Celastrol regulates the oligomeric state and chaperone activity of αB-crystallin linked with protein homeostasis in the lens.

Protein misfolding and aggregation are crucial pathogenic factors for cataracts, which are the leading cause of visual impairment worldwide. α-crystallin, as a small molecular chaperone, is involved in preventing protein misfolding and maintaining lens transparency. The chaperone activity of α-crystallin depends on its oligomeric state. Our previous work identified a natural compound, celastrol, which could regulate the oligomeric state of αB-crystallin. In this work, based on the UNcle and SEC analysis, we found that celastrol induced αB-crystallin to form large oligomers. Large oligomer formation enhanced the chaperone activity of αB-crystallin and prevented aggregation of the cataract-causing mutant ßA3-G91del. The interactions between αB-crystallin and celastrol were detected by the FRET (Fluorescence Resonance Energy Transfer) technique, and verified by molecular docking. At least 9 binding patterns were recognized, and some binding sites covered the groove structure of αB-crystallin. Interestingly, αB-R120G, a cataract-causing mutation located at the groove structure, and celastrol can decrease the aggregates of αB-R120G. Overall, our results suggested celastrol not only promoted the formation of large αB-crystallin oligomers, which enhanced its chaperone activity, but also bound to the groove structure of its α-crystallin domain to maintain its structural stability. Celastrol might serve as a chemical and pharmacological chaperone for cataract treatment.

A novel cataract-causing mutation Ile82Met of γA crystallin trends to aggregate with unfolding intermediate.

Cataract is the most common pathogenic ophthalmic disease leading to blindness in children worldwide. Genetic disorder is the leading cause of congenital cataract, among which crystallin mutations have a high incidence. There are few reports on γA-crystallin, one critical member of crystallin superfamilies. In this study, we identified a novel pathogenic mutation (Ile82Met) in γA-crystallin from a three-generation Chinese family with cataract, and investigated the potential molecular mechanism in detail. To elucidate the pathogenic mechanism of I82M mutant, spectroscopic and solubility experiments were performed to determine the difference between the purified γA-crystallin wild type (WT) and I82M mutant under both physiological conditions and environmental stresses (UV irradiation, thermal denaturation or chemical denaturation). The I82M mutant did not affect the secondary/tertiary structure of monomeric γA-crystallin under physiological status, but decreased protein stability and increased aggregatory potency under the stressful treatment. Surprisingly, the chemical denaturation caused I82M to switch from the two-state unfolding of γA-crystallin to three-state unfolding involving an unfolding intermediate. This study expands the genetic variation map of cataract, and provides novel insights into the pathomechanism, in particular, filling in a gap in the understanding of γA-crystallin mutants causing cataract.

Cataract-causing G91del mutant destabilised ßA3 heteromers formation linking with structural stability and cellular viability.

BACKGROUND/AIMS: Congenital cataracts, which are genetically heterogeneous eye disorders, result in visual loss in childhood around the world. CRYBA1/BA3 serves as an abundant structural protein in the lens, and forms homomers and heteromers to maintain lens transparency. In previous study, we identified a common cataract-causing mutation, ßA3-glycine at codon 91 (G91del) (c.271-273delGAG), which deleted a highly conserved G91del and led to perinuclear zonular cataract. In this study, we aimed to explore the underlying pathogenic mechanism of G91del mutation. METHODS: Protein purification, size-exclusion chromatography, spectroscopy and molecular dynamics simulation assays were used to investigate the effects on the heteromers formation and the protein structural properties of ßA3-crystallin caused by G91del mutation. Intracellular ßA3-G91del overexpression, MTT (3-(4,5)-dimethylthiahiazo (-z-y1)-3,5-di-phenytetrazoliumromide) and cell apoptosis were used to investigate the cellular functions of ßA3-G91del. RESULTS: ßA3-crystallin and ßB2-crystallin could form heteromers, which have much more stable structures than ßA3 homomers. Interestingly, ßA3/ßB2 heteromers improved their resistance against the thermal stress and the guanidine hydrochloride treatment. However, the pathogenic mutation ßA3-G91del destroyed the interaction with ßB2, and thereby decreased its structural stability as well as the resistance of thermal or chemical stress. What's more, the ßA3-G91del mutation induced cell apoptosis and escaped from the protection of ßB2-crystallin. CONCLUSIONS: ßA3/ßB2 heteromers play an indispensable role in maintaining lens transparency, while the ßA3-G91del mutation destabilises heteromers formation with ßB2-crystallin, impairs cellular viability and induces cellular apoptosis. These all might contribute to cataract development.

Pathogenic mechanism of congenital cataract caused by the CRYBA1/A3-G91del variant and related intervention strategies.

Congenital cataracts, which are genetically heterogeneous eye disorders, lead to visual impairment in childhood. In our previous study, we identified a novel mutation in exon 4 of the CRYBA1/BA3 gene, which resulted in the deletion of a highly conserved glycine at codon 91 (G91del) and perinuclear zonular cataract. The G91del variant is one of the most frequent pathogenic mutations in CRYBA1/BA3; however, its pathogenic mechanism remains unclear. In this study, we purified ßA3-crystallin and the ßA3-G91del variant. ßA3-G91del was prone to proteolysis and exhibited very low solubility and low structural stability. Next, we constructed a CRYBA1/BA3 mutant cell model and observed that G91del mutant proteins were more sensitive to environmental stress and prone to form aggregates. Size-exclusion chromatography and molecular dynamics simulation showed that the G91del mutation impaired the ability of ßA3 to form homo-oligomers. In addition, the protein folding process of ßA3-G91del was complicated and showed more intermediate states, resulting in amyloid fiber aggregation and induction of cellular apoptosis. Finally, we investigated intervention strategies for congenital cataract caused by the CRYBA1/A3-G91del variant. The addition of lanosterol reversed the negative effects of the G91del mutation under external stress. This study may help explore potential treatment strategies for related cataracts.

ßB2 W151R mutant is prone to degradation, aggregation and exposes the hydrophobic side chains in the fourth Greek Key motif.

Studies have established that congenital cataract is the major cause of blindness in children across the globe. The ß-crystallin protein family is the richest and most soluble structural protein in the lens. Their solubility and stability are essential in maintaining lens transparency. In this study, we identified a novel ßB2 mutation W151R in a rare progressive cortical congenital cataract family and explored its pathogenesis using purified protein and mutant related cataract-cell models. Due to its low solubility and poor structural stability, the ßB2 W151R mutation was prone to aggregation. Moreover, the W151R mutation enhanced the exposure of the hydrophobic side chains in the fourth Greek Key motif, which were readily degraded by trypsin. However, upon the administration of lanosterol, the negative effect of the W151R mutation was reversed. Therefore, lanosterol is a potential therapeutic option for cataracts.

Modulation Classification Based on Signal Constellation Diagrams and Deep Learning.

Deep learning (DL) is a new machine learning (ML) methodology that has found successful implementations in many application domains. However, its usage in communications systems has not been well explored. This paper investigates the use of the DL in modulation classification, which is a major task in many communications systems. The DL relies on a massive amount of data and, for research and applications, this can be easily available in communications systems. Furthermore, unlike the ML, the DL has the advantage of not requiring manual feature selections, which significantly reduces the task complexity in modulation classification. In this paper, we use two convolutional neural network (CNN)-based DL models, AlexNet and GoogLeNet. Specifically, we develop several methods to represent modulated signals in data formats with gridlike topologies for the CNN. The impacts of representation on classification performance are also analyzed. In addition, comparisons with traditional cumulant and ML-based algorithms are presented. Experimental results demonstrate the significant performance advantage and application feasibility of the DL-based approach for modulation classification.

RIP1 is a central signaling protein in regulation of TNF-α/TRAIL mediated apoptosis and necroptosis during Newcastle disease virus infection.

Newcastle disease virus (NDV) is an oncolytic virus which selectively replicates in tumor cells and exerts anti-tumor cytotoxic activity by promoting cell death. In this study, we focus on characterization of the underlying mechanisms of NDV-induced cell death in HeLa cells. We find that NDV Herts/33 strain triggers both extrinsic and intrinsic apoptosis at late infection times. The activation of NF-кB pathway and subsequent up-regulation of TNF-α/TRAIL initiates extrinsic apoptosis, leading to activation of caspase 8 and cleavage of Bid into tBid. tBid transmits the extrinsic apoptotic signals to mitochondria and mediates intrinsic apoptosis, which is hallmarked by cleavage of caspase 9. Moreover, RIP1 is cleaved into RIP1-N and RIP1-C at D324 by caspase 8, and this cleavage promotes apoptosis. Surprisingly, over expression of RIP1 reduces apoptosis and depletion of RIP1 promotes apoptosis, suggesting full length RIP1 is anti-apoptotic. Moreover, necroptosis hallmark protein MLKL is activated by phosphorylation at 12-24 h.p.i., and RIP1 regulates the level of phosphor-MLKL. Immunostaining shows that RIP1 aggregates to stress granules (SGs) at 8-24 h.p.i., and phosphor-MLKL is also recruited to SGs, instead of migrating to plasma membrane to exert its necrotic function. Immunoprecipitation study demonstrates that RIP1 bind to phosphor-MLKL, and depletion of RIP1 reduces the aggregation of MLKL to SGs, suggesting that RIP1 recruits MLKL to SGs. Altogether, NDV infection initiates extrinsic apoptosis via activation of NF-кB and secretion of TNF-α/TRAIL. Activation of caspase 8 by TNF-α/TRAIL and subsequent cleavage of Bid and RIP1 transmit the death signals to mitochondria. Meanwhile, virus subverts the host defensive necroptosis via recruiting phosphor-MLKL by RIP1 to SGs. Thus, RIP1 is a central signaling protein in regulation of apoptosis and necroptosis during NDV infection.

(DEAD)-box RNA helicase 3 modulates NF-κB signal pathway by controlling the phosphorylation of PP2A-C subunit.

Asp-Glu-Ala-Asp (DEAD)-box RNA helicase 3 (DDX3), an ATP-dependent RNA helicase, is associated with RNA splicing, mRNA export, transcription, translation, and RNA decay. Recent studies revealed that DDX3 participates in innate immune response during virus infection by interacting with TBK1 and regulating the production of IFN-ß. In our studies, we demonstrated that DDX3 regulated NF-κB signal pathway. We found that DDX3 knockdown reduced the phosphorylation of p65 and IKK-ß and ultimately attenuated the production of inflammatory cytokines induced by poly(I:C) or TNF-α stimulation. The regulatory effect of DDX3 on NF-κB signal pathway was not affected by the loss of its ATPase or helicase activity. We further identified PP2A C subunit (PP2A-C) as an interaction partner of DDX3 by co-immunoprecipitation and mass spectrum analysis. We confirmed that DDX3 formed the complex with PP2A-C/IKK-ß and regulated the interaction between IKK-ß and PP2A-C. Furthermore, we demonstrated that DDX3 modulated the activity of PP2A by controlling the phosphorylation of PP2A-C, which might enable PP2A-C to regulate NF-κB signal pathway by dephosphorylating IKK-ß. All these findings suggested DDX3 plays multiple roles in modulating innate immune system.

Glycyrrhizin inhibits porcine epidemic diarrhea virus infection and attenuates the proinflammatory responses by inhibition of high mobility group box-1 protein.

Porcine epidemic diarrhea (PED), caused by porcine epidemic diarrhea virus (PEDV) infection, leads to significant economic losses in the swine industry worldwide. In our studies, we found that glycyrrhizin, the major component of licorice root extracts, could moderately inhibit PEDV infection in Vero cells, when analyzed by western blot, qRT-PCR and a plaque formation assay. We also revealed that glycyrrhizin inhibited the entry and replication of PEDV. In addition, we demonstrated that glycyrrhizin decreased the mRNA levels of proinflammatory cytokines. Since glycyrrhizin is a competitive inhibitor of high mobility group box-1 (HMGB1), we confirmed that TLR4 and RAGE (£ associated with PEDV pathogenesis during the infection in Vero cells. In summary, our studies provide a molecular basis for developing novel therapeutic methods to control PEDV infection, based on glycyrrhizin and its derivatives.

Porcine epidemic diarrhea virus nucleoprotein contributes to HMGB1 transcription and release by interacting with C/EBP-ß.

Porcine epidemic diarrhea is a devastating swine enteric disease, which is caused by porcine epidemic diarrhea virus (PEDV) infection. Our studies demonstrated that PEDV infection resulted in the up-regulation of proinflammatory cytokines. Meanwhile, PEDV infection and overexpression of viral nucleoprotein resulted in the acetylation and release of high mobility group box 1 proteins in vitro, an important proinflammatory response mediator, which contributes to the pathogenesis of various inflammatory diseases. Our studies also showed that SIRT1, histone acetyltransferase, and NF-κB regulated the acetylation and release of HMGB1. Chromatin immunoprecipitation, dual-luciferase reporter gene assay, and co-immunoprecipitation experiments illustrated that PEDV-N could induce HMGB1 transcription by interacting with C/EBP-ß, which could bind to C/EBP motif in HMGB1 promotor region. Collectively, our data indicate PEDV-N contributes to HMGB1 transcription and the subsequent release/acetylation of HMGB1 during PEDV infection.

The LXR ligand GW3965 inhibits Newcastle disease virus infection by affecting cholesterol homeostasis.

Newcastle disease (ND) is a contagious disease that affects most species of birds. Its causative pathogen, Newcastle disease virus (NDV), also exhibits considerable oncolytic activity against mammalian cancers. A better understanding of the pathogenesis of NDV will help us design efficient vaccines and novel anticancer strategies. GW3965, a widely used synthetic ligand of liver X receptor (LXR), induces the expression of LXRs and its downstream genes, including ATP-binding cassette transporter A1 (ABCA1). ABCA1 regulates cellular cholesterol homeostasis. Here, we found that GW3965 inhibited NDV infection in DF-1 cells. It also inhibited NF-κB activation and reduced the upregulation of proinflammatory cytokines induced by the infection. Further studies showed that GW3965 exerted its inhibitory effects on virus entry and replication. NDV infection increased the mRNA levels of several lipogenic genes but decreased the ABCA1 mRNA level. Overexpression of ABCA1 inhibited NDV infection and reduced the cholesterol content in DF-1 cells, but when the cholesterol was replenished, NDV infection was restored. GW3965 treatment prevented cholesterol accumulation in the perinuclear area of the infected cells. In summary, our studies suggest that GW3965 inhibits NDV infection, probably by affecting cholesterol homeostasis.

Regulation of de novo translation of host cells by manipulation of PERK/PKR and GADD34-PP1 activity during Newcastle disease virus infection.

Viral infections result in cellular stress responses, which can trigger protein translation shutoff via phosphorylation of eukaryotic initiation factor 2 alpha (eIF2α). Newcastle disease virus (NDV) causes severe disease in poultry and selectively kills human tumour cells. In this report, we determined that infection of HeLa human cervical cancer cells and DF-1 chicken fibroblast cells with NDV maintained protein at early infection times, 0-12 h post-infection (p.i.), and gradually inhibited global protein translation at late infection times, 12-24 h p.i. Mechanistic studies showed that translation inhibition at late infection times was accompanied by phosphorylation of eIF2α, a checkpoint of translation initiation. Meanwhile, the eIF2α kinase, PKR, was upregulated and activated by phosphorylation and another eIF2α kinase, PERK, was phosphorylated and cleaved into two fragments. Pharmacological inhibition experiments revealed that only PKR activity was required for eIF2α phosphorylation, suggesting that recognition of viral dsRNA by PKR was responsible for translation shutoff. High levels of phospho-eIF2α led to preferential translation of the transcription factor ATF4 and an increase in GADD34 expression. Functionally, GADD34, in conjunction with PP1, dephosphorylated eIF2a and restored protein translation, benefiting virus protein synthesis. However, PP1 was degraded at late infection times, functionally counteracting the upregulation of GADD34. Taken together, our data support that NDV-induced translation shutoff at late infection times was attributed to sustaining phosphorylation of eIF2α, which is mediated by continual activation of PKR and degradation of PP1.