Ubiquitination-proteasome system: A new player in the pathogenesis of psoriasis and clinical implications

Human Beta Defensin-2 mRNA and Proteasome Subunit β Type 8 mRNA Analysis, Useful in Differentiating Skin Biopsies from Atopic Dermatitis and Psoriasis Vulgaris Patients

(1): Atopic dermatitis and psoriasis vulgaris are chronic, inflammatory diseases. Clinical presentation usually leads to a proper diagnosis, but sometimes neither clinical examination nor histopathological evaluation can be conclusive. Therefore, we aimed to build up a novel diagnostic tool and check it for accuracy. The main objective of our work was to differentiate between healthy skin (C), atopic dermatitis (AD) and psoriasis vulgaris (PV) biopsies on the base of involucrin (IVL) and human β-defensin-2 (hBD-2) concentrations and their mRNA, as well as mRNA for TPP2 and PSMB8. (2): ELISA for IVL and hBD-2 proteins and Real-time PCR for the relative expression of mRNA for: IVL (IVL mRNA), hBD-2 (hBD-2 mRNA), PSMB8 (PSMB8 mRNA) and TPP2 (TPP2 mRNA), isolated from skin biopsies taken from AD and PV patients and healthy volunteers were performed. (3): hBD-2 mRNA and PSMB8 mRNA correlated with some parameters of clinical assessment of inflammatory disease severity. hBD-2 mRNA expression, exclusively, was sufficient to distinguish inflammatory skin biopsies from the healthy ones. (4): hBD-2 mRNA and PSMB8 mRNA analysis were the most valuable parameters in differentiating AD and PV biopsies.

An overview of Skp2: a promising new therapeutic target of psoriasis

INTRODUCTION

Psoriasis is a chronic immune-mediated disorder affecting over 2-3% of the population worldwide, significantly impacting quality of life. Despite the availability of various therapeutic interventions, concerns persist regarding lesion recurrence and potential alterations in immune surveillance promoting cancer progression. Recent advancements in understanding cellular and molecular pathways have unveiled key factors in psoriasis etiology, including IL-17, 22, 23, TNF-α, PDE-4, JAK-STAT inhibitors, and AhR agonists. This work explores the potential of S-phase kinase-associated protein 2 (Skp2) as a therapeutic target in psoriasis.

AREA COVERED

This review covers the current understanding of psoriasis pathophysiology, including immune dysregulation, and the role of keratinocytes and ubiquitin. It also delves into Skp2 role in cell cycle regulation, and its correlation with angiogenesis and ubiquitin in psoriasis. The evolving therapeutic approaches targeting Skp2, including small molecule inhibitors, are also discussed.

EXPERT OPINION

Targeting Skp2 holds promise for developing novel therapeutic approaches for psoriasis. By modulating Skp2 activity or expression, it may be possible to intervene in inflammatory and proliferative processes underlying the disease. Further research into Skp2 inhibitors and their efficacy in preclinical and clinical settings is warranted to harness the full potential of Skp2 as a therapeutic target in psoriasis management.

GRP78 Downregulation in Keratinocytes Promotes Skin Inflammation through the Recruitment and Activation of CCR6+ IL-17A-Producing γδ T Cells

The migration of γδ T lymphocytes toward skin lesions and their concomitant pathogenic IL-17A production play a crucial role in the pathogenesis of psoriasis. However, the regulatory mechanisms of IL-17A production by γδ T cells and their migration remain to be fully explored. Intracellular GRP78 is a molecular chaperone that regulates endoplasmic reticulum stress, whereas secretory GRP78, as a member of the resolution-associated molecular patterns, exerts immunoregulatory effects. In this study, we reported that both the intracellular GRP78 in skin lesions and secretory GRP78 in the serum were significantly decreased in patients with psoriasis. A GRP78 knockdown exacerbated imiquimod-induced skin inflammation, whereas the application of recombinant GRP78 protein or BIP inducer X (a GRP78 inducer) attenuated the dermatitis. Mechanistically, the GRP78 knockdown in keratinocytes enhanced the production of chemokines, specifically CCL20, which regulates γδ T-cell migration. Moreover, recombinant GRP78 was found to directly bind to γδ T cells to suppress its migration ability and proinflammatory capacities by downregulating the CCR6 and IL-17A expression. Collectively, our results uncovered a pivotal role of GRP78 in the pathogenesis of psoriasis, which was mainly exerted by regulating the interaction between keratinocytes and γδ T cells, and might provide a promising target for psoriasis therapy.

The critical role of BTRC in hepatic steatosis as an ATGL E3 ligase

Non-alcoholic fatty liver disease (NAFLD), characterized by hepatic steatosis, is one of the commonest causes of liver dysfunction. Adipose triglyceride lipase (ATGL) is closely related to lipid turnover and hepatic steatosis as the speed-limited triacylglycerol lipase in liver lipolysis. However, the expression and regulation of ATGL in NAFLD remain unclear. Herein, our results showed that ATGL protein levels were decreased in the liver tissues of high-fat diet (HFD)-fed mice, naturally obese mice, and cholangioma/hepatic carcinoma patients with hepatic steatosis, as well as in the oleic acid-induced hepatic steatosis cell model, while ATGL mRNA levels were not changed. ATGL protein was mainly degraded through the proteasome pathway in hepatocytes. Beta-transducin repeat containing (BTRC) was upregulated and negatively correlated with the decreased ATGL level in these hepatic steatosis models. Consequently, BTRC was identified as the E3 ligase for ATGL through predominant ubiquitination at the lysine 135 residue. Moreover, adenovirus-mediated knockdown of BTRC ameliorated steatosis in HFD-fed mouse livers and oleic acid-treated liver cells via upregulating the ATGL level. Taken together, BTRC plays a crucial role in hepatic steatosis as a new ATGL E3 ligase and may serve as a potential therapeutic target for treating NAFLD.

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.

Modulation of Tau Pathology in Alzheimer's Disease by Dietary Bioactive Compounds

Tau is a microtubule-associated protein essential for microtubule assembly and stability in neurons. The abnormal intracellular accumulation of tau aggregates is a major characteristic of brains from patients with Alzheimer's disease (AD) and other tauopathies. In AD, the presence of neurofibrillary tangles (NFTs), which is composed of hyperphosphorylated tau protein, is positively correlated with the severity of the cognitive decline. Evidence suggests that the accumulation and aggregation of tau cause synaptic dysfunction and neuronal degeneration. Thus, the prevention of abnormal tau phosphorylation and elimination of tau aggregates have been proposed as therapeutic strategies for AD. However, currently tau-targeting therapies for AD and other tauopathies are limited. A number of dietary bioactive compounds have been found to modulate the posttranslational modifications of tau, including phosphorylation, small ubiquitin-like modifier (SUMO) mediated modification (SUMOylation) and acetylation, as well as inhibit tau aggregation and/or promote tau degradation. The advantages of using these dietary components over synthetic substances in AD prevention and intervention are their safety and accessibility. This review summarizes the mechanisms leading to tau pathology in AD and highlights the effects of bioactive compounds on the hyperphosphorylation, aggregation and clearance of tau protein. The potential of using these bioactive compounds for AD prevention and intervention is also discussed.

Proteomic analysis of lysine 2-hydroxyisobutyryl in SLE reveals protein modification alteration in complement and coagulation cascades and platelet activation Pathways

BACKGROUND

Post-translational modifications (PTMs) are considered to be an important factor in the pathogenesis of Systemic lupus erythematosus (SLE). Lysine 2-hydroxyisobutyryl (Khib), as an emerging post-translational modification of proteins, is involved in some important biological metabolic activities. However, there are poor studies on its correlation with diseases, especially SLE.

OBJECTIVE

We performed quantitative, comparative, and bioinformatic analysis of Khib proteins in Peripheral blood mononuclear cells (PBMCs) of SLE patients and PBMCs of healthy controls. Searching for pathways related to SLE disease progression and exploring the role of Khib in SLE.

METHODS

Khib levels in SLE patients and healthy controls were compared based on liquid chromatography tandem mass spectrometry, then proteomic analysis was conducted.

RESULTS

Compared with healthy controls, Khib in SLE patients was up-regulated at 865 sites of 416 proteins and down-regulated at 630 sites of 349 proteins. The site abundance, distribution and function of Khib protein were investigated further. Bioinformatics analysis showed that Complement and coagulation cascades and Platelet activation in immune-related pathways were significantly enriched, suggesting that differentially modified proteins among them may affect SLE.

CONCLUSION

Khib in PBMCs of SLE patients was significantly up- or down-regulated compared with healthy controls. Khib modification of key proteins in the Complement and coagulation cascades and Platelet activation pathways affects platelet activation and aggregation, coagulation functions in SLE patients. This result provides a new direction for the possible significance of Khib in the pathogenesis of SLE patients.

Protein adducts with lipid peroxidation products in patients with psoriasis

Psoriasis, one of the most frequent immune-mediated skin diseases, is manifested by numerous psoriatic lessons on the skin caused by excessive proliferation and keratinization of epidermal cells. These disorders of keratinocyte metabolism are caused by a pathological interaction with the cells of the immune system, including lymphocytes, which in psoriasis are also responsible for systemic inflammation. This is accompanied by oxidative stress, which promotes the formation of lipid peroxidation products, including reactive aldehydes and isoprostanes, which are additional pro-inflammatory signaling molecules. Therefore, the presented review is focused on highlighting changes that occur during psoriasis development at the level of lipid peroxidation products, including 4-hydroxynonenal, 4-oxononenal, malondialdehyde, and acrolein, and their influence on protein structures. Furthermore, we will examine inducing agents of cellular functioning, as well as intercellular signaling. These lipid peroxidation products can form adducts with a variety of proteins with different functions in the body, including proteins within skin cells and cells of the immune system. This is especially true in autoimmune diseases such as psoriasis. For example, these changes concern proteins involved in maintaining redox homeostasis or pro-inflammatory signaling. Therefore, the formation of such adducts should attract attention, especially during the design of preventive cosmetics or anti-psoriasis therapies.

Ubiquitin-proteasome system-based signature to predict the prognosis and drug sensitivity of hepatocellular carcinoma

Background: Ubiquitin-proteasome system (UPS) is implicated in cancer occurrence and progression. Targeting UPS is emerging as a promising therapeutic target for cancer treatment. Nevertheless, the clinical significance of UPS in hepatocellular carcinoma (HCC) has not been entirely elucidated. Methods: Differentially expressed UPS genes (DEUPS) were screened from LIHC-TCGA datasets. The least absolute shrinkage and selection operator (LASSO) and stepwise multivariate regression analysis were conducted to establish a UPS-based prognostic risk model. The robustness of the risk model was further validated in HCCDB18, GSE14520, and GSE76427 cohorts. Subsequently, immune features, clinicopathologic characteristics, enrichment pathways, and anti-tumor drug sensitivity of the model were further evaluated. Moreover, a nomogram was established to improve the predictive ability of the risk model. Results: Seven UPS-based signatures (ATG10, FBXL7, IPP, MEX3A, SOCS2, TRIM54, and PSMD9) were developed for the prognostic risk model. Individuals with HCC with high-risk scores presented a more dismal prognosis than those with low-risk scores. Moreover, larger tumor size, advanced TNM stage, and tumor grade were observed in the high-risk group. Additionally, cell cycle, ubiquitin-mediated proteolysis, and DNA repair pathways were intimately linked to the risk score. In addition, obvious immune cell infiltration and sensitive drug response were identified in low-risk patients. Furthermore, both nomogram and risk score showed a significant prognosis-predictive ability. Conclusion: Overall, we established a novel UPS-based prognostic risk model in HCC. Our results will facilitate a deep understanding of the functional role of UPS-based signature in HCC and provide a reliable prediction of clinical outcomes and anti-tumor drug responses for patients with HCC.

Identification and validation of a novel ubiquitination-related gene UBE2T in Ewing's sarcoma

Background

Ewing's sarcoma (ES) is one of the most prevalent malignant bone tumors worldwide. However, the molecular mechanisms of the genes and signaling pathways of ES are still not well sufficiently comprehended. To identify candidate genes involved in the development and progression of ES, the study screened for key genes and biological pathways related to ES using bioinformatics methods.

Methods

The GSE45544 and GSE17618 microarray datasets were downloaded from the Gene Expression Omnibus (GEO) database. Differentially expressed genes (DEGs) were identified, and functional enrichment analysis was performed. A protein-protein interaction (PPI) network was built, and key module analysis was performed using STRING and Cytoscape. A core-gene was gained and was validated by the validation dataset GSE67886 and immunohistochemistry (IHC). The diagnostic value and prognosis evaluation of ES were executed using, respectively, the ROC approach and Cox Regression.

Results

A total of 187 DEGs, consisting of 56 downregulated genes and 131 upregulated genes, were identified by comparing the tumor samples to normal samples. The enriched functions and pathways of the DEGs, including cell division, mitotic nuclear division, cell proliferation, cell cycle, oocyte meiosis, and progesterone-mediated oocyte maturation, were analyzed. There were 149 nodes and 1246 edges in the PPI network, and 15 hub genes were identified according to the degree levels. The core gene (UBE2T) showed high expression in ES, validated by using GSE67886 and IHC. The ROC analysis revealed UBE2T had outstanding diagnostic value in ES (AUC = 0.75 in the training set, AUC = 0.90 in the validation set). Kaplan-Meier (analysis of survival rate) and Cox Regression analyses indicated that UBE2T was a sign of adverse results for sufferers with ES.

Conlusion

UBE2T was a significant value biomarker for diagnosis and treatment of ES, thereby presenting a novel potential therapeutic target for ES as well as a new perspective for assessing the effect of treatment and prognostic prediction.

Profiling Blood Serum Extracellular Vesicles in Plaque Psoriasis and Psoriatic Arthritis Patients Reveals Potential Disease Biomarkers

Psoriasis vulgaris (PsV) and psoriatic arthritis (PsA) are inflammatory diseases with unresolved pathophysiological aspects. Extracellular vesicles (EVs) play an important role in intercellular communication. We compared the miRNA contents and surface proteome of the EVs in the blood serum of PsV and PsA patients to healthy controls. Size-exclusion chromatography was used to isolate EVs from the blood serum of 12 PsV patients, 12 PsA patients and 12 healthy control subjects. EV samples were characterized and RNA sequencing was used to identify differentially enriched EV-bound miRNAs. We found 212 differentially enriched EV-bound miRNAs present in both PsV and PsA groups—a total of 13 miRNAs at FDR ≤ 0.05. The predicted target genes of these miRNAs were significantly related to lesser known but potentially disease-relevant pathways. The EV array revealed that PsV patient EV samples were significantly enriched with CD9 EV-marker compared to controls. Analysis of EV-bound miRNAs suggests that signaling via EVs in the blood serum could play a role in the pathophysiological processes of PsV and PsA. EVs may be able to fill the void in clinically applicable diagnostic and prognostic biomarkers for PsV and PsA.

Emerging Roles of Post-Translational Modifications in Skin Diseases: Current Knowledge, Challenges and Future Perspectives

Post-translational modifications (PTMs) of proteins represent as a key step in regulating their biological functions and dynamic interaction with other players. This process is fine-tuned by a myriad of enzymes named “writers, readers and erasers” whose actions are precisely controlled. Either the mutation, aberration in the expression of the aforementioned enzymes or their substrates have shown to participate in the pathogenesis of various skin diseases such as melanoma, vitiligo, psoriasis, eczema, atopic dermatitis and inherited dermatological diseases. It is becoming increasingly clear that key transcriptional factors, inflammation-related molecules are prone to PTMs. Despite their importance in regulating key processes including inflammation, keratinocyte apoptosis, proliferation and differentiation, PTMs have received less attention due to the challenges involved. Here in this review we summarize the role of the most common types and the newly discovered PTMs, including acetylation, glycosylation, citrullination, PARylation and sumoylation in dermatoses and surveys the recent progress in PTM-based therapeutic approaches in skin diseases.

RNA Sequencing Analysis of Gene Expression by Electroacupuncture in Guinea Pig Gallstone Models

BACKGROUND

Clinical studies have shown that electroacupuncture (EA) promotes gallbladder motility and alleviates gallstone. However, the mechanism underlying the effects of EA on gallstone is poorly understood. In this study, the mRNA transcriptome analysis was used to study the possible therapeutic targets of EA.

METHODS

Hartley SPF guinea pigs were employed for the gallstone models. Illumina NovaSeq 6000 platform was used for the RNA sequencing of guinea pig gallbladders in the normal group (Normal), gallstone model group (Model), and EA-treated group (EA). Differently expressed genes (DEGs) were examined separately in Model vs. Normal and EA vs. Model. DEGs reversed by EA were selected by comparing the DEGs of Model vs. Normal and EA vs. Model. Biological functions were enriched by gene ontology (GO) analysis. The protein-protein interaction (PPI) network was analyzed.

RESULTS

After 2 weeks of EA, 257 DEGs in Model vs. Normal and 1704 DEGs in EA vs. Model were identified. 94 DEGs reversed by EA were identified among these DEGs, including 28 reversed upregulated DEGs and 66 reversed downregulated DEGs. By PPI network analysis, 10 hub genes were found by Cytohubba plugin of Cytoscape. Quantitative real-time PCR (qRT-PCR) verified the changes.

CONCLUSION

We identified a few GOs and genes that might play key roles in the treatment of gallstone. This study may help understand the therapeutic mechanism of EA for gallstone.

Deubiquitylating enzymes: potential target in autoimmune diseases

The ubiquitin-proteasome pathway is responsible for the turnover of different cellular proteins, such as transport proteins, presentation of antigens to the immune system, control of the cell cycle, and activities that promote cancer. The enzymes which remove ubiquitin, deubiquitylating enzymes (DUBs), play a critical role in central and peripheral immune tolerance to prevent the development of autoimmune diseases and thus present a potential therapeutic target for the treatment of autoimmune diseases. DUBs function by removing ubiquitin(s) from target protein and block ubiquitin chain elongation. The addition and removal of ubiquitin molecules have a significant impact on immune responses. DUBs and E3 ligases both specifically cleave target protein and modulate protein activity and expression. The balance between ubiquitylation and deubiquitylation modulates protein levels and also protein interactions. Dysregulation of the ubiquitin-proteasome pathway results in the development of various autoimmune diseases such as inflammatory bowel diseases (IBD), psoriasis, multiple sclerosis (MS), systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA). This review summarizes the current understanding of ubiquitination in autoimmune diseases and focuses on various DUBs responsible for the progression of autoimmune diseases.

Keratin 17 in psoriasis: Current understanding and future perspectives

Keratin 17 (K17) is a multifaceted cytoskeletal protein that is not commonly expressed in the epidermis under normal physiological conditions. However, in psoriasis, K17 is overexpressed in the suprabasal layer of the epidermis and plays an important role in the pathogenesis of the disease. In this review, we have summarized our findings and those reported in other studies concerning the pathogenic functions of K17, as well as the mechanisms underlying the increase in K17 expression in psoriasis. K17 exerts both pro-proliferative and pro-inflammatory effects on keratinocytes. Moreover, K17 peptides trigger autoreactive T cells and promote psoriasis-related cytokine production. In turn, these cytokines modulate the expression, stability, and protein-protein interactions of K17 through transcriptional and translational regulation and post-translational modification of K17 in keratinocytes. Thus, a K17/T-cell/cytokine autoimmune loop is implicated in the pathogenesis of psoriasis, which is supported by the fact that therapies targeting K17 have achieved good outcomes in psoriasis-like mouse models. Future perspectives of K17 in psoriasis have also been discussed to provide potential directions for further studies.

Downregulation of Cathepsin B Reduces Proliferation and Inflammatory Response and Facilitates Differentiation in Human HaCaT Keratinocytes, Ameliorating IL-17A and SAA-Induced Psoriasis-Like Lesion

Psoriasis is a common inflammatory dermatology disease. Strongly expressed serum amyloid A (SAA) promotes psoriasis exacerbation through inducing IL-17 secretion. What's more, SAA can stimulate the release of cathepsin B. The current work was performed to demonstrate the specific effects of cathepsin B silencing on inflammatory response, proliferation, and differentiation of IL-17A and SAA-induced keratinocytes and to report the precise role of cathepsin B in psoriasis-like lesion. HaCaT keratinocytes received treatment with IL-17A (0, 10, 50, 100 ng/ml) or SAA (0, 1, 5, 10, 20 μg/ml) for 24 h to establish psoriasis-like keratinocytes model. HaCaT keratinocytes were transfected with small interfering RNA (siRNA)-cathepsin B for the functional experiments. Cathepsin B mRNA and protein levels were separately assessed by performing RT-qPCR and Western blot analysis. Then, CCK-8 for detection of cell proliferative capacity and Western blot assay for detection of Ki67 and PCNA expression were adopted to evaluate the influence of silenced cathepsin B on proliferation of IL-17A/SAA-induced HaCaT keratinocytes. Furthermore, IL-6, IL-1β, TNF-α, and p-NF-κB p65 were detected to assess the effects of cathepsin B knockdown on inflammatory response in IL-17A/SAA-induced HaCaT keratinocytes. In addition, assessment of KRT10, FLG, and LOR levels were applied to analyze the function of cathepsin B silencing on differentiation of IL-17A/SAA-induced HaCaT keratinocytes. Cathepsin B expression is distinctly elevated in IL-17A/SAA-induced HaCaT keratinocytes. IL-17A or SAA treatment enhanced proliferation, promoted the release of inflammatory factors, and arrested differentiation in HaCaT keratinocytes. Furthermore, downregulation of cathepsin B reduced proliferation, suppressed inflammatory response, and boosted differentiation in IL-17A/SAA-induced HaCaT keratinocytes. To sum up, cathepsin B silencing rescued excessive proliferation and inflammatory response and scarce differentiation in HaCaT keratinocytes induced by IL-17A and SAA. These findings prompted that cathepsin B might be a promising therapeutic target for psoriasis-like lesion, which helps to develop an anti-psoriatic agent.

Role of Proteasomes in Inflammation

The ubiquitin–proteasome system (UPS) is involved in multiple cellular functions including the regulation of protein homeostasis, major histocompatibility (MHC) class I antigen processing, cell cycle proliferation and signaling. In humans, proteasome loss-of-function mutations result in autoinflammation dominated by a prominent type I interferon (IFN) gene signature. These genomic alterations typically cause the development of proteasome-associated autoinflammatory syndromes (PRAAS) by impairing proteasome activity and perturbing protein homeostasis. However, an abnormal increased proteasomal activity can also be found in other human inflammatory diseases. In this review, we cast a light on the different clinical aspects of proteasomal activity in human disease and summarize the currently studied therapeutic approaches.

Profiles of Innate Immune Cell Infiltration and Related Core Genes in Psoriasis

Psoriasis is an inflammatory skin disease with substantial morbidity. Numerous patients with psoriasis experience recurrence after therapy. The underlying mechanism about psoriasis is still not fully understood. Some evidences suggest that innate immunity may play an unexpected and important role in active severe psoriasis. In this work, the deconvolution algorithm CIBERSORT was conducted to identify the infiltration of innate immune cells and related core genes in psoriatic plaque. Datasets from the Gene Expression Omnibus, including skin samples from 405 psoriasis patients and 91 healthy donors, were downloaded for analysis. Considerable differences of the innate immune cell composition were uncovered between psoriatic plaque and control skin. Results revealed that γδ T cells, resting NK cells, M0 macrophages, M1 macrophages, activated dendritic cells, and neutrophils were significantly increased in psoriatic skin, while resting mast cells and active NK cells were significantly decreased. Moreover, the proportion of M0 macrophages or resting mast cells was found to be associated with disease severity. Spearman correlation analysis suggests that RORC and S100A12 genes were related to disease severity, while genes including S100A12, CLEC4C, IL-19, AIM2, IL-17F, and PPARGC1A were correlated with biologic treatment response. In conclusion, this work displays innate immune status in psoriatic skin and provides novel clues for clinical decisions and mechanism study.

Identification of UBE2T as an independent prognostic biomarker for gallbladder cancer

Gallbladder cancer is the most common biliary tract malignant tumor, with unfavorable patient outcomes. The present study aimed to identify potential diagnostic or prognostic biomarkers for gallbladder cancer. To do so, differentially expressed genes in the gallbladder walls and tumor tissues of patients with gallbladder cancer were analyzed via microarray. Furthermore, a protein-protein interaction network was constructed and genes with a degree score >10 were selected as hub genes. As ubiquitin conjugating enzyme E2T (UBE2T) was considered to be a hub gene, its expression was assessed via reverse transcription-quantitative (RT-q)PCR and immunohistochemistry (IHC). In addition, the association between UBE2T expression and the clinicopathological characteristics of patients with gallbladder cancer was analyzed using the χ² test. Furthermore, all patients were divided into high- and low groups based on UBE2T expression level and overall survival analysis was performed. Univariate and multivariate Cox regression analyses were performed to determine whether UBE2T may serve as an independent risk factor for gallbladder cancer. The results demonstrated that UBE2T expression was upregulated in the gallbladder walls and tumor tissues of patients with gallbladder cancer. Furthermore, UBE2T expression level was confirmed to be upregulated following RT-qPCR, and results from IHC demonstrated that UBE2T was predominantly expressed in the cytoplasm of gallbladder cancer cells. In addition, high UBE2T expression level was associated with clinical stage, T classification, N classification and M classification. The results from Univariate and multivariate analyses indicated that UBE2T expression level may be considered as an independent risk factor for gallbladder cancer. Taken together, the findings from this study suggested that high UBE2T expression level may contribute to the poor prognosis of patients with gallbladder cancer, and that UBE2T may act as an independent prognostic biomarker for these patients.

Towards Computational Models of Identifying Protein Ubiquitination Sites

Ubiquitination is an important post-translational modification (PTM) process for the regulation of protein functions, which is associated with cancer, cardiovascular and other diseases. Recent initiatives have focused on the detection of potential ubiquitination sites with the aid of physicochemical test approaches in conjunction with the application of computational methods. The identification of ubiquitination sites using laboratory tests is especially susceptible to the temporality and reversibility of the ubiquitination processes, and is also costly and time-consuming. It has been demonstrated that computational methods are effective in extracting potential rules or inferences from biological sequence collections. Up to the present, the computational strategy has been one of the critical research approaches that have been applied for the identification of ubiquitination sites, and currently, there are numerous state-of-the-art computational methods that have been developed from machine learning and statistical analysis to undertake such work. In the present study, the construction of benchmark datasets is summarized, together with feature representation methods, feature selection approaches and the classifiers involved in several previous publications. In an attempt to explore pertinent development trends for the identification of ubiquitination sites, an independent test dataset was constructed and the predicting results obtained from five prediction tools are reported here, together with some related discussions.

Epigenetically regulated co-expression network of genes significant for rheumatoid arthritis

Aim: To identify epigenetically regulated network of genes in peripheral blood mononuclear cells significant for rheumatoid arthritis (RA). Methods: Differentially expressed genes (DEGs) and their associated differentially expressed miRNAs and differentially methylated positions (DMPs) were identified. Causal inference test (CIT) identified the causal regulation chains. The analyses, for example, weighted gene co-expression network (WGCNA), protein-protein interaction and functional enrichment, evaluated interaction patterns among the DEGs and the associated epigenetic factors. Results: A total of 181 DEGs were identified. The DEGs were significantly regulated by DMPs and/or differentially expressed miRNAs. Causal inference test analyses identified 18 causal chains of DMP-DEG-RA and 16 intermediate DEGs enriched in 'protein kinase inhibitor activity'. BTN2A1 was co-expressed with other 9 intermediate genes and 11 known RA-associated genes and played a pivotal role in the co-expression network. Conclusion: Epigenetically regulated network of genes in peripheral blood mononuclear cells (PBMC) contributed to RA. The causal DMPs and key intermediate genes may serve as potential biomarkers for RA.

Keratin 17 in disease pathogenesis: from cancer to dermatoses

Keratin 17 (K17) is a type I intermediate filament mainly expressed in the basal cells of epithelia. As a multifaceted cytoskeletal protein, K17 regulates a myriad of biological processes, including cell proliferation and growth, skin inflammation and hair follicle cycling. Aberrant overexpression of K17 is found in various diseases ranging from psoriasis to malignancies such as breast, cervical, oral squamous and gastric carcinomas. Moreover, genetic mutation in KRT17 is related to tissue-specific diseases, represented by steatocystoma multiplex and pachyonychia congenita. In this review, we summarize our findings concerning the regulatory mechanisms of K17 overexpression in psoriasis and compare them to the literature relating to other diseases. We discuss data that proinflammatory cytokines, including interleukin-17 (IL-17), IL-22, interferon-gamma (IFN-γ), transforming growth factor-beta (TGF-β) and transcription factors glioma-associated oncogene homolog 1/2 (Gli1/2), Nrf2 and p53 can regulate K17 by transcriptional and translational control. Moreover, post-translational modification, including phosphorylation and ubiquitination, is involved in the regulation of K17 stability and biological functions. We therefore review the current understanding of the K17 regulatory mechanism and its pathogenic role in diseases from dermatoses to cancer. Prospects for anti-K17 therapy in diagnosis, prognosis and disease treatment are also discussed. Copyright © 2018 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

S100A7, Jab1, and p27kip1 expression in psoriasis and S100A7 CRISPR-activated human keratinocyte cell line

Psoriasis, a chronic immune-mediated inflammatory skin disease, is characterized by dysregulated keratinocyte proliferation. The EF-hand calcium binding protein S100A7 has been found to be overexpressed in psoriatic keratinocytes. It is know that S100A7 may interact with Jab1, a cofactor that stabilizes c-Jun. Jab1 is known to downregulate the expression of the cell cycle inhibitor p27^Kip1 in some cancer models. In this study, we aimed to investigate the possible interaction between S100A7 and Jab1 and the downstream effects on p27 ^Kip1 expression in normal human keratinocyte cells transfected with S100A7 CRISPR activation plasmid and in archival psoriatic skin samples. Our results showed that the upregulated S100A7 colocalizes with Jab1 at the nuclear level in transfected cells and psoriatic skin samples. We also showed a differential protein expression of Jab1 between cytoplasmic and nuclear compartments, thus suggesting Jab1 translocation from nucleus to cytoplasm. p27 ^Kip1 protein expression patterns would imply a translocation from nucleus and a subsequent degradation of this protein. The upregulation of S1007 and its interaction with Jab1 would contribute to the p27 ^Kip1 -dependent impaired proliferation that characterizes psoriatic skin.

UCHL1/PGP 9.5 Dynamic in Neuro-Immune-Cutaneous Milieu: Focusing on Axonal Nerve Terminals and Epidermal Keratinocytes in Psoriatic Itch

Psoriasis is an immunogenetic skin disease manifesting as plaque lesions on the skin. Patients with psoriasis frequently suffer from itch, an unpleasant sensation causing a desire to scratch. Psoriatic itch is mainly transmitted by unmyelinated C-fibers; however, the exact molecular mechanism of psoriatic itch is still unexplained. Protein gene product 9.5 (PGP 9.5) is a panneurological marker commonly used for analysis of peripheral peptidergic and nonpeptidergic nerves and identification of cutaneous neuro-immune-endocrine cells. However, some studies suggested that nonneuronal cells, like keratinocytes, may also express PGP 9.5. This phenomenon might be linked with impaired axonal transport, keratinocyte injury, or dysfunctions of neuro-immune-cutaneous connections. The aim of this study was to analyze the expression of PGP 9.5 in psoriatic skin. We observed significantly altered density of PGP 9.5-positive axonal nerve terminals in pruritic lesional (p=0.04) and nonlesional psoriatic skin (p>0.001) compared with controls. In contrast, no significant differences were observed between psoriatic skin without itch and controls. Furthermore, PGP 9.5 expression by suprabasal keratinocytes (SBKs) was significantly increased in itchy skin lesions (p=0.007) compared to skin without itch, and a positive correlation was observed between PGP 9.5 expression and itch intensity (r=0.64; p=0.02). Our findings indicate changes in peripheral innervations and psoriatic keratinocytes, which may influence neuro-immune-cutaneous homeostasis and modulate itch transmission.

E3 Ligase Trim21 Ubiquitylates and Stabilizes Keratin 17 to Induce STAT3 Activation in Psoriasis

Keratin 17 (K17), a marker of keratinocyte hyperproliferation, is a type I intermediate filament that is overexpressed in psoriatic epidermis and plays a critical pathogenic role by stimulating T cells. However, the posttranslational modification of K17, which is reversible and targetable, has not been elucidated. Herein, we reported that K17 could be modified through ubiquitination that controlled its stability and led to the phosphorylation and nuclear translocation of its interactor signal transducers and activators of transcription 3 (STAT3), which is a key regulator of cell proliferation in psoriasis. First, we stimulated human keratinocyte cell line HaCaT cells with psoriasis (pso)-mix, which is a cytokine pool (IL-17, IL-22, tumor necrosis factor-α, and IFN-γ) mimicking the in vitro "psoriasis-like" status and found that the ubiquitination of K17 was essential to stabilize its protein expression in pso-mix-treated HaCaT cells. Subsequently, tripartite motif-containing protein 21 was identified as the E3 ligase of K17, which ubiquitylated K17 via K63 linkage to maintain K17 stabilization. More importantly, we uncovered that K17 was a direct interactor of STAT3, and K17 ubiquitination could promote STAT3 activation in pso-mix-treated HaCaT cells. Our study demonstrated that targeting K17 ubiquitination may be a potential therapeutic approach by attenuating STAT3 signaling in psoriasis.