Phospho-PTM proteomic discovery of novel EPO- modulated kinases and phosphatases, including PTPN18 as a positive regulator of EPOR/JAK2 Signaling

Histidine Phosphorylation: Protein Kinases and Phosphatases

Phosphohistidine (pHis) is a reversible protein post-translational modification (PTM) that is currently poorly understood. The P-N bond in pHis is heat and acid-sensitive, making it more challenging to study than the canonical phosphoamino acids pSer, pThr, and pTyr. As advancements in the development of tools to study pHis have been made, the roles of pHis in cells are slowly being revealed. To date, a handful of enzymes responsible for controlling this modification have been identified, including the histidine kinases NME1 and NME2, as well as the phosphohistidine phosphatases PHPT1, LHPP, and PGAM5. These tools have also identified the substrates of these enzymes, granting new insights into previously unknown regulatory mechanisms. Here, we discuss the cellular function of pHis and how it is regulated on known pHis-containing proteins, as well as cellular mechanisms that regulate the activity of the pHis kinases and phosphatases themselves. We further discuss the role of the pHis kinases and phosphatases as potential tumor promoters or suppressors. Finally, we give an overview of various tools and methods currently used to study pHis biology. Given their breadth of functions, unraveling the role of pHis in mammalian systems promises radical new insights into existing and unexplored areas of cell biology.

Identification of RHEX as a novel biomarker related to progression and immunity of non-small cell lung carcinoma

Background

The therapeutic response and prognosis of patients with non-small cell lung carcinoma (NSCLC) are widely related to immunity. To improve the prognosis of patients and provide reliable information to guide appropriate personalized treatment strategies, it is necessary to identify reliable prognostic or predictive indicators closely related to tumor phenotype and immune traits in NSCLC.

Methods

Based on The Cancer Genome Atlas (TCGA)-NSCLC mRNA expression profile data, a novel approach combining differential gene expression analysis, single-sample gene set enrichment analysis (ssGSEA), and weighted gene co-expression network analysis (WGCNA) was used to screen hub genes. Subsequently, the regulator of hemoglobinization and erythroid cell expansion (RHEX) was identified as a key gene using the log-rank test and confirmed in the ArrayExpress database. The relationship between RHEX and clinicopathological parameters was analyzed using the Wilcoxon rank-sum test. More importantly, through gene set enrichment analysis (GSEA) and cell-type identification by estimating relative subsets of RNA transcripts (CIBERSORT) algorithms, and with reference to the Tumor IMmune Estimation Resource (TIMER) database, we explored the relevant pathways of RHEX and its relationship with tumor-infiltrating immune cells (TICs). Finally, we depicted the association between RHEX and immunomodulators in the TCGA and a web portal TISIDB.

Results

The RHEX mRNA expression levels in tumor tissues were lower than those in normal tissues and declined with the progression of NSCLC. Meanwhile, RHEX overexpression was associated with high immune infiltration levels and a favorable clinical prognosis. RHEX may participate in tumor microenvironment (TME) regulation through multiple tumor-immune related pathways, especially the JAK-STAT signaling pathway. Furthermore, RHEX expression affected the infiltrating abundance of multiple TICs and positively correlated with most of the immunomodulators in NSCLC.

Conclusions

Our study is the first to propose that RHEX is an immune-related gene with prognostic value in NSCLC and reveals the underlying mechanism between RHEX and tumor-immune system interactions. These results ultimately provide guidance for prognosis and immunotherapy for NSCLC patients.

Molecular Pathways Involved in the Development of Congenital Erythrocytosis

Patients with idiopathic erythrocytosis are directed to targeted genetic testing including nine genes involved in oxygen sensing pathway in kidneys, erythropoietin signal transduction in pre-erythrocytes and hemoglobin-oxygen affinity regulation in mature erythrocytes. However, in more than 60% of cases the genetic cause remains undiagnosed, suggesting that other genes and mechanisms must be involved in the disease development. This review aims to explore additional molecular mechanisms in recognized erythrocytosis pathways and propose new pathways associated with this rare hematological disorder. For this purpose, a comprehensive review of the literature was performed and different in silico tools were used. We identified genes involved in several mechanisms and molecular pathways, including mRNA transcriptional regulation, post-translational modifications, membrane transport, regulation of signal transduction, glucose metabolism and iron homeostasis, which have the potential to influence the main erythrocytosis-associated pathways. We provide valuable theoretical information for deeper insight into possible mechanisms of disease development. This information can be also helpful to improve the current diagnostic solutions for patients with idiopathic erythrocytosis.

Molecular dynamics simulation studies on the specific regulation of PTPN18 to the HER2 phospho-peptides

The specific regulation of PTPN18 protein to three HER2 phospho-peptides has been studied by molecular dynamics simulations and free energy calculations. The results revealed that the three HER2 phospho-peptides binding to the PTPN18 catalytic domain is energetically favorable due to substrate specificity of PTPN18, and moreover, the PTPN18 protein have significantly higher affinity to pY1248 peptide (-45.22 kcal/mol) than that of pY1112 (-25.3 kcal/mol) and pY1196 (-31.86 kcal/mol) peptides. Further, the binding of HER2 phospho-peptides to PTPN18 have also caused the closure of WPD-loop with the decrease of the centroid distances between the P-loop and the WPD loop. The WPD-loop closure of PTPN18 relates directly to the new hydrogen bond and hydrophobic interaction formations between the residues Tyr62, Asp64, Val65, Ala231, Arg235, and Ala273 in PTPN18 and Tyr(PO3) in the HER2 phospho-peptides, which suggests that these key residues would contribute to the specific regulation of PTPN18 to the substrates. The correlation analysis revealed the allosteric communication networks from the pY binding loop to the WPD loop through the structural change and the residue interactions in PTPN18. These results will be helpful to understand the specific regulation through the allosteric communication network in the PTPN18 catalytic domain.

Silencing of PTPN18 Induced Ferroptosis in Endometrial Cancer Cells Through p-P38-Mediated GPX4/xCT Down-Regulation

Background

Endometrial cancer (EC) is the fourth most common neoplasm and the eighth leading cause of cancer death in females worldwide. PTPN18 is a member of the protein tyrosine phosphatases (PTP) family, which is associated with the occurrence and progression of various human cancers. PTPN18 was up-regulated in endometrial cancer tissues and high level of PTPN18 promoted proliferation and metastasis of EC cells.

Methods

The expression of PTPN18, GPX4 and xCT in endometrial cancer tissues and KLE cells was detected by immunohistochemistry and Western blot, respectively. Lentiviral transfection were used to silence PTPN18 level in KLE cells. The Ros level in KLE cells was examined by ELISA assay.

Results

In the present study, we found that silencing of PTPN18 induced ferroptosis in KLE endometrial cancer cells. PTPN18 knockdown increased intracellular ROS level and down-regulated GPX4 and xCT expression. Besides, silencing of PTPN18 also induced the expression of p-p38.

Conclusion

We concluded that silencing of PTPN18 might induce ferroptosis by targeting the p-p38/GPX4/xCT axis. The results provide critical insight into the application of PTPN18 knockdown in EC intervention.

Mitochondrial Metabolism as Target of the Neuroprotective Role of Erythropoietin in Parkinson's Disease

Existing therapies for Parkinson's disease (PD) are only symptomatic. As erythropoietin (EPO) is emerging for its benefits in neurodegenerative diseases, here, we test the protective effect driven by EPO in in vitro (SH-SY5Y cells challenged by MPP⁺) and in vivo (C57BL/6J mice administered with MPTP) PD models. EPO restores cell viability in both protective and restorative layouts, enhancing the dopaminergic recovery. Specifically, EPO rescues the PD-induced damage to mitochondria, as shown by transmission electron microscopy, Mitotracker assay and PINK1 expression. Moreover, EPO promotes a rescue of mitochondrial respiration while markedly enhancing the glycolytic rate, as shown by the augmented extracellular acidification rate, contributing to elevated ATP levels in MPP⁺-challenged cells. In PD mice, EPO intrastriatal infusion markedly improves the outcome of behavioral tests. This is associated with the rescue of dopaminergic markers and decreased neuroinflammation. This study demonstrates cellular and functional recovery following EPO treatment, likely mediated by the 37 Kda isoform of the EPO-receptor. We report for the first time, that EPO-neuroprotection is exerted through restoring ATP levels by accelerating the glycolytic rate. In conclusion, the redox imbalance and neuroinflammation associated with PD may be successfully treated by EPO.