E3 ubiquitin ligase NEDD4L negatively regulates keratinocyte hyperplasia by promoting GP130 degradation

Immunoexpression Patterns of Adhesion Molecules (E-cadherin, β-catenin, CD56) and Cytokeratins (CK19, CK20, HMWCK, CAM5.2) During Hair Development in Human Fetuses Compared With Adults

ABSTRACT

Abnormalities in the expression of cytokeratins or adhesion molecules have been associated with hair disorders. The expression patterns of these molecules in the hair follicles of developing human fetuses are not obvious. We aimed to investigate the expression patterns of some cytokeratins and adhesion molecules in the hair follicle of human fetuses and compared them with adults. Forty-eight fetuses of >16 gestational weeks and 22 adult cases with total excisions of benign nevi or cysts were enrolled. The skin samples were taken from both the scalp and back of the fetuses. The histopathologically normal skin areas were evaluated in adults. CK19, CK20, CAM5.2, high-molecular-weight cytokeratin, E-cadherin, β-catenin, and CD56 immunohistochemical stainings were performed. In the fetus group, the staining scores declined in the third trimester but elevated and reached the highest level in adults, except for CD56, which did not stain any adult samples. All stainings were mostly observed in the outer root sheath, except CD56 that stained the perifollicular dermal sheath only in fetuses. E-cadherin, β-catenin, and high-molecular-weight cytokeratin strongly and diffusely stained all adult samples. CAM5.2 and CK19 scores were correlated in fetuses (scalp scores: rs = 0.405, P = 0.004; back scores: rs = 0.422, P = 0.003) and adults (back scores: rs = 0.562, P = 0.046). CD56 negativity indicated the immune-privilege feature of adult hair follicles. As CK19, CAM5.2 may be used to find the regions of stem cells or transient amplifying cells.

E3 Ubiquitin Ligase NEDD4L Negatively Regulates Skin Tumorigenesis by Inhibiting IL-6/GP130 Signaling Pathway

IL-6 signaling plays a crucial role in the survival and metastasis of skin cancer. NEDD4L acts as a suppressor of IL-6 signaling by targeting GP130 degradation. However, the effects of the NEDD4L-regulated IL-6/GP130 signaling pathway on skin cancer remain unclear. In this study, protein expression levels of NEDD4L and GP130 were measured in tumor tissues from patients with cutaneous squamous cell carcinoma. Skin tumors were induced in wild-type and Nedd4l-knockout mice, and activation of the IL-6/GP130/signal transducer and activator of transcription 3 signaling pathway was detected. The results indicated a negative correlation between the protein expression levels of NEDD4L and GP130 in cutaneous squamous cell carcinoma tissues from patients. Nedd4l deficiency significantly promoted 7,12-dimethylbenz[a]anthracene/12-O-tetradecanoylphorbol-13-acetate-induced skin tumorigenesis and benign-to-malignant conversion by activating the IL-6/GP130/signal transducer and activator of transcription 3 signaling pathway, which was abrogated by supplementation with the GP130 inhibitor SC144. Furthermore, our findings suggested that NEDD4L can interact with GP130 and promote its ubiquitination in skin tumors. In conclusion, our results indicate that NEDD4L could act as a tumor suppressor in skin cancer, and inhibition of GP130 could be a potential therapeutic method for treating this disease.

A critical role of the endothelial S-phase kinase-associated protein 2/phosphatase and tensin homologue axis in angiogenesis and psoriasis

BACKGROUND

Psoriasis is a common chronic skin disorder. Pathologically, it features abnormal epidermal proliferation, infiltrating inflammatory cells and increased angiogenesis in the dermis. Aberrant expression of E3 ubiquitin ligase and a dysregulated protein ubiquitination system are implicated in the pathogenesis of psoriasis.

OBJECTIVES

To examine the potential role of S-phase kinase-associated protein 2 (Skp2), an E3 ligase and oncogene, in psoriasis.

METHODS

Gene expression and protein levels were evaluated with quantitative reverse transcriptase polymerase chain reaction, Western blotting, immunohistochemistry and immunofluorescence staining of skin samples from patients with psoriasis vulgaris and an imiquimod (IMQ)-induced mouse model, as well as from cultured endothelial cells (ECs). Protein interaction, substrate ubiquitination and degradation were examined using co-immunoprecipitation, Western blotting and a cycloheximide chase assay in human umbilical vein ECs. Angiogenesis was measured in vitro using human dermal microvascular ECs (HDMECs) for BrdU incorporation, migration and tube formation. In vivo angiogenesis assays included chick embryonic chorioallantoic membrane, the Matrigel plug assay and quantification of vasculature in the mouse lesions. Skp2 gene global knockout (KO) mice and endothelial-specific conditional KO mice were used.

RESULTS

Skp2 was increased in skin samples from patients with psoriasis and IMQ-induced mouse lesions. Immunofluorescent double staining indicated a close association of Skp2 expression with excessive vascularity in the lesional dermal papillae. In HDMECs, Skp2 overexpression was enhanced, whereas Skp2 knockdown inhibited EC proliferation, migration and tube-like structure formation. Mechanistically, phosphatase and tensin homologue (PTEN), which suppresses the phosphoinositide 3-kinase/Akt pathway, was identified to be a novel substrate for Skp2-mediated ubiquitination. A selective inhibitor of Skp2 (C1) or Skp2 small interfering RNA significantly reduced vascular endothelial growth factor-triggered PTEN ubiquitination and degradation. In addition, Skp2-mediated ubiquitination depended on the phosphorylation of PTEN by glycogen synthase kinase 3β. In the mouse model, Skp2 gene deficiency alleviated IMQ-induced psoriasis. Importantly, tamoxifen-induced endothelial-specific Skp2 KO mice developed significantly ameliorated psoriasis with diminished angiogenesis of papillae. Furthermore, topical use of the Skp2 inhibitor C1 effectively prevented the experimental psoriasis.

CONCLUSIONS

The Skp2/PTEN axis may play an important role in psoriasis-associated angiogenesis. Thus, targeting Skp2-driven angiogenesis may be a potential approach to treating psoriasis.

Epigenetic Regulation of IL-23 by E3 Ligase FBXW7 in Dendritic Cells Is Critical for Psoriasis-like Inflammation

Dendritic cells (DCs), a driver of psoriasis pathogenesis, produce IL-23 and trigger IL-23/IL-17 cytokine axis activation. However, the mechanisms regulating IL-23 induction remain unclear. In the current study, we found that mice with E3 ligase FBXW7 deficiency in DCs show reduced skin inflammation correlated with the reduction of IL-23/IL-17 axis cytokines in the imiquimod-induced psoriasis model. Fbxw7 deficiency results in decreased production of IL-23 in DCs. FBXW7 interacts with the lysine N-methyltransferase suppressor of variegation 39 homolog 2 (SUV39H2), which catalyzes the trimethylation of histone H3 Lys9 (H3K9) during transcription regulation. FBXW7 mediates the ubiquitination and degradation of SUV39H2, thus decreasing H3K9m3 deposition on the Il23a promoter. The Suv39h2 knockout mice displayed exacerbated skin inflammation with the IL-23/IL-17 axis overactivating in the psoriasis model. Taken together, our results indicate that FBXW7 increases IL-23 expression in DCs by degrading SUV39H2, thereby aggravating psoriasis-like inflammation. Inhibition of FBXW7 or the FBXW7/SUV39H2/IL-23 axis may represent a novel therapeutic approach to psoriasis.

GABA regulates the proliferation and apoptosis of head and neck squamous cell carcinoma cells by promoting the expression of CCND2 and BCL2L1

Gamma-aminobutyric acid (GABA) is a multifunctional molecule that is widely present in the nervous system and nonneuronal tissues. It plays pivotal roles in neurotransmission, regulation of secretion, cell differentiation, proliferation, and tumorigenesis. However, the exact mechanisms of GABA in head and neck squamous cell carcinomas (HNSCCs) are unknown. We took advantage of RNA sequencing in this work and uncovered the potential gene expression profiles of the GABA-treated HNSCC cell line HN4-2. We found that the expression of CCND2 and BCL2L1 was significantly upregulated. Furthermore, GABA treatment inhibited the cell apoptosis induced by cisplatin and regulated the cell cycle after treatment with cisplatin in HN4-2 cells. Moreover, we also found that GABA could upregulate the expression of CCND2 and BCL2L1 after treatment with cisplatin. Our results not only reveal the potential pro-tumorigenic effect of GABA on HNSCCs but also provide a novel therapeutic target for HNSCC treatment.

E3 ligase Nedd4L promotes macrophage M1 polarization and exacerbates brain damage by TRAF3/TBK1 signaling pathway after ICH in mice

BACKGROUND

Intracerebral hemorrhage (ICH) is a serious medical problem, and promising strategy is limited. Macrophage initiated brain inflammatory injury following ICH, but the molecular mechanism had not been well identified. E3 ligase Nedd4L is implicated in the pathogenesis of the inflammatory immune response.

METHODS

In the present study, we detected the levels of Nedd4L in macrophages following ICH. Furthermore, Macrophage M1 polarization, pro-inflammatory cytokine production, BBB disruption, brain water content and neurological function were examined in ICH mice.

RESULTS

Here, we demonstrated that E3 ligase Nedd4L levels of macrophage increased following ICH, promoted M1 polarization inflammation by TRAF3. Nedd4L promoted BBB disruption, as well as neurological deficits. Inhibition of Nedd4L significantly attenuated M1 polarization in vivo. Inhibition of Nedd4L decreased TRAF3 and TBK1 levels, and subsequent phosphorylation of p38 and NF-κB p65 subunit following ICH.

CONCLUSIONS

Our data demonstrated that Nedd4L was involved in the pathogenesis of ICH, which promoted inflammatory responses and exacerbated brain damage by TRAF3 following ICH.

E3 ubiquitin ligase NEDD4L negatively regulates inflammation by promoting ubiquitination of MEKK2

Aberrant activation of inflammation signaling triggered by tumor necrosis factor α (TNF‐α), interleukin‐1 (IL‐1), and interleukin‐17 (IL‐17) is associated with immunopathology. Here, we identify neural precursor cells expressed developmentally down‐regulated gene 4‐like (NEDD4L), a HECT type E3 ligase, as a common negative regulator of signaling induced by TNF‐α, IL‐1, and IL‐17. NEDD4L modulates the degradation of mitogen‐activated protein kinase kinase kinase 2 (MEKK2) via constitutively and directly binding to MEKK2 and promotes its poly‐ubiquitination. In interleukin‐17 receptor (IL‐17R) signaling, Nedd4l knockdown or deficiency enhances IL‐17‐induced p38 and NF‐κB activation and the production of proinflammatory cytokines and chemokines in a MEKK2‐dependent manner. We further show that IL‐17‐induced MEKK2 Ser520 phosphorylation is required not only for downstream p38 and NF‐κB activation but also for NEDD4L‐mediated MEKK2 degradation and the subsequent shutdown of IL‐17R signaling. Importantly, Nedd4l‐deficient mice show increased susceptibility to IL‐17‐induced inflammation and aggravated symptoms of experimental autoimmune encephalomyelitis (EAE) in IL‐17R signaling‐dependent manner. These data suggest that NEDD4L acts as an inhibitor of IL‐17R signaling, which ameliorates the pathogenesis of IL‐17‐mediated autoimmune diseases.

Construction of a three commitment points for S phase entry cell cycle model and immune-related ceRNA network to explore novel therapeutic options for psoriasis

While competing endogenous RNAs (ceRNAs) play pivotal roles in various diseases, the proliferation and differentiation of keratinocytes are becoming a research focus in psoriasis. Therefore, the three commitment points for S phase entry (CP1-3) cell cycle model has pointed to a new research direction in these areas. However, it is unclear what role ceRNA regulatory mechanisms play in the interaction between keratinocytes and the immune system in psoriasis. In addition, the ceRNA network-based screening of potential therapeutic agents for psoriasis has not been explored. Therefore, we used multiple bioinformatics approaches to construct a ceRNA network for psoriasis, identified CTGF as the hub gene, and constructed a ceRNA subnetwork, after which validation datasets authenticated the results' accuracy. Subsequently, we used multiple online databases and the single-sample gene-set enrichment analysis algorithm, including the CP1-3 cell cycle model, to explore the mechanisms accounting for the increased proliferation and differentiation of keratinocytes and the possible roles of the ceRNA subnetwork in psoriasis. Next, we performed cell cycle and cell trajectory analyses based on a single-cell RNA-seq dataset of psoriatic skin biopsies. We also used weighted gene co-expression network analysis and single-gene batch correlation analysis-based gene set enrichment analysis to explore the functions of CTGF. Finally, we used the Connectivity Map to identify MS-275 (entinostat) as a novel treatment for psoriasis, SwissTargetPrediction to predict drug targets, and molecular docking to investigate the minimum binding energy and binding sites of the drug to target proteins.

β-Klotho promotes glycolysis and glucose-stimulated insulin secretion via GP130

Impaired glucose-stimulated insulin secretion (GSIS) is a hallmark of type-2 diabetes. However, cellular signaling machineries that control GSIS remain incompletely understood. Here, we report that β-klotho (KLB), a single-pass transmembrane protein known as a co-receptor for fibroblast growth factor 21 (FGF21), fine tunes GSIS via modulation of glycolysis in pancreatic β-cells independent of the actions of FGF21. β-cell-specific deletion of Klb but not Fgf21 deletion causes defective GSIS and glucose intolerance in mice and defective GSIS in islets of type-2 diabetic mice is mitigated by adenovirus-mediated restoration of KLB. Mechanistically, KLB interacts with and stabilizes the cytokine receptor subunit GP130 by blockage of ubiquitin-dependent lysosomal degradation, thereby facilitating interleukin-6-evoked STAT3-HIF1α signaling, which in turn transactivates a cluster of glycolytic genes for adenosine triphosphate production and GSIS. The defective glycolysis and GSIS in Klb-deficient islets are rescued by adenovirus-mediated replenishment of STAT3 or HIF1α. Thus, KLB functions as a key cell-surface regulator of GSIS by coupling the GP130 receptor signaling to glucose catabolism in β-cells and represents a promising therapeutic target for diabetes.

Advances in the pathogenesis of psoriasis: from keratinocyte perspective

Psoriasis is a complex long-lasting inflammatory skin disease with high prevalence and associated comorbidity. It is characterized by epidermal hyperplasia and dermal infiltration of immune cells. Here, we review the role of keratinocytes in the pathogenesis of psoriasis, focusing on factors relevant to genetics, cytokines and receptors, metabolism, cell signaling, transcription factors, non-coding RNAs, antimicrobial peptides, and proteins with other different functions. The critical role of keratinocytes in initiating and maintaining the inflammatory state suggests the great significance of targeting keratinocytes for the treatment of psoriasis.

Cyclophilin A is a key positive and negative feedback regulator within interleukin-6 trans-signaling pathway

Cyclophilin A (CypA), a member of the cyclophilin family, plays a vital role in microorganismal infections, inflammatory diseases, and cancers. Interleukin-6 (IL-6) is a pleiotropic cytokine, exerting variety of effects on inflammation, immune response, hematopoiesis, and tumor proliferation. Binding of IL-6 to soluble IL-6 receptor (sIL-6R) induces pro-inflammatory trans-signaling, which has been described to be stronger than anti-inflammatory classic signaling triggered by the binding of IL-6 to membrane-bound IL-6 receptor. Here we found that upon the treatment of IL-6 and sIL-6R, CypA inhibited the ubiquitination-mediated degradation of IL-6 membrane receptor gp130 and enhanced its dimerization, thereby positively regulated the IL-6 trans-signaling and increased the expression of downstream iNOS, IL-6, and CypA. Furthermore, CypA expression could be negatively regulated by suppressor of cytokine signaling 1 (SOCS1). The SH2 and Box domains of SOCS1 interacted with CypA and promoted its K48-linked ubiquitination-mediated degradation, which inhibited the IL-6 trans-signaling pathway. Collectively, our findings reveal an important role of CypA in the positive and negative feedback regulation of the IL-6 trans-signaling pathway.

Integrated Metabolomics and Transcriptomics Analyses Reveal Histidine Metabolism Plays an Important Role in Imiquimod-Induced Psoriasis-like Skin Inflammation

Psoriasis is a chronic inflammatory skin disease characterized by massive keratinocyte proliferation and immune cell infiltration into the epidermis. However, the specific mechanisms underlying the development of psoriasis remain unclear. Untargeted metabolomics and transcriptomics have been used separately to profile biomarkers and risk genes in the serum of psoriasis patients. However, the integration of metabolomics and transcriptomics to identify dysregulated metabolites and genes in the psoriatic skin is lacking. In this study, we performed an untargeted metabolomics analysis of imiquimod (IMQ)-induced psoriasis-like mice and healthy controls, and found that levels of a total of 4,188 metabolites differed in IMQ-induced psoriasis-like mice compared with those in control mice. Metabolomic data analysis using MetaboAnalyst showed that the metabolic pathways of primary metabolites, such as folate biosynthesis and galactose metabolism, were significantly altered in the skin of mice after treatment with IMQ. Furthermore, IMQ treatment also significantly altered metabolic pathways of secondary metabolites, including histidine metabolism, in mouse skin tissues. The metabolomic results were verified by transcriptomics analysis. RNA-seq results showed that histamine decarboxylase (HDC) mRNA levels were significantly upregulated after IMQ treatment. Targeted inhibition of histamine biosynthesis process using HDC-specific inhibitor, pinocembrin (PINO), significantly alleviated epidermal thickness, downregulated the expression of interleukin (IL)-17A and IL-23, and inhibited the infiltration of immune cells during IMQ-induced psoriasis-like skin inflammation. In conclusion, our study offers a validated and comprehensive understanding of metabolism during the development of psoriasis and demonstrated that PINO could protect against IMQ-induced psoriasis-like skin inflammation.

E3 ubiquitin ligase NEDD4L negatively regulates keratinocyte hyperplasia by promoting GP130 degradation

Psoriasis is mainly characterized by abnormal hyperplasia of keratinocytes and immune cells infiltrating into the dermis and epidermis. Neural precursor cell expressed developmentally downregulated 4-like (NEDD4L) is a highly conserved HECT type E3 ligase that plays an important role in regulating physiological and pathological processes. Here, we identify NEDD4L as a negative regulator of psoriasis. Nedd4l significantly inhibits imiquimod (IMQ)-induced skin hyperplasia, and this effect is attributed to the inhibitory effect of NEDD4L on IL-6/GP130 signaling in keratinocytes. Mechanistically, NEDD4L directly interacts with GP130 and mediates its Lys-27-linked ubiquitination and proteasomal degradation. Moreover, the expression of NEDD4L is downregulated in the epidermis from IMQ-treated mice and psoriasis patients and negatively correlates with the protein levels of GP130 and p-STAT3 in clinical samples. Collectively, we uncover an inhibitory role of NEDD4L in the pathogenesis of psoriasis and suggest a new therapeutic strategy for the treatment of psoriasis.