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

Messages in CD40L are encrypted for residue-specific functions

CD40-CD40-ligand (CD40L) interaction plays crucial immunoregulatory roles, as CD40 signals through different signaling intermediates to convert the messages from CD40L to effector functions. Being a TNFα receptor family member, CD40 binds TNFα receptor-associated factors, assembles signalosome complexes and decrypts the messages from CD40L through different signaling modules to result in residue-specific effector functions. The evidence for such a residue-specific message encryption first came from the CD40L mutations resulting in X-linked hyper-IgM syndrome, as the extent of effects varied with the residue mutated. The structural studies on the CD40-CD40L interaction implied differential involvement of the interacting residues on CD40L in influencing the effector functions. Three lines of evidence indicate the previously implied residue-specific message encryption in CD40L: screening of a dodecameric peptide library for CD40 binders identified two peptides with different sequences resulting in counteractive effector functions in macrophages; a series of CD40L mutants identified that the mutations in these residues selectively affected CD40 signaling and macrophage effector functions; and, a panel of 40-mer peptides, representing the CD40-interacting domain of mouse CD40L, with single substitutions resulted in altered CD40 signaling through various signaling intermediates and effector functions in mouse macrophages. We therefore construct the first-ever message encryption-decryption in a biological receptor-ligand system wherein the CD40L residues that interact with CD40 residues have encrypted messages, which are decoded by CD40 signaling to result in residue-specific effector functions. This review presents a novel perspective of receptor-ligand interaction as a system of message transmission, message decoding by signaling, and its transcription to various read-outs. [250 words].

Reactive oxygen species in biological systems: Pathways, associated diseases, and potential inhibitors-A review

Reactive oxygen species (ROS) are produced under normal physiological conditions and may have beneficial and harmful effects on biological systems. ROS are involved in many physiological processes such as differentiation, proliferation, necrosis, autophagy, and apoptosis by acting as signaling molecules or regulators of transcription factors. In this case, maintaining proper cellular ROS levels is known as redox homeostasis. Oxidative stress occurs because of the imbalance between the production of ROS and antioxidant defenses. Sources of ROS include the mitochondria, auto-oxidation of glucose, and enzymatic pathways such as nicotinamide adenine dinucleotide phosphate reduced (NAD[P]H) oxidase. The possible ROS pathways are NF-κB, MAPKs, PI3K-Akt, and the Keap1-Nrf2-ARE signaling pathway. This review covers the literature pertaining to the possible ROS pathways and strategies to inhibit them. Additionally, this review summarizes the literature related to finding ROS inhibitors.

FAF1 Gene Involvement in Pituitary Corticotroph Tumors

Cushing's disease (CD) is caused by rare pituitary corticotroph tumors that lead to corticotropin (ACTH) excess. Variants in FAF1, a pro-apoptotic protein involved in FAS-induced cell death, have been implicated in malignant disorders but the involvement of FAF1 in pituitary tumors has not been studied. Genetic data from patients with CD were reviewed for variants in FAF1 gene. Knockout mice (KO) were followed to assess the development of any pituitary disorder or cortisol excess. AtT-20 cells were used to study the effects of the variants of interest on ACTH secretion and cell proliferation. Three variants of interest were identified in 5 unique patients, two of which had rare allele frequency in genomic databases and were predicted to be likely pathogenic. KO mice were followed over time and no difference in their length/weight was noted. Additionally, KO mice did not develop any pituitary lesions and retained similar corticosterone secretion with wild type. AtT-20 cells transfected with FAF1 variants of interest or WT expression plasmids showed no significant difference in cell death or Pomc gene expression. However, in silico prediction models suggested significant differences in secondary structures of the produced proteins. In conclusion, we identified two FAF1 variants in patients diagnosed with CD with a potential pathogenic effect on the protein function and structure. Our in vitro and in vivo studies did not reveal an association of FAF1 defects with pituitary tumorigenesis and further studies may be needed to understand any association.

Candidate Biomarkers for Specific Intraoperative Near-Infrared Imaging of Soft Tissue Sarcomas: A Systematic Review

Simple Summary

Near-infrared imaging of tumors during surgery facilitates the oncologic surgeon to distinguish malignant from healthy tissue. The technique is based on fluorescent tracers binding to tumor biomarkers on malignant cells. Currently, there are no clinically available fluorescent tracers that specifically target soft tissue sarcomas. This review searched the literature to find candidate biomarkers for soft tissue sarcomas, based on clinically used therapeutic antibodies. The search revealed 7 biomarkers: TEM1, VEGFR-1, EGFR, VEGFR-2, IGF-1R, PDGFRα, and CD40. These biomarkers are abundantly present on soft tissue sarcoma tumor cells and are already being targeted with humanized monoclonal antibodies. The conjugation of these antibodies with a fluorescent dye will yield in specific tracers for image-guided surgery of soft tissue sarcomas to improve the success rates of tumor resections.

Abstract

Surgery is the mainstay of treatment for localized soft tissue sarcomas (STS). The curative treatment highly depends on complete tumor resection, as positive margins are associated with local recurrence (LR) and prognosis. However, determining the tumor margin during surgery is challenging. Real-time tumor-specific imaging can facilitate complete resection by visualizing tumor tissue during surgery. Unfortunately, STS specific tracers are presently not clinically available. In this review, STS-associated cell surface-expressed biomarkers, which are currently already clinically targeted with monoclonal antibodies for therapeutic purposes, are evaluated for their use in near-infrared fluorescence (NIRF) imaging of STS. Clinically targeted biomarkers in STS were extracted from clinical trial registers and a PubMed search was performed. Data on biomarker characteristics, sample size, percentage of biomarker-positive STS samples, pattern of biomarker expression, biomarker internalization features, and previous applications of the biomarker in imaging were extracted. The biomarkers were ranked utilizing a previously described scoring system. Eleven cell surface-expressed biomarkers were identified from which 7 were selected as potential biomarkers for NIRF imaging: TEM1, VEGFR-1, EGFR, VEGFR-2, IGF-1R, PDGFRα, and CD40. Promising biomarkers in common and aggressive STS subtypes are TEM1 for myxofibrosarcoma, TEM1, and PDGFRα for undifferentiated soft tissue sarcoma and EGFR for synovial sarcoma.

A novel function of FAF1, which induces dopaminergic neuronal death through cell-to-cell transmission

Background

Fas-associated factor 1 (FAF1) has been implicated in Parkinson’s disease (PD) and activates the cell death machinery in the cytosol. However, the presence of extracellular FAF1 has not been studied.

Methods

Serum-free conditioned medium (CM) from FAF1-transfected SH-SY5Y cells was concentrated and analyzed by western blotting. Exosomes were isolated from CM by ultracentrifugation and analyzed by western blotting, electron microscopy and nanoparticle tracking analysis. Soluble FAF1 from CM was immunodepleted using anti-FAF1 antibody. Transmission of secreted FAF1 was examined by transwell assay under a confocal microscope. CM-induced cell death was determined by measuring propidium iodide (PI) uptake using a flow cytometer.

Results

FAF1 was secreted from SH-SY5Y cells via exocytosis and brefeldin A (BFA)-resistant secretory pathways. Furthermore, FAF1 was secreted as a vesicle-free form and a genuine exosome cargo in the lumen of exosomes. In addition, FAF1 increased the number of exosomes, suggesting a regulatory role in exosome biogenesis. Extracellular FAF1 was transmitted via endocytosis to neighboring cells, where it induced cell death through apoptotic and necrotic pathways.

Conclusions

This study presents a novel route by which FAF1 induces neuronal death through cell-to-cell transmission.

The Hexavalent CD40 Agonist HERA-CD40L Induces T-Cell-mediated Antitumor Immune Response Through Activation of Antigen-presenting Cells

CD40 ligand (TNFSF5/CD154/CD40L), a member of the tumor necrosis factor (TNF) superfamily is a key regulator of the immune system. The cognate receptor CD40 (TNFRSF5) is expressed broadly on antigen-presenting cells and many tumor types, and has emerged as an attractive target for immunologic cancer treatment. Most of the CD40 targeting drugs in clinical development are antibodies which display some disadvantages: their activity typically depends on Fcγ receptor-mediated crosslinking, and depletion of CD40-expressing immune cells by antibody-dependent cellular cytotoxicity compromises an efficient antitumor response. To overcome the inadequacies of antibodies, we have developed the hexavalent receptor agonist (HERA) Technology. HERA compounds are fusion proteins composed of 3 receptor binding domains in a single chain arrangement, linked to an Fc-silenced human IgG1 thereby generating a hexavalent molecule. HERA-CD40L provides efficient receptor agonism on CD40-expressing cells and, importantly, does not require FcγR-mediated crosslinking. Strong activation of NFκB signaling was observed upon treatment of B cells with HERA-CD40L. Monocyte treatment with HERA-CD40L promoted differentiation towards the M1 spectrum and repolarization of M2 spectrum macrophages towards the M1 spectrum phenotype. Treatment of in vitro co-cultures of T and B cells with HERA-CD40L-triggered robust antitumor activation of T cells, which depended upon direct interaction with B cells. In contrast, bivalent anti-CD40 antibodies and trivalent soluble CD40L displayed weak activity which critically depended on crosslinking. In vivo, a murine surrogate of HERA-CD40L-stimulated clonal expansion of OT-I-specific murine CD8 T cells and showed single agent antitumor activity in the CD40 syngeneic MC38-CEA mouse model of colorectal cancer, suggesting an involvement of the immune system in controlling tumor growth. We conclude that HERA-CD40L is able to establish robust antitumor immune responses both in vitro and in vivo.

C18H17NO6 and Its Combination with Scutellarin Suppress the Proliferation and Induce the Apoptosis of Human Glioma Cells via Upregulation of Fas-Associated Factor 1 Expression

Background

Glioma is the most common malignant brain tumor and the patients are prone to poor prognosis. Due to limited treatments, new drug exploration has become a general trend. Therefore, the objective of this study is to investigate the effect of the new drugs C₁₈H₁₇NO₆ and its combination with Scutellarin on glioma cells and the underlying mechanism.

Method

U251 and LN229 cells were administrated with C₁₈H₁₇NO₆ and its combination with Scutellarin. The proliferation ability of glioma cells was determined by cell counting kit-8, plate clone formation assay, and EdU incorporation assay. The cell cycle and apoptosis detection were detected by flow cytometry. Moreover, TUNEL assay was also used for cell apoptosis analysis. Then, the transfer ability of cells was achieved through wound healing assay. Furthermore, polymerase chain reaction (PCR) test and western bolt analysis were used to detect the mRNA expression and protein expression, respectively. Lastly, immunofluorescence was for the purity identification of astrocyte.

Result

The results showed that, with the increasing dose of C₁₈H₁₇NO₆, the cell inhibition rate, the cells in G1 phase, and the apoptosis rate were gradually increased, but the clone number, proliferation rate, and the cells in G2 and S phases were gradually decreased in comparison with control group. However, with the increase of C₁₈H₁₇NO₆, the transferred rate of U251 and LN229 was not significantly augmented, expect that on U251 in C₁₈H₁₇NO₆ 5 μM group. In addition, Scutellarin 200 μM has little effect on proliferation, with the inhibition rate 10-20% and proliferation rate except U251 in Scutellarin 200 μM group similar to that in control group. Moreover, compared to control group, Scutellarin 300 μM increased the U251 cells in G2 and S phases and the apoptosis rate of LN229 but decreased the LN229 cells in G2 and S phases. Besides, in Scutellarin 200 μM group, the transfer ability of LN229 was inhibited, but not in U251. Furthermore, if C₁₈H₁₇NO₆ was combined with Scutellarin 200/300μM, the proliferation and transferred ability were suppressed and the apoptosis was elevated in LN229 cell in comparison with C₁₈H₁₇NO₆ alone. Dramatically, the combined effect on U251 was the exact opposite. Importantly, there was little toxicity on astrocyte under the dose of C₁₈H₁₇NO₆ and Scutellarin in the study. In molecular level, the mRNA and protein expression of Fas-associated factor 1 (FAF1) expression in U251 and LN229 were upregulated by C₁₈H₁₇NO₆ and its combination with Scutellarin, especially the protein expression.

Conclusion

C₁₈H₁₇NO₆ could efficiently suppress cell proliferation and induce cell apoptosis in glioma cells, and its combination with Scutellarin had a promoting effect, in which the underlying mechanism referred to the upregulation of Fas-associated factor 1.

The Human Papillomavirus (HPV) E6 Oncoprotein Regulates CD40 Expression via the AT-Hook Transcription Factor AKNA

Persistent infection with high-risk Human Papillomavirus (HR-HPV) is the main requisite for cervical cancer development. Normally, HPV is limited to the site of infection and regulates a plethora of cellular elements to avoid the immune surveillance by inducing an anti-inflammatory state, allowing the progress through the viral cycle and the carcinogenic process. Recent findings suggest that the AT-hook transcriptional factor AKNA could play a role in the development of cervical cancer. AKNA is strongly related to the expression of co-stimulatory molecules such CD40/CD40L to achieve an anti-tumoral immune response. To date, there is no evidence demonstrating the effect of the HPV E6 oncoprotein on the AT-hook factor AKNA. In this work, minimal expression of AKNA in cervical carcinoma compared to normal tissue was found. We show the ability of E6 from high-risk HPVs 16 and 18 to interact with and down-regulate AKNA as well as its co-stimulatory molecule CD40 in a proteasome dependent manner. We also found that p53 interacts with AKNA and promotes AKNA expression. Our results indicate that the de-regulation of CD40 and AKNA is induced by the HPV E6 oncoprotein, and this event involves the action of p53 suggesting that the axis E6/p53A/AKNA might play an important role in the de-regulation of the immune system during the carcinogenic process induced by HR-HPV.

Oxidative stress, consequences and ROS mediated cellular signaling in rheumatoid arthritis

There are numerous extra- and intra-cellular processes involved in the production of reactive oxygen species (ROS). Augmented ROS generation can cause the damage of biomolecules such as proteins, nucleic acid and lipids. ROS act as an intracellular signaling component and is associated with various inflammatory responses, chronic arthropathies, including rheumatoid arthritis (RA). It is well documented that ROS can activate different signaling pathways having a vital importance in the patho-physiology of RA. Hence, understanding of the molecular pathways and their interaction might be advantageous in the development of novel therapeutic approaches for RA.

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.

ROS and ROS-Mediated Cellular Signaling

It has long been recognized that an increase of reactive oxygen species (ROS) can modify the cell-signaling proteins and have functional consequences, which successively mediate pathological processes such as atherosclerosis, diabetes, unchecked growth, neurodegeneration, inflammation, and aging. While numerous articles have demonstrated the impacts of ROS on various signaling pathways and clarify the mechanism of action of cell-signaling proteins, their influence on the level of intracellular ROS, and their complex interactions among multiple ROS associated signaling pathways, the systemic summary is necessary. In this review paper, we particularly focus on the pattern of the generation and homeostasis of intracellular ROS, the mechanisms and targets of ROS impacting on cell-signaling proteins (NF-κB, MAPKs, Keap1-Nrf2-ARE, and PI3K-Akt), ion channels and transporters (Ca(2+) and mPTP), and modifying protein kinase and Ubiquitination/Proteasome System.