Stabilization of Pin1 by USP34 promotes Ubc9 isomerization and protein sumoylation in glioma stem cells.

The peptidyl-prolyl cis-trans isomerase Pin1 is a pivotal therapeutic target in cancers, but the regulation of Pin1 protein stability is largely unknown. High Pin1 expression is associated with SUMO1-modified protein hypersumoylation in glioma stem cells (GSCs), but the underlying mechanisms remain elusive. Here we demonstrate that Pin1 is deubiquitinated and stabilized by USP34, which promotes isomerization of the sole SUMO E2 enzyme Ubc9, leading to SUMO1-modified hypersumoylation to support GSC maintenance. Pin1 interacts with USP34, a deubiquitinase with preferential expression and oncogenic function in GSCs. Such interaction is facilitated by Plk1-mediated phosphorylation of Pin1. Disruption of USP34 or inhibition of Plk1 promotes poly-ubiquitination and degradation of Pin1. Furthermore, Pin1 isomerizes Ubc9 to upregulate Ubc9 thioester formation with SUMO1, which requires CDK1-mediated phosphorylation of Ubc9. Combined inhibition of Pin1 and CDK1 with sulfopin and RO3306 most effectively suppresses orthotopic tumor growth. Our findings provide multiple molecular targets to induce Pin1 degradation and suppress hypersumoylation for cancer treatment.

Protein sumoylation in normal and cancer stem cells.

Stem cells with the capacity of self-renewal and differentiation play pivotal roles in normal tissues and malignant tumors. Whereas stem cells are supposed to be genetically identical to their non-stem cell counterparts, cell stemness is deliberately regulated by a dynamic network of molecular mechanisms. Reversible post-translational protein modifications (PTMs) are rapid and reversible non-genetic processes that regulate essentially all physiological and pathological process. Numerous studies have reported the involvement of post-translational protein modifications in the acquirement and maintenance of cell stemness. Recent studies underscore the importance of protein sumoylation, i.e., the covalent attachment of the small ubiquitin-like modifiers (SUMO), as a critical post-translational protein modification in the stem cell populations in development and tumorigenesis. In this review, we summarize the functions of protein sumoylation in different kinds of normal and cancer stem cells. In addition, we describe the upstream regulators and the downstream effectors of protein sumoylation associated with cell stemness. We also introduce the translational studies aiming at sumoylation to target stem cells for disease treatment. Finally, we propose future directions for sumoylation studies in stem cells.

Astaxanthin protects retinal ganglion cells from acute glaucoma via the Nrf2/HO-1 pathway.

The death of retinal ganglion cells (RGCs) during acute glaucoma causes progressive degeneration of the retinal nerve and irreversible blindness. Astaxanthin (AST) is a type of xanthophyll carotenoids and naturally synthesized by multiple halobios. It has been reported to protect the retina from acute glaucoma due to its anti-oxidative and anti-neuroinflammatory properties. However, the mechanism underlying this process remains unclear. We designed a mouse model with acute glaucoma and AST was administered by oral gavage. Hematoxylin and eosin staining was utilized to evaluate the condition of retina and the number of ganglion cells was counted. QRT-PCR was performed to evaluate the mRNA levels of Bax and Bcl2 while Western blot assay was used to determine the protein levels of Bax, Bcl2, Nrf2 and HO-1. AST protected the retinal integrity of mice with acute glaucoma. The apoptosis of RGCs induced by ischemia and reperfusion was repressed by AST. The protective functions of AST on the retinal and ganglion cells decreased with the knock-down of Nrf2. AST promoted the activation of Nrf2 and Ho-1 in the RGCs of the model mice. AST protected the RGCs from apoptosis during acute glaucoma and alleviated the severe retinopathy symptoms through the Nrf2/Ho-1 pathway.

[Effect of Chidamide on the Killing Acitivity of NK Cells Targeting K562 Cells and Its Related Mechanism In Vitro].

OBJECTIVE: To investigate the effect of chidamide on the killing activity of NK (Natural killer cell, NK) cells targeting K562 cells and its related mechanism. METHODS: K562 cells were pretreated with chidamide at different concentrations and cocultured with NK cells at different effect-target ratios. The killing effect of chidamide on K562 cells by NK cells, the expression of natural killer group 2 member D (NKG2D) ligands and apoptosis rate of K562 cells were detected by flow cytometry. RESULTS: The killing sensitivity of NK cells to K562 cells could be enhanced by chidamide. The expression of ULBP2 on K562 cell surface could be up-regulate, however, the expression of ULBP1 and MICA/MICB showed no statistically difference as compared with control group. Chidamide showed no obvious cytotoxicity to K562 cells. CONCLUSION: Chidamide can significantly improve killing efficiency of NK cells on K562 cells, which may be related to the up-regulation of ULBP2 expression.

Baicalin protects human retinal pigment epithelial cell lines against high glucose-induced cell injury by up-regulation of microRNA-145.

BACKGROUND: Diabetic retinopathy (DR) is a common complication of diabetes mellitus, which is a major reason of blindness. Baicalin (BAI) is a flavonoid extracted from Scutellaria baicalensis, whose pharmacological characterizes have been widely reported in various diseases. However, it remains unclear the effect of BAI on DR. The study aimed to confirm the protective effect of BAI on DR. METHODS: ARPE-19 cells and HRMECs were exposed to the high glucose (HG) environment to construct a cell injury model. After treatment with HG and BAI, cell viability, apoptosis, inflammatory cytokines and ROS generations were determined in ARPE-19 cells and HRMECs. Subsequently, microRNA-145 (miR-145) inhibitor and its negative control were transfected into ARPE-19 cells, and the regulatory effects on HG-and BAI-co-treated cells were detected. NF-κB and p38MAPK signaling pathways were finally examined to state the underling mechanisms. RESULTS: HG treatment significantly induced ARPE-19 cells and HRMECs injury in vitro. BAI significantly promoted cell proliferation, reduced apoptosis, as well as inhibited the release of IL-1ß, IL-6, IL-8 and ROS level in HG-injured ARPE-19 cells and HRMECs. Additionally, the expression level of miR-145 was up-regulated in HG-and BAI-co-treated cells. More importantly, miR-145 inhibition reversed the protective effect of BAI on HG-injured ARPE-19 cells. Besides, we observed that BAI inhibited the activations of NF-κB and p38MAPK pathways by up-regulating miR-145. CONCLUSIONS: Results demonstrated that BAI exhibited the protective effect against HG-induced cell injury by up-regulation of miR-145.