Regulation of apoptosis by the Ft1 protein, a new modulator of protein kinase B/Akt

EZH2 contributes to sepsis-induced acute lung injury through regulating macrophage polarization

BACKGROUND

Zeste enhancer homolog 2 (EZH2) is a pivotal regulator of gene dynamics implicated in the progression of sepsis-induced acute lung injury (SALI). EZH2 regulates aberrant inflammatory and immune responses in macrophages via unconventional biochemical interactions. However, the mechanisms driving atypical behavior of EZH2 during sepsis remain elusive, and therapeutic strategies targeting EZH2 are currently underutilized.

PURPOSE

This study aimed to investigate how EZH2 regulates macrophage polarization through the AKT pathway to improve SALI and to explore therapeutic drugs targeting EZH2.

METHODS

We used Western blotting, hematoxylin-eosin stainin, immunofluorescence, flow cytometry, qRT-PCR, RNA sequencing, and chromatin immunoprecipitation sequencing methods to investigate regulation of macrophage immune response by EZH2 and explored its specific mechanism. These methods were also used to examine the protective effects of MS177 against SALI.

RESULTS

Specific deletion of EZH2 in macrophages reduced the level of AKTIP, downregulated the M1 macrophage markers CD86 and cytotoxic T cell marker CD8+, upregulated the M2 macrophage marker CD206 and regulatory T cell marker FOXP3+, decreased the levels of pro-inflammatory cytokines IL-6, TNF-α, and IL-β, and increased the level of anti-inflammatory cytokine IL-10. This ultimately improved lung injury and mortality in SALI mice. EZH2 promoted the M1 polarization of macrophages by activating AKT2 via direct binding to the promoter region of AKTIP in a SALI mouse model. Furthermore, MS177 alleviated SALI by degrading EZH2 both in vitro and in vivo.

CONCLUSION

EZH2 regulates macrophage polarization via the AKTIP-AKT2 pathway. Our findings suggest that MS177 is a promising therapeutic agent for EZH2-dependent SALI.

Higher levels of AKT-interacting protein in the frontal pole from people with schizophrenia are limited to a sub-group who have a marked deficit in cortical muscarinic M1 receptors

We are studying the molecular pathology of a sub-group within schizophrenia (∼ 25 %: termed Muscarinic Receptor Deficit subgroup of Schizophrenia (MRDS)) who can be separated because they have very low levels of cortical muscarinic M1 receptors (CHRM1). Based on our transcriptomic data from Brodmann's area ((BA) 9, 10 and 33 (controls, schizophrenia and mood disorders) and the cortex of the CHRM1-/- mouse (a molecular model of aberrant CHRM1 signaling), we predicted levels of AKT interacting protein (AKTIP), but not tubulin alpha 1b (TUBA1B) or AKT serine/threonine kinase 1 (AKT1) and pyruvate dehydrogenase kinase 1 (PDK1) (two AKTIP-functionally associated proteins), would be changed in MRDS. Hence, we used Western blotting to measure AKTIP (BA 10: controls, schizophrenia and mood disorders; BA 9: controls and schizophrenia) plus TUBA1B, AKT1 and PDK1 (BA 10: controls and schizophrenia) proteins. The only significant change with diagnosis was higher levels of AKTIP protein in BA 10 (Cohen's d = 0.73; p = 0.02) in schizophrenia compared to controls due to higher levels of AKTIP only in people with MRDS (Cohen's d = 0.80; p = 0.03). As AKTIP is involved in AKT1 signaling, our data suggests that signaling pathway is particularly disturbed in BA 10 in MRDS.

Genome-wide CRISPR/Cas9 screen shows that loss of GET4 increases mitochondria-endoplasmic reticulum contact sites and is neuroprotective

Organelles form membrane contact sites between each other, allowing for the transfer of molecules and signals. Mitochondria-endoplasmic reticulum (ER) contact sites (MERCS) are cellular subdomains characterized by close apposition of mitochondria and ER membranes. They have been implicated in many diseases, including neurodegenerative, metabolic, and cardiac diseases. Although MERCS have been extensively studied, much remains to be explored. To uncover novel regulators of MERCS, we conducted a genome-wide, flow cytometry-based screen using an engineered MERCS reporter cell line. We found 410 genes whose downregulation promotes MERCS and 230 genes whose downregulation decreases MERCS. From these, 29 genes were selected from each population for arrayed screening and 25 were validated from the high population and 13 from the low population. GET4 and BAG6 were highlighted as the top 2 genes that upon suppression increased MERCS from both the pooled and arrayed screens, and these were subjected to further investigation. Multiple microscopy analyses confirmed that loss of GET4 or BAG6 increased MERCS. GET4 and BAG6 were also observed to interact with the known MERCS proteins, inositol 1,4,5-trisphosphate receptors (IP3R) and glucose-regulated protein 75 (GRP75). In addition, we found that loss of GET4 increased mitochondrial calcium uptake upon ER-Ca2+ release and mitochondrial respiration. Finally, we show that loss of GET4 rescues motor ability, improves lifespan and prevents neurodegeneration in a Drosophila model of Alzheimer's disease (Aβ42Arc). Together, these results suggest that GET4 is involved in decreasing MERCS and that its loss is neuroprotective.

Identification of M2 Macrophage-Related Key Genes in Advanced Atherosclerotic Plaques by Network-Based Analysis

ABSTRACT

Atherosclerotic plaque accounts for major adverse cardiovascular events because of its vulnerability. The classically activated macrophage (M1) and alternatively activated macrophage (M2) are implicated in the progression and regression of plaque, respectively. However, the therapeutic targets related to M2 macrophages still remain largely elusive. In this study, cell-type identification by estimating relative subsets of RNA transcripts and weighted gene coexpression network analysis algorithms were used to establish a weighted gene coexpression network for identifying M2 macrophage-related hub genes using GSE43292 data set. The results showed that genes were classified into 7 modules, with the blue module (Cor = 0.67, P = 3e-05) being the one that was most related to M2 macrophage infiltration in advanced plaques, and then 99 hub genes were identified from blue module. Meanwhile, 1289 differentially expressed genes were produced in GSE43292 data set. Subsequently, the intersection genes of hub genes and differentially expressed genes, including AKTIP , ASPN , FAM26E , RAB23 , PLS3 , and PLSCR4 , were obtained by Venn diagrams and named as key genes. Further validation using data sets GSE100927 and GSE41571 showed that 6 key genes all downregulated in advanced and vulnerable plaques compared with early and stable plaque samples (|Log2 (fold change)| > 0.5, P < 0.05 or 0.001), respectively. Receiver operator characteristic curve analysis indicated that the 6 key genes might have potential diagnostic value. The validation of key genes in the model in vitro and in vivo also demonstrated decreased mRNA expressions of AKTIP , ASPN , FAM26E , RAB23 , PLS3 , and PLSCR4 ( P < 0.05 or 0.001). Collectively, we identified AKTIP, ASPN, FAM26E, RAB23, PLS3, and PLSCR4 as M2 macrophage-related key genes during atherosclerotic progression, proposing potential intervention targets for advanced atherosclerotic plaques.

Exploring the utility of FTS as a bonafide binding partner for EGFR: A potential drug target for cervical cancer

Establishment of human papilloma virus (HPV) infection and its progression to cervical cancer (CC) requires the participation of epidermal growth factor (EGF) receptor (EGFR) and fused toes homolog (FTS). This review is an attempt to understand the structure-function relationship between FTS and EGFR as a tool for the development of newer CC drugs. Motif analysis was performed using national center for biotechnology information (NCBI), kyoto encyclopedia of genes and genomes (KEGG), simple modular architecture research tool (SMART) and multiple expectation maximizations for motif elicitation (MEME) database. The secondary and tertiary structure prediction of FTS was performed using DISOPRED3 and threading assembly, respectively. A positive correlation was found between the transcript levels of FTS and EGFR. Amino acids responsible for interaction between EGFR and FTS were determined. The nine micro-RNAs (miRNAs) that regulates the expression of FTS were predicted using Network Analyst 3.0 database. hsa-miR-629-5p and hsa-miR-615-3p are identified as significant positive and negative regulators of FTS gene expression. This review opens up new avenues for the development of CC drugs which interfere with the interaction between FTS and EGFR.

A Live Cell Protein Complementation Assay for ORFeome-Wide Probing of Human HOX Interactomes

Biological pathways rely on the formation of intricate protein interaction networks called interactomes. Getting a comprehensive map of interactomes implies the development of tools that allow one to capture transient and low-affinity protein-protein interactions (PPIs) in live conditions. Here we presented an experimental strategy: the Cell-PCA (cell-based protein complementation assay), which was based on bimolecular fluorescence complementation (BiFC) for ORFeome-wide screening of proteins that interact with different bait proteins in the same live cell context, by combining high-throughput sequencing method. The specificity and sensitivity of the Cell-PCA was established by using a wild-type and a single-amino-acid-mutated HOXA9 protein, and the approach was subsequently applied to seven additional human HOX proteins. These proof-of-concept experiments revealed novel molecular properties of HOX interactomes and led to the identification of a novel cofactor of HOXB13 that promoted its proliferative activity in a cancer cell context. Taken together, our work demonstrated that the Cell-PCA was pertinent for revealing and, importantly, comparing the interactomes of different or highly related bait proteins in the same cell context.

AKTIP loss is enriched in ERα-positive breast cancer for tumorigenesis and confers endocrine resistance

Recurrent deletion of 16q12.2 is observed in luminal breast cancer, yet the causal genomic alterations in this region are largely unknown. In this study, we identify that loss of AKTIP, which is located on 16q12.2, drives tumorigenesis of estrogen receptor alpha (ERα)-positive, but not ERα-negative, breast cancer cells and is associated with poor prognosis of patients with ERα-positive breast cancer. Intriguingly, AKTIP-depleted tumors have increased ERα protein level and activity. Cullin-associated and neddylation-dissociated protein 1 (CAND1), which regulates the cullin-RING E3 ubiquitin ligases, protects ERα from cullin 2-dependent proteasomal degradation. Apart from ERα signaling, AKTIP loss triggers JAK2-STAT3 activation, which provides an alternative survival signal when ERα is inhibited. AKTIP-depleted MCF7 cells and ERα-positive patient-derived organoids are more resistant to ERα antagonists. Importantly, the resistance can be overcome by co-inhibition of JAK2/STAT3. Together, our results highlight the subtype-specific functional consequences of AKTIP loss and provide a mechanistic explanation for the enriched AKTIP copy-number loss in ERα-positive breast cancer.

Interaction of TLK1 and AKTIP as a Potential Regulator of AKT Activation in Castration-Resistant Prostate Cancer Progression

Prostate cancer (PCa) progression is characterized by the emergence of resistance to androgen deprivation therapy (ADT). AKT/PKB has been directly implicated in PCa progression, often due to the loss of PTEN and activation of PI3K>PDK1>AKT signaling. However, the regulatory network of AKT remains incompletely defined. Here, we describe the functional significance of AKTIP in PCa cell growth. AKTIP, identified in an interactome analysis as a substrate of TLK1B (that itself is elevated following ADT), enhances the association of AKT with PDK1 and its phosphorylation at T308 and S473. The interaction between TLK1 and AKTIP led to AKTIP phosphorylation at T22 and S237. The inactivation of TLK1 led to reduced AKT phosphorylation, which was potentiated with AKTIP knockdown. The TLK1 inhibitor J54 inhibited the growth of the LNCaP cells attributed to reduced AKT activation. However, LNCaP cells that expressed constitutively active, membrane-enriched Myr-AKT (which is expected to be active, even in the absence of AKTIP) were also growth-inhibited with J54. This suggested that other pathways (like TLK1>NEK1>YAP) regulating proliferation are also suppressed and can mediate growth inhibition, despite compensation by Myr-AKT. Nonetheless, further investigation of the potential role of TLK1>AKTIP>AKT in suppressing apoptosis, and conversely its reversal with J54, is warranted.

ER-mitochondria contact sites in neurodegeneration: genetic screening approaches to investigate novel disease mechanisms

Mitochondria-ER contact sites (MERCS) are known to underpin many important cellular homoeostatic functions, including mitochondrial quality control, lipid metabolism, calcium homoeostasis, the unfolded protein response and ER stress. These functions are known to be dysregulated in neurodegenerative diseases, including Parkinson's disease (PD), Alzheimer's disease (AD) and amyloid lateral sclerosis (ALS), and the number of disease-related proteins and genes being associated with MERCS is increasing. However, many details regarding MERCS and their role in neurodegenerative diseases remain unknown. In this review, we aim to summarise the current knowledge regarding the structure and function of MERCS, and to update the field on current research in PD, AD and ALS. Furthermore, we will evaluate high-throughput screening techniques, including RNAi vs CRISPR/Cas9, pooled vs arrayed formats and how these could be combined with current techniques to visualise MERCS. We will consider the advantages and disadvantages of each technique and how it can be utilised to uncover novel protein pathways involved in MERCS dysfunction in neurodegenerative diseases.

PI(3,4)P2-mediated membrane tubulation promotes integrin trafficking and invasive cell migration

Invadopodia are integrin-mediated adhesions with abundant PI(3,4)P₂ However, the functional role of PI(3,4)P₂ in adhesion signaling remains unclear. Here, we find that the PI(3,4)P₂ biogenesis regulates the integrin endocytosis at invadopodia. PI(3,4)P₂ is locally produced by PIK3CA and SHIP2 and is concentrated at the trailing edge of the invadopodium arc. The PI(3,4)P₂-rich compartment locally forms small puncta (membrane buds) in a SNX9-dependent manner, recruits dynein activator Hook1 through AKTIP, and rearranges into micrometer-long tubular invaginations (membrane tubes). The uncurving membrane tube extends rapidly, follows the retrograde movement of dynein along microtubule tracks, and disconnects from the plasma membrane. Activated integrin-beta3 is locally internalized through the pathway of PI(3,4)P₂-mediated membrane invagination and is then actively recycled. Blockages of PI3K, SHIP2, and SNX9 suppress integrin-beta3 endocytosis, delay adhesion turnover, and impede transwell invasion of MEF-Src and MDA-MB-231 cells. Thus, the production of PI(3,4)P₂ promotes invasive cell migration by stimulating the trafficking of integrin receptor at the invadopodium.

Do Epigenetic Changes Drive Corticosterone Responses to Alarm Cues in Larvae of an Invasive Amphibian?

The developmental environment can exert powerful effects on animal phenotype. Recently, epigenetic modifications have emerged as one mechanism that can modulate developmentally plastic responses to environmental variability. For example, the DNA methylation profile at promoters of hormone receptor genes can affect their expression and patterns of hormone release. Across taxonomic groups, epigenetic alterations have been linked to changes in glucocorticoid (GC) physiology. GCs are metabolic hormones that influence growth, development, transitions between life-history stages, and thus fitness. To date, relatively few studies have examined epigenetic effects on phenotypic traits in wild animals, especially in amphibians. Here, we examined the effects of exposure to predation threat (alarm cues) and experimentally manipulated DNA methylation on corticosterone (CORT) levels in tadpoles and metamorphs of the invasive cane toad (Rhinella marina). We included offspring of toads sampled from populations across the species' Australian range. In these animals, exposure to chemical cues from injured conspecifics induces shifts in developmental trajectories, putatively as an adaptive response that lessens vulnerability to predation. We exposed tadpoles to these alarm cues, and measured changes in DNA methylation and CORT levels, both of which are mechanisms that have been implicated in the control of phenotypically plastic responses in tadpoles. To test the idea that DNA methylation drives shifts in GC physiology, we also experimentally manipulated methylation levels with the drug zebularine. We found differentially methylated regions (DMRs) between control tadpoles and their full-siblings exposed to alarm cues, zebularine, or both treatments. However, the effects of these manipulations on methylation patterns were weaker than clutch (e.g., genetic, maternal, etc.) effects. CORT levels were higher in larval cane toads exposed to alarm cues and zebularine. We found little evidence of changes in DNA methylation across the GC receptor gene (NR3C1) promoter region in response to alarm cue or zebularine exposure. In both alarm cue and zebularine-exposed individuals, we found differentially methylated DNA in the suppressor of cytokine signaling 3 gene (SOCS3), which may be involved in predator avoidance behavior. In total, our data reveal that alarm cues have significant impacts on tadpole physiology, but show only weak links between DNA methylation and CORT levels. We also identify genes containing DMRs in tadpoles exposed to alarm cues and zebularine, particularly in range-edge populations, that warrant further investigation.

Genome-Wide Assessment for Resting Heart Rate and Shared Genetics With Cardiometabolic Traits and Type 2 Diabetes

BACKGROUND

High resting heart rate (RHR) occurs in parallel with type 2 diabetes (T2D) and metabolic disorders, implying shared etiology between them. However, it is unknown if they are causally related, and no study has been conducted to investigate the shared mechanisms underlying these associations.

OBJECTIVES

The objective of this study was to understand the genetic basis of the association between resting heart rate and cardiometabolic disorders/T2D.

METHODS

This study examined the genetic correlation, causality, and shared genetics between RHR and T2D using LD Score regression, generalized summary data-based Mendelian randomization, and transcriptome wide association scan (TWAS) in UK Biobank data (n = 428,250) and summary-level data for T2D (74,124 cases and 824,006 control subjects) and 8 cardiometabolic traits (sample size ranges from 51,750 to 236,231).

RESULTS

Significant genetic correlation between RHR and T2D (r_g = 0.22; 95% confidence interval: 0.18 to 0.26; p = 1.99 × 10^-22), and 6 cardiometabolic traits (fasting insulin, fasting glucose, waist-hip ratio, triglycerides, high-density lipoprotein, and body mass index; r_g range -0.12 to 0.24; all p < 0.05) were observed. RHR has significant estimated causal effect on T2D (odds ratio: 1.12 per 10-beats/min increment; p = 7.79 × 10^-11) and weaker causal estimates from T2D to RHR (0.32 beats/min per doubling increment in T2D prevalence; p = 6.14 × 10^-54). Sensitivity analysis by controlling for the included cardiometabolic traits did not modify the relationship between RHR and T2D. TWAS found locus chr2q23.3 (rs1260326) was highly pleiotropic among RHR, cardiometabolic traits, and T2D, and identified 7 genes (SMARCAD1, RP11-53O19.3, CTC-498M16.4, PDE8B, AKTIP, KDM4B, and TSHZ3) that were statistically independent and shared between RHR and T2D in tissues from the nervous and cardiovascular systems. These shared genes suggested the involvement of epigenetic regulation of energy and glucose metabolism, and AKT activation-related telomere dysfunction and vascular endothelial aging in the shared etiologies between RHR and T2D. Finally, FADS1 was found to be shared among RHR, fasting glucose, high-density lipoprotein, and triglycerides.

CONCLUSIONS

These findings provide evidence of significant genetic correlations and causation between RHR and T2D/cardiometabolic traits, advance our understanding of RHR, and provide insight into shared etiology for high RHR and T2D.

Skeletal Muscle Gene Expression in Long-Term Endurance and Resistance Trained Elderly

Physical exercise is deemed the most efficient way of counteracting the age-related decline of skeletal muscle. Here we report a transcriptional study by next-generation sequencing of vastus lateralis biopsies from elderly with a life-long high-level training practice (n = 9) and from age-matched sedentary subjects (n = 5). Unsupervised mixture distribution analysis was able to correctly categorize trained and untrained subjects, whereas it failed to discriminate between individuals who underwent a prevalent endurance (n = 5) or a prevalent resistance (n = 4) training, thus showing that the training mode was not relevant for sarcopenia prevention. KEGG analysis of transcripts showed that physical exercise affected a high number of metabolic and signaling pathways, in particular those related to energy handling and mitochondrial biogenesis, where AMPK and AKT-mTOR signaling pathways are both active and balance each other, concurring to the establishment of an insulin-sensitive phenotype and to the maintenance of a functional muscle mass. Other pathways affected by exercise training increased the efficiency of the proteostatic mechanisms, consolidated the cytoskeletal organization, lowered the inflammation level, and contrasted cellular senescence. This study on extraordinary individuals who trained at high level for at least thirty years suggests that aging processes and exercise training travel the same paths in the opposite direction.

Loss of tumor suppressor IGFBP4 drives epigenetic reprogramming in hepatic carcinogenesis

Genomic sequencing of hepatocellular carcinoma (HCC) uncovers a paucity of actionable mutations, underscoring the necessity to exploit epigenetic vulnerabilities for therapeutics. In HCC, EZH2-mediated H3K27me3 represents a major oncogenic chromatin modification, but how it modulates the therapeutic vulnerability of signaling pathways remains unknown. Here, we show EZH2 acts antagonistically to AKT signaling in maintaining H3K27 methylome through epigenetic silencing of IGFBP4. ChIP-seq revealed enrichment of Ezh2/H3K27me3 at silenced loci in HBx-transgenic mouse-derived HCCs, including Igfbp4 whose down-regulation significantly correlated with EZH2 overexpression and poor survivals of HCC patients. Functional characterizations demonstrated potent growth- and invasion-suppressive functions of IGFBP4, which was associated with transcriptomic alterations leading to deregulation of multiple signaling pathways. Mechanistically, IGFBP4 stimulated AKT/EZH2 phosphorylation to abrogate H3K27me3-mediated silencing, forming a reciprocal feedback loop that suppressed core transcription factor networks (FOXA1/HNF1A/HNF4A/KLF9/NR1H4) for normal liver homeostasis. Consequently, the in vivo tumorigenicity of IGFBP4-silenced HCC cells was vulnerable to pharmacological inhibition of EZH2, but not AKT. Our study unveils chromatin regulation of a novel liver tumor suppressor IGFBP4, which constitutes an AKT-EZH2 reciprocal loop in driving H3K27me3-mediated epigenetic reprogramming. Defining the aberrant chromatin landscape of HCC sheds light into the mechanistic basis of effective EZH2-targeted inhibition.

Manipulating Endoplasmic Reticulum-Plasma Membrane Tethering in Plants Through Fluorescent Protein Complementation

The bimolecular fluorescence complementation (BiFC) assay has been widely used to examine interactions between integral and peripheral proteins within putative plasma membrane (PM) microdomains. In the course of using BiFC assays to examine the co-localization of plasma membrane (PM) targeted receptor-like kinases (RLKs), such as FLS2, with PM micro-domain proteins such as remorins, we unexpectedly observed heterogeneous distribution patterns of fluorescence on the PM of Nicotiana benthamiana leaf cortical cells. These patterns appeared to co-localize with the endoplasmic reticulum (ER) and with ER-PM contact sites, and closely resembled patterns caused by over-expression of the ER-PM tether protein Synaptotagmin1 (SYT1). Using domain swap experiments with SYT1, we inferred that non-specific dimerization between FLS2-VenusN and VenusC-StRem1.3 could create artificial ER-PM tether proteins analogous to SYT1. The same patterns of ER-PM tethering were produced when a representative set of integral membrane proteins were partnered in BiFC complexes with PM-targeted peripheral membrane proteins, including PtdIns(4)P-binding proteins. We inferred that spontaneous formation of mature fluorescent proteins caused the BiFC complexes to trap the integral membrane proteins in the ER during delivery to the PM, producing a PM-ER tether. This phenomenon could be a useful tool to deliberately manipulate ER-PM tethering or to test protein membrane localization. However, this study also highlights the risk of using the BiFC assay to study membrane protein interactions in plants, due to the possibility of alterations in cellular structures and membrane organization, or misinterpretation of protein-protein interactions. A number of published studies using this approach may therefore need to be revisited.

Circulating Exosomal miR-20b-5p Is Elevated in Type 2 Diabetes and Could Impair Insulin Action in Human Skeletal Muscle

miRNAs are noncoding RNAs representing an important class of gene expression modulators. Extracellular circulating miRNAs are both candidate biomarkers for disease pathogenesis and mediators of cell-to-cell communication. We examined the miRNA expression profile of total serum and serum-derived exosome-enriched extracellular vesicles in people with normal glucose tolerance or type 2 diabetes. In contrast to total serum miRNA, which did not reveal any differences in miRNA expression, we identified differentially abundant miRNAs in patients with type 2 diabetes using miRNA expression profiles of exosome RNA (exoRNA). To validate the role of these differentially abundant miRNAs on glucose metabolism, we transfected miR-20b-5p, a highly abundant exoRNA in patients with type 2 diabetes, into primary human skeletal muscle cells. miR-20b-5p overexpression increased basal glycogen synthesis in human skeletal muscle cells. We identified AKTIP and STAT3 as miR-20b-5p targets. miR-20b-5p overexpression reduced AKTIP abundance and insulin-stimulated glycogen accumulation. In conclusion, exosome-derived extracellular miR-20b-5p is a circulating biomarker associated with type 2 diabetes that plays an intracellular role in modulating insulin-stimulated glucose metabolism via AKT signaling.

FTO associations with obesity and telomere length

This review examines the biology of the Fat mass- and obesity-associated gene (FTO), and the implications of genetic association of FTO SNPs with obesity and genetic aging. Notably, we focus on the role of FTO in the regulation of methylation status as possible regulators of weight gain and genetic aging. We present a theoretical review of the FTO gene with a particular emphasis on associations with UCP2, AMPK, RBL2, IRX3, CUX1, mTORC1 and hormones involved in hunger regulation. These associations are important for dietary behavior regulation and cellular nutrient sensing via amino acids. We suggest that these pathways may also influence telomere regulation. Telomere length (TL) attrition may be influenced by obesity-related inflammation and oxidative stress, and FTO gene-involved pathways. There is additional emerging evidence to suggest that telomere length and obesity are bi-directionally associated. However, the role of obesity risk-related genotypes and associations with TL are not well understood. The FTO gene may influence pathways implicated in regulation of TL, which could help to explain some of the non-consistent relationship between weight phenotype and telomere length that is observed in population studies investigating obesity.

Systematic review and meta-analysis of genetic studies of late-life depression

Late-life depression (LLD) is thought to be multifactorial in etiology, including a significant genetic component. While a number of candidate gene studies have been carried out, results remain inconclusive. We undertook a systematic review of all genetic association studies of depression or depressive symptoms in late life published before February 2016, and performed meta-analyses on polymorphisms investigated in three or more independent studies. A total of 46 candidate gene studies examining 56 polymorphisms in 23 genes as well as a genome-wide association study (GWAS) were included. Meta-analyses were conducted for four polymorphisms using random effects models, of which three (APOE, BDNF, SLC6A4) were associated with LLD. These genes are implicated in hippocampal plasticity and stress reactivity, suggesting that dysregulation of these pathways may contribute to LLD. Despite using a large sample, the only GWAS published to date identified only one genome-wide significant locus in the 5q21 region. In the future, larger genetic studies specifically examining LLD, including non-hypothesis-driven GWAS, are required to further identify genetic determinants of LLD.

Optical sensors to gain mechanistic insights into signaling assemblies

Protein complexes play a major role in transducing information from outside the cell into instructions for growth and survival, and understanding how these complexes relay and shape intracellular signals has been a central question in signaling biology. Fluorescent proteins have proven paramount in opening windows for researchers to peer into the architecture and inner workings of signaling assemblies within the living cell and in real-time. In this review, we will provide readers with a current perspective on the development and use of genetically encoded optical probes to dissect the function of signaling complexes.

Association of the miR-17-5p variants with susceptibility to cervical cancer in a Chinese population

MicroRNAs (miRNAs) are key regulators of gene expression; however, the extent to which single nucleotide polymorphisms (SNPs) interfere with miRNA gene regulation and affect cervical cancer (CC) susceptibility remains largely unknown. Here, we systematically analyzed miRNA-related SNPs and their association with CC risk, and performed a case-control study of miR-17-5p SNPs and CC risk in a Chinese population. Sixteen SNPs were genotyped in 247 CC cases and 285 controls. Three were associated with CC risk (p < 0.05): the minor allele (A) of rs217727 in H19 increased risk (OR = 1.53, p = 0.002), while the minor alleles (T) of rs9931702 and (T) of rs9302648 in AKTIP decreased CC risk (p = 0.018, p = 0.014). Analysis of the SNPs after stratification based on CC clinical stage and subtype revealed that rs1048512, rs6659346, rs217727, rs9931702, and rs9302648 were associated with CC risk in clinical stages I-II; rs2862833, rs2732044, rs1030389, and rs1045935 were associated with CC risk in clinical stages III-IV; and rs217727, rs9931702, and rs9302648 were associated with CC risk in squamous carcinomas. These data could serve as a useful resource for understanding the miR-17 function, identification of miRNAs associated with CC, and development of better CC screening strategies.

Lack of association between genetic polymorphism of FTO, AKT1 and AKTIP in childhood overweight and obesity

OBJECTIVE

Obesity is a chronic disease caused by both environmental and genetic factors. Epidemiological studies have documented that increased energy intake and sedentary lifestyle, as well as a genetic contribution, are forces behind the obesity epidemic. Knowledge about the interaction between genetic and environmental components can facilitate the choice of the most effective and specific measures for the prevention of obesity. The aim of this study was to assess the association between the FTO, AKT1, and AKTIP genes and childhood obesity and insulin resistance.

METHODS

This was a case-control study in which SNPs in the FTO (rs99396096), AKT1, and AKTIP genes were genotyped in groups of controls and obese/overweight children. The study included 195 obese/overweight children and 153 control subjects.

RESULTS

As expected, the obese/overweight group subjects had higher body mass index, higher fasting glucose, HOMA-IR index, total cholesterol, low-density lipoprotein, and triglycerides. However, no significant differences were observed in genes polymorphisms genotype or allele frequencies.

CONCLUSION

The present results suggest that AKT1, FTO, and AKTIP polymorphisms were not associated with obesity/overweight in Brazilians children. Future studies on the genetics of obesity in Brazilian children and their environment interactions are needed.

Carboxy-terminal modulator protein attenuated extracellular matrix deposit by inhibiting phospho-Akt, TGF-β1 and α-SMA in kidneys of diabetic mice

Glomerulosclerosis and tubular interstitial extracellular matrix deposit and fibrosis are the main features of diabetic nephropathy, which are mediated by activation of PI3K/Akt signal pathway. Carboxy-terminal modulator protein (CTMP) is known as a negative regulator of PI3K/Akt pathway. Whether CTMP regulates renal extracellular matrix metabolism of diabetic nephropathy is still not known. Here, renal decreased CTMP, enhanced phospho-Akt (Ser 473), TGF-β1, α-SMA and extracellular matrix deposit are found in diabetic mice. Furthermore, high glucose decreases CTMP expression accompanied by enhanced phospho-Akt (Ser 473), TGF-β1 and α-SMA in cultured human renal proximal tubular epithelial cells (HKC), which are effectively prevented by transfection of pYr-ads-4-musCTMP vector. Moreover, delivery of pYr-ads-4-musCTMP vector into kidneys via tail vein of diabetic mice increases CTMP expression by 8.84 times followed by 60.00%, 76.50% and 24.37% decreases of phospho-Akt (Ser 473), TGF-β1 and α-SMA compared with diabetic mice receiving pYr-adshuttle-4 vector. Again, increased renal extracellular matrix accumulation of diabetic mice is also inhibited with delivery of pYr-ads-4-musCTMP vector. Our results indicate that CTMP attenuates renal extracellular matrix deposit by regulating the phosphorylation of Akt, TGF-β1 and α-SMA expression in diabetic mice.

Hypomorphism of Fto and Rpgrip1l causes obesity in mice

Noncoding polymorphisms in the fat mass and obesity-associated (FTO) gene represent common alleles that are strongly associated with effects on food intake and adiposity in humans. Previous studies have suggested that the obesity-risk allele rs8050136 in the first intron of FTO alters a regulatory element recognized by the transcription factor CUX1, thereby leading to decreased expression of FTO and retinitis pigmentosa GTPase regulator-interacting protein-1 like (RPGRIP1L). Here, we evaluated the effects of rs8050136 and another potential CUX1 element in rs1421085 on expression of nearby genes in human induced pluripotent stem cell-derived (iPSC-derived) neurons. There were allele-dosage effects on FTO, RPGRIP1L, and AKT-interacting protein (AKTIP) expression, but expression of other vicinal genes, including IRX3, IRX5, and RBL2, which have been implicated in mediating functional effects, was not altered. In vivo manipulation of CUX1, Fto, and/or Rpgrip1l expression in mice affected adiposity in a manner that was consistent with CUX1 influence on adiposity via remote effects on Fto and Rpgrip1l expression. In support of a mechanism, mice hypomorphic for Rpgrip1l exhibited hyperphagic obesity, as the result of diminished leptin sensitivity in Leprb-expressing neurons. Together, the results of this study indicate that the effects of FTO-associated SNPs on energy homeostasis are due in part to the effects of these genetic variations on hypothalamic FTO, RPGRIP1L, and possibly other genes.

Roles of NlAKTIP in the Growth and Eclosion of the Rice Brown Planthopper, Nilaparvata lugens Stål, as Revealed by RNA Interference

AKT-interacting protein (AKTIP) interacts with serine/threonine protein kinase B (PKB)/AKT. AKTIP modulates AKT’s activity by enhancing the phosphorylation of the regulatory site and plays a crucial role in multiple biological processes. In this study, the full length cDNA of NlAKTIP, a novel AKTIP gene in the brown planthopper (BPH) Nilaparvata lugens, was cloned. The reverse transcription quantitive PCR (RT-qPCR) results showed that the NlAKTIP gene was strongly expressed in gravid female adults, but was relatively weakly expressed in nymphs and male adult BPH. In female BPH, treatment with dsAKTIP resulted in the efficient silencing of NlAKTIP, leading to a significant reduction of mRNA levels, about 50% of those of the untreated control group at day 7 of the study. BPH fed with dsAKTIP had reduced growth with lower body weights and smaller sizes, and the body weight of BPH treated with dsAKTIP at day 7 decreased to about 30% of that of the untreated control. Treatment of dsAKTIP significantly delayed the eclosion for over 7 days relative to the control group and restricted ovarian development to Grade I (transparent stage), whereas the controls developed to Grade IV (matured stage). These results indicated that NlAKTIP is crucial to the growth and development of female BPH. This study provided a valuable clue of a potential target NlAKTIP for inhibiting the BPH, and also provided a new point of view on the interaction between BPH and resistant rice.

AKTIP/Ft1, a New Shelterin-Interacting Factor Required for Telomere Maintenance

Telomeres are nucleoprotein complexes that protect the ends of linear chromosomes from incomplete replication, degradation and detection as DNA breaks. Mammalian telomeres are protected by shelterin, a multiprotein complex that binds the TTAGGG telomeric repeats and recruits a series of additional factors that are essential for telomere function. Although many shelterin-associated proteins have been so far identified, the inventory of shelterin-interacting factors required for telomere maintenance is still largely incomplete. Here, we characterize AKTIP/Ft1 (human AKTIP and mouse Ft1 are orthologous), a novel mammalian shelterin-bound factor identified on the basis of its homology with the Drosophila telomere protein Pendolino. AKTIP/Ft1 shares homology with the E2 variant ubiquitin-conjugating (UEV) enzymes and has been previously implicated in the control of apoptosis and in vesicle trafficking. RNAi-mediated depletion of AKTIP results in formation of telomere dysfunction foci (TIFs). Consistent with these results, AKTIP interacts with telomeric DNA and binds the shelterin components TRF1 and TRF2 both in vivo and in vitro. Analysis of AKTIP- depleted human primary fibroblasts showed that they are defective in PCNA recruiting and arrest in the S phase due to the activation of the intra S checkpoint. Accordingly, AKTIP physically interacts with PCNA and the RPA70 DNA replication factor. Ft1-depleted p53-/- MEFs did not arrest in the S phase but displayed significant increases in multiple telomeric signals (MTS) and sister telomere associations (STAs), two hallmarks of defective telomere replication. In addition, we found an epistatic relation for MST formation between Ft1 and TRF1, which has been previously shown to be required for replication fork progression through telomeric DNA. Ch-IP experiments further suggested that in AKTIP-depleted cells undergoing the S phase, TRF1 is less tightly bound to telomeric DNA than in controls. Thus, our results collectively suggest that AKTIP/Ft1 works in concert with TRF1 to facilitate telomeric DNA replication.

Bimolecular Fluorescence Complementation (BiFC) Analysis: Advances and Recent Applications for Genome-Wide Interaction Studies

Complex protein networks are involved in nearly all cellular processes. To uncover these vast networks of protein interactions, various high-throughput screening technologies have been developed. Over the last decade, bimolecular fluorescence complementation (BiFC) assay has been widely used to detect protein-protein interactions (PPIs) in living cells. This technique is based on the reconstitution of a fluorescent protein in vivo. Easy quantification of the BiFC signals allows effective cell-based high-throughput screenings for protein binding partners and drugs that modulate PPIs. Recently, with the development of large screening libraries, BiFC has been effectively applied for genome-wide PPI studies and has uncovered novel protein interactions, providing new insight into protein functions. In this review, we describe the development of reagents and methods used for BiFC-based screens in yeast, plants, and mammalian cells. We also discuss the advantages and drawbacks of these methods and highlight the application of BiFC in large-scale studies.

FTS is responsible for radiation-induced nuclear phosphorylation of EGFR and repair of DNA damage in cervical cancer cells

PURPOSE

Radiation-induced nuclear stabilization and phosphorylation of epidermal growth factor receptor (EGFR) confers radioresistance. Understanding of the factor(s) regulating the nuclear stabilization and phosphorylation of EGFR is important for the modulation of radioresistance. Present study was designed to delineate the regulation of EGFR nuclear stabilization and phosphorylation by fused toes homolog (FTS), an oncoprotein, which is responsible for the radioresistance in cervical cancer cells.

METHODS

A cervical cancer cell line, ME180 was used. Radiation-induced change in the levels of EGFR, p-EGFR and FTS were evaluated in the cytoplasm and nucleus using Western blot analyses. FTS was silenced using siRNA-based approach. Interaction between EGFR and FTS was assessed using immunofluorescence and immunoprecipitation analyses. Double-strand breaks (DSB) of DNA were assessed using γ H2AX.

RESULTS

Radiation increased the levels of EGFR and FTS in the cytoplasm and nucleus. EGFR and FTS are in physical association with each other and are co-localized in the cells. FTS silencing largely reduced the nuclear stabilization and phosphorylation of EGFR and DNA-protein kinase along with increased initial and residual DSBs.

CONCLUSION

EGFR and FTS physically associate with each other and FTS silencing radiosensitizes ME180 cells through impaired nuclear EGFR signaling.

Discovering protein-protein interactions within the programmed cell death network using a protein-fragment complementation screen

Apoptosis and autophagy are distinct biological processes, each driven by a different set of protein-protein interactions, with significant crosstalk via direct interactions among apoptotic and autophagic proteins. To measure the global profile of these interactions, we adapted the Gaussia luciferase protein-fragment complementation assay (GLuc PCA), which monitors binding between proteins fused to complementary fragments of a luciferase reporter. A library encompassing 63 apoptotic and autophagic proteins was constructed for the analysis of ∼3,600 protein-pair combinations. This generated a detailed landscape of the apoptotic and autophagic modules and points of interface between them, identifying 46 previously unknown interactions. One of these interactions, between DAPK2, a Ser/Thr kinase that promotes autophagy, and 14-3-3τ, was further investigated. We mapped the region responsible for 14-3-3τ binding and proved that this interaction inhibits DAPK2 dimerization and activity. This proof of concept underscores the power of the GLuc PCA platform for the discovery of biochemical pathways within the cell death network.

EGF-induced expression of Fused Toes Homolog (FTS) facilitates epithelial-mesenchymal transition and promotes cell migration in ME180 cervical cancer cells

The role of Fused Toes Homolog (FTS) in epidermal growth factor (EGF) induced epithelial-mesenchymal transition (EMT) in cervical cancer cells was studied. EGF treatment induced the change of EMT markers and increased cell migration. EGF treatment also increased phosphorylated EGFR and ERK and nuclear level of ATF-2. The binding of ATF-2 to the promoter region of FTS was evidenced after EGF treatment. Pretreatment with PD98059 and gefitinib prevented EGF-induced FTS expression. FTS silencing reduced EMT and cell migration by EGF treatment. These results demonstrate a novel function for FTS in EGF-mediated EMT process.

Genetic variant of AKT1 and AKTIP associated with late-onset depression in a Brazilian population

OBJECTIVES

Examine the association between polymorphisms in the AKT1 and AKTIP genes and late-onset depression (LOD). Major depressive disorder is one of the most prevalent neuropsychiatric diseases. LOD is a disorder that starts after 65 years old. AKT1 is a downstream enzyme that has been implicated in the pathogenesis of neurotransmitter-related disorders, such as depression. The identification of a novel AKT1-binding protein (AKTIP) was pointed as an important new target. AKTIP binds directly to AKT1, enhancing the phosphorylation of regulatory sites, and this modulation are affected by AKT1 activation. The association of AKT1 and AKTIP polymorphisms with depressive symptoms was not investigated in LOD.

DESIGN

Genotype tagSNPs in the AKT1 and AKTIP in LOD patients and controls.

SETTINGS

An academic medical center.

PARTICIPANTS

Sample composed by 190 outpatients with LOD and 77 healthy individuals.

MEASURES

The participants were evaluated using Diagnostic and Statistical Manual IV criteria, MINI-PLUS and the Geriatric Depression Scale.

RESULTS

Our findings suggested an association between the tagSNP rs3730358 homozygous A/A (p = 0.006) and LOD. A strong association of allele A and increased association for LOD was demonstrated with tagSNP rs3730358 (p-value = 0.003).

LIMITATIONS

Limitation include composition of our control group, where the exclusion criteria generated a kind of super-healthy older group what might have produced a hidden stratification when compared with the LOD.

CONCLUSION

This study is the first one to establish the association of the AKT1/AKTIP genes and LOD, and further studies are necessary to clarify the functional role of these proteins.

Unraveling aquaporin interaction partners

BACKGROUND

Insight into protein-protein interactions (PPIs) is highly desirable in order to understand the physiology of cellular events. This understanding is one of the challenges in biochemistry and molecular biology today, especially for eukaryotic membrane proteins where hurdles of production, purification and structural determination must be passed.

SCOPE OF REVIEW

We have explored the common strategies used to find medically relevant interaction partners of aquaporins (AQPs). The most frequently used methods to detect direct contact, yeast two-hybrid interaction assay and co-precipitation, are described together with interactions specifically found for the selected targets AQP0, AQP2, AQP4 and AQP5.

MAJOR CONCLUSIONS

The vast majority of interactions involve the aquaporin C-terminus and the characteristics of the interaction partners are strikingly diverse. While the well-established methods for PPIs are robust, a novel approach like bimolecular fluorescence complementation (BiFC) is attractive for screening many conditions as well as transient interactions. The ultimate goal is structural evaluation of protein complexes in order to get mechanistic insight into how proteins communicate at a molecular level.

GENERAL SIGNIFICANCE

What we learn from the human aquaporin field in terms of method development and communication between proteins can be of major use for any integral membrane protein of eukaryotic origin. This article is part of a Special Issue entitled Aquaporins.

EGCG suppresses Fused Toes Homolog protein through p53 in cervical cancer cells

The anticarcinogenic actions of epigallocatechin-3-gallate (EGCG), one of the main ingredients of green tea, against various cancer types including cervical cancer are well documented. Studies pertaining to the exact molecular mechanism by which EGCG induces cancer cell growth inhibition needs to be investigated extensively. In the present study, we observed a stupendous dose dependent reduction in the protein expression of Fused Toes Homolog (FTS) after treatment with EGCG at 1, 10, 25 and 50 μM. Further, we were interested in finding out whether the decrease in the protein expression of FTS was due to decreased mRNA synthesis. Real time reverse transcriptase polymerase chain reaction results revealed a similar dose dependent reduction in the FTS mRNA after EGCG treatment. Chromatin immunoprecipitation analysis revealed the interaction between p53 and the promoter region of FTS. A dose dependent increase in this interaction was evidenced at 25 and 50 μM EGCG treatment. p53 silencing increased the expression of FTS and also decreased the reduction in the levels of FTS expression after EGCG treatment. The decrease in the levels of FTS was more significant at 25 and 50 μM and is associated with reduced physical interaction of FTS with Akt, phosphorylation of Akt and survival of HeLa cells. Collectively, these results conclude that EGCG induced anti-proliferative action in the cervical cancer cell involves reduced mRNA expression of FTS through p53.

Whole-exome sequencing combined with functional genomics reveals novel candidate driver cancer genes in endometrial cancer

Endometrial cancer is the most common gynecological malignancy, with more than 280,000 cases occurring annually worldwide. Although previous studies have identified important common somatic mutations in endometrial cancer, they have primarily focused on a small set of known cancer genes and have thus provided a limited view of the molecular basis underlying this disease. Here we have developed an integrated systems-biology approach to identifying novel cancer genes contributing to endometrial tumorigenesis. We first performed whole-exome sequencing on 13 endometrial cancers and matched normal samples, systematically identifying somatic alterations with high precision and sensitivity. We then combined bioinformatics prioritization with high-throughput screening (including both shRNA-mediated knockdown and expression of wild-type and mutant constructs) in a highly sensitive cell viability assay. Our results revealed 12 potential driver cancer genes including 10 tumor-suppressor candidates (ARID1A, INHBA, KMO, TTLL5, GRM8, IGFBP3, AKTIP, PHKA2, TRPS1, and WNT11) and two oncogene candidates (ERBB3 and RPS6KC1). The results in the “sensor” cell line were recapitulated by siRNA-mediated knockdown in endometrial cancer cell lines. Focusing on ARID1A, we integrated mutation profiles with functional proteomics in 222 endometrial cancer samples, demonstrating that ARID1A mutations frequently co-occur with mutations in the phosphatidylinositol 3-kinase (PI3K) pathway and are associated with PI3K pathway activation. siRNA knockdown in endometrial cancer cell lines increased AKT phosphorylation supporting ARID1A as a novel regulator of PI3K pathway activity. Our study presents the first unbiased view of somatic coding mutations in endometrial cancer and provides functional evidence for diverse driver genes and mutations in this disease.

AKT/SGK-sensitive phosphorylation of GSK3 in the regulation of L-selectin and perforin expression as well as activation induced cell death of T-lymphocytes

Survival and function of T-lymphocytes critically depends on phosphoinositide (PI) 3 kinase. PI3 kinase signaling includes the PKB/Akt and SGK dependent phosphorylation and thus inhibition of glycogen synthase kinase GSK3α,β. Lithium, a known unspecific GSK3 inhibitor protects against experimental autoimmune encephalomyelitis. The present study explored, whether Akt/SGK-dependent regulation of GSK3 activity is a determinant of T cell survival and function. Experiments were performed in mutant mice in which Akt/SGK-dependent GSK3α,β inhibition was disrupted by replacement of the serine residue in the respective SGK/Akt-phosphorylation consensus sequence by alanine (gsk3(KI)). T cells from gsk3(KI) mice were compared to T cells from corresponding wild type mice (gsk3(WT)). As a result, in gsk3(KI) CD4(+) cells surface CD62L (L-selectin) was significantly less abundant than in gsk3(WT) CD4(+) cells. Upon activation in vitro T cells from gsk3(KI) mice reacted with enhanced perforin production and reduced activation induced cell death. Cytokine production was rather reduced in gsk3(KI) T cells, suggesting that GSK3 induces effector function in CD8(+) T cells. In conclusion, PKB/Akt and SGK sensitive phosphorylation of GSK3α,β is a potent regulator of perforin expression and activation induced cell death in T lymphocytes.

Live-cell visualization of transmembrane protein oligomerization and membrane fusion using two-fragment haptoEGFP methodology

Protein interactions play key roles throughout all subcellular compartments. In the present paper, we report the visualization of protein interactions throughout living mammalian cells using two oligomerizing MV (measles virus) transmembrane glycoproteins, the H (haemagglutinin) and the F (fusion) glycoproteins, which mediate MV entry into permissive cells. BiFC (bimolecular fluorescence complementation) has been used to examine the dimerization of these viral glycoproteins. The H glycoprotein is a type II membrane-receptor-binding homodimeric glycoprotein and the F glycoprotein is a type I disulfide-linked membrane glycoprotein which homotrimerizes. Together they co-operate to allow the enveloped virus to enter a cell by fusing the viral and cellular membranes. We generated a pair of chimaeric H glycoproteins linked to complementary fragments of EGFP (enhanced green fluorescent protein) – haptoEGFPs – which, on association, generate fluorescence. Homodimerization of H glycoproteins specifically drives this association, leading to the generation of a fluorescent signal in the ER (endoplasmic reticulum), the Golgi and at the plasma membrane. Similarly, the generation of a pair of corresponding F glycoprotein–haptoEGFP chimaeras also produced a comparable fluorescent signal. Co-expression of H and F glycoprotein chimaeras linked to complementary haptoEGFPs led to the formation of fluorescent fusion complexes at the cell surface which retained their biological activity as evidenced by cell-to-cell fusion.

A fluorogenic red fluorescent protein heterodimer

The expanding repertoire of genetically encoded biosensors constructed from variants of Aequorea victoria green fluorescent protein (GFP) enable the imaging of a variety of intracellular biochemical processes. To facilitate the imaging of multiple biosensors in a single cell, we undertook the development of a dimerization-dependent red fluorescent protein (ddRFP) that provides an alternative strategy for biosensor construction. An extensive process of rational engineering and directed protein evolution led to the discovery of a ddRFP with a K(d) of 33 μM and a 10-fold increase in fluorescence upon heterodimer formation. We demonstrate that the dimerization-dependent fluorescence of ddRFP can be used for detection of a protein-protein interaction in vitro, imaging of the reversible Ca²⁺-dependent association of calmodulin and M13 in live cells, and imaging of caspase-3 activity during apoptosis.

Characterization of the latent membrane protein 1 signaling complex of Epstein-Barr virus in the membrane of mammalian cells with bimolecular fluorescence complementation

Background

Bimolecular fluorescence complementation (BiFC) is a novel technique to examine protein-protein interaction through the assembly of fluorescent proteins. In the present study, BiFC was used to study the assembly of the Epstein-Barr virus latent membrane protein 1 (LMP1) signaling complex within the membrane of mammalian cells. LMP1 signaling requires oligomerization, localization to lipid rafts, and association of the cytoplasmic domain to adaptor proteins, such as the tumor necrosis factor receptor associated factors (TRAFs).

Methods

LMP1-TRAF and LMP1-LMP1 interactions were assayed by BiFC using fluorescence microscopy and flow cytometry. Function of LMP1 BiFC contructs were confirmed by transformation assays and nuclear factor- κB (NF-κB) reporter assays.

Results

BiFC was observed between LMP1 and TRAF2 or TRAF3 and mutation of the LMP1 signaling domains reduced complementation. Fluorescence was observed in previously described LMP1 signaling locations. Oligomerization of LMP1 with itself induced complementation and BiFC. LMP1-BiFC constructs were fully functional in rodent fibroblast transformation assays and activation of NF-κB reporter activity. The BiFC domain partially suppressed some LMP1 mutant phenotypes.

Conclusions

Together these data suggest that BiFC is a unique and novel platform to identify and characterize proteins recruited to the LMP1-signaling complex.

Phosphorylation of threonine 190 is essential for nuclear localization and endocytosis of the FTS (Fused Toes Homolog) protein

Fused Toes Homolog (FTS) is a member of a group of proteins termed as E2 variants and this group of proteins lacks an active cysteine residue that is required for ubiquitin transfer. We have identified the expression of this protein in early neoplastic stages of cervical cancer and its translocation into nucleus from cytoplasm upon irradiation. Here we have reported that a threonine residue at position 190 is essential for its nucleocytoplasmic shuttling and function. Upon LMB treatment we found that FTS was located in the nucleus and it suggests that direct role of nuclear export signal (NES) is required for the binding to CRM1 and facilitates nuclear export. The threonine residue was phosphorylated and promoted the phosphorylation of EGFR, p38 and JNK facilitating vesicular trafficking of early to late endosomes. Mutational change of the threonine into alanine resulted in the cytoplasmic localization of FTS and failed to phosphorylate EGFR and its downstream effector proteins. In addition the mutation also reduced the number of early endosomes formed and also resulted in the clustering of late endosomes around the perinuclear region. These data suggest that threonine residue of FTS at position 190 is not only essential for its function but also for the formation, maturation and trafficking of early endosomes to late endosome/lysosome, as well as we speculate that FTS may function at a connection point in the vesicle tethering.

Clinical significance of expression of PTEN, Akt and pAkt in hepatocellular carcinoma

AIM: To explore the expression of phosphatase and tensin homology deleted on chromosome ten (PTEN), Akt and pAkt proteins in hepatocellular carcinoma (HCC) and to elucidate their clinical significance.

METHODS: Immunohistochemical analysis was performed to detect the expression of PTEN, Akt and pAkt proteins in 78 specimens of hepatocellular carcinoma and 21 specimens of normal liver tissues. The relationship of their expression with clinicopathological and prognostic parameters was analyzed.

RESULTS: The rate of PTEN overexpression was significantly lower in HCC than in normal liver tissue (42.3% vs 90.5%, P < 0.05), while the rates of Akt and pAkt overexpression were significantly higher in HCC than in normal liver tissue (66.7% vs 33.3%; 43.6% vs 9.5%, both P < 0.05). PTEN expression was correlated with tumor size, cancer embolus of the portal vein, tumor invasion, lymph node metastasis and TNM stage. Akt and pAkt expression was correlated with tumor size, invasion, lymph node metastasis and TNM stage. PTEN expression was negatively correlated with Akt (r = -0.385, P = 0.000) and pAkt (r =- 0.334, P = 0.003) expression in HCC. Patients with low PTEN expression or high Akt and pAkt expression had a significantly worse survival time than those with high PTEN expression or low Akt and pAkt expression (P = 0.000). A multivariate analysis based on the COX regression model demonstrated that TNM stage and pAkt expression were independent prognostic factors for HCC.

CONCLUSION: The expression of PTEN, Akt and pAkt proteins is closely related to the malignant biological behavior of HCC. pAkt can be used as a key factor for predicting prognosis in HCC patients.

HIV-1 Vif interaction with APOBEC3 deaminases and its characterization by a new sensitive assay

The human APOBEC3 (A3) cytidine deaminases, such as APOBEC3G (A3G) and APOBEC3F (A3F), are potent inhibitors of Vif-deficient human immunodeficiency virus type 1 (HIV-1). HIV-1 Vif (viral infectivity factor) binds A3 proteins and targets these proteins for ubiquitination and proteasomal degradation. As such, the therapeutic blockage of Vif-A3 interaction is predicted to stimulate natural antiviral activity by rescuing APOBEC expression and virion packaging. In this study, we describe a successful application of the Protein Fragment Complementation Assay (PCA) based on the enzyme TEM-1 β-lactamase to study Vif-A3 interactions. PCA is based on the interaction between two protein binding partners (e.g., Vif and A3G), which are fused to the two halves of a dissected marker protein (β-lactamase). Binding of the two partners reassembles β-lactamase and hence reconstitutes its activity. To validate our assay, we studied the effect of well-described Vif (DRMR, YRHHY) and A3G (D128K) mutations on the interaction between the two proteins. Additionally, we studied the interaction of human Vif with other members of the A3 family: A3F and APOBEC3C (A3C). Our results demonstrate the applicability of PCA as a simple and reliable technique for the assessment of Vif-A3 interactions. Furthermore, when compared with co-immunoprecipitation assays, PCA appeared to be a more sensitive technique for the quantitative assessment of Vif-A3 interactions. Thus, with our results, we conclude that PCA could be used to quantitatively study specific domains that may be involved in the interaction between Vif and APOBEC proteins.

FTS (fused toes homolog) a novel oncoprotein involved in uterine cervical carcinogenesis and a potential diagnostic marker for cervical cancer

The high incidence and fatality rate of uterine cervical cancer warrant effective diagnostic and therapeutic target identification for this disease. Here, we have found a novel oncoprotein FTS (Fused Toes Homolog), which is involved in cervical cancer pathogenesis. Immunohistochemical analysis of human cervical biopsy samples revealed that the expression of FTS is absent in normal cervical epithelium but progressively overexpressed in human cervical intraneoplastic lesions (CIN-I to CIN-III), this characteristic phenomenon put this protein, a potential diagnostic marker for the screening of early neoplastic changes of cervix. Using FTS-specific small hairpin RNA (shRNA) in cervical cancer cells, we determined a specific role for FTS protein in, cervical neoplasia. Targeted stable knock down of FTS in HeLa cells led to the growth inhibition, cell-cycle arrest, and apoptosis with concurrent increase in p21 protein. FTS effectively represses the p21 mRNA expression in dual luciferase assay which indicates that p21 is transcriptionally regulated by this oncoprotein which in turn affect the regular cell-cycle process and its components. Consistent with this we found a reciprocal association between these proteins in early cervical neoplastic tissues. These data unraveled the involvement of new oncoprotein FTS in cervical cancer which plays a central role in carcinogenesis. Targeted inhibition of FTS lead to the shutdown of key elemental characteristics of cervical cancer and could lead to an effective therapeutic strategy for cervical cancer.

Fused Toes Homolog modulates radiation cytotoxicity in uterine cervical cancer cells

Radiotherapy is the major treatment modality for uterine cervical cancer, but in some cases, the disease is radioresistant. Defining the molecular events that contribute to radioresistance and progression of cancer are of critical importance. Here we evaluated the role of Fused Toes Homolog (FTS) in radiation resistance of cervical carcinoma. Immunostaning of cervical cancer cells and tissues revealed that FTS localization and expression was changed after radiation. Targeted stable knockdown of FTS in HeLa cells led to the growth inhibition after radiation. Radiation induced AKT mediated cytoprotective effect was countered by FTS knockdown which leads to PARP cleavage and caspase-3 activation leading to cell death. FTS knockdown promotes radiation induced cell cycle arrest at G0/G1 and apoptosis of HeLa cells with concurrent alterations in the display of cell cycle regulatory proteins. This study revealed FTS is involved in radioresistance of cervical cancer. Targeted inhibition of FTS led to the shutdown of key elemental characteristics of cervical cancer and could lead to an effective therapeutic strategy.

The fused toes locus is essential for somatic-germ cell interactions that foster germ cell maturation in developing gonads in mice

Ovarian development absolutely depends on communication between somatic and germ cell components. In contrast, it is not until after birth that interactions between somatic and germ cells play an important role in testicular maturation and spermatogenesis. Previously, we discovered that Irx3 expression was localized specifically to female gonads during embryonic development; therefore, we sought to determine the function of this genetic locus in developing gonads of both sexes. The fused toes (Ft) mutant mouse is missing 1.6 Mb of chromosome 8, which includes the entire IrxB cluster (Irx3, Irx5, Irx6), Ftm, Fts, and Fto genes. Homozygote Ft mutant embryos die around embryonic day 13.5 (E13.5); therefore, to assess later development, we harvested gonads at E11.5 and transplanted them into nude mouse hosts. Our results show defects in somatic and germ cell maturation in developing gonads of both sexes. Testis development was normal initially; however, by 3-wk posttransplantation, expression of Sertoli and peritubular myoid cell markers were decreased. In many cases, gonocytes failed to migrate to structurally impaired basement membranes of seminiferous cords. Developmental abnormalities of the ovary appeared earlier and were more severe. Over time, the Ft mutant ovary formed very few primordial or primary follicles, which contained oocytes that failed to grow and were surrounded by scarce granulosa cells that expressed low levels of FOXL2. By 3 wk after transplantation, it was difficult to identify ovarian tissue in Ft mutant ovary transplants. In summary, we conclude that the Ft locus contains genes essential for somatic-germ cell interactions, without which the germ cell niche fails to mature in both sexes.

Protein-fragment complementation assays for large-scale analysis, functional dissection and dynamic studies of protein-protein interactions in living cells

Protein-fragment Complementation Assays (PCAs) are a family of assays for detecting protein-protein interactions (PPIs) that have been developed to provide simple and direct ways to study PPIs in any living cell, multicellular organism, or in vitro. PCAs can be used to detect PPI between proteins of any molecular weight and expressed at their endogenous levels. Proteins are expressed in their appropriate cellular compartments and can undergo any posttranslational modification or degradation that, barring effects of the PCA fragment fusion, they would normally undergo. Assays can be performed in any cell type or model organism that can be transformed or transfected with gene expression DNA constructs. Here we focus on recent applications of PCA in the budding yeast, Saccharomyces cerevisiae, that cover the gamut of applications one could envision for studying any aspect of PPIs. We present detailed protocols for large-scale analysis of PPIs with the survival-selection dihydrofolate reductase (DHFR), reporter PCA, and a new PCA based on a yeast cytosine deaminase reporter that allows for both survival and death selection. This PCA should prove a powerful way to dissect PPIs. We then present methods to study spatial localization and dynamics of PPIs based on fluorescent protein reporter PCAs.