p28GANK inhibits endoplasmic reticulum stress-induced cell death via enhancement of the endoplasmic reticulum adaptive capacity. Cell Res. 2009;19:1243-1257. [PMID: 19736567 DOI: 10.1038/cr.2009.104]

iASPP suppression mediates terminal UPR and improves BRAF-inhibitor sensitivity of colon cancers

Unfolded protein response (UPR) signaling is activated under endoplasmic reticulum (ER) stress, an emerging cancer hallmark, leading to either adaptive survival or cell death, while the mechanisms underlying adaptation-death switch remain poorly understood. Here, we examined whether oncogene iASPP regulates the switch and how the mechanisms can be used in colon cancer treatment. iASPP is downregulated when cells undergo transition from adaptation to death during therapy-induced ER stress. Blocking iASPP's downregulation attenuates stress-induced cell death. Mechanistically, Hu-antigen R (HuR)-mediated stabilization of iASPP mRNA and subsequent iASPP protein production is significantly impaired with prolonged ER stress, which facilitates the degradation of GRP78, a key regulator of the UPR, in the cytosol. Because iASPP competes with GRP78 in binding the ER-resident E3 ligase RNF185, and tips the balance in favor of cell death. Positive correlation between the levels of HuR, iASPP, and GRP78 are detectable in colon cancer tissues in vivo. Genetic inhibition of iASPP/GRP78 or chemical inhibition of HuR not only inhibits tumor growth, but also sensitizes colon cancer cells' responses to BRAF inhibitor-induced ER stress and cell death. This study provides mechanistic insights into the switch between adaptation and death during ER stress, and also identifies a potential strategy to improve BRAF-inhibitor efficiency in colon cancers.

Interaction between PSMD10 and GRP78 accelerates endoplasmic reticulum stress-mediated hepatic apoptosis induced by homocysteine

Background

The liver plays an important role in production and metabolism of homocysteine (Hcy), which has been reported to be involved in liver injury. In our previous work, we confirm that Hcy can induce liver injury by activating endoplasmic reticulum (ER) stress. However, the underlying mechanisms remain largely unknown.

Results

In present study, we established the Hcy-induced liver injury model by feeding cbs^+/− mice with high methionine diet, and found that a considerable mass of disordered arrangement of hepatocytes and enlarged space between hepatocytes were frequently occurred in the liver of cbs^+/− mice, accompanied with elevated expression levels of apoptosis-related proteins. In addition, Hcy could activate ER stress both in cbs^+/− mice and hepatocytes. Mechanistically, Hcy promoted the expression levels of proteasome 26S subunit non-ATPase 10 (PSMD10) in hepatocytes; and the expression of ER stress indicators and apoptosis-associated proteins were significantly suppressed when PSMD10 was silenced in hepatocytes under Hcy treatment. Moreover, bioinformatics analysis and luciferase reporter assay demonstrated that PSMD10 was a target gene of miR-212-5p. Consistently, miR-212-5p overexpression could inhibit ER stress-mediated apoptosis of hepatocytes under Hcy treatment. With the help of co-immunoprecipitation assay, we identified that the interaction between PSMD10 and GRP78 accelerated ER stress-mediated hepatic apoptosis induced by Hcy.

Conclusions

Our findings indicate that miR-212-5p directly targets PSMD10 and subsequently activates ER stress to promote Hcy-induced apoptosis of hepatocytes. We propose that endogenous PSMD10 physically interacts with GRP78 to regulate ER stress. Our study may provide the therapeutic target for the liver injury induced by Hcy.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13099-021-00455-z.

p28GANK overexpression is associated with chemotherapy resistance and poor prognosis in ovarian cancer

The non-ATPase regulatory subunit 10 of the human 26S proteasome (p28GANK) has been implicated in the tumorigenesis and progression of several types of malignant tumor. The aim of the present study was to detect the expression of p28GANK in ovarian cancer (OC) and investigate its association with the clinicopathological features and prognosis of OC. The expression levels of p28GANK were determined in 114 OC tissue samples and 30 normal ovarian tissue samples using immunohistochemistry. An association was observed between p28GANK overexpression and certain clinicopathological factors, including advanced International Federation of Gynecology and Obstetrics stage (P=0.042), residual tumor size (P=0.005) and response to chemotherapy (P<0.001). Furthermore, patients with high expression of p28GANK demonstrated worse overall survival (OS) and disease-free survival (DFS) rates compared with patients with low expression of p28GANK (both P<0.001). Multivariate Cox regression analysis revealed that overexpression of p28GANK was an independent prognostic factor of OS and DFS in patients with OC (P=0.013 and P=0.001, respectively). In summary, the current results indicate that p28GANK may be a predictive marker and a therapeutic target for OC.

Genome-Wide Bimolecular Fluorescence Complementation-Based Proteomic Analysis of Toxoplasma gondii ROP18's Human Interactome Shows Its Key Role in Regulation of Cell Immunity and Apoptosis

Toxoplasma gondii rhoptry protein ROP18 (TgROP18) is a key virulence factor secreted into the host cell during invasion, where it modulates the host cell response by interacting with its host targets. However, only a few TgROP18 targets have been identified. In this study, we applied a high-throughput protein-protein interaction (PPI) screening in human cells using bimolecular fluorescence complementation (BiFC) to identify the targets of Type I strain ROP18 (ROP18_I) and Type II strain ROP18 (ROP18_II). From a pool of more than 18,000 human proteins, 492 and 141 proteins were identified as the targets of ROP18_I and ROP18_II, respectively. Gene ontology, search tool for the retrieval of interacting genes/proteins PPI network, and Ingenuity pathway analyses revealed that the majority of these proteins were associated with immune response and apoptosis. This indicates a key role of TgROP18 in manipulating host's immunity and cell apoptosis, which might contribute to the immune escape and successful parasitism of the parasite. Among the proteins identified, the immunity-related proteins N-myc and STAT interactor, IL20RB, IL21, ubiquitin C, and vimentin and the apoptosis-related protein P2RX1 were further verified as ROP18_I targets by sensitized emission-fluorescence resonance energy transfer (SE-FRET) and co-immunoprecipitation. Our study substantially contributes to the current limited knowledge on human targets of TgROP18 and provides a novel tool to investigate the function of parasite effectors in human cells.

Gankyrin is a predictive and oncogenic factor in well-differentiated and dedifferentiated liposarcoma

Liposarcoma is one of the most common histologic types of soft tissue sarcoma and is frequently an aggressive cancer with poor outcome. Hence, alternative approaches other than surgical excision are necessary to improve treatment of well-differentiated/dedifferentiated liposarcoma (WDLPS/DDLPS).

For this reason, we performed a two-dimensional gel electrophoresis (2-DE) and matrix-assisted laser desorption/ionization-time of flight mass spectrometry/mass spectrometry (MALDI-TOF/MS) analysis to identify new factors for WDLPS and DDLPS. Among the selected candidate proteins, gankyrin, known to be an oncoprotein, showed a significantly high level of expression pattern and inversely low expression of p53/p21 in WDLPS and DDLPS tissues, suggesting possible utility as a new predictive factor. Moreover, inhibition of gankyrin not only led to reduction of in vitro cell growth ability including cell proliferation, colony-formation, and migration, but also in vivo DDLPS cell tumorigenesis, perhaps via downregulation of the p53 tumor suppressor gene and its p21 target and also reduction of AKT/mTOR signal activation. This study identifies gankyrin, for the first time, as new potential predictive and oncogenic factor of WDLPS and DDLPS, suggesting the potential for service as a future LPS therapeutic approach.

Effect of N-linked glycosylation modification of pro-Met on function of c-Met

AIM: To investigate the effect of N-linked glycosylation modification of pro-Met on the function of c-Met in human hepatocellular carcinoma (HCC) cell line MHCC-97H and human cholangiocarcinoma cell line RBE.

METHODS: Tunicamycin (Tun), an inhibitor of N-glycosylation, MG132, a proteasome inhibitor, cycloheximide (CHX), a protein synthesis inhibitor, and PF-2341066, a c-Met inhibitor, were used in this study. The effect of N-linked glycosylation modification of pro-Met on c-Met function in MHCC-97H and RBE cells were determined by Western blot, immunofluorescence and confocal microscopy.

RESULTS: We found that both phosphatidylinositol 3 kinase/Akt (PI3K/Akt) and mitogen-activated protein kinase /extracellular signal-regulated kinase (MEK/ERK) were downstream to c-Met. Furthermore, c-Met was an N-linked glycosylated protein. N-glycosylation modification of p145Met was from pro-Met, but not due to the further modification of pro-Met. Importantly, blocking the N-glycosylation of pro-Met targeted pro-Met to the cytoplasm and initiated its phosphorylation independent of hepatocyte growth factor (HGF) engagement. Nonglycosylated pro-Met, which was phosphorylated, only in part activated c-Met downstream signals.

CONCLUSION: N-glycosylation is required for c-Met function.

JNK contributes to the tumorigenic potential of human cholangiocarcinoma cells through the mTOR pathway regulated GRP78 induction

Less is known about the roles of c-Jun N-terminal kinase (JNK) in cholangiocarcinoma (CCA). Here, we report that JNK exerts its oncogenic action in human CCA cells, partially due to the mammalian target of rapamycin (mTOR) pathway regulated glucose-regulated protein 78 (GRP78) induction. In human CCA cells, the phosphorylation of eukaryotic initiation factor alpha (eIF2α) results in the accumulation of activating transcription factor 4 (ATF4) and GRP78 independent of unfolded protein response (UPR). Suppression of GRP78 expression decreases the proliferation and invasion of human CCA cells. It's notable that mTOR is required for eIF2α phosphorylation-induced ATF4 and GRP78 expression. Importantly, JNK promotes eIF2α/ATF4-mediated GRP78 induction through regulating the activity of mTOR. Thus, our study implicates JNK/mTOR signaling plays an important role in cholangiocarcinogenesis, partially through promoting the eIF2α/ATF4/GRP78 pathway.

Regulation of the unfolded protein response by microRNAs

The unfolded protein response (UPR) is an adaptive response to the stress that is caused by an accumulation of misfolded proteins in the lumen of the endoplasmic reticulum (ER). It is an important component of cellular homeostasis. During ER stress, the UPR increases the protein-folding capacity of the endoplasmic reticulum to relieve the stress. Failure to recover leads to apoptosis. Specific cellular mechanisms are required for the cellular recovery phase after UPR activation. Using bioinformatics tools, we identified a number of microRNAs that are predicted to decrease the mRNA expression levels for a number of critical components of the UPR. In this review, we discuss the potential role of microRNAs as key regulators of this pathway and describe how microRNAs may play an essential role in turning off the UPR after the stress has subsided.

Micro(RNA)managing endoplasmic reticulum stress

Cellular disturbances that cause accumulation of misfolded proteins in the endoplasmic reticulum (ER) lead to a condition referred to as "ER stress" and trigger the unfolded protein response (UPR), a signaling pathway that attempts to restore ER homeostasis. The complexity of UPR signaling can generate adaptive and apoptotic outputs, depending on the nature and duration of the ER stress. MicroRNAs (miRNAs), small non-coding RNAs that typically repress gene expression, have recently emerged as key gene regulators of the proadaptive/proapoptotic molecular switch emanating from the ER. Importantly, select miRNAs have been shown to directly regulate key UPR components.

High expression of proline-rich tyrosine kinase 2 is associated with poor survival of hepatocellular carcinoma via regulating phosphatidylinositol 3-kinase/AKT pathway

BACKGROUND

The peritumoral environment has been implicated to be important in the process of metastasis and recurrence in hepatocellular carcinoma (HCC). Our aims were to assess the prognostic value of proline-rich tyrosine kinase 2 (Pyk2) in HCC and investigate related molecular mechanism.

METHODS

Expression of Pyk2 was tested by immunohistochemistry in tissue microarrays containing 141 paired HCC samples. Correlation between Pyk2 and vascular endothelial growth factor (VEGF) expression in clinical samples was analyzed by Spearman rank correlation. Matrigel invasion, anchorage-independent growth assay and immunoblotting were performed to study the effect of Pyk2 on the invasion and progression of HCC cells and phosphoinositide 3-kinase (PI3K)/AKT pathway activation.

RESULTS

Higher Pyk2 density in both tumor and peritumor was associated with lower overall survival (P = 0.044; P = 0.041, respectively), serum AFP levels > 1,000 ng/ml (P = 0.013; P = 0.032, respectively) and postoperative distant metastasis (both P < 0.001). However, only higher peritumoral Pyk2 density was related to lower disease-free survival (P = 0.014) and vascular invasion (P = 0.035). A significant correlation between Pyk2 and VEGF density in tumor or peritumoral liver tissue was observed (r = 0. 3133, P = 0.0002; r = 0.5176, P < 0.0001, respectively). Immunoblotting showed that Pyk2 activated PI3K-AKT pathway to upregulate VEGF expression in HL-7702, SMMC-7721 and HepG2 cells.

CONCLUSIONS

High Pyk2, especially peritumoral Pyk2 was associated with poor survival, disease recurrence, and metastasis in HCC. PI3K-AKT pathway was involved in Pyk2-mediated VEGF expression during HCC progression and invasion.

Disturbance of Ca2+ homeostasis converts pro-Met into non-canonical tyrosine kinase p190MetNC in response to endoplasmic reticulum stress in MHCC97 cells

c-Met, the tyrosine-kinase receptor for hepatocyte growth factor, plays a critical role in the tumorigenesis of hepatocellular carcinoma (HCC). However, the underlying mechanism remains incompletely understood. The mature c-Met protein p190Met(αβ) (consists of a α subunit and a β subunit) is processed from pro-Met. Here we show that pro-Met is processed into p190Met(NC) by sarco/endoplasmic reticulum calcium-ATPase (SERCA) inhibitor thapsigargin. p190Met(NC) compensates for the degradation of p190Met(αβ) and protects human HCC cells from apoptosis mediated by endoplasmic reticulum (ER) stress. In comparison with p190Met(αβ), p190Met(NC) is not cleaved and is expressed as a single-chain polypeptide. Thapsigargin-initiated p190Met(NC) expression depends on the disturbance of ER calcium homeostasis. Once induced, p190Met(NC) is activated independent of hepatocyte growth factor engagement. p190Met(NC) contributes to sustained high basal activation of c-Met downstream pathways during ER calcium disturbance-mediated ER stress. Both p38 MAPK-promoted glucose-regulated protein 78 (GRP78) expression and sustained high basal activation of PI3K/Akt and MEK/ERK are involved in the cytoprotective function of p190Met(NC). Importantly, the expression of p190Met(NC) is detected in some HCC cases. Taken together, these data provide a potential mechanism to explain how c-Met promotes HCC cells survival in response to ER stress. We propose that context-specific processing of c-Met protein is implicated in HCC progression in stressful microenvironments.

Modulation of the unfolded protein response is the core of microRNA-122-involved sensitivity to chemotherapy in hepatocellular carcinoma

The loss of microRNA-122 (miR-122) expression correlates to many characteristic properties of hepatocellular carcinoma (HCC) cells, including clonogenic survival, anchorage-independent growth, migration, invasion, epithelial-mesenchymal transition, and tumorigenesis. However, all of these findings do not sufficiently explain the oncogenic potential of miR-122. In the current study, we used two-dimensional differential in-gel electrophoresis to measure changes in the expression of thousands of proteins in response to the inhibition of miR-122 in human hepatoma cells. Several proteins that were upregulated on miR-122 inhibition were involved in the unfolded protein response (UPR) pathway. The overexpression of miR-122 resulted in the repression of UPR pathway activation. Therefore, miR-122 may act as an inhibitor of the chaperone gene expression and negatively regulate the UPR pathway in HCC. We further showed that the miR-122 inhibitor enhanced the stability of the 26S proteasome non-ATPase regulatory subunit 10 (PSMD10) through the up-regulation of its target gene cyclin-dependent kinase 4 (CDK4). This process may activate the UPR pathway to prevent chemotherapy-mediated tumor cell apoptosis. The current study suggests that miR-122 negatively regulates the UPR through the CDK4-PSMD10 pathway. The down-regulation of miR-122 activated the CDK4-PSMD10-UPR pathway to decrease tumor cell anticancer drug-mediated apoptosis. We identified a new HCC therapeutic target and proclaimed the potential risk of the therapeutic use of miR-122 silencing.

Proteomic profiling of human hepatocellular carcinoma SMMC-7721 cells under endoplasmic reticulum stress induced with dithiothreitol

AIM: To explore new therapy targets for human hepatocellular carcinoma by proteomic profiling of human hepatocellular carcinoma SMMC-7721 cells under endoplasmic reticulum stress.

METHODS: Cultured SMMC-7721 cells were divided into two groups: experimental group and control group. The experimental group was treated with dithiothreitol (DTT, 2.5 mmol/L), while the control group was treated with equal volume of culture medium. After treatment, total cell proteins were prepared and resolved by two-dimensional electrophoresis (2-DE). The two-dimensional electrophoresis maps for the two groups of cells were analyzed using ImageMaster 2D Platinum software. Proteins that showed obvious expression alteration in the experimental group were identified by matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF-MS).

RESULTS: There were 844 ± 46 protein spots in the 2-DE map for the experimental group and 1 015 ± 63 protein spots for the control group. There were 593 ± 23 pairs of matched protein spots between the two groups, and the matching rate was about 71%. Most of the proteins have an isoelectric point at pH5.2-6.5 and a molecular weight of 15 000-80 000 Da. Three protein spots showed 2-fold or greater differential expression between the two groups and were identified by MALDI-TOF-MS. They were protein fem-1 homolog B, cyclin A1, and proliferation-inducing protein 44.

CONCLUSION: Three differentially expressed proteins in SMMC-7721 cells under endoplasmic reticulum stress were identified and may be useful molecular targets for the diagnosis and treatment of hepatocellular carcinoma.

miR-221/222 suppression protects against endoplasmic reticulum stress-induced apoptosis via p27(Kip1)- and MEK/ERK-mediated cell cycle regulation

Cancer cells are relatively resistant to endoplasmic reticulum (ER) stress-induced apoptosis. However, the underlying mechanisms remain largely unclear. We observed that the microRNAs miR-221/222 are associated with apoptosis regulation under ER stress in human hepatocellular carcinoma (HCC) cells. Induction of ER stress does not trigger significant apoptosis but obviously causes downregulation of miR-221/222 in HCC cells. In these cells, ER stress-induced apoptosis is enhanced by miR-221/222 mimics and attenuated by miR-221/222 inhibitors. miR-221/222 promoted-apoptosis under ER stress is associated with p27(Kip1)- and MEK/ERK-mediated cell cycle regulation. Our results suggest that suppression of miR-221/222 plays a crucial role in the protection against apoptosis induced by ER stress in HCC cells.

p28GANK overexpression accelerates hepatocellular carcinoma invasiveness and metastasis via phosphoinositol 3-kinase/AKT/hypoxia-inducible factor-1α pathways

The overall survival of patients with hepatocellular carcinoma (HCC) remains poor, and the molecular mechanisms underlying HCC progression and aggressiveness are unclear. Here, we report that increased expression of p28(GANK) (Gankyrin, PSMD10, or p28) in human HCC predicts poor survival and disease recurrence after surgery. Patients with HCC who have large tumors, with vascular invasion and intrahepatic or distant metastasis, expressed high levels of p28(GANK) . Invasive tumors overexpressing p28(GANK) were featured by active epithelial-mesenchymal transition (EMT), and exhibited increased angiogenesis associated with vascular endothelial growth factor overexpression, whereas silencing p28(GANK) expression attenuated EMT and motility/invasion of tumor cells. The p28(GANK) activates phosphoinositide 3-kinase (PI3K)-V-akt Murine Thymoma Viral Oncogene Homolog (AKT)-hypoxia-inducible factor 1α (HIF-1α) signaling to promote TWIST1, vascular endothelial growth factor, and metalloproteinase 2 expression. Suppression of the PI3K-AKT-HIF-1α pathway interfered with p28(GANK) -mediated EMT and invasion. Consistently, we detected a significant correlation between p28(GANK) expression and p-AKT levels in a cohort of HCC biopsies, and the combination of these two parameters is a more powerful predictor of poor prognosis.

CONCLUSION

These results present novel mechanistic insight into a critical role of p28(GANK) in HCC progression and metastasis.

The critical role of GRP78 in physiologic and pathologic stress

GRP78 is a major endoplasmic reticulum chaperone as well as a master regulator of the unfolded protein response. In addition to playing an essential role in early embryonic development, recent studies have emerged specifically implicating GRP78 and chaperone integrity in the aging process and age-related diseases. Another exciting discovery is the regulation of GRP78 by insulin/IGF-1 signaling pathways impacting cell proliferation and survival. Mouse models of cancer, in combination with cell culture studies, validate the critical role of GRP78 in tumorigenesis and tumor angiogenesis. Further, these studies demonstrate the ability of GRP78 to suppress oncogenic PI3K/AKT signaling. The discovery of cell surface GRP78, in cancer cells and cells undergoing ER stress, presents a novel therapeutic strategy.

Glucose-regulated protein 78 (GRP78) silencing enhances cell migration but does not influence cell proliferation in hepatocellular carcinoma

BACKGROUND

GRP78 plays an essential role in embryonic development and in the therapeutic treatment and progression of cancer. However, little is known about the role of GRP78 in hepatocellular carcinoma (HCC).

METHODS

In this study, we characterized five different HCC cell lines to examine GRP78 expression patterns and found that only HepJ5 cells ectopically overexpress GRP78. We knocked down GRP78 expression in HepJ5 cells using a small interfering RNA (siRNA), and the proliferation assay and migration assay were performed.

RESULTS

Using siRNA technique, we could successfully reduce GRP78 expression levels in HepJ5 cells. In a cell growth study, we found that GRP78-siRNA caused no significant changes in cellular proliferation in 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), colony formation, and cell cycle distribution. In a cell migration study, we found that GRP78-siRNA HepJ5 cells had dramatically increased migration ability in Transwell assay.

CONCLUSIONS

We conclude that ectopically expressed GRP78 does not contribute to the increased proliferation of HepJ5 cells, but does correlate with the migration of HCC cells under normoxic conditions.