Pib2 is a cysteine sensor involved in TORC1 activation in Saccharomyces cerevisiae.

Target of rapamycin complex 1 (TORC1) is a master regulator that monitors the availability of various amino acids to promote cell growth in Saccharomyces cerevisiae. It is activated via two distinct upstream pathways: the Gtr pathway, which corresponds to mammalian Rag, and the Pib2 pathway. This study shows that Ser3 was phosphorylated exclusively in a Pib2-dependent manner. Using Ser3 as an indicator of TORC1 activity, together with the established TORC1 substrate Sch9, we investigated which pathways were employed by individual amino acids. Different amino acids exhibited different dependencies on the Gtr and Pib2 pathways. Cysteine was most dependent on the Pib2 pathway and increased the interaction between TORC1 and Pib2 in vivo and in vitro. Moreover, cysteine directly bound to Pib2 via W632 and F635, two critical residues in the T(ail) motif that are necessary to activate TORC1. These results indicate that Pib2 functions as a sensor for cysteine in TORC1 regulation.

HSP90-regulated CHIP/TRIM21/p21 Axis Involves in the Senescence of Osteosarcoma Cells.

BACKGROUND: OS is the most frequent malignant bone tumor with a poor prognosis. TRIM21 has been reported to play a critical role in OS by regulating the expression of the TXNIP/p21 axis and inhibiting the senescence of OS cells. AIM: Investigation of the molecular mechanism of tripartite motif 21 (TRIM21) in osteosarcoma (OS) would shed light on the understanding of the pathogenesis of OS. OBJECTIVE: This study aimed to explore the mechanism regulating the protein stability of TRIM21 in the process of OS senescence. METHODS: Human U2 OS cells were used to establish stable cells overexpressing TRIM21 (induced by Dox) or knocking down TRIM21. The co-immunoprecipitation (co-IP) assay was used to examine the interaction between TRIM21 and HSP90. Immunofluorescence (IF) assay was used to observe colocalization in OS cells. Western blot analysis was applied to detect the protein expression, and quantitative real-time PCR (qRT-PCR) assay was used to test the mRNA expression of corresponding genes. SA-ß-gal staining was used to evaluate OS senescence. RESULTS: In this study, we verified the interaction between HSP90 and TRIM21 using a co-IP assay. Knockdown or inhibition of HSP90 with its inhibitor 17-AAG accelerated the degradation of TRIM21 by the proteasome in OS cells. CHIP E3 ligase mediated this degradation of TRIM21, with the knockdown of CHIP rescuing the downregulation of TRIM21 induced by 17-AAG. TRIM21 inhibited OS senescence and downregulated the expression of senescence marker p21, while CHIP exhibited an opposite regulatory role on p21 expression. CONCLUSION: Taken together, our results demonstrated that HSP90 is responsible for the stabilization of TRIM21 in OS and that the CHIP/TRIM21/p21 axis controlled by HSP90 affects the senescence of OS cells.

Structural insights into a shared mechanism of human STING activation by a potent agonist and an autoimmune disease-associated mutation.

Stimulator of interferon gene (STING) is increasingly exploited for the potential in cancer immunotherapy, yet its mechanism of activation remains not fully understood. Herein, we designed a novel STING agonist, designated as HB3089 that exhibits robust and durable anti-tumor activity in tumor models across various cancer types. Cryo-EM analysis reveals that HB3089-bound human STING has structural changes similar to that of the STING mutant V147L, a constitutively activated mutant identified in patients with STING-associated vasculopathy with onset in infancy (SAVI). Both structures highlight the conformational changes of the transmembrane domain (TMD), but without the 180°-rotation of the ligand binding domain (LBD) previously shown to be required for STING activation. Further structure-based functional analysis confirmed a new STING activation mode shared by the agonist and the SAVI-related mutation, in which the connector linking the LBD and the TMD senses the activation signal and controls the conformational changes of the LBD and the TMD for STING activation. Together, our findings lead to a new working model for STING activation and open a new avenue for the rationale design of STING-targeted therapies either for cancer or autoimmune disorders.

MicroRNA-138 inhibits hypoxia-induced proliferation of endothelial progenitor cells via inhibition of HIF-1α-mediated MAPK and AKT signaling.

[This retracts the article DOI: 10.3892/etm.2017.4091.].

TRIM21-regulated Annexin A2 plasma membrane trafficking facilitates osteosarcoma cell differentiation through the TFEB-mediated autophagy.

Osteosarcoma (OS) is the most common primary malignant bone tumor in children and adolescents, which is characterized by dysfunctional autophagy and poor differentiation. Our recent studies have suggested that the tripartite motif containing-21 (TRIM21) plays a crucial role in regulating OS cell senescence and proliferation via interactions with several proteins. Yet, its implication in autophagy and differentiation in OS is largely unknown. In the present study, we first showed that TRIM21 could promote OS cell autophagy, as determined by the accumulation of LC3-II, and the degradation of cargo receptor p62. Further, we were able to identify that Annexin A2 (ANXA2), as a novel interacting partner of TRIM21, was critical for TIRM21-induced OS cell autophagy. Although TRIM21 had a negligible effect on the mRNA and protein expressions of ANXA2, we did find that TRIM21 facilitated the translocation of ANXA2 toward plasma membrane (PM) in OS cells through a manner relying on TRIM21-mediated cell autophagy. This functional link has been confirmed by observing a nice co-expression of TRIM21 and ANXA2 (at the PM) in the OS tissues. Mechanistically, we demonstrated that TRIM21, via facilitating the ANXA2 trafficking at the PM, enabled to release the transcription factor EB (TFEB, a master regulator of autophagy) from the ANXA2-TFEB complex, which in turn entered into the nucleus for the regulation of OS cell autophagy. In accord with previous findings that autophagy plays a critical role in the control of differentiation, we also demonstrated that autophagy inhibited OS cell differentiation, and that the TRIM21/ANXA2/TFEB axis is implicated in OS cell differentiation through the coordination with autophagy. Taken together, our results suggest that the TRIM21/ANXA2/TFEB axis is involved in OS cell autophagy and subsequent differentiation, indicating that targeting this signaling axis might lead to a new clue for OS treatment.

The overexpression of uPA promotes the proliferation and fibrinolytic activity of human umbilical vein endothelial cells.

The purpose of this article is to study whether the overexpression of urokinase-type plasminogen activator (uPA) can promote the proliferation and fibrinolytic activity of human umbilical vein endothelial cells (HUVECs). The recombinant adenovirus vectors containing the human uPA gene were constructed and transfected into HUVECs. In this study, the mRNA of uPA was detected by qPCR, and the uPA protein was measured by Western blot. The cell proliferation was measured using MTT. The fibrinolytic activity of uPA was quantified using a colorimetric assay. We also measured MMP2 (metalloproteinase-2), MMP9 (metalloproteinase-9), and VEGF (vascular endothelial growth factor) proteins using ELISA. The results showed that the levels of the uPA mRNA and the protein in the overexpression group were significantly higher compared to the other groups, (P < 0.05). The cell proliferation and uPA activity were increased significantly in the overexpression group, compared to the other groups, (P < 0.05). The secretions of MMP2, MMP9, and VEGF in the overexpression group were significantly higher than they were in the other two groups (P < 0.05). In conclusion, we successfully transfected a recombined adenovirus vector carrying uPA into a HUVEC. The exogenous uPA gene could transcribe and secrete the uPA protein in the HUVECs. The overexpression of uPA can increase cell proliferation and uPA activity. It can improve the invasion and angiogenesis ability in HUVECs by promoting their secretions of MMP2, MMP9, and VEGF.

MicroRNA-138 inhibits hypoxia-induced proliferation of endothelial progenitor cells via inhibition of HIF-1α-mediated MAPK and AKT signaling.

Endothelial progenitor cells (EPCs) participate in angiogenesis by differentiating into endothelial cells (ECs) and may be developed to treat ischemia/reperfusion injury. MicroRNAs (miRs) are a type of non-coding RNA that are 18-25 nucleotides in length and serve a role in angiogenesis. It has been demonstrated that miR-138 regulates hypoxia-induced EC dysfunction. However, to the best of our knowledge, the exact role of miR-138 in the regulation of hypoxia-induced EPCs has not previously been reported. In the present study, data collected from an MTT assay indicated that hypoxia treatment enhanced EPC proliferation, which was accompanied by an upregulation of hypoxia-inducible factor 1α (HIF-1α) expression. miR-138 overexpression inhibited hypoxia-induced EPC proliferation and induced cell cycle arrest at the G1 stage. A mechanistic investigation revealed that miR-138 negatively regulated HIF-1α protein levels but did not affect HIF-1α mRNA levels in EPCs. Moreover, results from a dual luciferase reporter assay demonstrated that HIF-1α was a direct target of miR-138 in EPCs. Furthermore, upregulation of miR-138 suppressed the hypoxia-induced upregulation of HIF-1α. Downstream factors of HIF-1α were also investigated and it was observed that the upregulation of miR-138 inhibited the hypoxia-induced upregulation of vascular endothelial growth factor, as well as the activity of mitogen-activated protein kinase and AKT signaling in EPCs. In summary, the present study suggested that miR-138 inhibits hypoxia-induced EPC proliferation, possibly by inhibiting HIF-1α-mediated signaling.

Pheretima aspergillum decoction suppresses inflammation and relieves asthma in a mouse model of bronchial asthma by NF-κB inhibition.

ETHNOPHARMACOLOGICAL RELEVANCE AND AIM OF THE STUDY: Guang-Pheretima, the live form of the earthworm Pheretima aspergillum, is a traditional Chinese medicine commonly used for the treatment of asthma, cough, stroke, epilepsy and other diseases due to its anti-inflammatory, anti-asthmatic, anti-seizure, thrombolytic and diuretic properties. Although Guang-Pheretima is effective in the relief of asthma, its pharmacological activity and the underlying molecular mechanisms are not fully understood. Hence, we investigated the effects of a Pheretima aspergillum decoction (PAD) against inflammation in a model of ovalbumin (OVA)-induced asthma in BALB/c mice, as well as the nuclear factor-κB (NF-κB) pathway involved in this process. MATERIALS AND METHODS: OVA was used to sensitize and challenge the airway of the mice, and PAD was administrated by gavage. We measured airway hyperresponsiveness (AHR) in the mice 24h following a final methacholine challenge with whole-body plethysmography. The bronchoalveolar lavage fluid (BALF), serum and pulmonary tissues were collected 48h after the last challenge. The levels of inflammatory factors and the related mRNAs were determined by enzyme-linked immunosorbent assay (ELISA) and real-time polymerase chain reaction (RT-PCR), respectively. The number of differential inflammatory cells in the BALF was counted. Serum total and OVA-specific IgE levels were measured with ELISA. The activation of NF-κB signaling in the lung was detected by western blotting. In addition, the lung tissues were stained with hematoxylin and eosin or periodic acid Schiff stain for histopathological examination. RESULTS: PAD treatment significantly alleviated AHR in the asthmatic mice, decreased the mRNA and protein levels of IL-4, IL-5 and IL-13 and downregulated IgE. In addition, PAD treatment attenuated mucus secretion and infiltration of inflammatory cells in the lung while inhibiting the activation of NF-κB signaling. CONCLUSIONS: PAD effectively inhibited the activation of NF-κB signaling in the lungs of mice with OVA-induced asthma, and mitigated AHR and Th2 type inflammatory reactions. Therefore, PAD may serve as a drug candidate for asthma treatment.

PKCα-GSK3ß-NF-κB signaling pathway and the possible involvement of TRIM21 in TRAIL-induced apoptosis.

Tumor necrosis factor related apoptosis-inducing ligand (TRAIL) is a highly promising therapeutic agent for cancer treatment, owing to its ability to selectively target tumor cells for cell death while having little effect on most normal cells. However, recent research has found that many cancers, including non-small cell lung cancer (NSCLC), display resistance to TRAIL. Therefore, it is important to elucidate the molecular mechanisms governing the resistance of tumor cells to TRAIL treatment. In this study, we show that GSK3ß antagonized TRAIL-induced apoptosis in H1299 NSCLC cells, and determined that the PKCα isozyme is an upstream regulator of GSK3ß that phosphorylates and inactivates GSK3ß, thereby sensitizing cancer cells to TRAIL-induced apoptosis. Furthermore, we demonstrated that the anti-apoptotic effect of GSK3ß is mediated by the NF-κB pathway, whereas the tripartite motif 21 (TRIM21) was able to inhibit the activation of NF-κB by GSK3ß, and leads to the promotion of cell apoptosis. Taken together, our study further delineated the underpinning mechanism of resistance to TRAIL-induced apoptosis in H1299 cells, and provided new clues for sensitizing NSCLC cells to TRAIL therapy.

Successful treatment of aberrant splenic artery aneurysm with a combination of coils embolization and covered stents.

BACKGROUND: Aneurysms of an aberrant splenic artery originating from the superior mesenteric artery (SMA) are extremely rare; however, they are clinically important because possible rupture could be catastrophic. The methods of treatment for this condition include surgical resection, minimally invasive techniques (include laparoscopic technique) and endovascular therapy. The purpose of this study is to evaluate the efficacy of coils embolization combined with covered stents to treat aberrant splenic artery aneurysm (SAA). CASES PRESENTATION: We report four consecutive cases of aberrant SAA that the aberrant splenic artery was embolized with coils and the superior mesenteric artery was excluded with a covered stent and an up-to-date review of all previous cases in the field. A follow-up computed tomography performed 6 to 12 months postoperatively showed persistent exclusion with marked shrinkage of the aneurysm sac. CONCLUSIONS: The authors believe although early results are promising, further careful follow-up will be needed to determine the long-term clinical efficacy, safety and applicability of this approach.

Hybrid procedure to treat aortic arch aneurysm combined with aortic arch coarctation and left internal carotid artery aneurysm (Case Report).

Aortic arch aneurysm is a rare condition but carries a high risk of rupture. We report one case of aortic arch aneurysm combined with aortic arch coarctation and left internal carotid artery aneurysm, which is extremely rare. Left internal carotid artery aneurysm resection and revascularization, carotid and carotid graft bypass combined with endovascular stent graft and embolization with coils were successfully performed. There were no any complaints and complications at 8 months follow-up. The follow-up CTA demonstrated thrombus formation in the aneurysm lumen, no endoleak and the aortic arch and bypass graft were all patent. We feel that hybrid procedure may be a valuable therapeutic alternative when treating this type of lesion. However, long-term clinical efficacy and safety have yet to be confirmed.