Expression and prognostic role of SGTA in human breast carcinoma correlates with tumor cell proliferation

The Molecular Biodiversity of Protein Targeting and Protein Transport Related to the Endoplasmic Reticulum

Looking at the variety of the thousands of different polypeptides that have been focused on in the research on the endoplasmic reticulum from the last five decades taught us one humble lesson: no one size fits all. Cells use an impressive array of components to enable the safe transport of protein cargo from the cytosolic ribosomes to the endoplasmic reticulum. Safety during the transit is warranted by the interplay of cytosolic chaperones, membrane receptors, and protein translocases that together form functional networks and serve as protein targeting and translocation routes. While two targeting routes to the endoplasmic reticulum, SRP (signal recognition particle) and GET (guided entry of tail-anchored proteins), prefer targeting determinants at the N- and C-terminus of the cargo polypeptide, respectively, the recently discovered SND (SRP-independent) route seems to preferentially cater for cargos with non-generic targeting signals that are less hydrophobic or more distant from the termini. With an emphasis on targeting routes and protein translocases, we will discuss those functional networks that drive efficient protein topogenesis and shed light on their redundant and dynamic nature in health and disease.

miRNA-365b promotes hepatocellular carcinoma cell migration and invasion by downregulating SGTB

Aim: miR-365b, a miRNA at chromosomal breakpoint, was often amplified and upregulated in human hepatocellular carcinoma (HCC). However, the role of miR-365b dysregulation remains unclear. Materials & methods: miR-365b function assays and its target gene analyses were performed. Results: We revealed that miR-365b promoted HCC cell motility and spreading. Furthermore, SGTB was found to be a downstream target of miR-365b, and knockdown of the SGTB gene could mimic the effect of miR-365b in hastening HCC cell migration and invasion. Conclusion: These results imply that miR-365b plays a tumor-promoting role in HCC by suppressing SGTB expression, offering novel potential targets for the treatment of HCC.

[MicroRNA-138 regulates cell adhesion-mediated drug resistance phenotype by targeting SGTA in non-Hodgkin's lymphoma]

目的

分析microRNA-138（miR-138）靶向调节小谷氨酰胺三角四肽重复区蛋白α（SGTA）对非霍奇金淋巴瘤（NHL）细胞黏附介导的耐药（cell adhesion-mediated drug resistance, CAM-DR）的影响。

方法

以HS-5细胞或纤连蛋白（FN）构建NHL细胞黏附模型；Western blotting与RQ-PCR分析miR-138对SGTA蛋白及mRNA表达的影响；双荧光素酶报告基因活性检测分析miR-138对SGTA mRNA 3′UTR活性的影响；分别用miR-138下调慢病毒载体（Lv-shmiR-138）、miR-138过表达慢病毒载体（Lv-miR-138）、对照慢病毒载体（Lv-Ctrl）感染Daudi及OCI-Ly8细胞，分析miR-138对细胞周期、黏附能力及CAM-DR的影响；收集35例弥漫大B细胞淋巴瘤患者的石蜡组织标本，分析miR-138的表达情况及其与疾病进展和耐药关系。

结果

①NHL细胞与FN或HS-5细胞黏附培养后miR-138表达水平显著高于悬浮培养组（P值均<0.05）。②下调miR-138的表达可增强SGTA蛋白的表达水平（P值均<0.05），而对SGTA mRNA的表达水平无显著影响（P值均>0.05）。③转染野生型SGTA 3′UTR载体时，过表达miR-138可显著抑制荧光素酶报告基因活性（0.73±0.03对1.00±0.02，t=0.914，P=0.002）；而转染结合位点突变的突变型载体时，过表达miR-138不能显著改变报告基因活性（0.93±0.04对1.00±0.02，t=1.375，P=0.241）。④在悬浮及黏附培养状态下，过表达miR-138可显著诱导Daudi及OCI-Ly8细胞G₁期停滞（P值均<0.05）。⑤下调miR-138的表达对Daudi及OCI-Ly8细胞的黏附能力均无显著影响（P值均>0.05）。⑥在悬浮培养状态下调miR-138的表达时，多柔比星诱导细胞死亡的比例显著下降，而在黏附培养状态下调miR-138的表达，多柔比星诱导细胞死亡的比例显著上升（P值均<0.05）。⑦miR-138在进展及稳定患者中的表达水平显著高于完全缓解以及部分缓解患者，差异具有统计学意义（9.72±1.11对3.06±0.22，t=9.144，P<0.001）。

结论

在黏附微环境中miR-138可通过靶向抑制SGTA诱导细胞周期G₁期停滞促进CAM-DR进程。

The roles of cytosolic quality control proteins, SGTA and the BAG6 complex, in disease

SGTA is a co-chaperone that, in collaboration with the complex of BAG6/UBL4A/TRC35, facilitates the biogenesis and quality control of hydrophobic proteins, protecting them from the aqueous cytosolic environment. This work includes targeting tail-anchored proteins to their resident membranes, sorting of membrane and secretory proteins that mislocalize to the cytoplasm and endoplasmic reticulum-associated degradation of misfolded proteins. Since these functions are all vital for the cell's continued proteostasis, their disruption poses a threat to the cell, with a particular risk of protein aggregation, a phenomenon that underpins many diseases. Although the specific disease implications of machinery involved in quality control of hydrophobic substrates are poorly understood, here we summarize much of the available information on this topic.

Polyglutamine Repeats in Viruses

This review explores the presence and functions of polyglutamine (polyQ) in viral proteins. In mammals, mutations in polyQ segments (and CAG repeats at the nucleotide level) have been linked to neural disorders and ataxias. PolyQ regions in normal human proteins have documented functional roles, in transcription factors and, more recently, in regulating autophagy. Despite the high frequency of polyQ repeats in eukaryotic genomes, little attention has been given to the presence or possible role of polyQ sequences in virus genomes. A survey described here revealed that polyQ repeats occur rarely in RNA viruses, suggesting that they have detrimental effects on virus replication at the nucleotide or protein level. However, there have been sporadic reports of polyQ segments in potyviruses and in reptilian nidoviruses (among the largest RNA viruses known). Conserved polyQ segments are found in the regulatory control proteins of many DNA viruses. Variable length polyQ tracts are found in proteins that contribute to transmissibility (cowpox A-type inclusion protein (ATI)) and control of latency (herpes viruses). New longer-read sequencing methods, using original biological samples, should reveal more details on the presence and functional role of polyQ in viruses, as well as the nucleotide regions that encode them. Given the known toxic effects of polyQ repeats, the role of these segments in neurovirulent and tumorigenic viruses should be further explored.

Canine REIC/Dkk-3 interacts with SGTA and restores androgen receptor signalling in androgen-independent prostate cancer cell lines

Background

The pathological condition of canine prostate cancer resembles that of human androgen-independent prostate cancer. Both canine and human androgen receptor (AR) signalling are inhibited by overexpression of the dimerized co-chaperone small glutamine-rich tetratricopeptide repeat-containing protein α (SGTA), which is considered to cause the development of androgen-independency. Reduced expression in immortalised cells (REIC/Dkk-3) interferes with SGTA dimerization and rescues AR signalling. This study aimed to assess the effects of REIC/Dkk-3 and SGTA interactions on AR signalling in the canine androgen-independent prostate cancer cell line CHP-1.

Results

Mammalian two-hybrid and Halo-tagged pull-down assays showed that canine REIC/Dkk-3 interacted with SGTA and interfered with SGTA dimerization. Additionally, reporter assays revealed that canine REIC/Dkk-3 restored AR signalling in both human and canine androgen-independent prostate cancer cells. Therefore, we confirmed the interaction between canine SGTA and REIC/Dkk-3, as well as their role in AR signalling.

Conclusions

Our results suggest that this interaction might contribute to the development of a novel strategy for androgen-independent prostate cancer treatment. Moreover, we established the canine androgen-independent prostate cancer model as a suitable animal model for the study of this type of treatment-refractory human cancer.

Electronic supplementary material

The online version of this article (doi:10.1186/s12917-017-1094-4) contains supplementary material, which is available to authorized users.

Proteome analysis of sheep B lymphocytes in the course of bovine leukemia virus-induced leukemia

Presented are the results of a study of the expression pattern of different proteins in the course of bovine leukemia virus-induced leukemia in experimental sheep and I discuss how the obtained data may be useful in gaining a better understanding of the pathogenesis of the disease, diagnosis, and for the selection of possible therapeutic targets. In cattle, the disease is characterized by life-long persistent lymphocytosis leading to leukemia/lymphoma in about 5% of infected animals. In sheep, as opposed to cattle, the course of the disease is always fatal and clinical symptoms usually occur within a three-year period after infection. For this reason, sheep are an excellent experimental model of retrovirus-induced leukemia. This model can be useful for human pathology, as bovine leukemia virus is closely related to human T-lymphotropic virus type 1. The data presented here provide novel insights into the molecular mechanisms of the bovine leukemia virus-induced tumorigenic process and indicate the potential marker proteins both for monitoring progression of the disease and as possible targets of pharmacological intervention. A study of the proteome of B lymphocytes from four leukemic sheep revealed 11 proteins with altered expression. Among them, cytoskeleton and intermediate filament proteins were the most abundant, although proteins belonging to the other functional groups, i.e. enzymes, regulatory proteins, and transcription factors, were also present. It was found that trypsin inhibitor, platelet factor 4, thrombospondin 1, vasodilator-stimulated phosphoprotein, fibrinogen alpha chain, zyxin, filamin-A, and vitamin D-binding protein were downregulated, whereas cleavage and polyadenylation specificity factor subunit 5, non-POU domain-containing octamer-binding protein and small glutamine-rich tetratricopeptide repeat-containing protein alpha were upregulated. Discussed are the possible mechanisms of their altered expression and its significance in the bovine leukemia virus-induced leukemogenic process. Impact statement The submitted manuscript provides new data on the molecular mechanisms of BLV-induced tumorigenic process indicating the potential marker proteins both for monitoring the progression of the disease and as possible targets of pharmacological intervention. This is to my knowledge the first study of the proteome of the transformed lymphocytes in the course of bovine leukemia virus-induced leukemia in susceptible animals. BLV can be considered as useful model for related human pathogen - HTLV-1, another member of the deltaretrovirus genus evolutionary closely related to BLV. Information gathered in this study can be useful to speculate on possible shared mechanisms of deltaretrovirus-induced carcinogenesis.

Tumor suppressor REIC/DKK-3 and co-chaperone SGTA: Their interaction and roles in the androgen sensitivity

REIC/DKK-3 is a tumor suppressor, however, its intracellular physiological functions and interacting molecules have not been fully clarified. Using yeast two-hybrid screening, we found that small glutamine-rich tetratricopeptide repeat-containing protein α (SGTA), known as a negative modulator of cytoplasmic androgen receptor (AR) signaling, is a novel interacting partner of REIC/DKK-3. Mammalian two-hybrid and pull-down assay results indicated that the SGTA-REIC/DKK-3 interaction involved the N-terminal regions of both REIC/DKK-3 and SGTA and that REIC/DKK-3 interfered with the dimerization of SGTA, which is a component of the AR complex and a suppressor of dynein motor-dependent AR transport and signaling. A reporter assay in human prostate cancer cells that displayed suppressed AR signaling by SGTA showed recovery of AR signaling by REIC/DKK-3 expression. Considering these results and our previous data that REIC/DKK-3 interacts with the dynein light chain TCTEX-1, we propose that the REIC/DKK-3 protein interferes with SGTA dimerization, promotes dynein-dependent AR transport and then upregulates AR signaling.

Downregulation of ubiquitin-specific protease 14 (USP14) inhibits breast cancer cell proliferation and metastasis, but promotes apoptosis

Breast cancer is the second leading cause of cancer-related death in women. Previously, evidence suggested that ubiquitin-specific protease 14 (USP14) was associated with various signal transduction pathways and tumourigenesis. In this study, we demonstrate that USP14 is a novel therapeutic target in breast cancer. A Western blot analysis of USP14 was performed using seven breast cancer tissues and paired adjacent normal tissues and showed that the expression of USP14 was increased in the breast cancer tissues. Immunohistochemistry was conducted on formalin-fixed paraffin-embedded sections of breast cancer samples from 100 cases. Using Pearson's χ(2) test, it was demonstrated that USP14 expression was associated with the histological grade, lymph node status and Ki-67 expression in the tumour. The Kaplan-Meier analysis revealed that increased USP14 expression in patients with breast cancer was associated with a poorer prognosis. In in vitro experiments, the highly migratory MDA-MB-231 cells that were treated with USP14-shRNA (shUSP14) exhibited decreased motility using Transwell migration assays. Next, we employed a starvation and re-feeding assay, and the CCK-8 assay demonstrated that USP14 regulated breast cancer cell proliferation. Furthermore, we used flow cytometry to analyse cellular apoptosis following USP14 knockdown. Taken together, our results suggested that USP14 was involved in the progression of breast cancer.

Structural and Functional Insights into Small, Glutamine-Rich, Tetratricopeptide Repeat Protein Alpha

The small glutamine-rich, tetratricopeptide repeat-containing protein alpha (SGTA) is an emerging player in the quality control of secretory and membrane proteins mislocalized to the cytosol, with established roles in tail-anchored (TA) membrane protein biogenesis. SGTA consists of three structural domains with individual functions, an N-terminal dimerization domain that assists protein sorting pathways, a central tetratricopeptide repeat (TPR) domain that mediates interactions with heat-shock proteins, proteasomal, and hormonal receptors, and viral proteins, and a C-terminal glutamine rich region that binds hydrophobic substrates. SGTA has been linked to viral lifecycles and hormone receptor signaling, with implications in the pathogenesis of various disease states. Thus far, a range of biophysical techniques have been employed to characterize SGTA structure in some detail, and to investigate its interactions with binding partners in different biological contexts. A complete description of SGTA structure, together with further investigation into its function as a co-chaperone involved quality control, could provide us with useful insights into its role in maintaining cellular proteostasis, and broaden our understanding of mechanisms underlying associated pathologies. This review describes how some structural features of SGTA have been elucidated, and what this has uncovered about its cellular functions. A brief background on the structure and function of SGTA is given, highlighting its importance to biomedicine and related fields. The current level of knowledge and what remains to be understood about the structure and function of SGTA is summarized, discussing the potential direction of future research.

TGFβ modulates inflammatory cytokines and growth factors to create premetastatic microenvironment and stimulate lung metastasis

The formation of tumor-promoting premetastatic microenvironment plays a pivotal role on metastatic progression. Understanding how the primary tumor can promote the formation of premetastatic microenvironment in the lung will aid discovery of a final cure for metastatic breast cancer. The murine 4T1 mammary carcinoma cells were injected into the mammary fat pads of the BALB/c mice. Days 0-14 were considered the premetastatic phase. Lung tissues were examined using hematoxylin-eosin staining and transmission electron microscopy. After intravenous injection of TGFβ1 pretreated 4T1 cells, the relative pulmonary vascular permeability was quantified, the extravasation, survival, and proliferation of tumor cells in premetastatic lungs were evaluated, and the levels of S100A8, S100A9, VEGF, and Angpt2 were detected in tumor-bearing mice. The results showed that during the premetastatic phase, an inflammatory response and inflammation-induced vascular hyperpermeability were established, leading to an abnormal pulmonary microenvironment, which facilitated extravasation of circulating tumor cells, and subsequent survival and proliferation of metastatic tumor cells in a TGFβ-dependent manner. Moreover, the expressions of S100A8, S100A9, VEGF, and Angpt2 were increased, and an induction of these genes by TGFβ was further observed in premetastatic lungs. Thus, this study demonstrated that TGFβ promoted the creation of premetastatic microenvironment by modulating certain crucial inflammatory cytokines and growth factors, and finally enhanced the ability of circulating cells to seed the lung.

Decreased expression and prognostic role of EHD2 in human breast carcinoma: correlation with E-cadherin

Decreased expression of epithelial cadherin (E-cadherin) has been noted to associate with aggressiveness and metastasis of breast cancer. The aim of this study was to examine the effect of C-Terminal EH domain-containing protein 2 (EHD2) expression on E-cadherin and related mechanism in the metastasis of breast cancer. Immunohistochemical analysis was performed in 96 human breast carcinoma samples and the data were correlated with clinicopathologic characteristics. Furthermore, Western blot analysis was performed for EHD2 and E-cadherin in breast carcinoma samples and cell lines to evaluate their protein levels and molecular interaction. We found that the expression of EHD2 was positively related with E-cadherin expression (P < 0.01), moreover, EHD2 expression was significantly correlated with histologic grade (P < 0.01). Meanwhile, E-cadherin expression obtained similar results. Kaplan-Meier survival analysis showed that decreased expression of EHD2 and E-cadherin exhibited a significant correlation with poor prognosis in human breast cancer (P < 0.01). While in vitro, we employed siRNA technique to knock down EHD2 expressions and observed their effects on breast cancer cells growth. EHD2 depletion by siRNA promoted PCNA expression, and it was concurrent with the decreased expression of epithelial marker E-cadherin and the increased expression of N-cadherin by Western blot analysis. Consistent with these observations, the suppression of EHD2 in breast cancer cells remarkably promoted cellular proliferation and migration. On the basis of these results, we suggested that EHD2 can inhibit the metastasis of human breast cancer by regulating the EMT key markers E-cadherin and N-cadherin.