations compared to B16-F1 cells, including dic(4)(pter->qter:qter->pter), +dic(6;15), +der(10)t(10;?1;16).

SIGNIFICANCE

In addition to well-known metastatic genes, numerous novel genes and genomic aberrations were identified, which may serve as targets for treatment in the future. Transcriptomic and genetic analyses in B16-F10 cells unraveled a range of novel metastasis mechanisms, which may also have important implications for future treatment strategies.

NAA10 p.(D10G) and NAA10 p.(L11R) Variants Hamper Formation of the NatA N-Terminal Acetyltransferase Complex

The majority of the human proteome is subjected to N-terminal (Nt) acetylation catalysed by N-terminal acetyltransferases (NATs). The NatA complex is composed of two core subunits—the catalytic subunit NAA10 and the ribosomal anchor NAA15. Furthermore, NAA10 may also have catalytic and non-catalytic roles independent of NatA. Several inherited and de novo NAA10 variants have been associated with genetic disease in humans. In this study, we present a functional analysis of two de novo NAA10 variants, c.29A>G p.(D10G) and c.32T>G p.(L11R), previously identified in a male and a female, respectively. Both of these neighbouring amino acids are highly conserved in NAA10. Immunoprecipitation experiments revealed that both variants hamper complex formation with NAA15 and are thus likely to impair NatA-mediated Nt-acetylation in vivo. Despite their common impact on NatA formation, in vitro Nt-acetylation assays showed that the variants had opposing impacts on NAA10 catalytic activity. While NAA10 c.29A>G p.(D10G) exhibits normal intrinsic NatA activity and reduced monomeric NAA10 NAT activity, NAA10 c.32T>G p.(L11R) displays reduced NatA activity and normal NAA10 NAT activity. This study expands the scope of research into the functional consequences of NAA10 variants and underlines the importance of understanding the diverse cellular roles of NAA10 in disease mechanisms.

NAA10 as a New Prognostic Marker for Cancer Progression

N-α-acetyltransferase 10 (NAA10) is an acetyltransferase that acetylates both N-terminal amino acid and internal lysine residues of proteins. NAA10 is a crucial player to regulate cell proliferation, migration, differentiation, apoptosis, and autophagy. Recently, mounting evidence presented the overexpression of NAA10 in various types of cancer, including liver, bone, lung, breast, colon, and prostate cancers, and demonstrated a correlation of overexpressed NAA10 with vascular invasion and metastasis, thereby affecting overall survival rates of cancer patients and recurrence of diseases. This evidence all points NAA10 toward a promising biomarker for cancer prognosis. Here we summarize the current knowledge regarding the biological functions of NAA10 in cancer progression and provide the potential usage of NAA10 as a prognostic marker for cancer progression.

Epigenetic crosstalk between hypoxia and tumor driven by HIF regulation

Hypoxia is the major influence factor in physiological and pathological courses which are mainly mediated by hypoxia-inducible factors (HIFs) in response to low oxygen tensions within solid tumors. Under normoxia, HIF signaling pathway is inhibited due to HIF-α subunits degradation. However, in hypoxic conditions, HIF-α is activated and stabilized, and HIF target genes are successively activated, resulting in a series of tumour-specific activities. The activation of HIFs, including HIF-1α, HIF-2α and HIF-3α, subsequently induce downstream target genes which leads to series of responses, the resulting abnormal processes or metabolites in turn affect HIFs stability. Given its functions in tumors progression, HIFs have been regarded as therapeutic targets for improved treatment efficacy. Epigenetics refers to alterations in gene expression that are stable between cell divisions, and sometimes between generations, but do not involve changes in the underlying DNA sequence of the organism. And with the development of research, epigenetic regulation has been found to play an important role in the development of tumors, which providing accumulating basic or clinical evidences for tumor treatments. Here, given how little has been reported about the overall association between hypoxic tumors and epigenetics, we made a more systematic review from epigenetic perspective in hope of helping others better understand hypoxia or HIF pathway, and providing more established and potential therapeutic strategies in tumors to facilitate epigenetic studies of tumors.

Telomerase reverse transcriptase downregulation by RNA interference modulates endoplasmic reticulum stress and mitochondrial energy production

Telomerase is a cancer promoting ribonucleoprotein complex and is a potential therapeutic target for cancer. In this study, the effects of telomerase downregulation on the whole cell proteome were investigated. Understanding how the effect of downregulation on the whole proteome profile will generate a greater understanding of the possible roles played by telomerase in cancer. Downregulation was achieved by RNA interference (RNAi), targeting the telomerase reverse transcriptase (TERT) subunits of telomerase. Transfection of TERT siRNA downregulates TERT gene expression and induced downregulation of telomerase activity. Investigation of the effect of silencing TERT in telomerase was further validated through proteomic analysis by performing 2-dimension electrophoresis (2DE) coupled with MALDI-TOF/TOF. 12 protein spots in HeLa cells were reported to be significantly differentially expressed with 11 of them were upregulated and 1 downregulated. Through STRING analysis, differentially expressed proteins demonstrated strong associations with endoplasmic reticulum stress marker and mitochondrial energy production marker. In conclusions, the result exhibited novel integrated proteomic response involving endoplasmic reticulum stress and mitochondrial energy production in response to the TERT downregulation in cervical cancer cells.

Critical review of non-histone human substrates of metal-dependent lysine deacetylases

Lysine acetylation is a posttranslational modification that occurs on thousands of human proteins, most of which are cytoplasmic. Acetylated proteins are involved in numerous cellular processes and human diseases. Therefore, how the acetylation/deacetylation cycle is regulated is an important question. Eleven metal-dependent lysine deacetylases (KDACs) have been identified in human cells. These enzymes, along with the sirtuins, are collectively responsible for reversing lysine acetylation. Despite several large-scale studies which have characterized the acetylome, relatively few of the specific acetylated residues have been matched to a proposed KDAC for deacetylation. To understand the function of lysine acetylation, and its association with diseases, specific KDAC-substrate pairs must be identified. Identifying specific substrates of a KDAC is complicated both by the complexity of assaying relevant activity and by the non-catalytic interactions of KDACs with cellular proteins. Here, we discuss in vitro and cell-based experimental strategies used to identify KDAC-substrate pairs and evaluate each for the purpose of directly identifying non-histone substrates of metal-dependent KDACs. We propose criteria for a combination of reproducible experimental approaches that are necessary to establish a direct enzymatic relationship. This critical analysis of the literature identifies 108 proposed non-histone substrate-KDAC pairs for which direct experimental evidence has been reported. Of these, five pairs can be considered well-established, while another thirteen pairs have both cell-based and in vitro evidence but lack independent replication and/or sufficient cell-based evidence. We present a path forward for evaluating the remaining substrate leads and reliably identifying novel KDAC substrates.

Post-translational modifications of Hsp70 family proteins: Expanding the chaperone code

Cells must be able to cope with the challenge of folding newly synthesized proteins and refolding those that have become misfolded in the context of a crowded cytosol. One such coping mechanism that has appeared during evolution is the expression of well-conserved molecular chaperones, such as those that are part of the heat shock protein 70 (Hsp70) family of proteins that bind and fold a large proportion of the proteome. Although Hsp70 family chaperones have been extensively examined for the last 50 years, most studies have focused on regulation of Hsp70 activities by altered transcription, co-chaperone "helper" proteins, and ATP binding and hydrolysis. The rise of modern proteomics has uncovered a vast array of post-translational modifications (PTMs) on Hsp70 family proteins that include phosphorylation, acetylation, ubiquitination, AMPylation, and ADP-ribosylation. Similarly to the pattern of histone modifications, the histone code, this complex pattern of chaperone PTMs is now known as the "chaperone code." In this review, we discuss the history of the Hsp70 chaperone code, its currently understood regulation and functions, and thoughts on what the future of research into the chaperone code may entail.

Severe syndromic ID and skewed X-inactivation in a girl with NAA10 dysfunction and a novel heterozygous de novo NAA10 p.(His16Pro) variant - a case report

Background

NAA10 is the catalytic subunit of the major N-terminal acetyltransferase complex NatA which acetylates almost half the human proteome. Over the past decade, many NAA10 missense variants have been reported as causative of genetic disease in humans. Individuals harboring NAA10 variants often display variable degrees of intellectual disability (ID), developmental delay, and cardiac anomalies. Initially, carrier females appeared to be oligo- or asymptomatic with X-inactivation pattern skewed towards the wild type allele. However, recently it has been shown that NAA10 variants can cause syndromic or non-syndromic intellectual disability in females as well. The impact of specific NAA10 variants and the X-inactivation pattern on the individual phenotype in females remains to be elucidated.

Case presentation

Here we present a novel de novo NAA10 (NM_003491.3) c.[47A > C];[=] (p.[His16Pro];[=]) variant identified in a young female. The 10-year-old girl has severely delayed motor and language development, disturbed behavior with hyperactivity and restlessness, moderate dilatation of the ventricular system and extracerebral CSF spaces. Her blood leukocyte X-inactivation pattern was skewed (95/5) towards the maternally inherited X-chromosome. Our functional study indicates that NAA10 p.(H16P) impairs NatA complex formation and NatA catalytic activity, while monomeric NAA10 catalytic activity appears to be intact. Furthermore, cycloheximide experiments show that the NAA10 H16P variant does not affect the cellular stability of NAA10.

Discussion and conclusions

We demonstrate that NAA10 p.(His16Pro) causes a severe form of syndromic ID in a girl most likely through impaired NatA-mediated Nt-acetylation of cellular proteins. X-inactivation analyses showed a skewed X-inactivation pattern in DNA from blood of the patient with the maternally inherited allele being preferentially methylated/inactivated.

Methylation of HSP70 Orchestrates Its Binding to and Stabilization of BCL2 mRNA and Renders Pancreatic Cancer Cells Resistant to Therapeutics

Pancreatic cancer is a lethal disease owing to its intrinsic and acquired resistance to therapeutic modalities. The altered balance between pro- and antiapoptosis signals within cancer cells is critical to therapeutic resistance. However, the molecular mechanisms underlying increased antiapoptosis signals remain poorly understood. In this study, we report that PRMT1 expression is increased in pancreatic cancer tissues and is associated with higher tumor grade, increased aggressiveness, and worse prognosis. PRMT1 overexpression increased arginine methylation of HSPs of 70 kDa (HSP70); this methylation enhanced HSP70 binding and stabilization of BCL2 mRNA through AU-rich elements in 3'-untranslated region and consequentially increased BCL2 protein expression and protected cancer cells from apoptosis induced by cellular stresses and therapeutics. RNA binding and regulation function of HSP70 was involved in pancreatic cancer drug resistance and was dependent on protein arginine methylation. These findings not only reveal a novel PRMT1-HSP70-BCL2 signaling axis that is crucial to pancreatic cancer cell survival and therapeutic resistance, but they also provide a proof of concept that targeted inhibition of this axis may represent a new therapeutic strategy. SIGNIFICANCE: This study demonstrates that a PRMT1-mediated stabilization of BCL2 mRNA contributes to therapeutic resistance in pancreatic cancer and that targeting this pathway could overcome said resistance.

Protein arginine methylation promotes therapeutic resistance in human pancreatic cancer

Pancreatic cancer is a lethal disease with limited treatment options for cure. A high degree of intrinsic and acquired therapeutic resistance may result from cellular alterations in genes and proteins involved in drug transportation and metabolism, or from the influences of cancer microenvironment. Mechanistic basis for therapeutic resistance remains unclear and should profoundly impact our ability to understand pancreatic cancer pathogenesis and its effective clinical management. Recent evidences have indicated the importance of epigenetic changes in pancreatic cancer, including posttranslational modifications of proteins. We will review new knowledge on protein arginine methylation and its consequential contribution to therapeutic resistance of pancreatic cancer, underlying molecular mechanism, and clinical application of potential strategies of its reversal.

On the structure and function of Sorghum bicolor CHIP (carboxyl terminus of Hsc70-interacting protein): A link between chaperone and proteasome systems

The co-chaperone CHIP (carboxy terminus of Hsc70 interacting protein) is very important for many cell activities since it regulates the ubiquitination of substrates targeted for proteasomal degradation. However, information on the structure-function relationship of CHIP from plants and how it interacts and ubiquitinates other plant chaperones is still needed. For that, the CHIP ortholog from Sorghum bicolor (SbCHIP) was identified and studied in detail. SbCHIP was purified and produced folded and pure, being capable of keeping its structural conformation up to 42 °C, indicating that cellular function is maintained even in a hot environment. Also, SbCHIP was able to bind plant Hsp70 and Hsp90 with high affinity and interact with E2 enzymes, performing E3 ligase activity. The data allowed to reveal the pattern of plant Hsp70 and Hsp90 ubiquitination and described which plant E2 enzymes are likely involved in SbCHIP-mediated ubiquitination. Aditionally, we obtained information on the SbCHIP conformation, showing that it is a non-globular symmetric dimer and allowing to put forward a model for the interaction of SbCHIP with chaperones and E2 enzymes that suggests a mechanism of ubiquitination. Altogether, the results presented here are useful additions to the study of protein folding and degradation in plants.

Protein kinase C-δ interacts with and phosphorylates ARD1

Protein kinase C-δ (PKCδ) is a diacylglycerol-dependent, calcium-independent novel PKC isoform that is engaged in various cell signaling pathways, such as cell proliferation, apoptosis, inflammation, and oxidative stress. In this study, we searched for proteins that bind PKCδ using a yeast two-hybrid assay and identified murine arrest-defective 1 (mARD1) as a binding partner. The interaction between PKCδ and mARD1 was confirmed by glutathione S-transferase pull-down and co-immunoprecipitation assays. Furthermore, recombinant PKCδ phosphorylated full-length mARD1 protein. The NetPhos online prediction tool suggested PKCδ phosphorylates Ser⁸⁰ , Ser¹⁰⁸ , and Ser¹¹⁴ residues of mARD1 with the highest probability. Based on these results, we synthesized peptides containing these sites and examined their phosphorylations using recombinant PKCδ. Autoradiography confirmed these sites were efficiently phosphorylated. Consequent mass spectrometry and peptide sequencing in combination with MALDI-TOF MS/MS confirmed that Ser⁸⁰ and Ser¹⁰⁸ were major phosphorylation sites. The alanine mutations of Ser⁸⁰ and Ser¹⁰⁸ abolished the phosphorylation of mARD1 by PKCδ in 293T cells supporting these observations. In addition, kinase assays using various PKC isotypes showed that Ser⁸⁰ of ARD1 was phosphorylated by PKCβI and PKCζ isotypes with the highest selectivity, while Ser¹⁰⁸ and/or Ser¹¹⁴ were phosphorylated by PKCγ with activities comparable to that of the PKCδ isoform. Overall, these results suggest the possibility that PKCδ transduces signals by regulating phosphorylation of ARD1.

Proteomic analysis reveals dysregulated cell signaling in ejaculated spermatozoa from infertile men

Dysfunctional sperm maturation is the primary reason for the poor sperm motility and morphology in infertile men. Spermatozoa from infertile men were fractioned on three-layer density gradient (80%, 60%, and 40%). Fraction 1 (F1) refers to the least mature stage having the lowest density, whereas the fraction 4 (F4) includes the most dense and morphologically mature motile spermatozoa. Fraction 2 (F2) and fraction 3 (F3) represent the intermediate stages. Proteins were extracted and separated by 1-dimensional gel. Bands were digested with trypsin and analyzed on a LTQ-Orbitrap Elite hybrid mass spectrometer system. Functional annotations of proteins were obtained using bioinformatics tools and pathway databases. A total of 1585 proteins were detected in the four fractions of spermatozoa. A dysregulated protein turnover and protein folding may lead to accumulation of defective proteins or proteins that otherwise would have been eliminated during the process of maturation, resulting in the impairment of sperm function. Aberrant chaperone expression may be a major contributing factor to the defective sperm function. Androgen receptor was predicted as a transcription regulator in one of the networks and the affected pathways were chaperone-mediated stress response, proteosomal pathway, and sperm function. The downregulation of key pathways and proteins which compromises the fertilizing potential of spermatozoa may provide insight into the mechanisms that lead to male infertility.

Differentiating between the effects of heat stress and lipopolysaccharide on the porcine ovarian heat shock protein response1

Heat stress (HS) negatively affects both human and farm-animal health and undermines efficiency in a variety of economically important agricultural variables, including reproduction. HS impairs the intestinal barrier, allowing for translocation of the resident microflora and endotoxins, such as lipopolysaccharide (LPS), from the gastrointestinal lumen into systemic circulation. While much is known about the cellular function of heat shock proteins (HSPs) in most tissues, the in vivo ovarian HSP response to stressful stimuli remains ill-defined. The purpose of this study was to compare the effects of HS or LPS on ovarian HSP expression in pigs. We hypothesized that ovarian HSPs are responsive to both HS and LPS. Altrenogest (15 mg/d) was administered per os for estrus synchronization (14 d) prior to treatment and three animal paradigms were used: (i) gilts were exposed to cyclical HS (31 ± 1.4 °C) or thermoneutral (TN; 20 ± 0.5 °C) conditions immediately following altrenogest withdrawal for 5 d during follicular development; (ii) gilts were subjected to repeated (4×/d) saline (CON) or LPS (0.1 μg/kg BW) i.v. infusion immediately following altrenogest withdrawal for 5 d; and (iii) gilts were subjected to TN (20 ± 1 °C) or cyclical HS (31 to 35 °C) conditions 2 d post estrus (dpe) until 12 dpe during the luteal phase. While no differences were detected for transcript abundances of the assessed ovarian HSP, the protein abundance of specific HSP was influenced by stressors during the follicular and luteal phases. HS during the follicular phase tended (P < 0.1) to increase ovarian protein abundance of HSP90AA1 and HSPA1A, and increased (P ≤ 0.05) HSF1, HSPD1, and HSPB1 compared with TN controls, while HS decreased HSP90AB1 (P = 0.01). Exposure to LPS increased (P < 0.05) HSP90AA1 and HSPA1A and tended (P < 0.1) to increase HSF1 and HSPB1 compared with CON gilts, while HSP90AB1 and HSPD1 were not affected by LPS. HS during the luteal phase increased (P < 0.05) abundance of HSPB1 in corpora lutea (CL), decreased (P < 0.05) CL HSP90AB1, but did not impact HSF1, HSPD1, HSP90AA1, or HSPA1A abundance. Thus, these data support that HS and LPS similarly regulate expression of specific ovarian HSP, which suggest that HS effects on the ovary are in part mediated by LPS.

Dynamics-function relationship in the catalytic domains of N-terminal acetyltransferases

N-terminal acetyltransferases (NATs) belong to the superfamily of acetyltransferases. They are enzymes catalysing the transfer of an acetyl group from acetyl coenzyme A to the N-terminus of polypeptide chains. N-terminal acetylation is one of the most common protein modifications. To date, not much is known on the molecular basis for the exclusive substrate specificity of NATs. All NATs share a common fold called GNAT. A characteristic of NATs is the β6β7 hairpin loop covering the active site and forming with the α1α2 loop a narrow tunnel surrounding the catalytic site in which cofactor and polypeptide meet and exchange an acetyl group. We investigated the dynamics-function relationships of all available structures of NATs covering the three domains of Life. Using an elastic network model and normal mode analysis, we found a common dynamics pattern conserved through the GNAT fold; a rigid V-shaped groove formed by the β4 and β5 strands and splitting the fold in two dynamical subdomains. Loops α1α2, β3β4 and β6β7 all show clear displacements in the low frequency normal modes. We characterized the mobility of the loops and show that even limited conformational changes of the loops along the low-frequency modes are able to significantly change the size and shape of the ligand binding sites. Based on the fact that these movements are present in most low-frequency modes, and common to all NATs, we suggest that the α1α2 and β6β7 loops may regulate ligand uptake and the release of the acetylated polypeptide.

Characterization of Lysine Acetyltransferase Activity of Recombinant Human ARD1/NAA10

Arrest defective 1 (ARD1), also known as N(alpha)-acetyltransferase 10 (NAA10) was originally identified as an N-terminal acetyltransferase (NAT) that catalyzes the acetylation of N-termini of newly synthesized peptides. After that, mammalian ARD1/NAA10 expanded its' role to lysine acetyltransferase (KAT) that post-translationally acetylates internal lysine residues of proteins. ARD1/NAA10 is the only enzyme with both NAT and KAT activities. However, recent studies on the role of human ARD1/NAA10 (hARD1/NAA10) in lysine acetylation are contradictory, as crystal structure and in vitro acetylation assay results revealed the lack of KAT activity. Thus, the role of hARD1/NAA10 in lysine acetylation is still debating. Here, we found a clue that possibly explains these complicated and controversial results on KAT activity of hARD1/NAA10. Recombinant hARD1/NAA10 exhibited KAT activity, which disappeared soon in vitro. Size-exclusion analysis revealed that most recombinant hARD1/NAA10 formed oligomers over time, resulting in the loss of KAT activity. While oligomeric recombinant hARD1/NAA10 lost its ability for lysine acetylation, its monomeric form clearly exhibited lysine acetylation activity in vitro. We also characterized the KAT activity of hARD1/NAA10 that was influenced by several experimental conditions, including concentration of reactants and reaction time. Taken together, our study proves that recombinant hARD1/NAA10 exhibits KAT activity in vitro but only under accurate conditions, including reactant concentrations and reaction duration.