SUMOylation of annexin A6 retards cell migration and tumor growth by suppressing RHOU/AKT1-involved EMT in hepatocellular carcinoma.

BACKGROUND: The protein annexin A6 (AnxA6) is involved in numerous membrane-related biological processes including cell migration and invasion by interacting with other proteins. The dysfunction of AnxA6, including protein expression abundance change and imbalance of post-translational modification, is tightly related to multiple cancers. Herein we focus on the biological function of AnxA6 SUMOylation in hepatocellular carcinoma (HCC) progression. METHODS: The modification sites of AnxA6 SUMOylation were identified by LC-MS/MS and amino acid site mutation. AnxA6 expression was assessed by immunohistochemistry and immunofluorescence. HCC cells were induced into the epithelial-mesenchymal transition (EMT)-featured cells by 100 ng/mL 12-O-tetradecanoylphorbol-13-acetate exposure. The ability of cell migration was evaluated under AnxA6 overexpression by transwell assay. The SUMO1 modified AnxA6 proteins were enriched from total cellular proteins by immunoprecipitation with anti-SUMO1 antibody, then the SUMOylated AnxA6 was detected by Western blot using anti-AnxA6 antibody. The nude mouse xenograft and orthotopic hepatoma models were established to determine HCC growth and tumorigenicity in vivo. The HCC patient's overall survival versus AnxA6 expression level was evaluated by the Kaplan-Meier method. RESULTS: Lys579 is a major SUMO1 modification site of AnxA6 in HCC cells, and SUMOylation protects AnxA6 from degradation via the ubiquitin-proteasome pathway. Compared to the wild-type AnxA6, its SUMO site mutant AnxA6K579R leads to disassociation of the binding of AnxA6 with RHOU, subsequently RHOU-mediated p-AKT1ser473 is upregulated to facilitate cell migration and EMT progression in HCC. Moreover, the SENP1 deSUMOylates AnxA6, and AnxA6 expression is negatively correlated with SENP1 protein expression level in HCC tissues, and a high gene expression ratio of ANXA6/SENP1 indicates a poor overall survival of patients. CONCLUSIONS: AnxA6 deSUMOylation contributes to HCC progression and EMT phenotype, and the combination of AnxA6 and SENP1 is a better tumor biomarker for diagnosis of HCC grade malignancy and prognosis.

SUMOylation of AnxA6 facilitates EGFR-PKCα complex formation to suppress epithelial cancer growth.

BACKGROUND: The Annexin A6 (AnxA6) protein is known to inhibit the epidermal growth factor receptor (EGFR)-extracellular signal regulated kinase (ERK)1/2 signaling upon EGF stimulation. While the biochemical mechanism of AnxA6 inactivating phosphorylation of EGFR and ERK1/2 is not completely explored in cancer cells. METHODS: Cells were transiently co-transfected with pFlag-AnxA6, pHA-UBC9 and pHis-SUMO1 plasmids to enrich the SUMOylated AnxA6 by immunoprecipitation, and the modification level of AnxA6 by SUMO1 was detected by Western blot against SUMO1 antibody. The SUMOylation level of AnxA6 was compared in response to chemical SUMOylation inhibitor treatment. AnxA6 SUMOylation sites were further identified by LC-MS/MS and amino acid site mutation validation. AnxA6 gene was silenced through AnxA6 targeting shRNA-containing pLKO.1 lentiviral transfection in HeLa cells, while AnxA6 gene was over-expressed within the Lenti-Vector carrying AnxA6 or mutant AnxA6K299R plasmid in A431 cells using lentiviral infections. Moreover, the mutant plasmid pGFP-EGFRT790M/L858R was constructed to test AnxA6 regulation on EGFR mutation-induced signal transduction. Moreover, cell proliferation, migration, and gefitinib chemotherapy sensitivity were evaluated in HeLa and A431 cells under AnxA6 konckdown or AnxA6 overexpression by CCK8, colony form and wound healing assays. And tumorigenicity in vivo was measured in epithelial cancer cells-xenografted nude mouse model. RESULTS: AnxA6 was obviously modified by SUMO1 conjugation within Lys (K) residues, and the K299 was one key SUMOylation site of AnxA6 in epithelial cancer cells. Compared to the wild type AnxA6, AnxA6 knockdown and its SUMO site mutant AnxA6K299R showed less suppression of dephosphorylation of EGFR-ERK1/2 under EGF stimulation. The SUMOylated AnxA6 was prone to bind EGFR in response to EGF inducement, which facilitated EGFR-PKCα complex formation to decrease the EGF-induced phosphorylation of EGFR-ERK1/2 and cyclin D1 expression. Similarly, AnxA6 SUMOylation inhibited dephosphorylation of the mutant EGFR, thereby impeding EGFR mutation-involved signal transduction. Moreover, AnxA6 knockdown or the K299 mutant AnxA6K299R conferred AnxA6 inability to suppress tumor progression, resulting in drug resistance to gefitinib in epithelial cancer cells. And in epithelial cancer cells-xenografted nude mouse model, both the weight and size of tumors derived from AnxA6 knockdown or AnxA6K299R mutation-expressing cells were much greater than that of AnxA6-expressing cells. CONCLUSIONS: Besides EGFR gene mutation, protein SUMOylation modification of EGFR-binding protein AnxA6 also functions pivotal roles in mediating epithelial cancer cell growth and gefitinib drug effect. Video Abstract.

N-acetylcysteine improves autism-like behavior by recovering autophagic deficiency and decreasing Notch-1/Hes-1 pathway activity.

N-acetylcysteine (NAC) has been reported to improve social interaction behavior, irritability, self-injury, and anxiety-like behavior in autism. However, the molecular mechanism underlying the therapeutic roles of NAC in autism remains unknown. This study mainly aimed to investigate the therapeutic effect of NAC on valproic acid (VPA)-induced autism model and the underlying mechanisms. Our results showed that NAC ameliorated the deficits in sociability and the anxiety- and repetitive-like behaviors displayed by VPA-exposed rats. In addition, VPA exposure induced autophagic deficiency and enhanced Notch-1/Hes-1 pathway activity based on lowered Beclin-1 and LC3B levels, while increased expression of p62, Notch-1, and Hes-1 expression at the protein level. However, NAC recovered VPA-induced autophagic deficiency and reduced Notch-1/Hes-1 pathway activity in a VPA-exposed autism rat model and SH-SY5Y neural cells. The present results demonstrated that NAC improves autism-like behavioral abnormalities by inactivating Notch-1/Hes-1 signaling pathway and recovering autophagic deficiency. Taken together, this study helps to elucidate a novel molecular mechanism that underlies the therapeutic actions of NAC in autism and suggests its potential to ameliorate behavioral abnormalities in neurodevelopmental disorders.

Roles of the Notch signaling pathway and microglia in autism.

The Notch signaling pathway is mainly involved in the regulation of neural stem cell proliferation, survival and differentiation during the development of the central nervous system. As a neurodevelopmental disorder, autism is associated with an abnormal increase in the number of microglia in several brain regions. These findings suggest that the pathogenesis of autism may be related to the Notch signaling pathway and microglia. In this review, we discuss how Notch pathway activity leads to behavioral abnormalities such as learning and memory impairment by influencing neuronal biological activities. An increase in microglial protein synthesis and abnormal autophagy can affect synaptic development and lead to behavioral abnormalities, and all of these changes can lead to autism. Furthermore, the Notch signaling pathway regulates the activation and differentiation of microglia and promotes inflammatory responses, leading to the occurrence of autism. When excessive reactive oxygen species (ROS) secreted by microglia cannot be cleared by autophagy in a timely manner, Notch signaling pathway activity is affected, possibly further increasing susceptibility to autism. This review reveals the mechanism underlying the role of the Notch signaling pathway, microglia and their interaction in the pathogenesis of autism and provides a theoretical reference for targeted clinical therapies for autism.

A wheat resistosome defines common principles of immune receptor channels.

Plant intracellular nucleotide-binding leucine-rich repeat receptors (NLRs) detect pathogen effectors to trigger immune responses1. Indirect recognition of a pathogen effector by the dicotyledonous Arabidopsis thaliana coiled-coil domain containing NLR (CNL) ZAR1 induces the formation of a large hetero-oligomeric protein complex, termed the ZAR1 resistosome, which functions as a calcium channel required for ZAR1-mediated immunity2-4. Whether the resistosome and channel activities are conserved among plant CNLs remains unknown. Here we report the cryo-electron microscopy structure of the wheat CNL Sr355 in complex with the effector AvrSr356 of the wheat stem rust pathogen. Direct effector binding to the leucine-rich repeats of Sr35 results in the formation of a pentameric Sr35-AvrSr35 complex, which we term the Sr35 resistosome. Wheat Sr35 and Arabidopsis ZAR1 resistosomes bear striking structural similarities, including an arginine cluster in the leucine-rich repeats domain not previously recognized as conserved, which co-occurs and forms intramolecular interactions with the 'EDVID' motif in the coiled-coil domain. Electrophysiological measurements show that the Sr35 resistosome exhibits non-selective cation channel activity. These structural insights allowed us to generate new variants of closely related wheat and barley orphan NLRs that recognize AvrSr35. Our data support the evolutionary conservation of CNL resistosomes in plants and demonstrate proof of principle for structure-based engineering of NLRs for crop improvement.

miR-26a enhances colorectal cancer cell growth by targeting RREB1 deacetylation to activate AKT-mediated glycolysis.

We previously reported the inhibitory effects of microRNA-26a (miR-26a) on the conversion of pyruvate to acetyl coenzyme A in glucose metabolism by directly targeting pyruvate dehydrogenase protein X component in colorectal cancer (CRC) cells (Chen B et al., BMC Cancer 2014). Here, using microRNA in situ hybridization, we confirmed that miR-26a levels were elevated in 77 human CRC tissue samples and further investigated the key miR-26a-mediated metabolic regulation elements and signaling pathways in CRC cells through quantitative proteomic dissection combined with cancer cell biology and biochemical loss-of-function analysis. We found that AKT transcription signaling was a target pathway via miR-26a-mediated deacetylation modification of Ras-responsive element-binding protein 1 (RREB1) at the Lys-60 residue. miR-26a improved the deacetylation level of RREB1, thus contributing to RREB1 binding to the AKT1 promoter to activate AKT transcription and its related signaling pathway in glycolysis. Moreover, miR-26a promoted CRC tumorigenesis in CRC cells and subcutaneous xenograft mice. Thus, miR-26a is a key regulator of CRC tumorigenesis that mediates the deacetylation modification of RREB1 to enhance AKT1 transcription and downstream target gene expression in glycolysis for CRC growth.

SUMOylation modification-mediated cell death.

SUMOylation dynamically conjugates SUMO molecules to the lysine residue of a substrate protein, which depends on the physiological state of the cell and the attached SUMO isoforms. A prominent role of SUMOylation in molecular pathways is to govern the cellular death process. Herein, we summarize the association between SUMOylation modification events and four types of cellular death processes: apoptosis, autophagy, senescence and pyroptosis. SUMOylation positively or negatively regulates a certain cellular death pattern depending on specific conditions including the attached SUMO isoforms, disease types, substrate proteins and cell context. Moreover, we also discuss the possible role of SUMOylation in ferroptosis and propose a potential role of the SUMOylated GPX4 in the regulation of ferroptosis. Mapping the exact SUMOylation network with cellular death contributes to develop novel SUMOylation-targeting disease therapeutic strategies.

Structure and activity of SLAC1 channels for stomatal signaling in leaves.

Stomata in leaves regulate gas exchange between the plant and its atmosphere. Various environmental stimuli elicit abscisic acid (ABA); ABA leads to phosphoactivation of slow anion channel 1 (SLAC1); SLAC1 activity reduces turgor pressure in aperture-defining guard cells; and stomatal closure ensues. We used electrophysiology for functional characterizations of Arabidopsis thaliana SLAC1 (AtSLAC1) and cryoelectron microscopy (cryo-EM) for structural analysis of Brachypodium distachyon SLAC1 (BdSLAC1), at 2.97-Å resolution. We identified 14 phosphorylation sites in AtSLAC1 and showed nearly 330-fold channel-activity enhancement with 4 to 6 of these phosphorylated. Seven SLAC1-conserved arginines are poised in BdSLAC1 for regulatory interaction with the N-terminal extension. This BdSLAC1 structure has its pores closed, in a basal state, spring loaded by phenylalanyl residues in high-energy conformations. SLAC1 phosphorylation fine-tunes an equilibrium between basal and activated SLAC1 trimers, thereby controlling the degree of stomatal opening.

Transcription Factor RREB1: from Target Genes towards Biological Functions.

The Ras-responsive element binding protein 1(RREB1) is a member of zinc finger transcription factors, which is widely involved in biological processes including cell proliferation, transcriptional regulation and DNA damage repair. New findings reveal RREB1 functions as both transcriptional repressors and transcriptional activators for transcriptional regulation of target genes. The activation of RREB1 is regulated by MAPK pathway. We have summarized the target genes of RREB1 and discussed RREB1 roles in the cancer development. In addition, increasing evidences suggest that RREB1 is a potential risk gene for type 2 diabetes and obesity. We also review the current clinical application of RREB1 as a biomarker for melanoma detection. In conclusion, RREB1 is a promising diagnostic biomarker or new drug target for cancers and metabolic diseases.

Essential Kinases and Transcriptional Regulators and Their Roles in Autoimmunity.

Kinases and transcriptional regulators are fundamental components of cell signaling that are expressed on many types of immune cells which are involved in secretion of cytokines, cell proliferation, differentiation, and apoptosis. Both play important roles in biological responses in health as well as in illnesses such as the autoimmune diseases which comprise at least 80 disorders. These diseases are caused by complex genetic and environmental interactions that lead to a breakage of immunologic tolerance and a disruption of the balance between self-reactive cells and regulatory cells. Kinases or transcriptional regulatory factors often have an abnormal expression in the autoimmune cells that participate in the pathogenesis of autoimmune disease. These abnormally expressed kinases or transcriptional regulators can over-activate the function of self-reactive cells to produce inflammatory cytokines or down-regulate the activity of regulatory cells, thus causing autoimmune diseases. In this review we introduce five kinds of kinase and transcriptional regulator related to autoimmune diseases, namely, members of the Janus kinase (JAK) family (JAK3 and/or tyrosine kinase 2 (TYK2)), fork head box protein 3 (Foxp3), the retinoic acid-related orphan receptor gamma t (RORγt), and T-box expressed in T cells (T-bet) factors. We also provide a mechanistic insight into how these kinases and transcriptional regulators affect the function of the immune cells related to autoimmune diseases, as well as a description of a current drug design targeting these kinases and transcriptional regulators. Understanding their exact role helps offer new therapies for control of the inflammatory responses that could lead to clinical improvement of the autoimmune diseases.

Emerging microRNA biomarkers for colorectal cancer diagnosis and prognosis.

MicroRNAs (miRNAs) are one abundant class of small, endogenous non-coding RNAs, which regulate various biological processes by inhibiting expression of target genes. miRNAs have important functional roles in carcinogenesis and development of colorectal cancer (CRC), and emerging evidence has indicated the feasibility of miRNAs as robust cancer biomarkers. This review summarizes the progress in miRNA-related research, including study of its oncogene or tumour-suppressor roles and the advantages of miRNA biomarkers for CRC diagnosis, treatment and recurrence prediction. Along with analytical technique improvements in miRNA research, use of the emerging extracellular miRNAs is feasible for CRC diagnosis and prognosis.

A magnetic adsorbent grafted with pendant naphthyl polymer brush for enrichment of the nonsteroidal anti-inflammatory drugs indomethacin and diclofenac.

Poly(2-naphthyl acrylate) was first grafted onto silica-coated magnetic nanoparticles by surface-initiated atom transfer radical polymerization to prepare a reversed-phase magnetic adsorbent. The resulting polymer brush displays enhanced extraction efficiency by offering active sites on the surfaces of adsorbent. It was applied to the preconcentration of the non-steroidal antiinflammatory drugs (NSAIDs) indomethacin (InDo) and diclofenac (DIC). These drugs interact with the sorbent through hydrophobic and π-interactions, and via electrostatic attraction. By coupling the magnetic solid-phase extraction with HPLC, a method for analysis of InDo and DIC in the environmental water samples was established. The limits of detection range from 0.62 to 0.64 ng·mL-1, and the relative standard deviations for intra-and inter-day analyses of spiked water samples are <11.9%, and relative recoveries are between 62.1 and 96.7%. Graphical abstract A reversed-phase magnetic adsorbent was prepared by grafting poly(2-naphthyl acrylate) brush on the surface of silica coated magnetic nanoparticles. Due to the two conjugated aromatic rings of the monomer, the polymer brush can effectively extract non-steroidal anti-inflammatory drugs through strong π- and hydrophobic interactions.

Preparation of a boronate affinity material with ultrahigh binding capacity for cis-diols by grafting polymer brush from polydopamine-coated magnetized graphene oxide.

Poly(3-acrylamidophenylboronic acid) (PAAPBA) was grafted onto polydopamine-coated magnetic graphene oxide via surface-initiated atom transfer radical polymerization to obtain a new kind of boronate affinity material (BAM). The BAM possesses good water dispersity and adsorption capacities as high as 154, 357, 588 and 1111 µmol·g-1 for adenosine, salbutamol, dopamine and catechol, respectively. For the molecules without nitrogen atoms, the BAM can selectively capture the cis-diols under the interference of non-cis-diols. For molecules containing nitrogen, the non-cis-diols are also retained, but much less than the cis-diols. The selectivity can be improved by adding salts to facilitate complexation and to suppress the electrostatic interaction between cis-diols and the boronic acid ligand. The BAM was successfully employed to the enrichment of catecholamines from real urine samples. Results indicate that it is a promising material for the pretreatment of real samples. Graphical abstract Schematic of the preparation of an ultrahigh capacity boronate affinity material by grafting polymer brush from polydopamine coated magnetic graphene oxide. The material has good selectivity to cis-diol-containing molecules and can be applied to enrich catecholamines in urine samples.

[Effects of ursodeoxycholic acid on mRNA expression of MDR3 and FXR in infants with cholestatic hepatitis].

OBJECTIVE: To analyze the effects of ursodeoxycholic acid (UDCA) on the mRNA expression of multidrug resistance protein 3 (MDR3) and farnesoid X receptor (FXR) in infants with cholestatic hepatitis. METHODS: Twenty-eight infants who were diagnosed with cholestatic hepatitis between July 2008 and July 2010 were included in the study. These patients received treatment with UDCA. The mRNA expression levels of MDR3 and FXR were measured by real-time quantitative RT-PCR with SYBR Green I, before and after treatment with UDCA. RESULTS: After treatment with UDCA, the infants with cholestatic hepatitis had significantly decreased serum levels of total bilirubin, direct bilirubin, alanine aminotransferase, and gamma-glutamyltransferase (P<0.05) and significantly increased mRNA expression of MDR3 (P<0.05). No significant change in mRNA expression of FXR was observed, however (P>0.05). CONCLUSIONS: UDCA improves liver function indices in infants with cholestatic hepatitis, which may be related to up-regulated mRNA expression of MDR3.

A novel heterozygous NR1H4 termination codon mutation in idiopathic infantile cholestasis.

BACKGROUND: This study aimed to evaluate the genetic effect of the NR1H4 gene in the pathogenesis of idiopathic infantile cholestasis of Chinese subjects in Guangxi, China. METHODS: Seventy-eight patients with idiopathic infantile cholestasis served as a study group and 95 infants without cholestasis as controls. Genomic DNA was extracted from peripheral venous blood leucocytes by phenol chloroform procedures. Polymerase chain reaction (PCR) was used to amplify all coded exons of NR1H4, and single-strand conformation polymorphism (SSCP) was used to analyze all amplification fragments. The PCR products with abnormal bands in SSCP were sequenced using an ABI 3100 sequencer. RESULTS: A novel heterozygous termination codon mutation in NR1H4 exon 5 (NR1H4 R176X, CGA-TGA) was found in one of the 78 patients. The patient with mutation R176X had high levels of bilirubin, alanine aminotransferase, γ-glutamyltransferase, cirrhosis and ascites despite biliary tract flushing procedures and drug therapy. In the other patients and controls, no mutation was detected. CONCLUSIONS: Heterozygous termination codon mutation of NR1H4 R176X was found in idiopathic infantile cholestasis. The novel mutation is useful to establish particular characteristics for differential diagnosis of idiopathic infantile cholestasis and to determine the influence of such gene defects in the prognosis.