Bioinformatic analysis reveals new determinants of antigenic 14-3-3 proteins and a novel antifungal strategy

14-3-3ζ suppresses RANKL signaling by destabilizing TRAF6

Macrophages are essential regulators of inflammation and bone loss. Receptor activator of nuclear factor-κβ ligand (RANKL), a pro-inflammatory cytokine, is responsible for macrophage differentiation to osteoclasts and bone loss. We recently showed that 14-3-3ζ-knockout (YwhazKO) rats exhibit increased bone loss in the inflammatory arthritis model. 14-3-3ζ is a cytosolic adaptor protein that actively participates in many signaling transductions. However, the role of 14-3-3ζ in RANKL signaling or bone remodeling is unknown. We investigated how 14-3-3ζ affects osteoclast activity by evaluating its role in RANKL signaling. We utilized 14-3-3ζ-deficient primary bone marrow-derived macrophages obtained from wildtype and YwhazKO animals and RAW264.7 cells generated using CRISPR-Cas9. Our results showed that 14-3-3ζ-deficient macrophages, upon RANKL stimulation, have bigger and stronger tartrate-resistant acid phosphatase-positive multinucleated cells and increased bone resorption activity. The presence of 14-3-3ζ suppressed RANKL-induced MAPK and AKT phosphorylation, transcription factors (NFATC1 and p65) nuclear translocation, and subsequently, gene induction (Rank, Acp5, and Ctsk). Mechanistically, 14-3-3ζ interacts with TRAF6, an essential component of the RANKL receptor complex. Upon RANKL stimulation, 14-3-3ζ-TRAF6 interaction was increased, while RANK-TRAF6 interaction was decreased. Importantly, 14-3-3ζ supported TRAF6 ubiquitination and degradation by the proteasomal pathway, thus dampening the downstream RANKL signaling. Together, we show that 14-3-3ζ regulates TRAF6 levels to suppress inflammatory RANKL signaling and osteoclast activity. To the best of our knowledge, this is the first report on 14-3-3ζ regulation of RANKL signaling and osteoclast activation.

Structural Features and Physiological Associations of Human 14-3-3ζ Pseudogenes

There are about 14,000 pseudogenes that are mutated or truncated sequences resembling functional parent genes. About two-thirds of pseudogenes are processed, while others are duplicated. Although initially thought dead, emerging studies indicate they have functional and regulatory roles. We study 14-3-3ζ, an adaptor protein that regulates cytokine signaling and inflammatory diseases, including rheumatoid arthritis, cancer, and neurological disorders. To understand how 14-3-3ζ (gene symbol YWHAZ) performs diverse functions, we examined the human genome and identified nine YWHAZ pseudogenes spread across many chromosomes. Unlike the 32 kb exon-to-exon sequence in YWHAZ, all pseudogenes are much shorter and lack introns. Out of six, four YWHAZ exons are highly conserved, but the untranslated region (UTR) shows significant diversity. The putative amino acid sequence of pseudogenes is 78-97% homologous, resulting in striking structural similarities with the parent protein. The OMIM and Decipher database searches revealed chromosomal loci containing pseudogenes are associated with human diseases that overlap with the parent gene. To the best of our knowledge, this is the first report on pseudogenes of the 14-3-3 family protein and their implications for human health. This bioinformatics-based study introduces a new insight into the complexity of 14-3-3ζ's functions in biology.

RDIVpSGP motif of ASPP2 binds to 14-3-3 and enhances ASPP2/k18/14-3-3 ternary complex formulation to promote BRAF/MEK/ERK signal inhibited cell proliferation in hepatocellular carcinoma

The Apoptosis Stimulating Protein of p53 2 (ASPP2) is a heterozygous insufficient tumor suppressor; however, its molecular mechanism(s) in tumor suppression is not completely understood. ASPP2 plays an essential role in cell growth, as shown by liver hepatocellular carcinoma (LIHC) RNA-seq assay using the Cancer Genome Atlas (TCGA) and High-Throughput-PCR assay using ASPP2 knockdown cells. These observations were further confirmed by in vivo and in vitro experiments. Mechanistically, N-terminus ASPP2 interacted with Keratin 18 (k18) in vivo and in vitro. Interestingly, the RDIVpSGP motif of ASPP2 associates with 14-3-3 and promotes ASPP2/k18/14-3-3 ternary-complex formation which promotes MEK/ERK signal activation by impairing 14-3-3 and BRAF association. Additionally, ASPP2-rAd injection promotes paclitaxel-suppressed tumor growth by suppressing cell proliferation in the BALB/c nude mice model. ASPP2 and k18 were preferentially downregulated in Hepatocellular Carcinoma (HCC), which predicted poor prognosis in HCC patients. Overall, these findings suggested that ASPP2 promoted BRAF/MEK/ERK signal activation by promoting the formation of an ASPP2/k18/14-3-3 ternary complex via the RDIVpSGP motif at the N terminus. Moreover, this study provides novel insights into the molecular mechanism of tumor suppression in HCC patients.

Immune regulations by 14-3-3: A misty terrain

The 14-3-3 proteins are known for their functions related to the cell cycle and play a prominent role in cancer-related diseases. Recent studies show that 14-3-3 proteins are also regulators of immune responses and are involved in the pathogenesis of autoimmune and infectious diseases. This focused review highlights the significant and recent studies on how 14-3-3 proteins influence innate and adaptive immune responses; specifically, their roles as immunogens and cytokine signaling regulators are discussed. These revelations have added numerous questions to the pre-existing list of challenges, including understanding the 14-3-3 proteins' mechanism of immunogenicity to dissecting the isoform-specific immune regulations.

14-3-3ζ: A suppressor of inflammatory arthritis

Inflammatory arthritis (IA) is a common disease that affects millions of individuals worldwide. Proinflammatory events during IA pathogenesis are well studied; however, loss of protective immunity remains underexplored. Earlier, we reported that 14-3-3zeta (ζ) has a role in T-cell polarization and interleukin (IL)-17A signal transduction. Here, we demonstrate that 14-3-3ζ knockout (KO) rats develop early-onset severe arthritis in two independent models of IA, pristane-induced arthritis and collagen-induced arthritis. Arthritic 14-3-3ζ KO animals showed an increase in bone loss and immune cell infiltration in synovial joints. Induction of arthritis coincided with the loss of anti-14-3-3ζ antibodies; however, rescue experiments to supplement the 14-3-3ζ antibody by passive immunization did not suppress arthritis. Instead, 14-3-3ζ immunization during the presymptomatic phase resulted in significant suppression of arthritis in both wild-type and 14-3-3ζ KO animals. Mechanistically, 14-3-3ζ KO rats exhibited elevated inflammatory gene signatures at the messenger RNA and protein levels, particularly for IL-1β. Furthermore, the immunization with recombinant 14-3-3ζ protein suppressed IL-1β levels, significantly increased anti-14-3-3ζ antibody levels and collagen production, and preserved bone quality. The 14-3-3ζ protein increased collagen expression in primary rat mesenchymal cells. Together, our findings indicate that 14-3-3ζ causes immune suppression and extracellular remodeling, which lead to a previously unrecognized IA-suppressive function.

Immunization with a Recombinant Protein of Trichinella britovi 14-3-3 Triggers an Immune Response but No Protection in Mice

14-3-3 proteins are present in all eukaryotic organisms and are ubiquitously expressed in a broad range of tissues and cellular compartments. They are regulatory adapter proteins that play key roles in a variety of signaling pathways, and have been proposed as suitable targets for the control and detection of certain parasites. Trichinella britovi is a widely-distributed parasitic nematode, transmitted through ingestion of meat products containing invasive larvae. The present study describes the cloning and expression of Tb14-3-3, and investigates the immunological and protective potential of the recombinant protein. Immunization of mice with rTb14-3-3 triggered an IgG response, and significant differences, in the profiles of secreted cytokines observed in vitro, between experimental groups. Nonetheless, neither specific antibodies, nor increased secretion of IFNγ, IL-4, and IL-10 cytokines, conferred greater protection against infection. No reduction in larval burden was observed during recovery at 48 dpi. Additionally, rTb14-3-3 was not recognized by sera from the infected control mice, except for one, suggesting some mismatch between native and recombinant Tb14-3-3 antigenic sites. Therefore, before 14-3-3 can be considered a potential tool for Trichinella detection and vaccination, more research regarding its target proteins, and actual specific function, is needed.

Mechanism and biomarkers in aortitis--a review

Aortitis can be the manifestation of an underlying infectious or noninfectious disease process. An autoimmune cause is suggested in a large proportion of noninfectious causes. Similar to other autoimmune diseases, the pathophysiology of aortitis has been investigated in detail, but the etiology remains unknown. Most cases of aortitis often go undetected for a long time and are often identified at late stages of the disease. Recent advances in imaging techniques have significantly improved the diagnosis of aortitis. However, significant challenges associated with the imaging techniques limit their use. Several routine inflammation-based markers, such as erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), and inflammatory cytokines, are nonspecific and, therefore, have limited use in the diagnosis of aortitis. The search for more specific serum biomarkers, which can facilitate detection and progression is under progress. Several autoantibodies have been identified, but assigning their role in the pathogenesis as well as their specificity remains a challenge. The current review addresses some of these issues in detail. KEY MESSAGES: • Noninfectious aortitis is an autoimmune disease. • Several biomarkers, including cytokines and autoantibodies, are increased in aortitis. • Imaging techniques, commonly used to detect aortitis, are associated with the high cost and technical challenges. • There is a need to develop low-cost biomarker-based detection tools. • The knowledge of biomarkers in aortitis detection is discussed.

The protein 14-3-3: A functionally versatile molecule in Giardia duodenalis

Giardia duodenalis is a cosmopolitan zoonotic protozoan parasite causing giardiasis, one of the most common diarrhoeal diseases in human and animals. Beyond its public health relevance, Giardia represents a valuable and fascinating model microorganism. The deep-branching phylogenetic position of Giardia, its simple life cycle and its minimalistic genomic and cellular organization provide a unique opportunity to define basal and "ancestral" eukaryotic functions. The eukaryotic 14-3-3 protein family represents a distinct example of phosphoserine/phosphothreonine-binding proteins. The extended network of protein-protein interactions established by 14-3-3 proteins place them at the crossroad of multiple signalling pathways that regulate physiological and pathological cellular processes. Despite the remarkable insight on 14-3-3 protein in different organisms, from yeast to humans, so far little attention was given to the study of this protein in protozoan parasites. However, in the last years, research efforts have provided evidences on unique properties of the single 14-3-3 protein of Giardia and on its association in key aspects of Giardia life cycle. In the first part of this chapter, a general overview of the features commonly shared among 14-3-3 proteins in different organisms (i.e. structure, target recognition, mode of action and regulatory mechanisms) is included. The second part focus on the current knowledge on the biochemistry and biology of the Giardia 14-3-3 protein and on the possibility to use this protein as target to propose new strategies for developing innovative antigiardial therapy.

The survival analysis and oncogenic effects of CFP1 and 14-3-3 expression on gastric cancer

Background & aim

Gastric cancer (GC) is the third-leading cause of cancer-related deaths. We established a prospective database of patients with GC who underwent surgical treatment. In this study, we explored the prognostic significance of the expression of CFP1 and 14-3-3 in gastric cancer, by studying the specimens collected from clinical subjects.

Materials & methods

Immunohistochemistry was used to detect the expression of CFP1 and 14-3-3 in 84 GC subjects, including 73 patients who have undergone radical gastrectomy and 11 patients who have not undergone radical surgery. Survival analysis was performed by km-plot data.

Results

According to the survival analysis, we can see that the survival time of patients with high expression of CFP1 is lower than the patients with low expression in gastric cancer, while the effect of 14-3-3 is just the opposite. The survival time of patients with higher expression of 14-3-3 is also longer.

Conclusion

The CFP1 and 14-3-3 genes can be used as prognostic markers in patients with GC, but the study is still needed to confirm.

14-3-3ζ-A Novel Immunogen Promotes Inflammatory Cytokine Production

The presence of autoantibodies against 14-3-3ζ in human autoimmune diseases indicates its antigenic function. However, neither the cause nor the consequence of this newly-identified antigenic function of 14-3-3ζ protein is known. To address this, we investigated the immunological functions of 14-3-3ζ by studying ex vivo effects on human peripheral blood mononuclear cells (PBMC) proliferation, polarization, and cytokine production. Exogenous 14-3-3ζ promoted PBMC proliferation and T cell polarization toward Th1 and Th17 populations. Significant increases in IFN-γ and IL-17 levels were observed in the presence of 14-3-3ζ. A specific increase in Th1 cells and IFN-γ production provided strong evidence for MHC class II presentation of 14-3-3ζ antigen. Particularly HLA-DRB1^*0401 allele strongly promoted 14-3-3ζ-induced IFN-γ producing cells. In contrast, prednisolone treatment suppressed both 14-3-3ζ-induced T cell polarization and cytokine production. Overall, we show that MHC presentation and the adaptor functions of 14-3-3ζ participate in promoting IFN-γ and IL-17 production, two of the cytokines commonly associated with autoimmune diseases. To the best of our knowledge, this is the first report describing the ex vivo antigenic function of 14-3-3ζ with human PBMC, thereby providing the basis of its immunological role in human diseases.

Increased 14-3-3β and γ protein isoform expressions in parasitic eosinophilic meningitis caused by Angiostrongylus cantonensis infection in mice

The 14-3-3 proteins are cerebrospinal fluid (CSF) markers of neuronal damage during infectious meningitis and Creutzfeldt-Jakob disease. Little is known about dynamic changes in the individual isoforms in response to parasitic eosinophilic meningitis. The purposes of this study were to determine the 14-3-3 protein isoform patterns, examine the kinetics and correlate the severity of blood brain barrier (BBB) damage with the expressions of these markers in mice with eosinophilic meningitis.

Mice were orally infected with 50 A. cantonensis L3 via an oro-gastric tube and sacrificed every week for 3 consecutive weeks after infection. The Evans blue method and BBB junctional protein expressions were used to measure changes in the BBB. Hematoxylin and eosin staining was used to analyze pathological changes in the mice brains following 1–3 weeks of infection with A. cantonensis. The levels of 14-3-3 protein isoforms in serum/CSF and brain homogenates were analyzed by Western blot, and immunohistochemistry (IHC) was used to explore the different isoform distributions of 14-3-3 proteins and changes in BBB junctional proteins in the mice brain meninges. Dexamethasone was injected intraperitoneally from the seventh day post infection (dpi) until the end of the study (21 dpi) to study the changes in BBB junctional proteins. The amounts of Evans blue, tight junction and 14-3-3 protein isoforms in the different groups of mice were compared using the nonparametric Kruskal-Wallis test.

There were significant increases in 14-3-3 protein isoforms β and γ in the CSF in the second and third weeks after infection compared to the controls and first week of infection, which were correlated with the severity of BBB damage in brain histology, and Evans blue extravasation. Using IHC to assess the distribution of 14-3-3 protein isoforms and changes in BBB junctional proteins in the mice brain meninges, the expressions of isoforms β, γ, ε, and θ and junctional proteins occludin and claudin-5 in the brain meninges increased over a 3-week period after infection compared to the controls and 1 week after infection. The administration of dexamethasone decreased the expressions of BBB junctional proteins occludin and claudin-5 in the mice brain meninges.

Our findings support that 14-3-3 proteins β and γ can potentially be used as a CSF marker of neuronal damage in parasitic eosinophilic meningitis caused by A. cantonensis.