Hsp40 regulates the amount of keratin proteins via ubiquitin-proteasome pathway in cultured human cells

In silico analysis of the profilaggrin sequence indicates alterations in the stability, degradation route, and intracellular protein fate in filaggrin null mutation carriers

Background: Loss of function mutation in FLG is the major genetic risk factor for atopic dermatitis (AD) and other allergic manifestations. Presently, little is known about the cellular turnover and stability of profilaggrin, the protein encoded by FLG. Since ubiquitination directly regulates the cellular fate of numerous proteins, their degradation and trafficking, this process could influence the concentration of filaggrin in the skin. Objective: To determine the elements mediating the interaction of profilaggrin with the ubiquitin-proteasome system (i.e., degron motifs and ubiquitination sites), the features responsible for its stability, and the effect of nonsense and frameshift mutations on profilaggrin turnover. Methods: The effect of inhibition of proteasome and deubiquitinases on the level and modifications of profilaggrin and processed products was assessed by immunoblotting. Wild-type profilaggrin sequence and its mutated variants were analysed in silico using the DEGRONOPEDIA and Clustal Omega tool. Results: Inhibition of proteasome and deubiquitinases stabilizes profilaggrin and its high molecular weight of presumably ubiquitinated derivatives. In silico analysis of the sequence determined that profilaggrin contains 18 known degron motifs as well as multiple canonical and non-canonical ubiquitination-prone residues. FLG mutations generate products with increased stability scores, altered usage of the ubiquitination marks, and the frequent appearance of novel degrons, including those promoting C-terminus-mediated degradation routes. Conclusion: The proteasome is involved in the turnover of profilaggrin, which contains multiple degrons and ubiquitination-prone residues. FLG mutations alter those key elements, affecting the degradation routes and the mutated products' stability.

Post-Translational Modifications in Atopic Dermatitis: Current Research and Clinical Relevance

Atopic dermatitis (AD) is a chronic and relapsing cutaneous disorder characterized by compromised immune system, excessive inflammation, and skin barrier disruption. Post-translational modifications (PTMs) are covalent and enzymatic modifications of proteins after their translation, which have been reported to play roles in inflammatory and allergic diseases. However, less attention has been paid to the effect of PTMs on AD. This review summarized the knowledge of six major classes (including phosphorylation, acetylation, ubiquitination, SUMOylation, glycosylation, o-glycosylation, and glycation) of PTMs in AD pathogenesis and discussed the opportunities for disease management.

Development and validation of an autophagy-related prognostic signature in esophageal cancer

Background

Autophagy has a dual function in cancer, and its role in carcinogenesis of the esophagus remains poorly understood. In the present study, we explored the prognostic value of autophagy in esophageal cancer (ESCA), one of the leading causes of cancer-related deaths worldwide.

Methods

Using ESCA RNA-sequencing (RNA-Seq) data from 158 primary patients with ESCA, including esophageal adenocarcinoma and esophageal squamous cell carcinoma, were downloaded from The Cancer Genome Atlas (TCGA) for this study. We obtained differentially expressed autophagy-related genes (ARGs) by the “limma” package of R. The Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genome (KEGG) analyses unveiled several fundamental signaling pathways associated with the differentially expressed ARGs in ESCA. Univariate Cox regression analyses were used to estimate associations between ARGs and overall survival (OS) in the TCGA ESCA cohort. A Cox proportional hazards model (iteration =1,000) with a lasso penalty was used to create the optimal multiple-gene prognostic signature utilizing an R package called “glmnet”.

Results

A prognostic signature was constructed with four ARGs (DNAJB1, BNIP1, VAMP7 and TBK1) in the training set, which significantly divided ESCA patients into high- and low-risk groups in terms of OS [hazard ratio (HR) =1.508, 95% confidence interval (CI): 1.201–1.894, P<0.001]. In the testing set, the risk score remained an independent prognostic factor in the multivariate analyses (HR =1.572, 95% CI: 1.096–2.257, P=0.014). The area under the curve (AUC) of the receiver operating characteristic (ROC) predicting 1-year survival showed a better predictive power for the prediction model. The AUC in training and testing cohorts were 0.746 and 0.691, respectively. Therefore, the prognostic signature of the four ARGs was successfully validated in the independent cohort.

Conclusions

The prognostic signature may be an independent predictor of survival for ESCA patients. The prognostic nomogram may improve the prediction of individualized outcome. This study also highlights the importance of autophagy in the outcomes of patients with ESCA.

Autophagy-related genes are potential diagnostic and prognostic biomarkers in prostate cancer

Background

Recently, autophagy was found related to several malignances.

Methods

To explore the diagnostic and prognostic values of autophagy in prostate cancer (PCa), we first identified differentially expressed autophagy-related genes (DEARGs) based on The Cancer Genome Atlas (TCGA) Prostate Adenocarcinoma (PRAD) dataset. Gene ontology (GO) analysis and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment were applied to perform gene functional annotation. Then, multivariate logistic regression analysis was applied to construct the risk index (RI). Receiver operating characteristic (ROC), calibration and decision curve analysis (DCA) curves were performed to identify the effectiveness of RI. Next, multivariate Cox regression analyses were performed to construct the prognostic index (PI) and autophagy-clinical prognostic index (ACPI).

Results

We identified 16 DEARGs and functional annotation demonstrated the relevance of these genes to autophagy and revealed the association of these DEARGs with digestive system, drug resistance and apoptosis. Then, the RI was constructed based on 5 DEARGs and the area under the ROC curve (AUC) was 0.9858. Validation based on Gene Expression Omnibus (GEO) datasets suggested that the RI was effective. Next, 7 ARGs were identified associated with overall survival (OS) and the PI was developed composed of 3 ARGs. Finally, ACPI was constructed based on PI and the M stage.

Conclusions

This study provided potential models for predicting the risk and prognosis of PCa and indicated the molecular insights of autophagy in PCa. While no other dataset was applied to test the effectiveness of the PI and ACPI models attribute to the well prognosis of PCa.

Identification of TPD52 and DNAJB1 as two novel bile biomarkers for cholangiocarcinoma by iTRAQ‑based quantitative proteomics analysis

Cholangiocarcinoma (CCA) represents a type of epithelial cancer with a late diagnosis and poor outcome. However, the molecular mechanisms responsible for the development of CCA have not yet been fully identified. Thus, in this study, we aimed to elucidate some of these mechanisms. For this purpose, isobaric tags for relative and absolute quantification (iTRAQ) was performed to analyze the secretory proteins from the 2 CCA cell lines, TFK1 and HuCCT1, as well as from a normal biliary epithelial cell line, human intrahepatic biliary epithelial cells (HiBECs). Differentially expressed proteins (DEPs) were identified and biological process analysis was performed according to the Gene Ontology (GO) functional classification annotation and KEGG metabolic pathway map analysis. tumor protein D52 (TPD52) and DnaJ heat shock protein family (Hsp40) member B1 (DNAJB1) were validated using RT-qPCR, western blot analysis and immunohistochemistry. In total, 778 proteins were identified as DEPs. Following validation, TPD52 and DNAJB1 were used for further analysis. The expression levels of TPD52 and DNAJB1 were elevated in CCA cell lines, tissues and bile samples, suggesting that these proteins may contribute to tumor pathogenesis. In addition, the expression levels of TPD52 and DNAJB1 were found to be closely associated with the clinical parameters and prognosis of patients with CCA. On the whole, the findings of this study indicate that TPD52 and DNAJB1 may serve as novel bile biomarkers for CCA.

Multiple roles for keratin intermediate filaments in the regulation of epithelial barrier function and apico-basal polarity

As multicellular organisms evolved a family of cytoskeletal proteins, the keratins (types I and II) expressed in epithelial cells diversified in more than 20 genes in vertebrates. There is no question that keratin filaments confer mechanical stiffness to cells. However, such a number of genes can hardly be explained by evolutionary advantages in mechanical features. The use of transgenic mouse models has revealed unexpected functional relationships between keratin intermediate filaments and intracellular signaling. Accordingly, loss of keratins or mutations in keratins that cause or predispose to human diseases, result in increased sensitivity to apoptosis, regulation of innate immunity, permeabilization of tight junctions, and mistargeting of apical proteins in different epithelia. Precise mechanistic explanations for these phenomena are still lacking. However, immobilization of membrane or cytoplasmic proteins, including chaperones, on intermediate filaments (“scaffolding”) appear as common molecular mechanisms and may explain the need for so many different keratin genes in vertebrates.

FOXE3 contributes to Peters anomaly through transcriptional regulation of an autophagy-associated protein termed DNAJB1

FOXE3 is a lens-specific transcription factor that has been associated with anterior segment ocular dysgenesis. To determine the transcriptional target(s) of FOXE3 that are indispensable for the anterior segment development, we examined the transcriptome and the proteome of cells expressing truncated FOXE3 responsible for Peters anomaly identified through linkage-coupled next-generation whole-exome sequencing. We found that DNAJB1, an autophagy-associated protein, was the only candidate exhibiting differential expression in both screens. We confirmed the candidacy of DNAJB1 through chromatin immunoprecipitation and luciferase assays while knockdown of DNAJB1 in human lens epithelial cells resulted in a mitotic arrest. Subsequently, we targeted dnajb1a in zebrafish through injection of a splice-blocking morpholino. The dnajb1a morphants exhibited underdeveloped cataractous lenses with persistent apoptotic nuclei. In conclusion, here we report DNAJB1 is a transcriptional target of FOXE3 in a novel pathway that is crucial for the development of the anterior segment of the eye.

Functional Analysis of Keratin-Associated Proteins in Intestinal Epithelia: Heat-Shock Protein Chaperoning and Kinase Rescue

A growing body of evidence from several laboratories points at nonmechanical functions of keratin intermediate filaments (IF), such as control of apoptosis, modulation of signaling, or regulation of innate immunity, among others. While these functions are generally assigned to the ability of IF to scaffold other proteins, direct mechanistic causal relationships between filamentous keratins and the observed effects of keratin knockout or mutations are still missing. We have proposed that the scaffolding of chaperones such as Hsp70/40 may be key to understand some IF nonmechanical functions if unique features or specificity of the chaperoning activity in the IF scaffold can be demonstrated. The same criteria of uniqueness could be applied to other biochemical functions of the IF scaffold. Here, we describe a subcellular fractionation technique based on established methods of keratin purification. The resulting keratin-enriched fraction contains several proteins tightly associated with the IF scaffold, including Hsp70/40 chaperones. Being nondenaturing, this fractionation method enables direct testing of chaperoning and other enzymatic activities associated with IF, as well as supplementation experiments to determine the need for soluble (cytosolic) proteins. This method also permits to analyze inhibitory activity of cytosolic proteins at independently characterized physiological concentrations. When used as complementary approaches to knockout, knockdown, or site-directed mutagenesis, these techniques are expected to shed light on molecular mechanisms involved in the effects of IF loss of function.

Desmosomes: regulators of cellular signaling and adhesion in epidermal health and disease

Desmosomes are intercellular junctions that mediate cell-cell adhesion and anchor the intermediate filament network to the plasma membrane, providing mechanical resilience to tissues such as the epidermis and heart. In addition to their critical roles in adhesion, desmosomal proteins are emerging as mediators of cell signaling important for proper cell and tissue functions. In this review we highlight what is known about desmosomal proteins regulating adhesion and signaling in healthy skin-in morphogenesis, differentiation and homeostasis, wound healing, and protection against environmental damage. We also discuss how human diseases that target desmosome molecules directly or interfere indirectly with these mechanical and signaling functions to contribute to pathogenesis.

Interactive cellular proteins related to classical swine fever virus non-structure protein 2 by yeast two-hybrid analysis

Classical swine fever is caused by the classical swine fever virus (CSFV), which has a special affinity to endothelial cells. This fever is characterized by hemorrhage and necrosis of vascular injury. Very little information is available on the interaction between vascular endothelial cells and CSFV. In the current report, the cDNA library of swine umbilical vein endothelial cell (SUVEC) was constructed by the switching mechanism at 5' end of the RNA transcript approach. The yeast two-hybrid (Y2H) system was adopted to screen non-structure 2 protein (NS2) interactive proteins in the SUVEC line. Alignment with the NCBI database revealed 11 interactive proteins: GOPC, HNRNPH1, DNAJA1, ATP6, CSDE1, CNDP2, FANCL, TMED4, DNAJA4, MOAP1, and PNMA1. These proteins were mostly related to apoptosis, stress response and oxidation reduction, or metabolism. In the protein interaction network constructed based on proteins with NS2, the more important proteins were MOAP1, DNAJA1, GOPC, FANCL, TMED4, and CSDE1. The interactions detected by the Y2H should be regarded only as preliminary indications. However, the CSFV NS2 interactive proteins in the SUVEC cDNA library obtained in the current study provides valuable information for gaining a better understanding of the host protein-virus interactions of the CSFV NS2 protein.

The Hsp90 inhibitor 17-AAG represses calcium-induced cytokeratin 1 and 10 expression in HaCaT keratinocytes

Hsp90 is essential for maintaining the activity of numerous signaling factors, and plays a key role in cellular signal transduction networks. 17-Allylamino-17-demethoxygeldanamycin (17-AAG) is an ansamycin antibiotic that binds to Hsp90 and inhibits its function. HaCaT human keratinocytes were used to investigate the cellular and molecular functions of Hsp90 in keratinocyte differentiation. Inhibition of Hsp90 by 17-AAG leads to downregulation of the differentiation markers cytokeratin 1 and cytokeratin 10 at the protein and mRNA levels.