A MET-PTPRK kinase-phosphatase rheostat controls ZNRF3 and Wnt signaling

Comprehensive analysis of zinc and ring finger 3 in prognostic value and pan-cancer immunity

Zinc and ring finger 3 (ZNRF3) is a negative suppressor of Wnt signal and newly identified as an important regulator in tumorigenesis and development. However, the pan-cancer analysis of ZNRF3 has not been reported. We found that ZNRF3 was significantly decreased in six tumors including CESC, KIRP, KIRC, SKCM, OV, and ACC, but increased in twelve tumors, namely LGG, ESCA, STES, COAD, STAD, LUSC, LIHC, THCA, READ, PAAD, TGCT, and LAML. Clinical outcomes of cancer patients were closely related to ZNRF3 expression in ESCA, GBM, KIRC, LUAD, STAD, UCEC, LGG, and SARC. The highest genetic alteration frequency of ZNRF3 occurred in ACC. Abnormal expression of ZNRF3 could be attributed to the differences of copy number variation (CNV) and DNA methylation as well as ZNRF3-interacting proteins. Besides, ZNRF3 were strongly associated with tumor heterogeneity, tumor stemness, immune score, stromal score and ESTIMATE score in certain cancers. In terms of immune cell infiltration, ZNRF3 was positively correlated to infiltration of cancer-associated fibroblasts in CESC, HNSC, OV, PAAD, PRAD, and THYM, but negatively associated with infiltration of CD8 T cells in HNSC, KIRC, KIRP and THYM. Moreover, ZNRF3 expression was correlated with most immune checkpoint genes in SARC, LUSC, LUAD, PRAD, THCA, UVM, TGCT, and OV, and associated with overwhelming majority of immunoregulatory genes in almost all cancers. Most RNA modification genes were also remarkably related to ZNRF3 level in KIRP, LUAD, LUSC, THYM, UVM, PRAD, and UCEC, indicating that ZNRF3 might have an important effect on cancer epigenetic regulation. Finally, we verified the expression and role of ZNRF3 in clinical specimens and cell lines of renal cancer and liver cancer. This study provides a comprehensive pan-cancer analysis of ZNRF3 and reveals the complexity of its carcinogenic effect.

RNF43 and ZNRF3 in Wnt Signaling - A Master Regulator at the Membrane

The Wnt β-catenin signaling pathway is a highly conserved mechanism that plays a critical role from embryonic development and adult stem cell homeostasis. However, dysregulation of the Wnt pathway has been implicated in various diseases, including cancer. Therefore, multiple layers of regulatory mechanisms tightly control the activation and suppression of the Wnt signal. The E3 ubiquitin ligases RNF43 and ZNRF3, which are known negative regulators of the Wnt pathway, are critical component of Wnt signaling regulation. These E3 ubiquitin ligases control Wnt signaling by targeting the Wnt receptor Frizzled to induce ubiquitination-mediated endo-lysosomal degradation, thus controlling the activation of the Wnt signaling pathway. We also discuss the regulatory mechanisms, interactors, and evolution of RNF43 and ZNRF3. This review article summarizes recent findings on RNF43 and ZNRF3 and their potential implications for the development of therapeutic strategies to target the Wnt signaling pathway in various diseases, including cancer.

Hepatocyte Growth Factor Promotes Differentiation Potential and Stress Response of Human Stem Cells from Apical Papilla

Harsh local microenvironment, such as hypoxia and lack of instructive clues for transplanted stem cells, presents the serious obstacle for stem cell therapies' efficacy. Therefore, continued efforts have been taken to improve stem cells' viability and plasticity. Hepatocyte growth factor (HGF) has previously been reported to mitigate the complications of various human diseases in animal model studies and in some clinical trials. Besides, human stem cells from the root apical papilla (SCAP) are deemed a better resource of mesenchymal stem cells due to derived stem cells holding greater amplification ability in vitro compared with those from other dental resources. To move forward, evaluating effects and understanding underlying molecular mechanisms of HGF on SCAP for periodontal regeneration are needed. In this study, HGF was transgenically expressed in SCAP, and it was found that HGF enhanced osteo/dentinogenic differentiation capacity of SCAP compared with those of non-treated control in an ectopic mineralization model. Moreover, HGF reduced the apoptosis of SCAP under both normoxic and hypoxic conditions, whereas the combination of HGF and hypoxia exposure had inhibitory effects on cell proliferation during an 8-day in vitro culture period. Transcriptome analysis further revealed that suppressed cell cycle progression and activated BMP/TGFβ, Hedgehog, WNT, FGF, HOX, and other morphogen family members result upon HGF overexpression, which may render SCAP recapitulate part of neural crest stem cell characteristics. Moreover, strengthened stress response modulation such as unfolded protein response, macroautophagy, and anti-apoptotic molecules might explain the increased viability of SCAP. In all, our results imply that these potential mechanisms underlying HGF-promoting SCAP differentiation could be further elucidated and harnessed to improve periodontal tissue regeneration.

Receptor control by membrane-tethered ubiquitin ligases in development and tissue homeostasis

Paracrine cell-cell communication is central to all developmental processes, ranging from cell diversification to patterning and morphogenesis. Precise calibration of signaling strength is essential for the fidelity of tissue formation during embryogenesis and tissue maintenance in adults. Membrane-tethered ubiquitin ligases can control the sensitivity of target cells to secreted ligands by regulating the abundance of signaling receptors at the cell surface. We discuss two examples of this emerging concept in signaling: (1) the transmembrane ubiquitin ligases ZNRF3 and RNF43 that regulate WNT and bone morphogenetic protein receptor abundance in response to R-spondin ligands and (2) the membrane-recruited ubiquitin ligase MGRN1 that controls Hedgehog and melanocortin receptor abundance. We focus on the mechanistic logic of these systems, illustrated by structural and protein interaction models enabled by AlphaFold. We suggest that membrane-tethered ubiquitin ligases play a widespread role in remodeling the cell surface proteome to control responses to extracellular ligands in diverse biological processes.