UHRF1P contributes to IL-17A-mediated systemic lupus erythematosus via UHRF1-MAP4K3 axis

Inflammatory T cells contribute to the pathogenesis of autoimmune diseases such as systemic lupus erythematosus (SLE). Analysis of the T-cell transcriptomics data of two independent SLE patient cohorts by three machine learning models revealed the pseudogene UHRF1P as a novel SLE biomarker. The pseudogene-encoded UHRF1P protein was overexpressed in peripheral blood T cells of SLE patients. The UHRF1P protein lacks the amino-terminus of its parental UHRF1 protein, resulting in missing the proteasome-binding ubiquitin-like (Ubl) domain of UHRF1. T-cell-specific UHRF1P transgenic mice manifested the induction of IL-17A and autoimmune inflammation. Mechanistically, UHFR1P prevented UHRF1-induced Lys48-linked ubiquitination and degradation of MAP4K3 (GLK), which is a kinase known to induce IL-17A. Consistently, IL-17A induction and autoimmune phenotypes of UHRF1P transgenic mice were obliterated by MAP4K3 knockout. Collectively, UHRF1P overexpression in T cells inhibits the E3 ligase function of its parental UHRF1 and induces autoimmune diseases.

Association of TRAIL receptor with phosphatase SHP-1 enables repressing T cell receptor signaling and T cell activation through inactivating Lck

BACKGROUND

T cell receptor (TCR) signaling and T cell activation are tightly regulated by gatekeepers to maintain immune tolerance and avoid autoimmunity. The TRAIL receptor (TRAIL-R) is a TNF-family death receptor that transduces apoptotic signals to induce cell death. Recent studies have indicated that TRAIL-R regulates T cell-mediated immune responses by directly inhibiting T cell activation without inducing apoptosis; however, the distinct signaling pathway that regulates T cell activation remains unclear. In this study, we screened for intracellular TRAIL-R-binding proteins within T cells to explore the novel signaling pathway transduced by TRAIL-R that directly inhibits T cell activation.

METHODS

Whole-transcriptome RNA sequencing was used to identify gene expression signatures associated with TRAIL-R signaling during T cell activation. High-throughput screening with mass spectrometry was used to identify the novel TRAIL-R binding proteins within T cells. Co-immunoprecipitation, lipid raft isolation, and confocal microscopic analyses were conducted to verify the association between TRAIL-R and the identified binding proteins within T cells.

RESULTS

TRAIL engagement downregulated gene signatures in TCR signaling pathways and profoundly suppressed phosphorylation of TCR proximal tyrosine kinases without inducing cell death. The tyrosine phosphatase SHP-1 was identified as the major TRAIL-R binding protein within T cells, using high throughput mass spectrometry-based proteomics analysis. Furthermore, Lck was co-immunoprecipitated with the TRAIL-R/SHP-1 complex in the activated T cells. TRAIL engagement profoundly inhibited phosphorylation of Lck (Y394) and suppressed the recruitment of Lck into lipid rafts in the activated T cells, leading to the interruption of proximal TCR signaling and subsequent T cell activation.

CONCLUSIONS

TRAIL-R associates with phosphatase SHP-1 and transduces a unique and distinct immune gatekeeper signal to repress TCR signaling and T cell activation via inactivating Lck. Thus, our results define TRAIL-R as a new class of immune checkpoint receptors for restraining T cell activation, and TRAIL-R/SHP-1 axis can serve as a potential therapeutic target for immune-mediated diseases.

The phosphatase DUSP22 inhibits UBR2-mediated K63-ubiquitination and activation of Lck downstream of TCR signalling

DUSP22 is a dual-specificity phosphatase that inhibits T cell activation by inactivating the kinase Lck. Here we show that the E3 ubiquitin ligase UBR2 is a positive upstream regulator of Lck during T-cell activation. DUSP22 dephosphorylates UBR2 at specific Serine residues, leading to ubiquitin-mediated UBR2 degradation. UBR2 is also modified by the SCF E3 ubiquitin ligase complex via Lys48-linked ubiquitination at multiple Lysine residues. Single-cell RNA sequencing analysis and UBR2 loss of function experiments showed that UBR2 is a positive regulator of proinflammatory cytokine expression. Mechanistically, UBR2 induces Lys63-linked ubiquitination of Lck at Lys99 and Lys276 residues, followed by Lck Tyr394 phosphorylation and activation as part of TCR signalling. Inflammatory phenotypes induced by TCR-triggered Lck activation or knocking out DUSP22, are attenuated by genomic deletion of UBR2. UBR2-Lck interaction and Lck Lys63-linked ubiquitination are induced in the peripheral blood T cells of human SLE patients, which demonstrate the relevance of the UBR2-mediated regulation of inflammation to human pathology. In summary, we show here an important regulatory mechanism of T cell activation, which finetunes the balance between T cell response and aggravated inflammation.

Dual-Specificity Phosphatase 6 Deficiency Attenuates Arterial-Injury-Induced Intimal Hyperplasia in Mice

In response to injury, vascular smooth muscle cells (VSMCs) of the arterial wall dedifferentiate into a proliferative and migratory phenotype, leading to intimal hyperplasia. The ERK1/2 pathway participates in cellular proliferation and migration, while dual-specificity phosphatase 6 (DUSP6, also named MKP3) can dephosphorylate activated ERK1/2. We showed that DUSP6 was expressed in low baseline levels in normal arteries; however, arterial injury significantly increased DUSP6 levels in the vessel wall. Compared with wild-type mice, Dusp6-deficient mice had smaller neointima. In vitro, IL-1β induced DUSP6 expression and increased VSMC proliferation and migration. Lack of DUSP6 reduced IL-1β-induced VSMC proliferation and migration. DUSP6 deficiency did not affect IL-1β-stimulated ERK1/2 activation. Instead, ERK1/2 inhibitor U0126 prevented DUSP6 induction by IL-1β, indicating that ERK1/2 functions upstream of DUSP6 to regulate DUSP6 expression in VSMCs rather than downstream as a DUSP6 substrate. IL-1β decreased the levels of cell cycle inhibitor p27 and cell-cell adhesion molecule N-cadherin in VSMCs, whereas lack of DUSP6 maintained their high levels, revealing novel functions of DUSP6 in regulating these two molecules. Taken together, our results indicate that lack of DUSP6 attenuated neointima formation following arterial injury by reducing VSMC proliferation and migration, which were likely mediated via maintaining p27 and N-cadherin levels.

DUSP8 induces TGF-β-stimulated IL-9 transcription and Th9-mediated allergic inflammation by promoting nuclear export of Pur-α

Dual-specificity phosphatase 8 (DUSP8) is a MAPK phosphatase that dephosphorylates and inactivates the kinase JNK. DUSP8 is highly expressed in T cells; however, the in vivo role of DUSP8 in T cells remains unclear. Using T cell-specific Dusp8 conditional KO (T-Dusp8 cKO) mice, mass spectrometry analysis, ChIP-Seq, and immune analysis, we found that DUSP8 interacted with Pur-α, stimulated interleukin-9 (IL-9) gene expression, and promoted Th9 differentiation. Mechanistically, DUSP8 dephosphorylated the transcriptional repressor Pur-α upon TGF-β signaling, leading to the nuclear export of Pur-α and subsequent IL-9 transcriptional activation. Furthermore, Il-9 mRNA levels were induced in Pur-α-deficient T cells. In addition, T-Dusp8-cKO mice displayed reduction of IL-9 and Th9-mediated immune responses in the allergic asthma model. Reduction of Il-9 mRNA levels in T cells and allergic responses of T-Dusp8-cKO mice was reversed by Pur-α knockout. Remarkably, DUSP8 protein levels and the DUSP8-Pur-α interaction were indeed increased in the cytoplasm of T cells from people with asthma and patients with atopic dermatitis. Collectively, DUSP8 induces TGF-β-stimulated IL-9 transcription and Th9-induced allergic responses by inhibiting the nuclear translocation of the transcriptional repressor Pur-α. DUSP8 may be a T-cell biomarker and therapeutic target for asthma and atopic dermatitis.

Stroke Risk in Survivors of Head and Neck Cancer: A Descriptive Epidemiologic Cohort Study

PURPOSE/OBJECTIVE(S)

Survivors of head and neck cancer (HNC) have an increased risk of stroke. However, the evidence on the risk of stroke in various subpopulations of HNC defined by patient, disease and treatment factors remains unclear. This study aimed to determine whether age-standardized incidence rate ratios (SIRs) and risk differences (SIRDs) of stroke varied across different subpopulations of survivors of HNC.

MATERIALS/METHODS

We used data from the national stroke and cancer registries to identify all cases of HNC who developed their first stroke after HNC diagnosis from January 2005 to December 2020. We estimated the SIRs and SIRDs of stroke in various subgroups of HNC defined by patient, disease and treatment factors using the Singapore general population as the reference group.

RESULTS

A total of 8839 cases of HNC were identified and 308 cases (3.4%) developed stroke after HNC diagnosis at median follow up of 42.5 months (interquartile range 15.0 - 94.5 months). The overall SIR and SIRD were 2.46 (95% CI 2.21 - 2.74) and 4.11 cases per 1000 person-years (PY) (95% CI 3.37 - 4.85). The SIR and SIRD were higher among those post five years from HNC diagnosis compared to those with 5 or fewer years from HNC diagnosis (SIR: 3.92 (3.36 - 4.58) vs 1.84 (1.59 - 2.14), SIRD: 6.64 (5.26 - 8.03) vs 2.65 (1.80 - 3.50) cases per 1000 PY). The SIR was highest for those less than 40 years old (< 40 years: 30.55; 40 - 49 years: 5.84; 50 - 59 years: 3.13; 60 - 69 years: 2.38, 70 - 79 years: 1.53, > = 80 years: 1.41) while SIRD was highest for those with age 80 years and above (< 40 years: 2.16; 40 - 49 years: 3.44, 50 - 59 years: 4.25, 60 - 69 years: 5.55, 70 - 79 years: 4.16, > = 80 years: 6.14). Among those who had treatment within 6 months of HNC diagnosis, the SIR and SIRD were significantly higher among those who had primary radiation treatment approach (radiation only, radiation and chemotherapy) (SIR: 3.01 (2.64 - 3.43), SIRD: 5.12 (4.18 - 6.29) cases per 1000 PY) compared to primary surgery treatment approach (surgery only, surgery and radiation, surgery and chemotherapy and radiation) (SIR: 1.64 (1.31 - 2.05), SIRD: 1.84 (0.92 - 3.67)).

CONCLUSION

The risk of stroke varied across different subpopulations of survivors of HNC with higher risk observed in those surviving five years post HNC diagnosis, less than 40 years old or received primary radiation treatment approach within 6 months from HNC diagnosis. A risk based prophylactic measures for stroke should be considered for different subpopulations of survivors of HNC.

Adjuvant Breast Radiation Therapy for Early-Stage Breast Cancer or Ductal Carcinoma In-Situ in the Breast: A Systematic Review and Network Meta-Analysis of Randomized Trials

PURPOSE/OBJECTIVE(S)

For selected patients with early-stage breast cancer (BC) or ductal carcinoma in-situ (DCIS) in the breast, adjuvant breast radiation therapy (RT) approaches include partial breast irradiation (PBI), altered fractionation (AF) whole breast irradiation (WBI) or tumor bed boost (TBB). However, it is unclear which is the optimal approach. This study aims to compare the effects of different PBI, AF-WBI and TBB options on ipsilateral breast tumor recurrence (IBTR), overall survival (OS) and patient reported cosmesis (PRC) outcomes.

MATERIALS/METHODS

We searched various biomedical electronic databases for eligible randomized trials (RCTs) from date of inception to January 2023. We constructed six separate random effects frequentist network meta-analyses (NMA) to compare the effects of various PBI options using WBI as the reference; various AF-WBI options using conventional fractionated (CF) WBI as the reference and various TBB options using no TBB as the reference on IBTR and OS. The GRADE approach was used to assess the certainty of evidence. The synthesis without meta-analysis approach was pre-specified for evaluation of PRC in anticipation of various assessment and reporting methods.

RESULTS

We included 34 RCTs comprising 49,899 participants and 11 treatment options. Evidence suggests that accelerated PBI (Hazard Ratio (HR) 1.36 (95% confidence interval (CI) 0.77 - 2.41, moderate certainty), moderately hypofractionated (MHF) PBI (HR 1.38 (0.60 - 3.19), moderate certainty) and intraoperative PBI (HR 1.47 (0.81 - 2.68), low certainty) was associated with a modest but not statistically significant increase in the hazards for IBTR when compared to WBI. There was moderate certainty evidence that there were no significant differences among the accelerated ultra-hypo fractionated (AUHF) WBI (HR 0.76 (0.50 - 1.14)), MHF-WBI (HR 0.99 (0.84 - 1.16)) or UHF-WBI (HR (1.35 (0.47 - 3.92)) when compared with CF-WBI for IBTR. The effects of sequential TBB (seqTBB) (HR 0.61 (0.52 - 0.70), high certainty) and simultaneous integrated TBB (simTBB) (HR 0.77 (0.55 - 1.09), moderate certainty) on IBTR were similar when compared to no TBB. There were no significant differences in OS between PBI options and WBI, AF-WBI options and CF-WBI, TBB options and no TBB. Among the PBI vs WBI trials, MHF-PBI and APBI may be associated with fewer adverse PRC events. Among the AF-WBI vs CF-WBI trials, half of the included trials reported fewer adverse PRC events with MHF-WBI. SeqTBB and simTBB had similar adverse PRC outcome.

CONCLUSION

There were no significant differences among the PBI, AF-WBI and TBB options for IBTR and OS. PBI and AF-WBI may be associated with less adverse PRC events compared with WBI and CF-WBI respectively. There was no evidence to suggest a difference between seqTBB and simTBB for PRC outcome. This study is registered with PROSPERO CRD 42021245074.

ACE2 in chronic disease and COVID-19: gene regulation and post-translational modification

Angiotensin-converting enzyme 2 (ACE2), a counter regulator of the renin-angiotensin system, provides protection against several chronic diseases. Besides chronic diseases, ACE2 is the host receptor for SARS-CoV or SARS-CoV-2 virus, mediating the first step of virus infection. ACE2 levels are regulated by transcriptional, post-transcriptional, and post-translational regulation or modification. ACE2 transcription is enhanced by transcription factors including Ikaros, HNFs, GATA6, STAT3 or SIRT1, whereas ACE2 transcription is reduced by the transcription factor Brg1-FoxM1 complex or ERRα. ACE2 levels are also regulated by histone modification or miRNA-induced destabilization. The protein kinase AMPK, CK1α, or MAP4K3 phosphorylates ACE2 protein and induces ACE2 protein levels by decreasing its ubiquitination. The ubiquitination of ACE2 is induced by the E3 ubiquitin ligase MDM2 or UBR4 and decreased by the deubiquitinase UCHL1 or USP50. ACE2 protein levels are also increased by the E3 ligase PIAS4-mediated SUMOylation or the methyltransferase PRMT5-mediated ACE2 methylation, whereas ACE2 protein levels are decreased by AP2-mediated lysosomal degradation. ACE2 is downregulated in several human chronic diseases like diabetes, hypertension, or lung injury. In contrast, SARS-CoV-2 upregulates ACE2 levels, enhancing host cell susceptibility to virus infection. Moreover, soluble ACE2 protein and exosomal ACE2 protein facilitate SARS-CoV-2 infection into host cells. In this review, we summarize the gene regulation and post-translational modification of ACE2 in chronic disease and COVID-19. Understanding the regulation and modification of ACE2 may help to develop prevention or treatment strategies for ACE2-mediated diseases.

Hematopoietic progenitor kinase 1 inhibits the development and progression of pancreatic intraepithelial neoplasia

Ras plays an essential role in the development of acinar to ductal metaplasia (ADM) and pancreatic ductal adenocarcinoma (PDAC). However, mutant Kras is an inefficient driver for PDAC development. The switching mechanisms from low Ras activity to high Ras activity that is required for development and progression of pancreatic intraepithelial neoplasia (PanIN) are unclear. In this study, we found that HPK1 was upregulated during pancreatic injury and ADM. HPK1 interacted with the SH3 domain and phosphorylated Ras GTPase activating protein (RasGAP) and upregulated RasGAP activity. Using the transgenic mouse models of HPK1 or M46, a kinase-dead mutant of HPK1, we showed that HPK1 inhibited Ras activity and its downstream signaling and regulated acinar cell plasticity. M46 promoted the development of ADM and PanINs. Expression of M46 in KrasG12D;Bac mice promoted the infiltration of myeloid-derived suppressor cells and macrophages, inhibited the infiltration of T cells, and accelerated the progression of PanINs to invasive and metastatic PDAC, while HPK1 attenuated mutant Kras-driven PanIN progression. Our results showed that HPK1 plays an important role in ADM and the progression of PanINs by regulating Ras signaling. Loss of HPK1 kinase activity promotes an immunosuppressive tumor microenvironment and accelerates the progression of PanINs to PDAC.

DUSP6 Deficiency Attenuates Neurodegeneration after Global Cerebral Ischemia

Transient global cerebral ischemia (tGCI) resulting from cardiac arrest causes selective neurodegeneration in hippocampal CA1 neurons. Although the effect is clear, the underlying mechanisms directing this process remain unclear. Previous studies have shown that phosphorylation of Erk1/2 promotes cell survival in response to tGCI. DUSP6 (also named MKP3) serves as a cytosolic phosphatase that dephosphorylates Erk1/2, but the role of DUSP6 in tGCI has not been characterized. We found that DUSP6 was specifically induced in the cytoplasm of hippocampal CA1 neurons 4 to 24 h after tGCI. DUSP6-deficient mice showed normal spatial memory acquisition and retention in the Barnes maze. Impairment of spatial memory acquisition and retention after tGCI was attenuated in DUSP6-deficient mice. Neurodegeneration after tGCI, revealed by Fluoro-Jade C and H&E staining, was reduced in the hippocampus of DUSP6-deficient mice and DUSP6 deficiency enhanced the phosphorylation and nuclear translocation of Erk1/2 in the hippocampal CA1 region. These data support the role of DUSP6 as a negative regulator of Erk1/2 signaling and indicate the potential of DUSP6 inhibition as a novel therapeutic strategy to treat neurodegeneration after tGCI.

Dual-specificity phosphatases 22-deficient T cells contribute to the pathogenesis of ankylosing spondylitis

BACKGROUND

Dual-specificity phosphatases (DUSPs) can dephosphorylate both tyrosine and serine/threonine residues of their substrates and regulate T cell-mediated immunity and autoimmunity. The aim of this study was to investigate the potential roles of DUSPs in ankylosing spondylitis (AS).

METHODS

Sixty AS patients and 45 healthy controls were enrolled in this study. Associations of gene expression of 23 DUSPs in peripheral T cells with inflammatory cytokine gene expression and disease activity of AS were analyzed. Finally, we investigated whether the characteristics of AS are developed in DUSP-knockout mice.

RESULTS

The mRNA levels of DUSP4, DUSP5, DUSP6, DUSP7, and DUSP14 in peripheral T cells were significantly higher in AS group than those of healthy controls (all p < 0.05), while DUSP22 (also named JKAP) mRNA levels were significantly lower in AS group than healthy controls (p < 0.001). The mRNA levels of DUSP4, DUSP5, DUSP6, DUSP7, and DUSP14 in T cells were positively correlated with mRNA levels of tumor necrosis factor-α (TNF-α), whereas DUSP22 was inversely correlated (all p < 0.05). In addition, inverse correlations of DUSP22 gene expression in peripheral T cells with C-reactive protein, erythrocyte sedimentation rate, and Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) were observed (all p < 0.05). More importantly, aged DUSP22 knockout mice spontaneously developed syndesmophyte formation, which was accompanied by an increase of TNF-α⁺, interleukin-17A⁺, and interferon-γ⁺ CD3⁺ T cells.

CONCLUSIONS

DUSP22 may play a crucial role in the pathogenesis and regulation of disease activity of AS.

SARS-CoV-2 spike protein enhances MAP4K3/GLK-induced ACE2 stability in COVID-19

ACE2 on epithelial cells is the SARS-CoV-2 entry receptor. Single-cell RNA-sequencing data derived from two COVID-19 cohorts revealed that MAP4K3/GLK-positive epithelial cells were increased in patients. SARS-CoV-2-induced GLK overexpression in epithelial cells was correlated with COVID-19 severity and vesicle secretion. GLK overexpression induced the epithelial cell-derived exosomes containing ACE2; the GLK-induced exosomes transported ACE2 proteins to recipient cells, facilitating pseudovirus infection. Consistently, ACE2 proteins were increased in the serum exosomes from another COVID-19 cohort. Remarkably, SARS-CoV-2 spike protein-stimulated GLK, and GLK stabilized ACE2 in epithelial cells. Mechanistically, GLK phosphorylated ACE2 at two serine residues (Ser776, Ser783), leading to the dissociation of ACE2 from its E3 ligase UBR4. Reduction in UBR4-induced Lys48-linked ubiquitination at three lysine residues (Lys26, Lys112, Lys114) of ACE2 prevented its degradation. Furthermore, SARS-CoV-2 pseudovirus or live virus infection in humanized ACE2 mice induced GLK and ACE2 protein levels, and ACE2-containing exosomes. Collectively, ACE2 stabilization by SARS-CoV-2-induced MAP4K3/GLK may contribute to the pathogenesis of COVID-19.

DUSP3 regulates phosphorylation-mediated degradation of occludin and is required for maintaining epithelial tight junction

Background

Tight junctions (TJ) are multi-protein complexes that hold epithelial cells together and form structural and functional barriers for maintaining proper biological activities. Dual specificity phosphatase 3 (DUSP3), a suppressor of multiple protein tyrosine (Tyr) kinases, is decreased in lung cancer tissues. Here we demonstrated the role of DUSP3 in regulation of epithelial TJ.

Methods

Barrier functions of TJ were examined in wild-type or DUSP3-deficient lung epithelial cells. Animal and clinical data were analyzed for the association between DUSP3 deficiency and lung cancer progression. Proximity ligation assay, immunoblotting, and phosphatase assay were performed to study the effect of DUSP3 on the TJ protein occludin (OCLN). Mutations of Tyr residues on OCLN showed the role of Tyr phosphorylation in regulating OCLN.

Results

Compared to those of the DUSP3-expressing cells, we found the expression and distribution of ZO-1, a TJ-anchoring molecule, were abnormal in DUSP3-deficient cells. OCLN had an increased phosphorylation level in DUSP3-deficient cells. We identified that OCLN is a direct substrate of DUSP3. DUSP3 regulated OCLN ubiquitination and degradation through decreasing OCLN tyrosine phosphorylation directly or through suppressing focal adhesion kinase, the OCLN kinase.

Conclusion

Our study revealed that DUSP3 is an important TJ regulatory protein and its decrease may be involved in progression of epithelial cancers.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12929-022-00826-x.

T-cell-derived Exosomal Proteins ECP and BPI Induce Cytokines and Tissue Inflammation in Systemic Lupus Erythematosus

T cells play critical roles in the pathogenesis of systemic lupus erythematosus (SLE). Serum-derived exosomes are increased in human SLE patients and are correlated with disease severity; however, the property of T-cell-derived exosomes from SLE patients remains unclear. We characterized proteins of SLE T cell-derived exosomes by exosome MACSPlex analysis and proteomics using T-cell supernatants from human SLE patients and healthy controls. We identified two exosoaml proteins, eosinophil cationic protein (ECP, also named human RNase 3) and bactericidal/permeability-increasing protein (BPI), which were overexpressed in SLE T-cell-derived exosomes and T cells. Both T-cell-specific ECP transgenic (Lck-ECP Tg) and BPI transgenic (Lck-BPI Tg) mice displayed multi-tissue inflammation. Lck-ECP and Lck-BPI Tg mice displayed early induction of serum IFN-γ levels and IL-1β levels, respectively. Single-cell RNA sequencing (scRNA-seq) showed the induction of IFN-γ mRNA and inflammatory pathways in ECP Tg T cells. ScRNA-seq also showed the reduction of Treg population in BPI Tg T cells; conversely, Treg differentiation was enhanced by BPI knockout. Remarkably, adoptively transferred ECP-containing or BPI-containing exosomes stimulated serum autoantibodies levels and induced nephritis/nephritis/arthritis in the recipient mice. Collectively, ECP or BPI overexpression in T-cell-derived exosomes or T cells are novel biomarkers and pathogenic factors for human SLE nephritis, hepatitis, and arthritis.

MAP4K3/GLK inhibits Treg differentiation by direct phosphorylating IKKβ and inducing IKKβ-mediated FoxO1 nuclear export and Foxp3 downregulation

Rationale: GLK (MAP4K3) activates PKCθ-IKKβ axis in T-cell activation and induces IL-17A-mediated autoimmune diseases. Attenuation of Treg differentiation and function by GLK could also contribute to autoimmune diseases.

Methods: We analyzed the roles of GLK and IKKβ in Treg differentiation and function using T-cell-specific GLK transgenic mice and IKKβ conditional knockout mice. The mechanism of GLK/IKKβ-mediated attenuation of Treg differentiation/function was studied by chromatin-immunoprecipitation, reporter assays, in vitro kinase assays, protein-protein interaction assays, mass spectrometry, confocal microscopy, flow cytometry, and single-cell RNA sequencing (scRNA-seq) analysis.

Results: We found that GLK signaling inhibited Foxp3 transcription by blocking the function of the transcription factor FoxO1. Mechanistically, GLK directly phosphorylated and activated IKKβ at Ser733 in a PKCθ-independent manner. The phospho-IKKβ Ser733 induced FoxO1 Ser319 phosphorylation and nuclear export, leading to Foxp3 downregulation. Consistently, scRNA-seq analyses showed that Foxp3 mRNA levels were inversely correlated with FoxO1 mRNA levels in GLK transgenic CD4⁺ T cells.

Conclusions: GLK-IKKβ-FoxO1 signaling axis inhibits Foxp3 transcription, leading to reduction of Treg differentiation and suppressive activity, as well as induction of autoimmune disease.

BPI overexpression suppresses Treg differentiation and induces exosome-mediated inflammation in systemic lupus erythematosus

Background: Serum-derived exosomes are correlated with disease severity of human systemic lupus erythematosus (SLE). The proteins in the T-cell-derived exosomes from SLE patients could contribute to inflammation.

Methods: We characterized proteins of T cell-derived exosomes from SLE patients and healthy controls by proteomics. To study the potential pathogenic role of the identified exosomal protein, we generated and characterized T-cell-specific transgenic mice that overexpressed the identified protein in T cells using immunohistochemistry, immunoblotting, and single-cell RNA sequencing.

Results: We identified an overexpressed protein, bactericidal/permeability-increasing protein (BPI), in SLE T cells and T-cell-derived exosomes. T-cell-specific BPI transgenic (Lck-BPI Tg) mice showed multi-tissue inflammation with early induction of serum IL-1β levels, as well as serum triglyceride and creatinine levels. Interestingly, exosomes of Lck-BPI Tg T cells stimulated IL-1β expression of wild-type recipient macrophages. Remarkably, adoptive transfer of BPI-containing exosomes increased serum IL-1β and autoantibody levels in recipient mice. The transferred exosomes infiltrated into multiple tissues of recipient mice, resulting in hepatitis, nephritis, and arthritis. ScRNA-seq showed that Lck-BPI Tg T cells displayed a decrease of Treg population, which was concomitant with ZFP36L2 upregulation and Helios downregulation. Furthermore, in vitro Treg differentiation was reduced by BPI transgene and enhanced by BPI knockout.

Conclusions: BPI is a negative regulator of Treg differentiation. BPI overexpression in T-cell-derived exosomes or peripheral blood T cells may be a biomarker and pathogenic factor for human SLE nephritis, hepatitis, and arthritis.

Identification of a gut microbiota member that ameliorates DSS-induced colitis in intestinal barrier enhanced Dusp6-deficient mice

Strengthening the gut epithelial barrier is a potential strategy for management of gut microbiota-associated illnesses. Here, we demonstrate that dual-specificity phosphatase 6 (Dusp6) knockout enhances baseline colon barrier integrity and ameliorates dextran sulfate sodium (DSS)-induced colonic injury. DUSP6 mutation in Caco-2 cells enhances the epithelial feature and increases mitochondrial oxygen consumption, accompanied by altered glucose metabolism and decreased glycolysis. We find that Dusp6-knockout mice are more resistant to DSS-induced dysbiosis, and the cohousing and fecal microbiota transplantation experiments show that the gut/fecal microbiota derived from Dusp6-knockout mice also confers protection against colitis. Further culturomics and mono-colonialization experiments show that one gut microbiota member in the genus Duncaniella confers host protection from DSS-induced injury. We identify Dusp6 deficiency as beneficial for shaping the gut microbiota eubiosis necessary to protect against gut barrier-related diseases.

Genomic sequencing and functional analyses identify MAP4K3/GLK germline and somatic variants associated with systemic lupus erythematosus

OBJECTIVES

MAP4K3 (GLK) overexpression in T cells induces interleukin (IL)-17A production and autoimmune responses. GLK overexpressing T-cell population is correlated with severity of human systemic lupus erythematosus (SLE); however, it is unclear how GLK is upregulated in patients with SLE.

METHODS

We enrolled 181 patients with SLE and 250 individuals without SLE (93 healthy controls and 157 family members of patients with SLE) in two independent cohorts from different hospitals/cities. Genomic DNAs of peripheral blood mononuclear cells were subjected to next-generation sequencing to identify GLK gene variants. The functional consequences of the identified GLK germline or somatic variants were investigated using site-directed mutagenesis and cell transfection, followed by reporter assays, mass spectrometry, immunoblotting, coimmunoprecipitation, and in situ proximity ligation assays.

RESULTS

We identified 58 patients with SLE from Cohort #1 and #2 with higher frequencies of a somatic variant (chr2:39 477 124 A>G) in GLK 3'-untranslated region (UTR); these patients with SLE showed increased serum anti-double-stranded DNA levels and decreased serum C3/C4 levels. This somatic variant in 3'-UTR enhanced GLK mRNA levels in T cells. In addition, we identified five patients with SLE with GLK (A410T) germline variant in Cohort #1 and #2, as well as two other patients with SLE with GLK (K650R) germline variant in Cohort #1. Another GLK germline variant, A579T, was also detected in one patient with SLE from Cohort #2. Both GLK (A410T) and GLK (K650R) mutants inhibited GLK ubiquitination induced by the novel E3 ligase makorin ring-finger protein 4 (MKRN4), leading to GLK protein stabilisation.

CONCLUSIONS

Multiple GLK germline and somatic variants cause GLK induction by increasing mRNA or protein stability in patients with SLE.

Malaysian consensus statement on FDG PET-CT reporting format for lymphoma

Over the past decade, 18F-Fluorodeoxyglucose (FDG) positron emission tomography-computed tomography (PETCT) has emerged as an important imaging modality in the management of lymphoma. Since the introduction of Deauville scoring system (2009) and the Lymphoma Response Assessment Criteria (2014), clinicians are now sharing a common language in the management of lymphoma. In Malaysia, nearly a third of PET-CT request is related to lymphoma imaging. Though there are extensive publications regarding these scoring systems and assessment criteria for lymphoma, there are hardly any literature on the reporting format for the 18F-FDG PET-CT in this disease. The variable reporting formats have on many occasions caused confusion not only to the referring clinicians but also to nuclear medicine physicians. Thus, a working committee comprising experienced nuclear medicine physicians and haematologists in Malaysia have agreed and made a joint recommendation on the standard reporting format for 18F-FDG PET-CT in Lymphoma. This recommendation will minimize inter-observer discrepancies in reporting, facilitate the understanding of the report of the referring clinicians as well as facilitate counseling between patients and clinicians in the management of the disease.

ECP Overexpression in T Cells and Exosomes Induces IFN-γ Production and Tissue Inflammation

Objective

T cells play a critical role in the pathogenesis of systemic lupus erythematosus (SLE). Serum‐derived exosomes are increased in SLE patients and are correlated with disease severity. This study was undertaken to investigate whether T cell–derived exosomal proteins play a role in SLE pathogenesis.

Methods

We characterized proteins in T cell–derived exosomes from SLE patients and healthy controls by MACSPlex exosome analysis and proteomics. To study the potential pathogenic functions of the exosomal protein identified, we generated and characterized T cell–specific transgenic mice that overexpressed that protein in T cells.

Results

We identified eosinophil cationic protein (ECP, also called human RNase III) as overexpressed in SLE T cell–derived exosomes. T cell–specific ECP–transgenic mice (n = 5 per group) displayed early induction of serum interferon‐γ (IFNγ) levels (P = 0.062) and inflammation of multiple tissue types. Older T cell–specific ECP–transgenic mice (n = 3 per group) also displayed an increase in follicular helper T cell and plasma B cell numbers, and in autoantibody levels (P < 0.01). Single‐cell RNA sequencing showed the induction of IFNγ messenger RNA (P = 2.2 × 10^‐13) and inflammatory pathways in ECP‐transgenic mouse T cells. Notably, adoptively transferred ECP‐containing exosomes stimulated serum autoantibody levels (P < 0.01) and tissue IFNγ levels in the recipient mice (n = 3 per group). The transferred exosomes infiltrated into multiple tissues of the recipient mice, resulting in hepatitis, nephritis, and arthritis.

Conclusion

Our findings indicate that ECP overexpression in T cells or T cell–derived exosomes may be a biomarker and pathogenic factor for nephritis, hepatitis, and arthritis associated with SLE.

DUSP11 Attenuates Lipopolysaccharide-Induced Macrophage Activation by Targeting TAK1

Dual-specificity phosphatase 11 (DUSP11, also named as PIR1) is a member of the atypical DUSP protein tyrosine phosphatase family. DUSP11 is only known to be an RNA phosphatase that regulates noncoding RNA stability. To date, the role of DUSP11 in immune cell signaling and immune responses remains unknown. In this study, we generated and characterized the immune cell functions of DUSP11-deficient mice. We identified TGF-β-activated kinase 1 (TAK1) as a DUSP11-targeted protein. DUSP11 interacted directly with TAK1, and the DUSP11-TAK1 interaction was enhanced by LPS stimulation in bone marrow-derived macrophages. DUSP11 deficiency enhanced the LPS-induced TAK1 phosphorylation and cytokine production in bone marrow-derived macrophages. Furthermore, DUSP11-deficient mice were more susceptible to LPS-induced endotoxic shock. The LPS-induced serum levels of IL-1β, TNF-α, and IL-6 were significantly elevated in DUSP11-deficient mice compared with those of wild-type mice. The data indicate that DUSP11 inhibits LPS-induced macrophage activation by targeting TAK1.

MAP4K Family Kinases and DUSP Family Phosphatases in T-Cell Signaling and Systemic Lupus Erythematosus

T cells play a critical role in the pathogenesis of systemic lupus erythematosus (SLE), which is a severe autoimmune disease. In the past 60 years, only one new therapeutic agent with limited efficacy has been approved for SLE treatment; therefore, the development of early diagnostic biomarkers and therapeutic targets for SLE is desirable. Mitogen-activated protein kinase kinase kinase kinases (MAP4Ks) and dual-specificity phosphatases (DUSPs) are regulators of MAP kinases. Several MAP4Ks and DUSPs are involved in T-cell signaling and autoimmune responses. HPK1 (MAP4K1), DUSP22 (JKAP), and DUSP14 are negative regulators of T-cell activation. Consistently, HPK1 and DUSP22 are downregulated in the T cells of human SLE patients. In contrast, MAP4K3 (GLK) is a positive regulator of T-cell signaling and T-cell-mediated immune responses. MAP4K3 overexpression-induced RORγt–AhR complex specifically controls interleukin 17A (IL-17A) production in T cells, leading to autoimmune responses. Consistently, MAP4K3 and the RORγt–AhR complex are overexpressed in the T cells of human SLE patients, as are DUSP4 and DUSP23. In addition, DUSPs are also involved in either human autoimmune diseases (DUSP2, DUSP7, DUSP10, and DUSP12) or T-cell activation (DUSP1, DUSP5, and DUSP14). In this review, we summarize the MAP4Ks and DUSPs that are potential biomarkers and/or therapeutic targets for SLE.

DUSP22 suppresses prostate cancer proliferation by targeting the EGFR-AR axis

Dual-specificity phosphatases (DUSPs) regulate the activity of various downstream kinases through serine or threonine or tyrosine dephosphorylation. Loss of function and aberrant expression of DUSPs has been implicated in cancer progression and poor survival, yet the function of DUSP22 in prostate cancer (PCa) cells is not clear. Gene Expression Omnibus and cBioPortal microarray database analyses showed that DUSP22 expression was lower in PCa tissues than normal prostate tissues, and altered DUSP22 expression was associated with shorter progression-free and disease-free survival of patients with PCa. Exogenous DUSP22 expression in LNCaP, PC3, and C4-2B PCa cells inhibited cellular proliferation and colony formation, supporting a growth inhibitory role for DUSP22 in PCa cells. DUSP22 expression significantly attenuated epidermal growth factor (EGF) receptor (EGFR) and its downstream ERK1/2 signaling by dephosphorylation. However, DUSP22 failed to suppress the growth of CWR22Rv1 and DU145 cells with elevated phosphorylated (p-)ERK1/2 levels. A serine-to-alanine mutation at position 58, a potential ERK1/2-targeted phosphorylation site in DUSP22, was sufficient to suppress growth of CWR22Rv1 cells with elevated p-ERK1/2 levels, suggesting a mutually antagonistic relationship between DUSP22 and ERK1/2 dependent on phosphorylation status. We showed that DUSP22 can suppress prostate-specific antigen gene expression through phosphatase-dependent pathways, suggesting that DUSP22 is an important regulator of the androgen receptor (AR) in PCa cells. Mechanistically, DUSP22 can interact with AR as a regulatory partner and interfere with EGF-induced AR phosphorylation at Tyr534, suggesting that DUSP22 serves as a crucial suppressor of both EGFR and AR-dependent signaling in PCa cells via dephosphorylation. Our findings indicate that loss of function of DUSP22 in PCa cells leads to aberrant activation of both EGFR-ERKs and AR signaling and ultimately progression of PCa, supporting the potential for novel therapeutic design of harnessing DUSP22 in the treatment of PCa.-Lin, H.-P., Ho, H.-M., Chang, C.-W., Yeh, S.-D., Su, Y.-W., Tan, T.-H., Lin, W.-J. DUSP22 suppresses prostate cancer proliferation by targeting the EGFR-AR axis.

MAP4K3/GLK in autoimmune disease, cancer and aging

MAP4K3 (also named GLK) is a serine/threonine kinase, which belongs to the mammalian Ste20-like kinase family. At 22 years of age, GLK was initially cloned and identified as an upstream activator of the MAPK JNK under an environmental stress and proinflammatory cytokines. The data derived from GLK-overexpressing or shRNA-knockdown cell lines suggest that GLK may be involved in cell proliferation through mTOR signaling. GLK phosphorylates the transcription factor TFEB and retains TFEB in the cytoplasm, leading to inhibition of cell autophagy. After generating and characterizing GLK-deficient mice, the important in vivo roles of GLK in T-cell activation were revealed. In T cells, GLK directly interacts with and activates PKCθ through phosphorylating PKCθ at Ser-538 residue, leading to activation of IKK/NF-κB. Thus, GLK-deficient mice display impaired T-cell-mediated immune responses and decreased inflammatory phenotypes in autoimmune disease models. Consistently, the percentage of GLK-overexpressing T cells is increased in the peripheral blood from autoimmune disease patients; the GLK-overexpressing T cell population is correlated with disease severity of patients. The pathogenic mechanism of autoimmune disease by GLK overexpression was unraveled by characterizing T-cell-specific GLK transgenic mice and using biochemical analyses. GLK overexpression selectively promotes IL-17A transcription by inducing the AhR-RORγt complex in T cells. In addition, GLK overexpression in cancer tissues is correlated with cancer recurrence of human lung cancer and liver cancer; the predictive power of GLK overexpression for cancer recurrence is higher than that of pathologic stage. GLK directly phosphorylates and activates IQGAP1, resulting in induction of Cdc42-mediated cell migration and cancer metastasis. Furthermore, treatment of GLK inhibitor reduces disease severity of mouse autoimmune disease models and decreases IL-17A production of human autoimmune T cells. Due to the inhibitory function of HPK1/MAP4K1 in T-cell activation and the promoting effects of GLK on tumorigenesis, HPK1 and GLK dual inhibitors could be useful therapeutic drugs for cancer immunotherapy. In addition, GLK deficiency results in extension of lifespan in Caenorhabditis elegans and mice. Taken together, targeting MAP4K3 (GLK) may be useful for treating/preventing autoimmune disease, cancer metastasis/recurrence, and aging.

AhR-ROR-γt complex is a therapeutic target for MAP4K3/GLKhighIL-17Ahigh subpopulation of systemic lupus erythematosus

The cytokine IL-17A plays critical roles in the pathogenesis of autoimmune diseases. The frequencies of MAP kinase kinase kinase kinase 3 [also named germinal center kinase-like kinase (GLK)]-overexpressing T cells are correlated with disease severity of systemic lupus erythematosus (SLE). T-cell-specific GLK-transgenic mice develop spontaneous autoimmune responses through IL-17A. GLK signaling selectively stimulates IL-17A production in murine T cells through inducing aryl hydrocarbon receptor (AhR)-retinoic acid receptor-related orphan nuclear receptor-γt (ROR-γt) complex formation. Here, we investigated whether GLK-induced AhR-ROR-γt complex in T cells is a therapeutic target for human SLE. The population of GLK⁺IL-17A⁺ T cells was enhanced in the peripheral blood from patients with SLE compared with that of healthy controls using flow cytometry. The receiver operating characteristic curve analysis showed that increased GLK⁺IL-17A⁺ T-cell population in peripheral blood reflected an active stage of SLE. In addition, peripheral blood T cells from patients with SLE displayed induction of ROR-γt phosphorylation and the AhR-ROR-γt (and AhR-phosphorylated ROR-γt) complex. Moreover, we identified a small-molecule inhibitor, verteporfin, that inhibited GLK kinase activity and AhR-ROR-γt interaction. The small-molecule inhibitor verteporfin suppressed the disease severity in autoimmune mouse models and IL-17A production in T cells from patients with SLE. Collectively, the GLK-induced AhR-ROR-γt (and AhR-phosphorylated ROR-γt) complex is a therapeutic target for the GLK^highIL-17A^high subpopulation of human patients with SLE.-Chuang, H.-C., Chen, Y.-M., Chen, M.-H., Hung, W.-T., Yang, H.-Y., Tseng, Y.-H., Tan, T.-H. AhR-ROR-γt complex is a therapeutic target for MAP4K3/GLK^highIL-17A^high subpopulation of systemic lupus erythematosus.

Application of 18F-FDG PET-CT in the management of pulmonary nodule and mass - a pictorial review

BACKGROUND

Lung cancer is one of the leading causes of cancer-related mortality worldwide. Pulmonary nodules are commonly encountered in clinical practice because of the recent implementation of low-dose CT lung screening programme, incidental finding on cardiac CT or CT for nonthoracic related disease. ¹⁸F-FDG PET-CT plays an important role in the management of pulmonary nodules.

METHODS

In this pictorial review, we present six different scenarios of using ¹⁸F-FDG PET-CT in the management of suspicious pulmonary nodule or mass. The advantages and limitations of ¹⁸F-FDG PET-CT and Herder model are discussed.

RESULTS

¹⁸F-FDG PET-CT with risk assessment using Herder model provides added value in characterising indeterminate pulmonary nodules. Besides, ¹⁸F-FDG PET-CT is valuable to guide the site of biopsy and provide accurate staging of lung cancer.

CONCLUSION

To further improve its diagnostic accuracy, careful history taking, and CT morphological evaluation should be taken into consideration when interpreting ¹⁸FFDG PET-CT findings in patients with these nodules.

T-cell signaling in Th17-mediated inflammation

MAP kinase kinase kinase kinases (MAP4Ks) are a subfamily of mammalian Ste20-like serine/threonine kinases that activate the JNK kinase cascade. We have cloned and characterized three MAP4Ks, namely HPK1 (MAP4K1), GLK (MAP4K3) and HGK (MAP4K4). Epigenetic downregulation of HGK (MAP4K4) in T cell results in differentiation of IL-6+ Th17 cells, which play important roles in the pathogenesis of Asia-prevalent non-obese T2D.

HPK1 (MAP4K1) is a negative regulator of T-cell signaling through phosphorylation and sequential ubiquitination of the T-cell adaptor SLP-76. GLK (MAP4K3) also interacts with SLP-76 but does not negatively regulate SLP-76. GLK activates PKC-θ during TCR signaling; GLK-deficient mice showed impaired Th17 differentiation. T-cell specific GLK transgenic mice spontaneously developed autoimmune diseases with an induction of systemic inflammation. We found that GLK signaling specifically induced IL-17A transcription in the T cells of GLK transgenic mice. We will present the data on a novel signal transduction mechanism of IL-17A transcriptional activation of AhR and RORγt by GLK in inflammatory T cells and activated T cells. In addition, we found that GLK negatively regulated differentiation and activity of Treg cells through IKKβ. Collectively, MAP4K3/GLK plays a critical role in IL-17A-induced inflammation.

Control of mucosal barrier functions and gut microbiome homeostasis by DUSP6 in colitis

Inflammatory bowel disease (IBD) is a common intermittent gastrointestinal condition and the incidence and prevalence of IBD are usually high in industrialized countries in North America and Europe. Several gut microbiome studies have been conducted in different IBD cohorts and certain specific taxonomic shifts have been associated with IBD. Although there is a relative escalation in the abundance of Enterobacteriaceae, including Escherichia coli and Fusobacterium, so far no single microbe has been demonstrated to cause IBD. It is plausible that intestinal microbiota dysbiosis may contribute to IBD pathogenesis by loss of health-promoting commensal symbionts or gain of pathobionts. We applied phosphoproteomics profiling and RNA-seq analysis in DUSP6-deficient Caco-2 cells. Our results suggested that DUSP6 could affect gut barrier functions and this is further confirmed with a dextran sulfate sodium (DSS)-induced colitis mouse model. Interestingly, with 16S rRNA gene sequencing we found that the gut/fecal microbiota in Dusp6-deficient mice was more resistant to DSS-induced dysbiosis compared with wild-type mice. In summary, these findings indicate that Dusp6-deficiency is a novel host genetic factor that could modulate gut barrier functions and mucosal immunity and inhibiting DUSP6 might be a novel strategy to shape the homeostasis of microbiota and beat IBD.

MAP4K3/GLK-induced AhR-RORγt complex is a novel therapeutic target for GLKhighIL-17Ahigh subpopulation of SLE patients

The cytokine IL-17A plays critical roles in the pathogenesis of autoimmune diseases. The frequencies of MAP4K3 (also named GLK)-overexpressing T cells are correlated with disease severity of systemic lupus erythematosus (SLE), rheumatoid arthritis (RA), and adult-onset Still’s disease. T-cell specific GLK transgenic mice develop spontaneous autoimmune responses. GLK signaling selectively stimulates IL-17A production in murine T cells through inducing AhR-RORγt complex formation. Here, we investigated whether GLK-induced AhR-RORγt complex in T cell is a therapeutic target for human SLE or RA. The population of GLK+IL-17A+ T cells was enhanced in the peripheral blood from SLE patients compared to that of healthy controls using flow cytometry. The ROC curve analyses showed that increased GLK+IL-17A+ T cell population in peripheral blood reflected an active stage of SLE. In addition, peripheral blood T cells from SLE or RA patients displayed induction of RORγt phosphorylation and the AhR-RORγt complex. Moreover, we identified a small-molecule GLK inhibitor that inhibited GLK kinase activity and AhR-RORγt interaction. The GLK inhibitor suppressed the disease severity in autoimmune mouse models and IL-17A production in T cells from SLE or RA patients. Collectively, GLK-induced AhR-RORγt complex is a therapeutic target for the GLKhighIL-17Ahigh subpopulation of SLE or RA patients.

MAP4K4 Inhibition Promotes Survival of Human Stem Cell-Derived Cardiomyocytes and Reduces Infarct Size In Vivo

Heart disease is a paramount cause of global death and disability. Although cardiomyocyte death plays a causal role and its suppression would be logical, no clinical counter-measures target the responsible intracellular pathways. Therapeutic progress has been hampered by lack of preclinical human validation. Mitogen-activated protein kinase kinase kinase kinase-4 (MAP4K4) is activated in failing human hearts and relevant rodent models. Using human induced-pluripotent-stem-cell-derived cardiomyocytes (hiPSC-CMs) and MAP4K4 gene silencing, we demonstrate that death induced by oxidative stress requires MAP4K4. Consequently, we devised a small-molecule inhibitor, DMX-5804, that rescues cell survival, mitochondrial function, and calcium cycling in hiPSC-CMs. As proof of principle that drug discovery in hiPSC-CMs may predict efficacy in vivo, DMX-5804 reduces ischemia-reperfusion injury in mice by more than 50%. We implicate MAP4K4 as a well-posed target toward suppressing human cardiac cell death and highlight the utility of hiPSC-CMs in drug discovery to enhance cardiomyocyte survival.

PP4 deficiency leads to DNA replication stress that impairs immunoglobulin class switch efficiency

The serine/threonine phosphatase PP4 has been implicated in DNA damage repair and cell cycle regulation through its dephosphorylation of specific substrates. We previously showed that PP4 is required for mouse B cell development, germinal center (GC) formation and immunoglobulin (Ig) class switch recombination (CSR). Here, we investigate the mechanisms underlying this requirement and demonstrate that murine PP4-deficient B lymphocytes have a defect in cell proliferation. Strikingly, the DNA damage response pathway that involves ATM/p53 and is linked to cell cycle arrest and impaired cell survival is strongly induced in these mutant B cells. In response to LPS + IL-4, stimuli that trigger IgG1 production, these PP4-deficient B cells show inefficient phosphorylation of ATR, leading to reduced retention of γH2AX-NBS1 complexes at sites of DNA damage, and compromised switching to IgG1. However, beyond the cell proliferation phase, conditional deletion of PP4 under the control of AID/cre completely restores normal IgG1 production in mutant B cell cultures. In vivo, co-deletion of PP4 and p53 by AID/cre partially rescues switching to IgG1 in B cells of mice immunized with TNP-KLH. Our findings establish that PP4 is indispensable for preventing DNA replication stress that could interfere with CSR, thereby promoting antibody switching during the humoral immune response.

RBM4a-SRSF3-MAP4K4 Splicing Cascade Constitutes a Molecular Mechanism for Regulating Brown Adipogenesis

An increase in mitogen-activated protein kinase kinase kinase kinase 4 (MAP4K4) reportedly attenuates insulin-mediated signaling which participates in the development of brown adipose tissues (BATs). Nevertheless, the effect of MAP4K4 on brown adipogenesis remains largely uncharacterized. In this study, results of a transcriptome analysis (also referred as RNA-sequencing) showed differential expressions of MAP4K4 or SRSF3 transcripts isolated from distinct stages of embryonic BATs. The discriminative splicing profiles of MAP4K4 or SRSF3 were noted as well in brown adipocytes (BAs) with RNA-binding motif protein 4-knockout (RBM4-/-) compared to the wild-type counterparts. Moreover, the relatively high expressions of authentic SRSF3 transcripts encoding the splicing factor functioned as a novel regulator toward MAP4K4 splicing during brown adipogenesis. The presence of alternatively spliced MAP4K4 variants exerted differential effects on the phosphorylation of c-Jun N-terminal protein kinase (JNK) which was correlated with the differentiation or metabolic signature of BAs. Collectively, the RBM4-SRSF3-MAP4K4 splicing cascade constitutes a novel molecular mechanism in manipulating the development of BAs through related signaling pathways.

GLK-IKKβ signaling induces dimerization and translocation of the AhR-RORγt complex in IL-17A induction and autoimmune disease

Retinoic-acid-receptor-related orphan nuclear receptor γt (RORγt) controls the transcription of interleukin-17A (IL-17A), which plays critical roles in the pathogenesis of autoimmune diseases. Severity of several human autoimmune diseases is correlated with frequencies of germinal center kinase-like kinase (GLK) (also known as MAP4K3)-overexpressing T cells; however, the mechanism of GLK overexpression-induced autoimmunity remains unclear. We report the signal transduction converging on aryl hydrocarbon receptor (AhR)-RORγt interaction to activate transcription of the IL-17A gene in T cells. T cell-specific GLK transgenic mice spontaneously developed autoimmune diseases with selective induction of IL-17A in T cells. In GLK transgenic T cells, protein kinase Cθ (PKCθ) phosphorylated AhR at Ser³⁶ and induced AhR nuclear translocation. AhR also interacted with RORγt and transported RORγt into the nucleus. IKKβ (inhibitor of nuclear factor κB kinase β)-mediated RORγt Ser⁴⁸⁹ phosphorylation induced the AhR-RORγt interaction. T cell receptor (TCR) signaling also induced the novel RORγt phosphorylation and subsequent AhR-RORγt interaction. Collectively, TCR signaling or GLK overexpression induces IL-17A transcription through the IKKβ-mediated RORγt phosphorylation and the AhR-RORγt interaction in T cells. Our findings suggest that inhibitors of GLK or the AhR-RORγt complex could be used as IL-17A-blocking agents for IL-17A-mediated autoimmune diseases.

Induction of DUSP14 ubiquitination by PRMT5-mediated arginine methylation

Dual-specificity phosphatase (DUSP)14 (also known as MAP-kinase phosphatase 6) inhibits T-cell receptor (TCR) signaling and T-cell-mediated immune responses by inactivation of the TGF-β activated kinase 1 binding protein (TAB1)-TGF-β activated kinase 1 (TAK1) complex and ERK. DUSP14 phosphatase activity is induced by the E3 ligase TNF receptor associated factor (TRAF)2-mediated Lys63-linked ubiquitination. Here we report an interaction between DUSP14 and protein arginine methyltransferase (PRMT)5 by proximity ligation assay; similarly, DUSP14 directly interacted with TAB1 but not TAK1. DUSP14 is methylated by PRMT5 at arginine 17, 38, and 45 residues. The DUSP14 triple-methylation mutant was impaired in PRMT5-mediated arginine methylation, TRAF2-mediated lysine ubiquitination, and DUSP14 phosphatase activity. Consistently, DUSP14 methylation, TRAF2 binding, and DUSP14 ubiquitination were attenuated by PRMT5 short hairpin RNA knockdown. Furthermore, DUSP14 was inducibly interacted with PRMT5 and was methylated during TCR signaling in T cells. Together, these findings reveal a novel regulatory mechanism of DUSP14 by which PRMT5-mediated arginine methylation may sequentially stimulate TRAF2-mediated DUSP14 ubiquitination and phosphatase activity, leading to inhibition of TCR signaling.-Yang, C.-Y., Chiu, L.-L., Chang, C.-C., Chuang, H.-C., Tan, T.-H. Induction of DUSP14 ubiquitination by PRMT5-mediated arginine methylation.

Features of post-radioiodine whole body scan in non-invasive Follicular Thyroid Neoplasm with papillary-like nuclear features (NIFTP)

Recently, encapsulated follicular variant of papillary thyroid carcinoma has been reclassified as non-invasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) to emphasize the benign nature of this entity. In our institution, we have assessed 455 patients treated with radioiodine ablation for differentiated thyroid carcinoma and 20 of them were retrospectively found to fulfill the new NIFTP criteria. There was no evidence of metastasis on post radioiodine whole body scans for NIFTP cases and these patients were in remission subsequently. The benign features of these patients' whole body scans and good clinical outcome following treatment further support NIFTP as a low risk thyroid neoplasm.

GLK/MAP4K3 overexpression associates with recurrence risk for non-small cell lung cancer

Lung cancer is the leading cause of cancer death worldwide. Non-small cell lung cancer (NSCLC) accounts for 85% of total lung cancers; 40% to 60% of NSCLC patients die of cancer recurrence after cancer resection. Since GLK (also named MAP4K3) induces activation of NF-κB, which contributes to tumor progression, we investigated the role of GLK in NSCLC. GLK protein levels of 190 samples from pulmonary tissue arrays and 58 pulmonary resection samples from stage I to stage III NSCLC patients were studied using immunohistochemistry or immunoblotting. High levels of GLK proteins were detected in pulmonary tissues from NSCLC patients. Elevated GLK protein levels were correlated with increased recurrence risks and poor recurrence-free survival rates in NSCLC patients after adjusting for pathologic stage, smoking status, alcohol status, and EGFR levels. Thus, GLK is a novel prognostic biomarker for NSCLC recurrence.

Epigenetic regulation of HGK/MAP4K4 in T cells of type 2 diabetes patients

Type 2 diabetes (T2D) is a complex and heterogeneous disease. Obesity increases the risk of obese T2D; but in Asia non-obese T2D is prevalent. The cause of non-obese T2D has remained elusive. We studied the potential involvement of HGK/MAP4K4 in T2D using clinical samples from newly diagnosed, drug-naïve patients and healthy controls. HGK levels fell and IL-6 levels increased in T cells from T2D patients. Frequencies of IL-6-producing T cells were correlated with glucose levels after glucose-tolerance tests (but not body mass index and waist circumference) and inversely correlated with HGK expression levels. Moreover, methylation frequencies of the HGK promoter were increased in T2D patients and correlated with glucose levels after glucose-tolerance tests. The correlation was independent of body mass index. Demethylation treatment increased HGK expression levels and reduced IL-6 production in T2D T cells. This report identifies HGK methylation/downregulation in T cells as a potential biomarker for non-obese T2D.

MAP4K4 and IL-6+ Th17 cells play important roles in non-obese type 2 diabetes

Obesity is a causal factor of type 2 diabetes (T2D); however, people without obesity (including lean, normal weight, or overweight) may still develop T2D. Non-obese T2D is prevalent in Asia and also frequently occurs in Europe. Recently, multiple evidences oppose the notion that either obesity or central obesity (visceral fat accumulation) promotes non-obese T2D. Several factors such as inflammation and environmental factors contribute to non-obese T2D. According to the data derived from gene knockout mice and T2D clinical samples in Asia and Europe, the pathogenesis of non-obese T2D has been unveiled recently. MAP4K4 downregulation in T cells results in enhancement of the IL-6⁺ Th17 cell population, leading to insulin resistance and T2D in both human and mice. Moreover, MAP4K4 single nucleotide polymorphisms and epigenetic changes are associated with T2D patients. Interactions between MAP4K4 gene variants and environmental factors may contribute to MAP4K4 attenuation in T cells, leading to non-obese T2D. Future investigations of the pathogenesis of non-obese T2D shall lead to development of precision medicine for non-obese T2D.

A multi-prong global study provides insights to gut microbiota and mucosal immunity in dusp6-deficiency conferred obesity-resistance

Obesity is now a plague in developed countries and more than one third of U.S. adults are obese. Gut microbiota plays profound roles in host energy harvest, metabolism and inflammatory response associated with the development of obesity. Dusp6-deficient mice have been shown to be resistant to diet-induced-obesity (DIO) but the mechanism is still unclear. Using a gnotobiotic mouse model, we found that the transplantation of fecal/gut microbiota derived from dusp6-deficient mice can significantly increase energy expenditure and reduce weight-gain of the recipient mice. By analyzing fecal 16s rRNA genes, dusp6-deficient mice have different composition of gut microbiota when compared with wild-type mice. We also demonstrated that dusp6-deficient mice were resistant to DIO-mediated dysbiosis of gut microbiota. Upon further analysis of the intestinal transcriptome, we found that dusp6 deficiency is an important regulator of several metabolic pathways and genes related to intestinal barrier. Moreover, our analyses have shown that dusp6-deficient mice could alleviate DIO-induced inflammation.. This study demonstrates that dusp6 deficiency is a strong genetic factor that dominates diet effect on shaping gut microbiota and it remodels mucosal immunity to retain HFD-resistant homeostasis of gut microbiota. Our findings shed lights on obesity and obesity-derived metabolic disease treatment with novel therapeutic candidates/strategies such as DUSP6 pharmacological inhibitors and the development of microbiota-based therapeutics.

Roles of innate immune regulator TAPE in RIG-I signaling and antiviral defenses

Pattern-recognition receptors detect pathogen-associated molecular patterns to trigger downstream pathways leading to type I IFN and inflammatory cytokines production to defend pathogen infection. RIG-I-like receptors (RLRs) are key cytosolic sensors for recognizing viral RNA to trigger antiviral immunity. The underlying mechanisms linking RLR-mediated viral recognition to antiviral immunity remain to be further explored. Through our previous work, we uncovered an innate immune regulator termed TAPE (TBK1-Associated Protein in Endolysosomes), also known as CC2D1A, which is implicated in the viral RNA senor TLR3 and RLR pathways. Yet, the in vivo role of TAPE in antiviral defenses and the mechanistic mechanisms of how TAPE regulates cytosolic RIG-I signaling still remain to be established. TAPE conditional knockout mice were generated for our study. Results from in vivo studies showed that TAPEf/f CD11c-Cre mice exhibited a more severe mortality than WT mice upon influenza A virus (IAV) infection. Ex vivo studies also showed that TAPE-deficient mouse embryonic fibroblasts and macrophages were defective in type-I interferon induction upon RLR ligand stimulation. In addition, our biochemical analyses showed that the N-terminal region of TAPE was critical for interacting with the CARD domain of RIG-I while the C-terminal region of TAPE contributed most to the interaction with MAVS/IPS-1, a RLR downstream mediator. Together, our results suggest a crucial role for TAPE in linking RIG-I to type I IFN-mediated antiviral responses. Future work will further determine the in vivo role of TAPE in IAV and other RNA virus infection, and explore the mechanistic mechanisms of how TAPE regulates RIG-I signaling.

Emerging roles of an innate immune regulator TAPE in Toll-like receptors, RIG-I-like receptors, and beyond

Pattern-recognition receptors (PRRs) trigger innate immune defenses against pathogen infection via downstream signaling pathways linking to inflammation and cell-autonomous immunity like phagocytosis and autophagy. IKK family kinases, IKKα and IKKβ, function to relay PRR signals to proinflammatory cytokine production to amplify innate immune responses. TBK1, a non-canonical IKK kinase, links nucleic acid sensors to type I interferon induction against viral infection and also regulates the autophagic clearance of intracellular bacteria. TBK1-Associated Protein in Endolysosomes designated TAPE, also known as CC2D1A, is an innate immune regulator acting upstream of Trif to regulate the TLR3 and TLR4 pathways, or upstream of MAVS to regulate the cytosolic RIG-I-like receptor (RLR) pathways. To our best knowledge, TAPE is the first regulator implicated in both the endosomal TLR and cytosolic RLR pathways at such an early step. We are thus interested in investigating in vivo roles of TAPE in innate immunity and molecular mechanisms by which TAPE regulates TLRs, RLRs, and possibly other PRRs. TAPE conditional knockout (cKO) mice, in which TAPE is selectively disrupted in immune cells, have been generated for our study. Our results showed that upon influenza A virus infection, TAPE cKO mice exhibited a more severe mortality than wild type mice. Further, TAPE cKO mice were shown to be more susceptible to Salmonella Typhimurium infection but more resistant to LPS-induced septic shock. Notably, ex vivo results showed that TAPE was critical for the autophagic clearance of Salmonella Typhimurium. Together, our data support a critical role for TAPE in regulating innate immune defenses through TLRs, RLRs, and autophagy.

Abstract 4437: Fbxw8 targets hematopoietic progenitor kinase 1 for proteasomal degradation

HPK1, a member of mammalian Ste20-like serine/threonine kinases, is lost in &gt;95% pancreatic cancer through proteasomemediated degradation. However, the mechanism of HPK1 loss has not been defined. The aims of this study are to identify the ubiquitin ligase and to examine the mechanisms that targets HPK1 degradation. We found that the CUL7 ubiquitin ligase targeted HPK1 for degradation via the 26S proteasome. The ubiquitination of HPK1 required its kinase activity and autophosphorylation. Wild-type protein phosphatase 4 (PP4), but not the phosphatase-dead PP4 mutant, PP4-RL, inhibits the interaction of Fbxw8 with HPK1 and Fbxw8-mediated ubiquitination of HPK1.

In addition, we showed that Thr355 of HPK1 is a key PP4 dephosphorylation site, through which Fbxw8 and PP4 regulates HPK1 stability. Our study demonstrated that CUL7 ubiquitin ligase targets HPK1 for degradation which requires HPK1 kinase activity and autophosphorylation. Fbxw8-mediated HPK1 degradation revealed a direct link and novel role of CUL7 ubiquitin ligase in the MAPK pathway, which plays a critical role in cell proliferation and differentiation.

Citation Format: Hua Wang, Yue Chen, Ping Lin, Lei Li, Guisheng Zhou, Guangchao Liu, Craig Logsdon, Jianping Jin, James L. Abbruzzese, Tse-Hua Tan, Huamin Wang. Fbxw8 targets hematopoietic progenitor kinase 1 for proteasomal degradation. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4437. doi:10.1158/1538-7445.AM2014-4437

PP4 is essential for germinal center formation and class switch recombination in mice

PP4 is a serine/threonine phosphatase required for immunoglobulin (Ig) VDJ recombination and pro-B/pre-B cell development in mice. To elucidate the role of PP4 in mature B cells, we ablated the catalytic subunit of murine PP4 invivo utilizing the CD23 promoter and cre-loxP recombination and generated CD23^crePP4^F/F mice. The development of follicular and marginal zone B cells was unaffected in these mutants, but the proliferation of mature PP4-deficient B cells stimulated by invitro treatment with either anti-IgM antibody (Ab) or LPS was partially impaired. Interestingly, the induction of CD80 and CD86 expression on these stimulated B cells was normal. Basal levels of serum Igs of all isotypes were strongly reduced in CD23^crePP4^F/F mice, and their B cells showed a reduced efficiency of class switch recombination (CSR) invitro upon stimulation by LPS or LPS plus IL-4. When CD23^crePP4^F/F mice were challenged with either the T cell-dependent antigen TNP-KLH or the T cell-independent antigen TNP-Ficoll, or by H1N1 virus infection, the mutant animals failed to form germinal centers (GCs) in the spleen and the draining mediastinal lymph nodes, and did not efficiently mount antigen-specific humoral responses. In the resting state, PP4-deficient B cells exhibited pre-existing DNA fragmentation. Upon stimulation by DNA-damaging drug etoposide invitro, mutant B cells showed increased cleavage of caspase 3. In addition, the mutant B cells displayed impaired CD40-mediated MAPK activation, abnormal IgM-mediated NF-κB activation, and reduced S phase entry upon IgM/CD40-stimulation. Taken together, our results establish a novel role for PP4 in CSR, and reveal crucial functions for PP4 in the maintenance of genomic stability, GC formation, and B cell-mediated immune responses.