Down-regulation of TRAF4 targeting RSK4 inhibits proliferation, invasion and metastasis in breast cancer xenografts.

Ribosomal S6 protein kinase 4 (RSK4) was known as a novel tumor suppressor gene, and the tumor necrosis factor receptor-associated factor 4 (TRAF4) was linked to carcinogenesis. The purpose of this study is to further investigate the effect of the TRAF4 gene on cell proliferation, invasion and metastasis in vivo and explore whether there is an interaction between TRAF4 and RSK4 in breast cancer. MDA-MB-231 cells were transfected with lentivirus TRAF4-shRNA to specifically block the expression of TRAF4, or transfected with lentivirus negative-shRNA as a negative control. Four-six weeks female BALB/c nude mice were randomly assigned to three groups (n = 14): TRAF4-shRNA, negative and control, and then inoculated subcutaneously with the corresponding cells. In-vivo metastasis model was constructed by injecting above cells into tail vein. Tumor proliferation was assessed in terms of the tumor growth curve, tumor size and weight. Invasion and metastasis were evaluated by the histopathologic examination in lung or/and liver tissues. Measurement of TRAF4 and RSK4 expression and their correlation factors (AKT, NF-κB, TGF-ß1, TNF-α, MMP2 and MMP9) were performed by immunohistochemistry, western blot or fluorescence quantitative RT-PCR. We found that the size and weight of tumors in TRAF4-shRNA group was significantly smaller than the negative and blank group, and the number of the lung and liver metastases lesions was also fewer (P < 0.05). And TRAF4 and its correlation factors (P-AKT, P-NF-κB, TGF-ß1, TNF-α, MMP2 and MMP9) in the TRAF4-shRNA group were significantly decreased compared with the negative and blank group. However, the expression of RSK4 mRNA and protein in TRAF4-shRNA group were significantly increased. Collectively, TRAF4 knockdown significantly inhibited proliferation, invasion and metastasis in the xenograft nude mouse model, possibly involving in the interaction with RSK4 through down-regulation of AKT signaling pathway and then inactivating NF-κB pathway.

Deubiquitylase OTUD3 Mediates Endoplasmic Reticulum Stress through Regulating Fortilin Stability to Restrain Dopaminergic Neurons Apoptosis.

OTU domain-containing protein 3 (OTUD3) knockout mice exhibited loss of nigral dopaminergic neurons and Parkinsonian symptoms. However, the underlying mechanisms are largely unknown. In this study, we observed that the inositol-requiring enzyme 1α (IRE1α)-induced endoplasmic reticulum (ER) stress was involved in this process. We found that the ER thickness and the expression of protein disulphide isomerase (PDI) were increased, and the apoptosis level was elevated in the dopaminergic neurons of OTUD3 knockout mice. These phenomena were ameliorated by ER stress inhibitor tauroursodeoxycholic acid (TUDCA) treatment. The ratio of p-IRE1α/IRE1α, and the expression of X-box binding protein 1-spliced (XBP1s) were remarkably increased after OTUD3 knockdown, which was inhibited by IRE1α inhibitor STF-083010 treatment. Moreover, OTUD3 regulated the ubiquitination level of Fortilin through binding with the OTU domain. OTUD3 knockdown resulted in a decrease in the interaction ability of IRE1α with Fortilin and finally enhanced the activity of IRE1α. Taken together, we revealed that OTUD3 knockout-induced injury of dopaminergic neurons might be caused by activating IRE1α signaling in ER stress. These findings demonstrated that OTUD3 played a critical role in dopaminergic neuron neurodegeneration, which provided new evidence for the multiple and tissue-dependent functions of OTUD3.

Correlation of Ferroptosis and Other Types of Cell Death in Neurodegenerative Diseases.

Ferroptosis is defined as an iron-dependent, non-apoptotic cell death pathway, with specific morphological phenotypes and biochemical changes. There is a growing realization that ferroptosis has significant implications for several neurodegenerative diseases. Even though ferroptosis is different from other forms of programmed death such as apoptosis and autophagic death, they involve a number of common protein molecules. This review focuses on current research on ferroptosis and summarizes the cross-talk among ferroptosis, apoptosis, and autophagy that are implicated in neurodegenerative diseases. We hope that this information provides new ideas for understanding the mechanisms and searching for potential therapeutic approaches and prevention of neurodegenerative diseases.