SPOP promotes ubiquitination and degradation of MyD88 to suppress the innate immune response

Identification of potential substrates of LNX1 in chicken cells

Ubiquitination of proteins is involved in numerous life activities. In poultry, several ubiquitin ligases tightly control the innate immune response, imbalance of which may result in autoimmune diseases and seriously impair poultry growth, development, and productivity. LNX1, an E3 ubiquitin ligase, catalyzes the ubiquitination and subsequent degradation of specific substrate proteins. A cell line with stable knockdown of the LNX1 gene was developed using chicken macrophages (HD11) as the model. The relative quantitative values of each protein were analyzed using 4D-FastDIA quantitative proteomics. This identified 319 proteins with up-regulated expression, a majority of which relate to the immune system. Overall, this study uncovered potential substrate proteins targeted by LNX1 and their associated biological pathways. The findings suggest that LNX1 could be implicated in the regulation of the chicken innate immune system by mediating protein ubiquitination.

Spop deficiency impairs adipogenesis and promotes thermogenic capacity in mice

As the adaptor protein that determines substrate specificity of the Cul3-SPOP-Rbx1 E3 ligase complex, SPOP is involved in numerous biological processes. However, its physiological connections with adipogenesis and thermogenesis remain poorly understood. In the current study, we report that the conditional knockout of Spop in mice results in substantial changes in protein expression, including the upregulation of a critical factor associated with thermogenesis, UCP1. Loss of SPOP also led to defects in body weight gain. In addition, conditional knockout mice exhibited resistance to high-fat-diet-induced obesity. Proteomics analysis found that proteins upregulated in the knockout mice are primarily enriched for functions in glycolysis/gluconeogenesis, oxidative phosphorylation, and thermogenesis. Furthermore, Spop knockout mice were more resilient during cold tolerance assay compared with the wild-type controls. Finally, the knockout of SPOP efficiently impaired adipogenesis in primary preadipocytes and the expression of associated genes. Collectively, these findings demonstrate the critical roles of SPOP in regulating adipogenesis and thermogenic capacity in mice.

Cullin-Conciliated Regulation of Plant Immune Responses: Implications for Sustainable Crop Protection

Cullins are crucial components of the ubiquitin-proteasome system, playing pivotal roles in the regulation of protein metabolism. This review provides insight into the wide-ranging functions of cullins, particularly focusing on their impact on plant growth, development, and environmental stress responses. By modulating cullin-mediated protein mechanisms, researchers can fine-tune hormone-signaling networks to improve various agronomic traits, including plant architecture, flowering time, fruit development, and nutrient uptake. Furthermore, the targeted manipulation of cullins that are involved in hormone-signaling pathways, e.g., cytokinin, auxin, gibberellin, abscisic acids, and ethylene, can boost crop growth and development while increasing yield and enhancing stress tolerance. Furthermore, cullins also play important roles in plant defense mechanisms through regulating the defense-associated protein metabolism, thus boosting resistance to pathogens and pests. Additionally, this review highlights the potential of integrating cullin-based strategies with advanced biological tools, such as CRISPR/Cas9-mediated genome editing, genetic engineering, marker-associated selections, gene overexpression, and gene knockout, to achieve precise modifications for crop improvement and sustainable agriculture, with the promise of creating resilient, high-yielding, and environmentally friendly crop varieties.

OTUD5 promotes the inflammatory immune response by enhancing MyD88 oligomerization and Myddosome formation

Myddosome is an oligomeric complex required for the transmission of inflammatory signals from TLR/IL1Rs and consists of MyD88 and IRAK family kinases. However, the molecular basis for the self-assemble of Myddosome proteins and regulation of intracellular signaling remains poorly understood. Here, we identify OTUD5 acts as an essential regulator for MyD88 oligomerization and Myddosome formation. OTUD5 directly interacts with MyD88 and cleaves its K11-linked polyubiquitin chains at Lys95, Lys231 and Lys250. This polyubiquitin cleavage enhances MyD88 oligomerization after LPS stimulation, which subsequently promotes the recruitment of downstream IRAK4 and IRAK2 to form Myddosome and the activation of NF-κB and MAPK signaling and production of inflammatory cytokines. Consistently, Otud5-deficient mice are less susceptible to LPS- and CLP-induced sepsis. Taken together, our findings reveal a positive regulatory role of OTUD5 in MyD88 oligomerization and Myddosome formation, which provides new sights into the treatment of inflammatory diseases.

STAM2 negatively regulates the MyD88-mediated NF-κB signaling pathway in miiuy croaker, Miichthys miiuy

Signal transducing adapter molecule 2 (STAM2), a member of the Signal Transducing Adapter Molecule (STAM) family, is a protein with significant implications in diverse signaling pathways and endocytic membrane trafficking. However, the role of the STAM2, especially in fish, remains largely unknown. In this study, we discovered that STAM2 negatively regulates the NF-κB signaling pathway, and its inhibitory effect is enhanced upon LPS induction. Our study confirmed that STAM2 can enhance the degradation of myeloid differentiation primary-response protein 88 (MyD88), an upstream regulator of NF-κB pathway. Furthermore, the UIM domain of STAM2 is important for the inhibition of MyD88. Mechanistically, STAM2 inhibits the NF-κB signaling pathway by targeting the MyD88 autophagy pathway. In addition, we showed that STAM2 promotes the proliferation of Vibrio harveyi. In summary, our study reveals that STAM2 inhibits NF-κB signaling activation and mediates innate immunity in teleost via the autophagy pathway.

SPOP negatively regulates mTORC1 activity by ubiquitinating Sec13

The mammalian target of rapamycin complex1 (mTORC1) can response to amino acid to regulate metabolism and cell growth. GATOR2 act as important role in amino acid mediated mTORC1 signaling pathway by repressing GTPase activity (GAP) of GATOR1. However, it is still unclear how GATOR2 regulates mTORC1 signaling pathway. Here, we found that K63-ubiquitination of Sce13, one component of GATOR2, suppresses the mTORC1 activity by lessening the inter-interaction of GATOR2. Mechanistically, the ubiquitination of Sec13 was mediated by SPOP. Subsequently, the ubiquitination of Sec13 attenuated its interaction with the other component of GATOR2, thus suppressing the activity of mTORC1. Importantly, the deficiency of SPOP promoted the faster proliferation and migration of breast cancer cells, which was attenuated by knocking down of Sec13. Therefore, SPOP can act as a tumor suppressor gene by negatively regulating mTORC1 signaling pathway.

Chicken speckle-type POZ protein (SPOP) negatively regulates MyD88/NF-κB signaling pathway mediated proinflammatory cytokine production to promote the replication of Newcastle disease virus

The speckle-type POZ protein (SPOP) is demonstrated to be a specific adaptor of the cullin-RING-based E3 ubiquitin ligase complex that participates in multiple cellular processes. Up to now, SPOP involved in inflammatory response has attracted more attention, but the association of SPOP with animal virus infection is scarcely reported. In this study, chicken MyD88 (chMyD88), an innate immunity-associated protein, was screened to be an interacting partner of chSPOP using co-immunoprecipitation (Co-IP) combined with liquid chromatography-tandem mass spectrometry methods. This interaction was further confirmed by fluorescence co-localization, Co-IP, and pull-down assays. It was interesting that exogenous recombinant protein HA-chSPOP or endogenous chSPOP alone was mainly located in the nucleus but was translocated to the cytoplasm upon co-expression with chMyD88 or lipopolysaccharide stimulation. In addition, chSPOP reduced chMyD88 expression by ubiquitination in a dose-dependent manner, and the regulation of NF-κB activity by chSPOP was dependent solely on chMyD88. Importantly, chSPOP played a negative regulatory role in the MyD88/NF-κB signaling pathway and the production of proinflammatory cytokines. Moreover, we found that velogenic Newcastle disease virus (NDV) infection changed the subcellular localization of chSPOP and the expression patterns of chSPOP and chMyD88, and overexpression of chSPOP decreased the production of proinflammatory cytokines to enhance velogenic and lentogenic NDV replication, while siRNA-mediated chSPOP knockdown obtained the opposite results, thereby indicating that chSPOP negatively regulated MyD88/NF-κB signaling pathway mediated proinflammatory cytokine production to promote NDV replication. These findings highlight the important role of the SPOP/MyD88/NF-κB signaling pathway in NDV replication and may provide insightful information about NDV pathogenesis.

Zebrafish spop promotes ubiquitination and degradation of mavs to suppress antiviral response via the lysosomal pathway

Retinoic acid-inducible gene I (RIG-I)-like receptors (RLRs) signaling pathways are required to be tightly controlled to initiate host innate immune responses. Fish mitochondrial antiviral signaling (mavs) is a key determinant in the RLR pathway, and its ubiquitination is associated with mavs activation. Here, we identified the zebrafish E3 ubiquitin ligase Speckle-type BTB-POZ protein (spop) negatively regulates mavs-mediated the type I interferon (IFN) responses. Consistently, overexpression of zebrafish spop repressed the activity of IFN promoter and reduced host ifn transcription, whereas knockdown spop by small interfering RNA (siRNA) transfection had the opposite effects. Accordingly, overexpression of spop dampened the cellular antiviral responses triggered by spring viremia of carp virus (SVCV). A functional domain assay revealed that the N-terminal substrate-binding MATH domain regions of spop were necessary for IFN suppression. Further assays indicated that spop interacts with mavs through the C-terminal transmembrane (TM) domain of mavs. Moreover, zebrafish spop selectively promotes K48-linked polyubiquitination and degradation of mavs through the lysosomal pathway to suppress IFN expression. Our findings unearth a post-translational mechanism by which mavs is regulated and reveal a role for spop in inhibiting antiviral innate responses.

SPOP inhibits HBV transcription and replication by ubiquitination and degradation of HNF1α

Hepatitis B virus (HBV) infection remains a significant public health burden worldwide. The persistence of covalently closed circular DNA (cccDNA) within the nucleus of infected hepatocytes is responsible for the failure of antiviral treatments. The ubiquitin proteasome system (UPS) has emerged as a promising antiviral target, as it can regulate HBV replication by promoting critical protein degradation in steps of viral life cycle. Speckle-type POZ protein (SPOP) is a critical adaptor for Cul3-RBX1 E3 ubiquitin ligase complex, but the effect of SPOP on HBV replication is less known. Here, we identified SPOP as a novel host antiviral factor against HBV infection. SPOP overexpression significantly inhibited the transcriptional activity of HBV cccDNA without affecting cccDNA level in HBV-infected HepG2-NTCP and primary human hepatocyte cells. Mechanism studies showed that SPOP interacted with hepatocyte nuclear factor 1α (HNF1α), and induced HNF1α degradation through host UPS pathway. Moreover, the antiviral role of SPOP was also confirmed in vivo. Together, our findings reveal that SPOP is a novel host factor which inhibits HBV transcription and replication by ubiquitination and degradation of HNF1α, providing a potential therapeutic strategy for the treatment of HBV infection.

Ubiquitin E3 ligase SPOP is a host negative regulator of enterovirus 71-encoded 2A protease

IMPORTANCE

EV71 poses a significant health threat to children aged 5 and below. The process of EV71 infection and replication is predominantly influenced by ubiquitination modifications. Our previous findings indicate that EV71 prompts the activation of host deubiquitinating enzymes, thereby impeding the host interferon signaling pathway as a means of evading the immune response. Nevertheless, the precise mechanisms by which the host employs ubiquitination modifications to hinder EV71 infection remain unclear. The present study demonstrated that the nonstructural protein 2Apro, which is encoded by EV71, exhibits ubiquitination and degradation mediated by the host E3 ubiquitin ligase SPOP. In addition, it is the first report, to our knowledge, that SPOP is involved in the host antiviral response.

C-type lectin receptor 2d forms homodimers and heterodimers with TLR2 to negatively regulate IRF5-mediated antifungal immunity

Dimerization of C-type lectin receptors (CLRs) or Toll-like receptors (TLRs) can alter their ligand binding ability, thereby modulating immune responses. However, the possibilities and roles of dimerization between CLRs and TLRs remain unclear. Here we show that C-type lectin receptor-2d (CLEC2D) forms homodimers, as well as heterodimers with TLR2. Quantitative ligand binding assays reveal that both CLEC2D homodimers and CLEC2D/TLR2 heterodimers have a higher binding ability to fungi-derived β-glucans than TLR2 homodimers. Moreover, homo- or hetero-dimeric CLEC2D mediates β-glucan-induced ubiquitination and degradation of MyD88 to inhibit the activation of transcription factor IRF5 and subsequent IL-12 production. Clec2d-deficient female mice are resistant to infection with Candida albicans, a human fungal pathogen, owing to the increase of IL-12 production and subsequent generation of IFN-γ-producing NK cells. Together, these data indicate that CLEC2D forms homodimers or heterodimers with TLR2, which negatively regulate antifungal immunity through suppression of IRF5-mediated IL-12 production. These homo- and hetero-dimers of CLEC2D and TLR2 provide an example of receptor dimerization to regulate host innate immunity against microbial infections.

SPOP targets the immune transcription factor IRF1 for proteasomal degradation

Adaptation of the functional proteome is essential to counter pathogens during infection, yet precisely timed degradation of these response proteins after pathogen clearance is likewise key to preventing autoimmunity. Interferon regulatory factor 1 (IRF1) plays an essential role as a transcription factor in driving the expression of immune response genes during infection. The striking difference in functional output with other IRFs is that IRF1 also drives the expression of various cell cycle inhibiting factors, making it an important tumor suppressor. Thus, it is critical to regulate the abundance of IRF1 to achieve a 'Goldilocks' zone in which there is sufficient IRF1 to prevent tumorigenesis, yet not too much which could drive excessive immune activation. Using genetic screening, we identified the E3 ligase receptor speckle type BTB/POZ protein (SPOP) to mediate IRF1 proteasomal turnover in human and mouse cells. We identified S/T-rich degrons in IRF1 required for its SPOP MATH domain-dependent turnover. In the absence of SPOP, elevated IRF1 protein levels functionally increased IRF1-dependent cellular responses, underpinning the biological significance of SPOP in curtailing IRF1 protein abundance.

Zuojinwan ameliorates CUMS-induced depressive-like behavior through inducing ubiquitination of MyD88 via SPOP/MyD88/NF-κB pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Zuojinwan (ZJW) is a traditional Chinese medicine compound, which is often used clinically to treat gastritis and has anti-inflammatory activity. It was found that ZJW is involved in suppressing the expression of inflammatory factors, and neuroinflammation is thought to be associated with the development of depression.

AIM OF THE STUDY

In this study, we investigated whether ZJW could exert antidepressant effects by regulating MyD88 ubiquitination in depressed mice and attempted to elucidate the possible mechanisms.

MATERIALS AND METHODS

Six active compounds of Zuojinwan (ZJW) were identified by HPLC. Then, the effects of ZJW on depression-like behavior in mice were investigated by constructing a chronic unpredictable mild stimulation (CUMS) mouse model. Meanwhile, the effect of ZJW on hippocampal neurons was investigated by Nissl staining. In addition, western blotting, PCR, ELISA, co-immunoprecipitation and immunostaining were used to explore whether ZJW could inhibit neuroinflammation through SPOP/MyD88/NF-κB pathway and thus produce antidepressant effects. Finally, we constructed the AAV-Sh-SPOP virus vector to silence SPOP and verify the mechanism of ZJW's antidepressant action.

RESULTS

ZJW could dramatically ameliorate the depressive behavior induced by CUMS stimulation and alleviate hippocampal neuronal damage. CUMS stimulation resulted in decreased SPOP expression, impaired MyD88 ubiquitination, and activation of downstream NF-κB signaling, which could be reversed by ZJW. In addition, ZJW could significantly ameliorate the abnormal activation of microglia, and the excessive levels of pro-inflammatory factors were inhibited. By blocking the expression of SPOP, we found that ZJW exerted anti-inflammatory and antidepressant effects mainly by promoting the ubiquitination of MyD88 and inhibiting the activation of downstream inflammatory signals.

CONCLUSION

In conclusion, ZJW possesses alleviating effects on depression induced by CUMS stimulation. ZJW can inhibit neuroinflammation and improve neuroinflammation-induced depression-like behaviors through SPOP/MyD88/NF-κB pathway.

LncRNA Kcnq1ot1relieves neuropathic pain through downregulation of Myd88

BACKGROUND

Long non-coding RNAs (lncRNAs) have already been documented to become the therapeutic targets for neuropathic pain. Here, this work focused on exploring the specific mechanism underlying Kcnq1 overlapping transcript 1 (kcnq1ot1) in neuropathic pain.

METHODS

Sciatic nerve chronic constriction injury (CCI) in vivo and LPS-stimulated microglia BV2 cell injury in vitro were adopted to construct neuropathic pain models. Expressions of kcnq1ot1, MyD88, and microglia activation marker Iba-1 were measured. In this study, we carried out fluorescence in-situ Hybridization (FISH) and immunofluorescence for examining Kcnq1ot1 localization within microglial cells in mouse spinal dorsal horn. Subsequently, we evaluated binding between Kcnq1ot1 and Myd88, together with the expressions of IL-1β, IL-6, TNF-α, and Myd88 ubiquitination.

RESULTS

Kcnq1ot1 levels decreased within CCI mice and LPS-induced BV2 cells. According to the results of FISH and immunofluorescence, Kcnq1ot1 is located in microglia. Overexpression of Kcnq1ot1 suppressed Iba-1, IL-1β, IL-6 together with TNF-α expression. RNA pull-down and RIP assay confirmed that Kcnq1ot1 bound to Myd88. In addition, Kcnq1ot1 overexpression promoted the degradation, enhanced the ubiquitination, and reduced protein level of Myd88. Overexpression of Myd88 eliminated the effects of Kcnq1ot1 overexpression on Iba-1level and production of pro-inflammatory cytokines. Further in vivo results revealed that increased Kcnq1ot1 level alleviated neuropathic pain and myelinated nerve fiber injury of CCI mice.

CONCLUSION

Kcnq1ot1 downregulated Myd88 protein expression by binding to Myd88 and promoting its ubiquitination, which in turn suppressed microglia activation, pro-inflammatory cytokine production, and relieved neuropathic pain.

Transcriptome Analysis of Diffuse Large B-Cell Lymphoma Cells Inducibly Expressing MyD88 L265P Mutation Identifies Upregulated CD44, LGALS3, NFKBIZ, and BATF as Downstream Targets of Oncogenic NF-κB Signaling

During innate immune responses, myeloid differentiation primary response 88 (MyD88) functions as a critical signaling adaptor protein integrating stimuli from toll-like receptors (TLR) and the interleukin-1 receptor (IL-1R) family and translates them into specific cellular outcomes. In B cells, somatic mutations in MyD88 trigger oncogenic NF-κB signaling independent of receptor stimulation, which leads to the development of B-cell malignancies. However, the exact molecular mechanisms and downstream signaling targets remain unresolved. We established an inducible system to introduce MyD88 to lymphoma cell lines and performed transcriptomic analysis (RNA-seq) to identify genes differentially expressed by MyD88 bearing the L265P oncogenic mutation. We show that MyD88L265P activates NF-κB signaling and upregulates genes that might contribute to lymphomagenesis, including CD44, LGALS3 (coding Galectin-3), NFKBIZ (coding IkBƺ), and BATF. Moreover, we demonstrate that CD44 can serve as a marker of the activated B-cell (ABC) subtype of diffuse large B-cell lymphoma (DLBCL) and that CD44 expression is correlated with overall survival in DLBCL patients. Our results shed new light on the downstream outcomes of MyD88L265P oncogenic signaling that might be involved in cellular transformation and provide novel therapeutical targets.

Regulation of innate immune signaling by IRAK proteins

The Toll-like receptors (TLRs) and interleukin-1 receptors (IL-1R) families are of paramount importance in coordinating the early immune response to pathogens. Signaling via most TLRs and IL-1Rs is mediated by the protein myeloid differentiation primary-response protein 88 (MyD88). This signaling adaptor forms the scaffold of the myddosome, a molecular platform that employs IL-1R-associated kinase (IRAK) proteins as main players for transducing signals. These kinases are essential in controlling gene transcription by regulating myddosome assembly, stability, activity and disassembly. Additionally, IRAKs play key roles in other biologically relevant responses such as inflammasome formation and immunometabolism. Here, we summarize some of the key aspects of IRAK biology in innate immunity.

Toxoplasma gondii microneme protein MIC3 induces macrophage TNF-α production and Ly6C expression via TLR11/MyD88 pathway

Toxoplasma gondii is the most successful parasite worldwide. It is of great interest to understand how T. gondii induce different immune responses in different hosts. In this study, we found that a peptide of T. gondii microneme protein MIC3 induced TNF-α production, NF-κB phosphorylation, iNOS transcription and Ly6C expression in mouse macrophage RAW264.7 cells. MyD88 inhibition, small interfering RNA against Tlr11 and CRISPR/Cas9-mediated knock-out of Tlr11 all reduced MIC3-induced TNF-α production, NF-κB phosphorylation, iNOS transcription and Ly6C expression. Additionally, we determined the location of MIC3 peptide in mouse macrophages using immunofluorescence. MIC3 could both adhere to the cell membrane of mouse macrophages and enter the cells. These results suggest that MIC3 triggered the immune responses in mouse macrophages via TLR11/MyD88/NF-κB pathway. It is known that human macrophages lacking TLR11. We predicted that the immune responses induced by MIC3 in human macrophages were significantly different from those in mouse macrophages. As expected, MIC3 peptide failed to induce TNF-α expression, iNOS expression and NF-κB phosphorylation in human THP-1 derived macrophages. MIC3 induced macrophage immune responses via TLR11. Intriguingly, the amino acid sequence of MIC3 is completely different from the well-known TLR11 ligand profilin, which generates a potent IL-12p40, TNF-α and IL-6 response. In marked contrast to profilin, MIC3 could not induce IL-12p40 expression in both mouse RAW264.7 cells and human THP-1 derived macrophages. Furthermore, the simulated tertiary structure of MIC3 peptide shows poor similarity with the crystal structure of profilin, suggesting that MIC3 might be a different ligand from profilin. These findings about MIC3 and TLR11 will provide us with important insights into the pathogenesis of toxoplasmosis and coevolution during host-parasite interaction.

USP7 Promotes deubiquitination and stabilization of MyD88 to enhance immune responses

Toll-like receptors (TLRs) are involved in the sensing of pathogen-associated molecular patterns (PAMPs) such as lipopolysaccharide (LPS), flagellin, unmethylated double-stranded DNA (CpG), single-stranded RNA (ssRNA) and lipoproteins. Myeloid differentiation primary response protein 88 (MyD88) is a canonical adaptor for the Toll-like receptor family which has crucial roles in host defense against infection by microbial pathogens. The dysregulation of MyD88 may also induce autoimmune diseases. Here, we demonstrate that the deubiquitinase USP7 interacts with MyD88 in chicken, with knockdown or overexpression of USP7 leading to the regulation of MyD88 protein in a positive manner. Consequently, USP7 positively regulates the expression of proinflammatory factors upon LPS challenge. Furthermore, we observed USP7-deficient mice to be more susceptible to infection by Salmonella typhimurium. Collectively, our findings demonstrate MyD88 as a bona fide substrate of USP7 and uncover a mechanism by which USP7 regulates innate immune signaling.

Counting Degrons: Lessons From Multivalent Substrates for Targeted Protein Degradation

E3s comprise a structurally diverse group of at least 800 members, most of which target multiple substrates through specific and regulated protein-protein interactions. These interactions typically rely on short linear motifs (SLiMs), called "degrons", in an intrinsically disordered region (IDR) of the substrate, with variable rules of engagement governing different E3-docking events. These rules of engagement are of importance to the field of targeted protein degradation (TPD), where substrate ubiquitination and destruction require tools to effectively harness ubiquitin ligases (E3s). Substrates are often found to contain multiple degrons, or multiple copies of a degron, contributing to the affinity and selectivity of the substrate for its E3. One important paradigm for E3-substrate docking is presented by the Anaphase-Promoting Complex/Cyclosome (APC/C), a multi-subunit E3 ligase that targets hundreds of proteins for destruction during mitotic exit. APC/C substrate targeting takes place in an ordered manner thought to depend on tightly regulated interactions of substrates, with docking sites provided by the substoichiometric APC/C substrate adaptors and coactivators, Cdc20 or Cdh1/FZR1. Both structural and functional studies of individual APC/C substrates indicate that productive ubiquitination usually requires more than one degron, and that degrons are of different types docking to distinct sites on the coactivators. However, the dynamic nature of APC/C substrate recruitment, and the influence of multiple degrons, remains poorly understood. Here we review the significance of multiple degrons in a number of E3-substrate interactions that have been studied in detail, illustrating distinct kinetic effects of multivalency and allovalency, before addressing the role of multiple degrons in APC/C substrates, key to understanding ordered substrate destruction by APC/C. Lastly, we consider how lessons learnt from these studies can be applied in the design of TPD tools.

Novel insights into the SPOP E3 ubiquitin ligase: From the regulation of molecular mechanisms to tumorigenesis

Ubiquitin-mediated protein degradation is the primary biological process by which protein abundance is regulated and protein homeostasis is maintained in eukaryotic cells. Speckle-type pox virus and zinc finger (POZ) protein (SPOP) is a typical substrate adaptor of the Cullin 3-RING ligase (CRL3) family; it serves as a bridge between the Cullin 3 (Cul3) scaffold protein and its substrates. In recent years, SPOP has received increasing attention because of its versatility in its regulatory pathways and the diversity of tumor types involved. Mechanistically, SPOP substrates are involved in a wide range of biological processes, and abnormalities in SPOP function perturb downstream biological processes and promote tumorigenesis. Additionally, liquid-liquid phase separation (LLPS), a potential mechanism of membraneless organelle formation, was recently found to mediate the self-triggered colocalization of substrates with higher-order oligomers of SPOP. Herein, we summarize the structure of SPOP and the specific mechanisms by which it mediates the efficient ubiquitination of substrates. Additionally, we review the biological functions of SPOP, the regulation of SPOP expression, the role of SPOP in tumorigenesis and its therapeutic value.

Genome-wide identification and characterization of Toll-like receptor genes in black rockfish (Sebastes schlegelii) and their response mechanisms following poly (I:C) injection

Toll-like receptors (TLRs) are canonical transmembrane receptors that play an important role in defending against invading pathogens. In this study, we identified a total of 12 TLR genes in black rockfish (Sebastes schlegelii) with an analysis of their sequence characterizations. The phylogenetic analysis suggested that 12 distinct TLRs were grouped into five subfamilies (i.e., TLR1, TLR3, TLR5, TLR7, and TLR11 subfamilies), and each SsTLR gene respectively corresponded to the orthologs genes of other species. The protein domain analysis indicated that TLRs are type I transmembrane proteins, including an extracellular leucine-rich repeat (LRR), a transmembrane region (TM) domain and an intracellular Toll/IL-1 receptor (TIR) domain. The evolutionary ratios indicted that 12 SsTLRs were under purifying selection. qRT-PCR assays exhibited diverse TLRs molecular expression patterns in the heart, brain, head kidney, kidney, liver, intestine, and spleen of 3 black rockfish, and the expression levels were high in some immune tissues (e.g., head kidney, kidney, and spleen). Subsequently, 30 fish were equally divided into 2 groups i.e., poly (I:C)-treated and PBS-Control groups. After poly (I:C) injection, eight SsTLRs, i.e., SsTLR2, SsTLR2-1, SsTLR2-2, SsTLR3, SsTLR5S, SsTLR7, SsTLR8 and SsTLR22, were dramatically increased. Altogether these results contribute to understanding how SsTLRs respond to immune defense after poly (I:C) injection and provide researchers with comprehensive TLR gene family data of black rockfish.

Association of Heterophil/Lymphocyte Ratio with Intestinal Barrier Function and Immune Response to Salmonella enteritidis Infection in Chicken

Simple Summary

Salmonella represents a serious threat to the poultry industry and human health. The heterophil/lymphocyte (H/L) ratio indicates the robustness and immune system status of the chicken. Thus, the H/L ratio has been used for the selection of chickens that are resistant to Salmonella. However, the mechanisms conferring the resistance ability to the chickens with a low H/L ratio compared to those with a high H/L ratio remain unclear. Therefore, the present study aimed to investigate the association of the H/L ratio with the intestinal barrier function and immune response to Salmonella enteritidis infection in chicken. First, we enumerated the number of goblet cells in the ileum and caecum, measured the ileal villi morphology, and the expression of immune genes in the ileum and caecum of non-infected and SE-infected chickens at 7- and 21-days post-infection. Then, we assessed the correlation with the H/L ratio. The H/L ratio was negatively correlated to the number of goblet cells, IL-1β, IL-8, and IFN-γ ileal expressions, indicating that the individuals with a low H/L ratio displayed enhanced intestinal barrier and immunity. These results suggest that the H/L ratio is associated with intestinal immunity and could be a potential resistance indicator in chickens.

Abstract

The heterophil/lymphocyte (H/L) ratio has been extensively studied to select poultry that are resistant to environmental stressors. Chickens with a low H/L ratio are superior to the chickens with a high H/L ratio in survival, immune response, and resistance to Salmonella infection. However, this disease resistance ability is likely to be associated with enhanced intestinal immunity. Therefore, to expand our understanding of these underlying resistance mechanisms, it is crucial to investigate the correlation between the H/L ratio as a blood immune indicator in live chickens and the intestinal barrier function and immunity. Jinxing yellow chickens H/L line one-day-old were divided into non-infected (NI) and Salmonella enteritidis infected (SI) at 7-days old. After dividing the birds into NI and SI, blood samples were taken for H/L ratios determination, and subsequently, birds from the SI group were infected with Salmonella enteritidis (SE). We assessed the effects of SE infection on the (i) goblet cells number from the ileum and caecum gut-segments, (ii) ileal mucosa morphology, and (iii) immune gene mRNA expressions from the ileum and caecum of NI and SI chickens at 7 and 21 days-post-infection (dpi). We found that the H/L ratio was negatively correlated with most intestinal immune indices, particularly with the goblet cells number and with IL-1β, IL-8, and IFN-γ ileal expressions. In conclusion, these results suggest that the H/L ratio is associated with the intestinal barrier and immune response for SE clearance and that the chickens with a low H/L ratio displayed enhanced intestinal immunity. This study expands the current knowledge that is related to using the H/L ratio to select and breed resistant broiler chickens.

FOSL2 Is Involved in the Regulation of Glycogen Content in Chicken Breast Muscle Tissue

The glycogen content in muscle of livestock and poultry animals affects the homeostasis of their body, growth performance, and meat quality after slaughter. FOS-like 2, AP-1 transcription factor subunit (FOSL2) was identified as a candidate gene related to muscle glycogen (MG) content in chicken in our previous study, but the role of FOSL2 in the regulation of MG content remains to be elucidated. Differential gene expression analysis and weighted gene coexpression network analysis (WGCNA) were performed on differentially expressed genes (DEGs) in breast muscle tissues from the high-MG-content (HMG) group and low-MG-content (LMG) group of Jingxing yellow chickens. Analysis of the 1,171 DEGs (LMG vs. HMG) identified, besides FOSL2, some additional genes related to MG metabolism pathway, namely PRKAG3, CEBPB, FOXO1, AMPK, and PIK3CB. Additionally, WGCNA revealed that FOSL2, CEBPB, MAP3K14, SLC2A14, PPP2CA, SLC38A2, PPP2R5E, and other genes related to the classical glycogen metabolism in the same coexpressed module are associated with MG content. Also, besides finding that FOSL2 expression is negatively correlated with MG content, a possible interaction between FOSL2 and CEBPB was predicted using the STRING (Search Tool for the Retrieval of Interacting Genes) database. Furthermore, we investigated the effects of lentiviral overexpression of FOSL2 on the regulation of the glycogen content in vitro, and the result indicated that FOSL2 decreases the glycogen content in DF1 cells. Collectively, our results confirm that FOSL2 has a key role in the regulation of the MG content in chicken. This finding is helpful to understand the mechanism of MG metabolism regulation in chicken and provides a new perspective for the production of high-quality broiler and the development of a comprehensive nutritional control strategy.

Differential mRNA and miRNA Profiles Reveal the Potential Roles of Genes and miRNAs Involved in LPS Infection in Chicken Macrophages

Lipopolysaccharide (LPS) is a component of the cell wall of Gram-negative bacteria, and triggers an inflammatory response both in vitro and in vivo. Here, we used LPS from Escherichia coli serotype enteritidis to stimulate chicken macrophages (HD11) and conducted the transcriptome analysis using a bioinformatics approach to explore the functions of immune-related genes and miRNAs. In total, 1759 differentially expressed genes (DEGs) and 18 differentially expressed (DE)-miRNAs were detected during LPS infection. At 6 h post infection, 1025 DEGs and 10 miRNAs were up-regulated, and 734 DEGs and 8 DE-miRNAs were down-regulated. Based on both RNA hybrid and miRanda systems, 55 DEGs could be targeted by 14 DE-miRNAs. The target genes were related to the immune response, such as IRF8, STAT3, TRAF7, and other potential candidate genes. The DE-miRNAs miR146a-3p, miR6583-5p, and miR30c-2-3p were investigated further. They were predicted to target 34 genes that may also be candidates for immune-related miRNAs and genes. Our results enhanced our understanding of the pathogenic mechanisms of Gram-negative bacteria in chickens.

Negative Regulation of the Innate Immune Response through Proteasomal Degradation and Deubiquitination

The rapid and dynamic activation of the innate immune system is achieved through complex signaling networks regulated by post-translational modifications modulating the subcellular localization, activity, and abundance of signaling molecules. Many constitutively expressed signaling molecules are present in the cell in inactive forms, and become functionally activated once they are modified with ubiquitin, and, in turn, inactivated by removal of the same post-translational mark. Moreover, upon infection resolution a rapid remodeling of the proteome needs to occur, ensuring the removal of induced response proteins to prevent hyperactivation. This review discusses the current knowledge on the negative regulation of innate immune signaling pathways by deubiquitinating enzymes, and through degradative ubiquitination. It focusses on spatiotemporal regulation of deubiquitinase and E3 ligase activities, mechanisms for re-establishing proteostasis, and degradation through immune-specific feedback mechanisms vs. general protein quality control pathways.