Apoptosis induced by human Fas-associated factor 1, hFAF1, requires its ubiquitin homologous domain, but not the Fas-binding domain

Age-dependent dynamics of neuronal VAPBALS inclusions in the adult brain

Amyotrophic Lateral Sclerosis (ALS) is a relentlessly progressive and fatal disease, caused by the degeneration of upper and lower motor neurons within the brain and spinal cord in the ageing human. The dying neurons contain cytoplasmic inclusions linked to the onset and progression of the disease. Here, we use a Drosophila model of ALS8 (VAPP58S) to understand the modulation of these inclusions in the ageing adult brain. The adult VAPP58S fly shows progressive deterioration in motor function till its demise 25 days post-eclosion. The density of VAPP58S-positive brain inclusions is stable for 5-15 days of age. In contrast, adding a single copy of VAPWT to the VAPP58S animal leads to a large decrease in inclusion density with concomitant rescue of motor function and lifespan. ER stress, a contributing factor in disease, shows reduction with ageing for the disease model. Autophagy, rather than the Ubiquitin Proteasome system, is the dominant mechanism for aggregate clearance. We explored the ability of Drosophila Valosin-containing protein (VCP/TER94), the ALS14 locus, which is involved in cellular protein clearance, to regulate age-dependent aggregation. Contrary to expectation, TER94 overexpression increased VAPP58S punctae density, while its knockdown led to enhanced clearance. Expression of a dominant positive allele, TER94R152H, further stabilised VAPP58S puncta, cementing roles for an ALS8-ALS14 axis. Our results are explained by a mechanism where autophagy is modulated by TER94 knockdown. Our study sheds light on the complex regulatory events involved in the neuronal maintenance of ALS8 aggregates, suggesting a context-dependent switch between proteasomal and autophagy-based mechanisms as the larvae develop into an adult. A deeper understanding of the nucleation and clearance of the inclusions, which affect cellular stress and function, is essential for understanding the initiation and progression of ALS.

An update on multiple system atrophy

PURPOSE OF REVIEW

Multiple system atrophy (MSA) is a rapidly progressive synucleinopathy characterized by autonomic failure, parkinsonism, and cerebellar ataxia. Here, we provide an update on α-synuclein's role in MSA pathophysiology and review the new Movement Disorders Society (MDS) diagnostic criteria and the utility of α-synuclein-based biomarkers. We also highlight ongoing efforts toward clinical trial readiness and review potential disease-modifying therapies undergoing clinical trials.

RECENT FINDINGS

A role of urinary tract infections in triggering α-synuclein aggregation and contribution of genes implicated in oligodendroglial development have been suggested in the MSA pathophysiology. The clinically probable MSA category of the new diagnostic criteria shows improved accuracy in early disease stages. Predictors of phenoconversion from pure autonomic failure to MSA are now better defined. Alpha-synuclein strains in CSF and serum, phosphorylated α-synuclein deposits in the skin, and brain α-synuclein pathology visualized using PET ligand [18F]ACI-12589 are emerging as valuable diagnostic tools. Clinical trials in MSA investigate drugs targeting α-synuclein aggregation or preventing α-synuclein expression, along with stem cell and gene therapies to halt disease progression.

SUMMARY

New MSA diagnostic criteria and α-synuclein-based biomarkers may enhance diagnostic accuracy while promising therapies are in development to address disease progression.

MiR-26a-5p Serves as an Oncogenic MicroRNA in Non-Small Cell Lung Cancer by Targeting FAF1

Purpose

Non-small cell lung cancer (NSCLC) accounts for approximately 80–85% of all lung cancers, with the FAS-associated factor 1 (FAF1) acting as a tumor suppressor. MicroRNAs (miRNAs) can influence cancer progression by targeting oncogenes or anti-oncogenes. In this study, we aimed to reveal the influence of miR-26a-5p on the regulation of FAF1 expression and NSCLC progression, with the motivation of identifying a potential therapeutic target for NSCLC treatment.

Methods

A dual-luciferase reporter assay was used to check for the direct targeting of FAF1 by miR-26a-3p. The miR-26a-5p inhibitor or FAF1 shRNA plasmid was transfected into A549 and H1299 cells to modulate FAF1 expression. Then, the effect of miR-26a-5p/FAF1 on cellular functions was investigated. MTT assay was used to evaluate cell viability. EdU proliferation assay and cell cycle assay were performed to analyze the effect of miR-26a-5p on cell replication and cell cycle. We used annexin V-FITC and PI to stain apoptotic cells, followed by flow cytometric analysis. Transwell and wound healing assays were performed to investigate metastasis. Moreover, the effect of miR-26a-5p/FAF1 on cancer progression was examined in vivo. Lastly, the underlying mechanism was uncovered using RT-qPCR, Western blotting, and TOP/FOP flash assay.

Results

miR-26a-5p was found to directly target FAF1 and downregulate its expression. Blocking miR-26a-5p inhibited the cell growth, migration, and invasion, but promoted cell apoptosis. In addition, this inhibited the growth of tumor in mice. FAF1 knockdown reversed the functions of miR-26a-5p. Further, miR-26a-5p/FAF1 was observed to play an important role in the Wnt signaling pathway, regulating the expression of genes such as AXIN, c-Myc, and cyclin-D1.

Conclusion

Taken together, we show that miR-26a-5p functions as an oncogenic microRNA in NSCLC by targeting FAF1 and may serve as a potential target for NSCLC treatment.

Novel NGLY1 gene variants in Chinese children with global developmental delay, microcephaly, hypotonia, hypertransaminasemia, alacrimia, and feeding difficulty

NGLY1 deficiency is the first and only autosomal recessive congenital disorder of N-linked deglycosylation (NGLY1-CDDG). To date, no patients with NGLY1 deficiency has been reported from mainland China or East Asia in English literature. Here, we present six patients with a diagnosis of NGLY1-CDDG on the basis of clinical phenotype, genetic testing, and functional studies. We retrospectively analyzed clinical phenotypes and NGLY1 genotypes of six cases from four families. Informed consent was obtained for diagnosis and treatment. In-silico tools and in vitro enzyme activity assays were used to determine pathogenicity of NGLY1 varaints. All patients had typical features of NGLY1-CDDG, including global developmental delay, microcephaly, hypotonia, hypertransaminasemia, alacrimia, and feeding difficulty. Dysmorphic features found in our patients include flat nasal bridge, loose and hollow cheeks, short stature, malnutrition, and ptosis. Pachylosis could be a novel cutaneous feature that may be explained by lack of sweat. We found three novel variants, including one missense (c.982C > G/p.Arg328Gly), one splice site (c.1003+3A > G), and one frame-shift (c.1637-1652delCATCTTTTGCTTATAT/p.Ser546PhefsTer) variant. All mutations were predicted to be disease causing with in-silico prediction tools, and affected at least one feature of gene splicing. Protein modeling showed missense variants may affect covalent bonding within the protein structure, or interrupt active/binding amino-acid residues. In vitro studies indicated that proteins carrying missense variants (p.Arg328Gly and p.Tyr342Cys) lost the enzyme activity. We expanded clinical phenotype and genetic mutation spectrum of NGLY1-CDDG by reporting six cases, three novel variants, and novel clinical features from mainland China.

Fas-associated factor 1 mediates NADPH oxidase-induced reactive oxygen species production and proinflammatory responses in macrophages against Listeria infection

Fas-associated factor 1 is a death-promoting protein that induces apoptosis by interacting with the Fas receptor. Until now, FAF1 was reported to interact potentially with diverse proteins and to function as a negative and/or positive regulator of several cellular possesses. However, the role of FAF1 in defense against bacterial infection remains unclear. Here, we show that FAF1 plays a pivotal role in activating NADPH oxidase in macrophages during Listeria monocytogenes infection. Upon infection by L. monocytogenes, FAF1 interacts with p67phox (an activator of the NADPH oxidase complex), thereby facilitating its stabilization and increasing the activity of NADPH oxidase. Consequently, knockdown or ectopic expression of FAF1 had a marked effect on production of ROS, proinflammatory cytokines, and antibacterial activity, in macrophages upon stimulation of TLR2 or after infection with L. monocytogenes. Consistent with this, FAF1^gt/gt mice, which are knocked down in FAF1, showed weaker inflammatory responses than wild-type mice; these weaker responses led to increased replication of L. monocytogenes. Collectively, these findings suggest that FAF1 positively regulates NADPH oxidase-mediated ROS production and antibacterial defenses.

Phagocytic NADPH oxidase plays a pivotal role in generating reactive oxygen species (ROS) and in defense against bacterial infections such as L. monocytogenes. ROS eliminate phagocytosed bacteria directly and are implicated in transduction of signals that mediate inflammatory responses. Here, we show that the apoptotic protein FAF1 regulates ROS production in macrophages by regulating phagocytic NADPH oxidase activity upon infection by L. monocytogenes. FAF1 interacts directly with and stabilizes p67phox, a regulatory protein of the phagocytic NADPH oxidase complex, to induce ROS production during L. monocytogenes infection. Production of ROS leads to release of proinflammatory cytokines, chemokines and, ultimately, to bacterial clearance. Interestingly, FAF1^gt/gt mice deficient in FAF1 expression exhibit weakened inflammatory responses and are thus more vulnerable to bacterial infection than FAF1^+/+ mice. This study reveals that FAF1 is a crucial regulator that induces inflammatory responses to bacterial infection via ROS production.

A first-in-human study to investigate the safety, tolerability, pharmacokinetics, and pharmacodynamics of KM-819 (FAS-associated factor 1 inhibitor), a drug for Parkinson's disease, in healthy volunteers

Background

KM-819 is a novel FAS-associated factor 1 (FAF1) inhibitor, and a neuroprotective agent, under clinical development for the treatment of Parkinson’s disease as a disease-modifying drug.

Methods

This first-in-human, single and multiple ascending dose study investigated the safety, tolerability, pharmacokinetics, and pharmacodynamics of KM-819 in healthy volunteers. Additionally, the effect of age on safety and pharmacokinetics were assessed. The starting dose was determined considering the no observed adverse effect level based on preclinical studies, and the dose escalations in subsequent cohorts were decided based on safety, tolerability, and pharmacokinetic data from previous dose cohorts.

Results

After a single dose, the KM-819 plasma exposure showed a less than dose-proportional increase across a dose range of 10–400 mg. After repeated dosing, KM-819 plasma exposure increased in an approximately dose-proportional manner across the evaluated dose range (30–400 mg once daily for 7 days). The mean elimination half-life was 1.8 to 4.8 h with the lower KM-819 doses (≤30 mg), which increased to around 9 h with the higher doses (100–400 mg). When administered to the elderly population, KM-819 plasma exposure increased to 102% after a 200 mg once-daily dosing for 7 days. No clear treatment-related effects on the estimated pharmacodynamic variables were observed. Single or multiple doses of KM-819 were generally well tolerated.

Conclusion

The data from this study can be used to guide rational drug dosing and choose therapeutic regimens in subsequent clinical studies.

NLRP2 and FAF1 deficiency blocks early embryogenesis in the mouse

Nlrp2 is a maternal effect gene specifically expressed by mouse ovaries; deletion of this gene from zygotes is known to result in early embryonic arrest. In the present study, we identified FAF1 protein as a specific binding partner of the NLRP2 protein in both mouse oocytes and preimplantation embryos. In addition to early embryos, both Faf1 mRNA and protein were detected in multiple tissues. NLRP2 and FAF1 proteins were co-localized to both the cytoplasm and nucleus during the development of oocytes and preimplantation embryos. Co-immunoprecipitation assays were used to confirm the specific interaction between NLRP2 and FAF1 proteins. Knockdown of the Nlrp2 or Faf1 gene in zygotes interfered with the formation of a NLRP2-FAF1 complex and led to developmental arrest during early embryogenesis. We therefore conclude that NLRP2 interacts with FAF1 under normal physiological conditions and that this interaction is probably essential for the successful development of cleavage-stage mouse embryos. Our data therefore indicated a potential role for NLRP2 in regulating early embryo development in the mouse.

Clear cell renal cell carcinoma: a comparative study of histological and chromosomal characteristics between primary tumors and their corresponding metastases

Clear cell renal cell carcinoma (ccRCC) has a poor prognosis with a 50% risk of metastases. Little is known about the phenotypic and molecular profiles of metastases regarding their corresponding primary tumors. This study aimed to screen phenotypic and genotypic differences between metastases and their corresponding primary tumors. We selected four cases with available frozen material. The histological, immunohistochemical (VEGFA, CD31, SMA, Ki67, p53, PAR-3), FISH (VHL gene), next-generation sequencing (VHL and c-MET genes), multiplex ligation-dependent probe amplification, and array-(comparative genomic hybridization) CGH analyses were realized. Metastases were nodal, hepatic (synchronous), adrenal, and pulmonary (metachronous). High-grade tumor cells were significantly more frequent in metastases (p = 0.019). Metastases and high-grade zones of primary tumors shared similar characteristics compared to low-grade zones: a lower microscopic vascular density (43.5 vs 382.5 vessels/mm²; p = 0.0027), a higher expression of VEGF (73 vs 10%, p = 0.045), Ki67 (37.6 vs 8.3%; p = 0.011), and p53 (54 vs 10.6%; p = 0.081), and a cytoplasmic and membranous PAR-3 staining. Metastases exhibited more chromosomal imbalances than primary tumors in total (18.75 ± 6.8; p = 0.044) with more genomic gains (13.5 ± 7; p = 0.013). The loss of chromosome 9 and gain of Xq were found in both primary tumors and metastases but gains of loci or chromosomes 2p, 3q, 5, 8q, 12, and 20 were only found in metastases. The VHL gene status was similar in each tumor couple. Although metastases and primary tumors share common histological features, this study highlights chromosomal differences specific to metastases which could be involved in ccRCC metastatic evolution.

XIAP Interacts with and Regulates the Activity of FAF1

Cell death depends on the balance between the activities of pro- and anti-apoptotic factors. X-linked inhibitor of apoptosis protein (XIAP) plays an important role in the cytoprotective process by inhibiting the caspase cascade and regulating pro-survival signaling pathways. While searching for novel interacting partners of XIAP, we identified Fas-associated factor 1 (FAF1). Contrary to XIAP, FAF1 is a pro-apoptotic factor that also regulates several signaling pathways in which XIAP is involved. However, the functional relationship between FAF1 and XIAP is unknown. Here, we describe a new interaction between XIAP and FAF1 and describe the functional implications of their opposing roles in cell death and NF-κB signaling. Our results clearly demonstrate the interaction of XIAP with FAF1 and define the specific region of the interaction. We observed that XIAP is able to block FAF1-mediated cell death by interfering with the caspase cascade and directly interferes in NF-κB pathway inhibition by FAF1. Furthermore, we show that XIAP promotes ubiquitination of FAF1. Conversely, FAF1 does not interfere with the anti-apoptotic activity of XIAP, despite binding to the BIR domains of XIAP; however, FAF1 does attenuate XIAP-mediated NF-κB activation. Altered expression of both factors has been implicated in degenerative and cancerous processes; therefore, studying the balance between XIAP and FAF1 in these pathologies will aid in the development of novel therapies.

Overproduction of reactive oxygen species - obligatory or not for induction of apoptosis by anticancer drugs

Many studies demonstrate that conventional anticancer drugs elevate intracellular level of reactive oxygen species (ROS) and alter redox-homeostasis of cancer cells. It is widely accepted that anticancer effect of these chemotherapeutics is due to induction of oxidative stress and ROS-mediated apoptosis in cancer. On the other hand, the harmful side effects of conventional anticancer chemotherapy are also due to increased production of ROS and disruption of redox-homeostasis of normal cells and tissues. This article describes the mechanisms for triggering and modulation of apoptosis through ROS-dependent and ROS-independent pathways. We try to answer the question: "Is it possible to induce highly specific apoptosis only in cancer cells, without overproduction of ROS, as well as without harmful effects on normal cells and tissues?" The review also suggests a new therapeutic strategy for selective killing of cancer cells, without significant impact on viability of normal cells and tissues, by combining anticancer drugs with redox-modulators, affecting specific signaling pathways and avoiding oxidative stress.

New perspectives on the mutated NGLY1 enigma

The enzyme N-glycanase 1 (NGLY1) is considered a component of the endoplasmic reticulum-associated degradation (ERAD) machinery and clinical manifestations of its dysfunction include global developmental delay, a movement disorder, peripheral neuropathy, liver disorders, microcephaly, diminished reflexes and seizures. Although several mutations in NGLY1 have been identified, the relation between the defected protein and the above described pathologies is yet unknown. We hypothesised that NGLY1 failure to degrade certain proteins may result in their accumulation and overexpression and used a systems biology approach to identify proteins that may be affected by NGLY1 deficiency. Genes that interact with the NGLY1 gene according to BioGRID database of physical and genetic interactions were analysed with STRING Protein-Protein interaction database. Network analysis identified FAF1 (Fas-Associated Factor 1), an apoptosis-potentiating protein, as a possible degradation substrate of NGLY1. Examination of normal tissue microarrays demonstrated that FAF1-to-NGLY1 ratio is maximal (more than 3:1) in skeletal muscle and brain tissues microarrays. This evidence may explain the pathologies in brain and muscle tissues of patients with mutated NGLY1. To test this hypothesis, laboratory studies that will assess if FAF1 protein is overexpressed in tissues of patients with mutated NGLY1 are required.

The expression of FAS-associated factor 1 and heat shock protein 70 in ovarian cancer

OBJECTIVE

In this study, we evaluated the expression of FAS-associated factor 1 (FAF1) and heat shock protein 70 (HSP70) in normal ovary and ovarian cancer, and also analyzed the correlation between FAF1 and HSP70 in ovarian cancer.

METHODS

The patient group consisted of 29 unrelated Korean women diagnosed as ovarian cancers and control samples were obtained from 7 patients who underwent oophorectomy for benign disease of uterus, and normal ovary was confirmed histologically from biopsy. We examined FAF1 and HSP70 expression by western blot analysis and immunohistochemical staining in normal ovary and ovarian cancer. Furthermore, we examined a correlation between FAF1 and HSP70 in ovarian cancer.

RESULTS

The expression of FAF1 was lower in ovarian cancer than that in normal ovary (P=0.02), and the expression of HSP70 was increased in ovarian cancer in comparison to that in normal ovary (P=0.03). The expression of FAF1 was decreased in advanced stages (stage III or stage IV) as compared with early stages (stage I or stage II) (P=0.01). The expression of HSP70 was not significantly related with ovarian cancer histology (P=0.10), but the expression of HSP70 was most increased with papillary serous carcinomas and undifferentiated ovarian cancer. The expression of FAF1 was inversely correlated with the expression of HSP70 in ovarian cancer (Spearman correlation coefficience=-0.47).

CONCLUSION

We concluded that the expression of FAF1 or HSP70 each seems to have a meaning as a biomarker for early detection of ovarian cancer. The expressions of FAF1 and HSP70 seem to be more valuable in predicting ovarian cancer when used together because of their inverse correlation. This is the first study about the expression of FAF1 in ovarian cancer and the correlation between FAF1 and HSP70 expression in ovarian cancer.

Fas-associated factor (Faf1) is a novel CD40 interactor that regulates CD40-induced NF-κB activation via a negative feedback loop

CD40-induced signalling through ligation with its natural ligand (CD40L/CD154) is dependent on recruitment of TRAF molecules to the cytoplasmic domain of the receptor. Here, we applied the yeast two-hybrid system to examine whether other proteins can interact with CD40. Fas-Associated Factor 1(FAF1) was isolated from a HeLa cDNA library using the CD40 cytoplasmic tail (216–278 aa) as a bait construct. FAF1 was able to interact with CD40 both in vitro and in vivo. The FAF1 N-terminal domain was sufficient to bind CD40 and required the TRAF6-binding domain within the cytoplasmic tail of CD40 for binding. CD40 ligation induced FAF1 expression in an NFκB-dependent manner. Knockdown of FAF1 prolonged CD40-induced NFκB, whereas overexpression of FAF1 suppressed CD40-induced NFκB activity and this required interaction of FAF1 with the CD40 receptor via its FID domain. Thus, we report a novel role for FAF1in regulating CD40-induced NFκB activation via a negative feedback loop. Loss of FAF1 function in certain human malignancies may contribute to oncogenesis through unchecked NFκB activation, and further understanding of this process may provide a biomarker of NFκB-targeted therapies for such malignancies.

High entomotoxicity and mechanism of the fungal GalNAc/Gal-specific Rhizoctonia solani lectin in pest insects

Whole insect assays where Rhizoctonia solani agglutinin (RSA) was fed to larval stages of the cotton leaf-worm Spodoptera littoralis and the pea aphid Acyrthosiphon pisum demonstrated a high concentration-dependent entomotoxicity, suggesting that this GalNAc/Gal-specific fungal lectin might be a good control agent for different pest insects. RSA at 10 mg/g in the solid diet of 2nd-instar caterpillars caused 84% weight reduction after 8 days with none of the caterpillars reaching the 4th-instar stage. In sucking aphids, 50% mortality was achieved after 3 days with 9 μM of RSA in the liquid diet. Feeding of FITC-labeled RSA to both insect pest species revealed strong lectin binding at the apical/luminal side of the midgut epithelium with the brush border zone, suggesting the insect midgut as a primary insecticide target tissue for RSA. This was also confirmed with cell cultures in vitro, where there was high fluorescence binding at the microvillar zone with primary cultures of larval midgut columnar cells of S. littoralis, and also at the surface with the insect midgut CF-203 cell line without lectin uptake in the midgut cells. In vitro assays using insect midgut CF-203 cells, revealed that RSA was highly toxic with an EC50 of 0.3 μM. Preincubation with GalNAc and saponin indicated that this action of RSA was carbohydrate-binding dependent and happened at the surface of the cells. Intoxicated CF-203 cells showed symptoms of apoptosis as nuclear condensation and DNA fragmentation, and this concurred with an increase of caspase-3/7, -8 and -9 activities. Finally, RSA affinity chromatography of membrane extracts of CF-203 cells followed by LC-MS/MS allowed the identification of 5747 unique peptides, among which four putatively glycosylated membrane proteins that are associated with apoptosis induction, namely Fas-associated factor, Apoptosis-linked gene-2, Neuroglian and CG2076, as potential binding targets for RSA. These data are discussed in relation to the physiological effects of RSA.

Association of MicroRNA-146a with autoimmune diseases

MicroRNAs (miRNAs) are a group of approximately 20-22-nucleotide-long non-coding RNAs that repress target gene expression through mRNA degradation and translation inhibition. MiRNA (miR)-146a, located in the second exon of the LOC285628 gene on human chromosome 5, is a negative regulator in immune and inflammatory responses. Studies have indicated that miR-146a is associated with the pathogenesis of several autoimmune diseases, such as systemic lupus erythematosus, rheumatoid arthritis, and Sjögren's syndrome. In this review, emphasis will be laid on the recent progress in the functional roles of miR-146a in these autoimmune diseases.

Accumulation of the parkin substrate, FAF1, plays a key role in the dopaminergic neurodegeneration

This study reports the physical and functional interplay between Fas-associated factor 1 (FAF1), a death-promoting protein, and parkin, a key susceptibility protein for Parkinson's disease (PD). We found that parkin acts as an E3 ubiquitin ligase to ubiquitinate FAF1 both in vitro and at cellular level, identifying FAF1 as a direct substrate of parkin. The loss of parkin function due to PD-linked mutations was found to disrupt the ubiquitination and degradation of FAF1, resulting in elevated FAF1 expression in SH-SY5Y cells. Moreover, FAF1-mediated cell death was abolished by wild-type parkin, but not by PD-linked parkin mutants, implying that parkin antagonizes the death potential of FAF1. This led us to investigate whether FAF1 participates in the pathogenesis of PD. To address this, we used a gene trap mutagenesis approach to generate mutant mice with diminished levels of FAF1 (Faf1(gt/gt)). Using the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-treated mouse model of PD, we found that FAF1 accumulated in the substantia nigra pars compacta (SNc) of MPTP-treated PD mice, and that MPTP-induced dopaminergic cell loss in the SNc was significantly attenuated in Faf1(gt/gt) mice versus Faf1(+/+) mice. MPTP-induced reduction of locomotor activity was also lessened in Faf1(gt/gt) mice versus Faf1(+/+) mice. Furthermore, we found that FAF1 deficiency blocked PD-linked biochemical events, including caspase activation, ROS generation, JNK activation and cell death. Taken together, these results suggest a new role for FAF1: that of a positive modulator for PD.

Reduced FAF1 Expression and Helicobacter Infection: Correlations with Clinicopathological Features in Gastric Cancer

Background. This study aimed to investigate possible associations between FAF1 expression and aspects of gastric cancer, in particular its clinical characteristics and Helicobacter infection. Materials and Methods. RT-PCR and immunohistochemistry were used to analyze expression of FAF1 mRNA and protein in 40 gastric cancer patients. H. pylori infection was detected by three staining protocols. Results. The expression level of FAF1 mRNA was significantly lower in gastric cancer tissue than in normal gastric mucosa from the same patient (P < 0.05). FAF1 mRNA expression was significantly lower in stage IV gastric cancer than in stage I+II or IIIA+IIIB (P = 0.004) and also significantly lower in gastric cancer with distant metastasis. FAF1 mRNA expression was higher in well-differentiated cancer than in poorly-differentiated cancer (0.39 ± 0.06 versus 0.19 ± 0.06, t = 9.966, P < 0.01). FAF1 protein was detected in 15 of 40 (37.5%) cancerous tissue samples and in 29 of 40 (72.5%) corresponding normal tissue samples (P < 0.01). FAF1 mRNA expression was lower in H. pylori-positive cancerous tissue samples than in H. pylori-negative ones (P < 0.05). Conclusions. Downregulation of FAF1 expression may be related to the carcinogenesis and progression of gastric cancer, and H. pylori infection during gastric carcinogenesis may downregulate FAF1 expression.

Ubiquitin-associated (UBA) domain in human Fas associated factor 1 inhibits tumor formation by promoting Hsp70 degradation

Human Fas associated factor 1 (hFAF1) is a pro-apoptotic scaffolding protein containing ubiquitin-associating (UBA), ubiquitin like 1 and 2 (UBL1, UBL2), and ubiquitin regulatory X (UBX) domains. hFAF1 interacts with polyubiquitinated proteins via its N-terminal UBA domain and with valosin containing protein (VCP) via its C-terminal UBX domain. Overexpression of hFAF1 or its N-terminal UBA domain significantly increases cell death by increasing the degradation of polyubiquitinated proteins. In this study, we investigated whether hFAF1, whose expression level is reduced in cervical cancer, plays a role in tumor formation. We found that HeLa cells overexpressing full-length hFAF1 or the hFAF1 UBA domain alone, significantly suppressed the anchorage independent tumor growth in soft agar colony formation, increased cell death, and activated JNK and caspase 3. Employing UBA-specific tandem immunoprecipitation, we identified moieties specifically interacting with UBA domain of hFAF1, and found that polyubiquitinated Hsp70s are recruited to UBA domain. We also demonstrated that hFAF1 overexpression promotes Hsp70 degradation via the proteasome. We further found that mutating the UBA domain (I41N), as well as knocking down hFAF1 with specific RNAi, abolishs its ability to increase the proteasomal degradation of Hsp70. These findings suggest that hFAF1 inhibits tumor formation by increasing the degradation of Hsp70 mediated via its UBA domain.

Fas-associated factor 1 as a regulator of olfactory axon guidance

Axon guidance is a crucial part of neural circuit formation. While precise axonal targeting forms the basis of accurate information delivery, the mechanisms that regulate this process are still unclear. Apoptotic signaling molecules have been identified in the axon terminal, but their specific role in axon guidance is not well understood. Here we use the mouse olfactory system as an in vivo model to demonstrate that by modulating Fas-associated factor 1 (FAF1), an apoptosis regulatory molecule, we can rewire axonal projections. Interestingly, FAF1 is highly expressed in the developing mouse olfactory system, but its expression is downregulated postnatally. Using a tetracycline-inducible promoter Tet-Off system, we generated transgenic mice in which FAF1 is specifically expressed in immature olfactory sensory neurons (OSNs) and show that overexpression of FAF1 not only misroutes OSN axons to deep layers of the olfactory bulb but also leads to widespread disruption of the glomerular layer. In addition, we also demonstrate that the specific convergence of P2 receptor OSN axons is completely distorted in the FAF1 mice. Strikingly, all of the mutant phenotypes can be recovered by shutting down FAF1 expression through the administration of doxycycline. Together, our study provides clear in vivo evidence that an apoptotic molecule can indeed regulate axon targeting and that OSNs can restore their organization even after broad disruption.

Altered microRNA expression profile with miR-146a upregulation in CD4+ T cells from patients with rheumatoid arthritis

Introduction

Increasing evidence indicates that microRNAs (miRNAs) play a critical role in the pathogenesis of inflammatory diseases. The aim of the study was to investigate the expression pattern and function of miRNAs in CD4⁺ T cells from patients with rheumatoid arthritis (RA).

Methods

The expression profile of miRNAs in CD4⁺ T cells from synovial fluid (SF) and peripheral blood of 33 RA patients was determined by microarray assay and validated by qRT-PCR analysis. The correlation between altered expression of miRNAs and cytokine levels was determined by linear regression analysis. The role of miR-146a overexpression in regulating T cell apoptosis was evaluated by flow cytometry. A genome-wide gene expression analysis was further performed to identify miR-146a-regulated genes in T cells.

Results

miRNA expression profile analysis revealed that miR-146a expression was significantly upregulated while miR-363 and miR-498 were downregulated in CD4⁺ T cells of RA patients. The level of miR-146a expression was positively correlated with levels of tumor necrosis factor-alpha (TNF-α), and in vitro studies showed TNF-α upregulated miR-146a expression in T cells. Moreover, miR-146a overexpression was found to suppress Jurkat T cell apoptosis. Finally, transcriptome analysis of miR-146a overexpression in T cells identified Fas associated factor 1 (FAF1) as a miR-146a-regulated gene, which was critically involved in modulating T cell apoptosis.

Conclusions

We have detected increased miR-146a in CD4⁺ T cells of RA patients and its close correlation with TNF-α levels. Our findings that miR-146a overexpression suppresses T cell apoptosis indicate a role of miR-146a in RA pathogenesis and provide potential novel therapeutic targets.

miR-24 regulates apoptosis by targeting the open reading frame (ORF) region of FAF1 in cancer cells

Background

microRNAs (miRNAs) are small noncoding RNAs that regulate cognate mRNAs at the post-transcriptional stage. Several studies have shown that miRNAs modulate gene expression in mammalian cells by base pairing to complementary sites in the 3′-untranslated region (3′-UTR) of the target mRNAs.

Methodology/Principal Findings

In the present study, miR-24 was found to target fas associated factor 1(FAF1) by binding to its amino acid coding sequence (CDS) region, thereby regulating apoptosis in DU-145 cells. This result supports an augmented model whereby animal miRNAs can exercise their effects through binding to the CDS region of the target mRNA. Transfection of miR-24 antisense oligonucleotide (miR-24-ASO) also induced apoptosis in HGC-27, MGC-803 and HeLa cells.

Conclusions/Significance

We found that miR-24 regulates apoptosis by targeting FAF1 in cancer cells. These findings suggest that miR-24 could be an effective drug target for treatment of hormone-insensitive prostate cancer or other types of cancers. Future work may further develop miR-24 for therapeutic applications in cancer biology.

FAS-associated factor 1 (FAF1): diverse functions and implications for oncogenesis

FAS-associated factor 1, FAF1, is an evolutionarily conserved protein that has several protein interaction domains. Although FAF1 was initially identified as a member of the FAS death-inducing signaling complex, subsequent work has revealed that FAF1 functions in diverse biological processes. FAF1 has been shown to play an important role in normal development and neuronal cell survival, whereas FAF1 downregulation may contribute to multiple aspects of tumorigenesis. In particular, there is compelling evidence implicating FAF1 as a tumor suppressor involved in the regulation of apoptosis and NFkappaB activity, as well as in ubiquitination and proteasomal degradation. Here, we highlight FAF1's role in NFkappaB signaling and postulate that this pathway has critical connotations for the pathogenesis and treatment of human cancers.

Fas-associated factor 1 is a negative regulator in capsaicin induced cancer cell apoptosis

Vanilloid receptor1 (VR1/TRPV1) is expressed on peripheral nerves and involved in sensing of temperature and pain. Recent reports have demonstrated that tumor cells express TRPV1 and that capsaicin (CP), a ligand for TRPV1, induces apoptosis in cancer cells. The mechanism underlying CP-induced tumor cell apoptosis remains unclear. Here, we investigated the role of TRPV1 in tumor apoptosis using TRPV1-expressing cancer cell lines. We demonstrate that iodo-resiniferatoxin (I-RTX), an antagonist of TRPV1 does not inhibit CP mediated apoptosis nor is it cytotoxic by itself, but acts as a partial agonist and shows synergistic effect with CP. We further demonstrate that CP treatment degrades Fas-associated factor1 (FAF1); a TRPV1 associated protein. Moreover, using RNA interference with small inhibitory RNAs (siRNA) for FAF1 we observed that down-regulation of FAF1 by siRNA makes the cell susceptible to enhanced apoptosis with CP. In summary, our data shows for the first time that the underlying mechanisms of CP-induced cancer cell apoptosis involves FAF1, a TRPV1 associated protein and serves as an important foundation for further understanding of anticancer activity of CP.

Fas-associated factor 1 and Parkinson's disease

Fas-associated factor 1 or FAF1 is a Fas-binding protein implicated in apoptosis. FAF1 is the product of a gene at PARK 10 locus on chromosome 1p32, a locus associated with late-onset PD [Hicks, A.A., Petursson, H., Jonsson, T., Stefansson, H., Johannsdottir, H.S., Sainz, J., Frigge, M.L.et al., 2002. A susceptibility gene for late-onset idiopathic Parkinson's disease. Ann Neurol. 52, 549-555.]. In the present study we investigated the role of FAF1 in cell death and in Parkinson's disease (PD) pathogenesis. FAF1 levels were significantly increased in frontal cortex of PD as well as in PD cases with Alzheimer's disease (AD) pathology compared to control cases. Changes in FAF1 expression were specific to PD-related alpha-synuclein pathology and nigral cell loss. In addition, PD-related insults including, mitochondrial complex I inhibition, oxidative stress, and increased alpha-synuclein expression specifically increased endogenous FAF1 expression in vitro. Increased FAF1 levels induced cell death and significantly potentiated toxic effects of PD-related stressors including, oxidative stress, mitochondrial complex I inhibition and proteasomal inhibition. These studies, together with previous genetic linkage studies, highlight the potential significance of FAF1 in pathogenesis of idiopathic PD.

FAF1 suppresses IkappaB kinase (IKK) activation by disrupting the IKK complex assembly

This study presents a molecular inhibitory mechanism by Fas-associated factor 1 (FAF1) on IkappaB kinase (IKK) activation, where divergent NF-kappaB-activating stimuli converge. FAF1 interacts with IKKbeta in response to proinflammatory stimuli (such as tumor necrosis factor-alpha, interleukin-1beta, and lipopolysaccharide) and suppresses IKK activation. Interaction of the leucine-zipper domain of IKKbeta with FAF1 affected the IKK heterocomplex (IKKalpha/beta) and homocomplex (IKKalpha/alpha, IKKbeta/beta) formations and attenuated IKKgamma recruitment to IKKbeta. Overexpression of FAF1 reduced the level of IKKbeta activity, whereas FAF1 depletion increased the activity. These results indicate that FAF1 inhibits IKK activation and its downstream signaling by interrupting the IKK complex assembly through physical interaction with IKKbeta. Taken together, FAF1 robustly suppresses NF-kappaB activation through the inhibition of IKK activation in combination with previously reported cytoplasmic retention of NF-kappaB p65 (Park, M. Y., Jang, H. D., Lee, S. Y., Lee, K. J., and Kim, E. (2004) J. Biol. Chem. 279, 2544-2549). Such redundant suppression would prevent inadvertent activation of the NF-kappaB pathway.

Fas-associated factor-1 mediates chemotherapeutic-induced apoptosis via death effector filament formation

Fas-associated factor-1 (FAF1) is a newly introduced member of the Fas death-inducing signaling complex and potentiates Fas-mediated apoptosis. Clinical study has revealed that FAF1 is significantly reduced in gastric carcinomas. The present study demonstrates that FAF1 mediates chemotherapeutic-induced apoptosis via participation in the formation of death effector filament (DEF), a cytoskeleton-like structure found in receptor-independent apoptosis. Overexpression of FAF1 enhanced DEF assembly and cell death induced by chemotherapeutics such as staurosporine (STS), cisplatin (CDDP) and etoposide (VP16). FAF1 sensitized cells to STS, CDDP and VP16 in dose- and time-dependent manner. Introduction of antisense FAF1 construct inhibited DEF assembly and chemotherapeutic-induced apoptosis. Analysis using FAF1 truncates showed that the FAF1 domain interacting with DEDs of FADD and caspase-8 was sufficient to enhance DEF assembly. Confocal microscopy revealed that FAF1 was present in DEFs together with FADD and caspase-8. Collectively, our data provide a molecular mechanism for the chemosensitization by FAF1 (i.e., mediating DEF assembly).

Human Fas-associated factor 1 interacts with heat shock protein 70 and negatively regulates chaperone activity

We examined the cell death-inducing property of human Fas-associated factor 1 (hFAF1) in the heat shock signaling pathway. By employing co-immunoprecipitation and peptide mass fingerprinting using matrix-assisted laser desorption ionization time-of-flight mass spectrometry, we found that hFAF1 binds to the 70-kDa heat shock protein family (Hsc70/Hsp70). Interaction mapping indicated that the 82-180 sequence of hFAF1 directly binds to the N-terminal region containing sequence 1-120 of Hsc70/Hsp70. This binding is very tight regardless of ATP and heat shock treatment. Hsc70/Hsp70 and hFAF1 co-localized in the cytosol and nucleus and concentrated to the perinuclear region by heat shock treatment. We examined how hFAF1 regulates Hsp70 function, and found that hFAF1 inhibited the Hsp70 chaperone activity of refolding denatured protein substrates, accelerated heat shock-induced SAPK/JNK activation, and raised heat shock-induced cell death in a binding dependent manner. These results suggest that hFAF1 prevents cells from recovery after stress by binding to and inhibiting the chaperone activity of Hsp70.

Integral UBL domain proteins: a family of proteasome interacting proteins

The family of ubiquitin-like (UBL) domain proteins (UDPs) comprises a conserved group of proteins involved in a multitude of different cellular activities. However, recent studies on UBL-domain proteins indicate that these proteins appear to share a common property in their ability to interact with 26S proteasomes. The 26S proteasome is a multisubunit protease which is responsible for the majority of intracellular proteolysis in eukaryotic cells. Before degradation commences most proteins are first marked for destruction by being coupled to a chain of ubiquitin molecules. Some UBL-domain proteins catalyse the formation of ubiquitin-protein conjugates, whereas others appear to target ubiquitinated proteins for degradation and interact with chaperones. Hence, by binding to the 26S proteasome the UBL-domain proteins seem to tailor and direct the basic proteolytic functions of the particle to accommodate various cellular substrates.

The Ubx2 and Ubx3 cofactors direct Cdc48 activity to proteolytic and nonproteolytic ubiquitin-dependent processes

Valosin-containing protein, VCP/p97 or Cdc48, is a eukaryotic ATPase involved in membrane fusion, protein transport, and protein degradation. We describe two proteins, Ubx2 and Ubx3, which interact with Cdc48 in fission yeast. Ubx3 is the ortholog of p47/Shp1, a previously described Cdc48 cofactor involved in membrane fusion, whereas Ubx2 is a novel protein. Cdc48 binds the UBX domains present in both Ubx2 and Ubx3, indicating that this domain is a general Cdc48-interacting module. Ubx2 and Ubx3 also interact with ubiquitin chains. Disruption of the ubx3(+)-gene causes both temperature and canavanine sensitivity and stabilizes some ubiquitin-protein conjugates including the CDK inhibitor Rum1, but not a model substrate of the ER-degradation pathway. Moreover the ubx3 null displays synthetic lethality with a pus1 null mutant, a multiubiquitin binding subunit of the 26S proteasome. In contrast, the ubx2 null mutant did not display any obvious protein-degradation phenotype. In conclusion Ubx3/p47 is not, as previously thought, only important for membrane fusion; it's also important for the specific degradation of a subset of cell proteins. Our genetic analyses revealed that Ubx3/p47 functionally parallels a substrate receptor of the 26S proteasome, Pus1/Rpn10, indicating that the Cdc48-Ubx3 complex is involved in delivering substrates to the 26S proteasome.

Live and let die: regulatory mechanisms in Fas-mediated apoptosis

Activation of Fas receptor by Fas ligand causes caspase 8 activation and apoptosis in cells and is an important mechanism by which normal tissue homeostasis and function are maintained. Activation of caspase 8 is preceded by the formation of a death-inducing signalling complex (DISC), and a number of redundant mechanisms regulate DISC formation in vivo. Fas receptor is widely expressed in tissues, and dysfunction of the regulatory mechanisms in Fas receptor signalling has been reported in several diseases including autoimmune disease and cancer. This review aims to identify and discuss the various mechanisms employed by cells to alter their sensitivity to Fas-mediated apoptosis by regulating DISC formation. We also discuss a number of defects identified with Fas receptor signalling and the associated pathologies.

Fas-associated factor-1 inhibits nuclear factor-kappaB (NF-kappaB) activity by interfering with nuclear translocation of the RelA (p65) subunit of NF-kappaB

Fas-associated factor-1 (FAF1) is a Fas-binding pro-apoptotic protein that is a component of the death-inducing signaling complex in Fas-mediated apoptosis. Here, we show that FAF1 is involved in negative regulation of NF-kappaB activation. Overexpression of FAF1 decreased the basal level of NF-kappaB activity in 293 cells. NF-kappaB activation induced by tumor necrosis factor (TNF)-alpha, interleukin-1beta, and lipopolysaccharide was also inhibited by FAF1 overexpression. Moreover, FAF1 suppressed NF-kappaB activation induced by transducers of diverse NF-kappaB-activating signals such as TNF receptor-associated factor-2 and -6, MEKK1, and IkappaB kinase-beta as well as NF-kappaB p65, one of the end point molecules in the NF-kappaB activation pathway, suggesting that NF-kappaB p65 might be a target molecule upon which FAF1 acts. Subsequent study disclosed that FAF1 physically interacts with NF-kappaB p65 and that the binding domain of FAF1 is the death effector domain (DED)-interacting domain (amino acids 181-381), where DEDs of the Fas-associated death domain protein and caspase-8 interact. The NF-kappaB activity-modulating potential of FAF1 was also mapped to the DED-interacting domain. Finally, overexpression of FAF1 prevented translocation of NF-kappaB p65 into the nucleus and decreased its DNA-binding activity upon TNFalpha treatment. This study presents a novel function of FAF1, in addition to the previously known function as a component of the Fas death-inducing signaling complex, i.e. NF-kappaB activity suppressor by cytoplasmic retention of NF-kappaB p65 via physical interaction.

Protein kinase CK2 phosphorylates the Fas-associated factor FAF1 in vivo and influences its transport into the nucleus

We previously identified the Fas-associated factor FAF1 as an in vitro substrate of protein kinase CK2 and determined Ser289 and Ser291 as phosphorylation sites. Here we demonstrate that these two serine residues are the only sites phosphorylated by CK2 in vitro, and that at least one site is phosphorylated in vivo. Furthermore, we analyzed putative physiological functions of FAF1 phosphorylation. The ability of FAF1 to potentiate Fas-induced apoptosis is not influenced by the FAF1 phosphorylation status; however, the nuclear import of a phosphorylation-deficient FAF1 mutant was delayed in comparison to wild-type FAF1.

Fas-associated factor 1, FAF1, is a member of Fas death-inducing signaling complex

FAF1 has been introduced as a Fas-binding protein. However, the function of FAF1 in apoptotic execution is not established. Based on the fact that FAF1 is a Fas-binding protein, we asked if FAF1 interacted with other members of the Fas-death-inducing signaling complex (Fas-DISC) such as Fas-associated death domain protein (FADD) and caspase-8. FAF1 could interact with caspase-8 and FADD in vivo as well as in vitro. The death effector domains (DEDs) of caspase-8 and FADD interacted with the amino acid 181-381 region of FAF1, previously known to have apoptotic potential. Considering that FAF1 directly binds to Fas and caspase-8, FAF1 shows similar protein-interacting characteristics to that of FADD. In the coimmunoprecipitation with an anti-Fas antibody (APO-1) in Jurkat cells, endogenous FAF1 was associated with the precipitates in which caspase-8 was present. By confocal microscopic analysis, both Fas and FAF1 were detected in the cytoplasmic membrane before Fas activation, and in the cytoplasm after Fas activation. FADD and caspase-8 colocalized with Fas in Jurkat cells validating the presence of FAF1 in the authentic Fas-DISC. Overexpression of FAF1 in Jurkat cells caused significant apoptotic death. In addition, the FAF1 deletion mutant lacking the N terminus where Fas, FADD, and caspase-8 interact protected Jurkat cells from Fas-induced apoptosis demonstrating dominant-negative phenotype. Cell death by overexpression of FAF1 was suppressed significantly in both FADD- and caspase-8-deficient Jurkat cells when compared with that in their parental Jurkat cells. Collectively, our data show that FAF1 is a member of Fas-DISC acting upstream of caspase-8.

Regulation of apoptosis: the ubiquitous way

Ubiquitin is a ubiquitously expressed 76 amino acid protein that can be covalently attached to target proteins, leading to their ubiquitination. Many ubiquitinated proteins are degraded by the proteasome, a 2000 kDa ATP-dependent proteolytic complex. Numerous studies have demonstrated that the ubiquitination and proteasome system plays an important role in controlling the levels of various cellular proteins and therefore regulates basic cellular processes such as cell cycle progression, signal transduction, and cell transformation. Ubiquitination also directly affects the function and location of target proteins. Recent studies found that ubiquitination-mediated degradation and change in activity regulate many molecules of the cell death machinery, such as p53, caspases, and Bcl-2 family members. Ring finger-containing members of the IAP (inhibitor of apoptosis) family proteins themselves can function as ubiquitin protein ligases to ubiquitinate their target proteins or promote autoubiquitination. It has been demonstrated that degradation of the IAP proteins is required for apoptosis to occur in some systems, indicating apoptosis proceeds by activating death pathways as well as eliminating "roadblocks" through ubiquitination. These new findings also suggest that ubiquitination is one of the major mechanisms that regulate apoptotic cell death and could be a unique target for therapeutic intervention.

Cloning and characterization of the highly expressed ETEA gene from blood cells of atopic dermatitis patients

Analysis of patients with atopic dermatitis (AD) for differential expression of genes, as compared to normal individuals, will be useful for understanding the molecular pathogenesis of AD. We found that the expression of the gene ETEA in human peripheral blood CD3-positive cells from patients with atopic dermatitis was significantly higher than in normal individuals. Eosinophils from AD patients expressed ETEA at a significantly higher level than the healthy controls. The overall sequence of the 445 aa deduced polypeptide from the cloned ETEA cDNA showed homology to human Fas-associated factor 1 (FAF1), which is involved in Fas-mediated apoptosis. However, the interaction of ETEA with the Fas death domain was weaker than that of FAF1, as studied in yeast two-hybrid experiments. The ETEA-EGFP fusion protein was expressed in cytoplasm. During the course of activation-induced cell death of primary T cells, transcription levels of ETEA and FAF1 were upregulated with similar kinetics. The enhanced expression of ETEA may play a role in the regulating the resistance to apoptosis that is observed in T cells and eosinophils of AD patients.