Expression and clinical role of small glutamine-rich tetratricopeptide repeat (TPR)-containing protein alpha (SGTA) as a novel cell cycle protein in NSCLC

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.

Knockdown of Nemo‑like kinase promotes metastasis in non‑small‑cell lung cancer

The evolutionarily conserved serine/threonine kinase Nemo-like kinase (NLK) serves an important role in cell proliferation, migration, invasion and apoptosis by regulating transcription factors among various cancers. In the present study, the function of NLK in human non-small cell lung cancer (NSCLC) was investigated. Immunohistochemical analysis and western blotting demonstrated that NLK expression was significantly reduced in NSCLC tissues compared with corresponding peritumoral tissues. Statistical analysis revealed that decreased NLK expression was associated with the presence of primary tumors, tumor node metastasis (TNM) staging, differentiation, lymph node metastasis, and E-cadherin and vimentin expression. Univariate analysis indicated that NLK expression, differentiation, lymph node metastasis, TNM stage, and E-cadherin and vimentin expression affected the prognosis of NSCLC. Cox regression analyses revealed NLK expression and TNM as independent factors that affected prognosis. Kaplan-Meier survival analysis revealed that patients with NSCLC and low NLK expression had relatively shorter durations of overall survival. In vitro, NLK overexpression inhibited A549 ncell migration and invasion as determined by wound healing and Transwell migration assays, respectively. Additionally, immunofluorescence staining indicated that downregulation of NLK expression could induce epithelial-mesenchymal transition in NSCLC. NLK knockdown significantly decreased the expression of the epithelial marker E-cadherin, and markedly increased that of β-catenin and the mesenchymal marker vimentin. Furthermore, NLK was reported to directly interact with β-catenin as determined by a co-immunoprecipitation assay. Collectively, the results of the present study indicated that decreased NLK expression could promote tumor metastasis in NSCLC.

SGTb regulates a surface localization of a guidance receptor BOC to promote neurite outgrowth

Neuritogenesis is a critical event for neuronal differentiation and neuronal circuitry formation during neuronal development and regeneration. Our previous study revealed a critical role of a guidance receptor BOC in a neuronal differentiation and neurite outgrowth. However, regulatory mechanisms for BOC signaling pathway remain largely unexplored. In the current study, we have identified Small glutamine-rich tetratricopeptide repeat (TPR)-containing b (SGTb) as a BOC interacting protein through yeast two-hybrid screening. Like BOC, SGTb is highly expressed in brain and P19 embryonal carcinoma (EC) cells differentiated into neuronal cells. BOC and SGTb proteins co-precipitate in mouse brain and differentiated P19 EC cells. Furthermore, BOC and SGTb co-localize in neurites and especially are concentrated at the tip of neurites in various neuronal cells. SGTb depletion attenuates neuronal differentiation of P19 cells through reduction of the surface level of BOC. Additionally, SGTb depletion causes BOC localization at neurite tip, coinciding with decreased p-JNK levels critical for actin cytoskeleton remodeling. The overexpression of SGTb or BOC restores JNK activation in BOC or SGTb-depleted cells, respectively. Finally, SGTb elevates the level of surface-resident BOC in BOC-depleted cells, restoring JNK activation. Taken together, our data suggest that SGTb interacts with BOC and regulates its surface level and consequent JNK activation, thereby promoting neuronal differentiation and neurite outgrowth.

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.

Detection of Highly Differentiated Genomic Regions Between Lotus (Nelumbo nucifera Gaertn.) With Contrasting Plant Architecture and Their Functional Relevance to Plant Architecture

The lotus (Nelumbo nucifera Gaertn.) is one of the most economically and ornamentally important perennial aquatic plants. Plant architecture is an important trait for lotus classification, cultivation, breeding, and applications. In this study, traits representing plant architecture were measured in 390 lotus germplasms for 3 years. According to the phenotypic distribution, 21 large architecture (LA) and 22 small architecture (SA) germplasms exhibiting extreme phenotypes were selected as representatives of plant architecture. Microscopy analyses revealed that LA lotuses possessed far more vertical cells and longer cell lengths than SA lotuses, and there was a closer linear relationship between vertical cell number and plant architecture than cell length and plant architecture. Furthermore, based on whole genome re-sequencing data from 10 LA and 10 SA lotus germplasms, fixation index (FST) genome scan identified 11.02 Mb of genomic regions that were highly differentiated between the LA and SA lotus groups. Chi-square test revealed that 17,154 single nucleotide polymorphisms (SNPs) and 1,554 insertions and deletions (InDels) showed distinct allelic distribution between the LA and SA lotus groups within these regions. A total of 126 variants with distinct allelic distribution in the highly differentiated region were predicted to cause amino acid changes in 60 genes. Among the 41 genes with functional annotation, the expression patterns of six genes involved in cell division and cell wall construction were confirmed using quantitative reverse-transcription PCR (qRT-PCR). In addition, 34 plant architecture-associated InDel markers were developed and verified in the remaining 11 LA and 12 SA lotus plant architecture representatives. This study identified promising functional markers and candidates for molecular breeding and will facilitate further elucidation of the genetic mechanisms underlying plant architecture in the lotus.

Augmented expression of Ki-67 is correlated with clinicopathological characteristics and prognosis for lung cancer patients: an up-dated systematic review and meta-analysis with 108 studies and 14,732 patients

Background

Lung cancer ranks as the leading cause of cancer-related deaths worldwide and we performed this meta-analysis to investigate eligible studies and determine the prognostic effect of Ki-67.

Methods

In total, 108 studies in 95 articles with 14,732 patients were found to be eligible, of which 96 studies reported on overall survival (OS) and 19 studies reported on disease-free survival (DFS) with relation to Ki-67 expression in lung cancer patients.

Results

The pooled hazard ratio (HR) indicated that a high Ki-67 level could be a valuable prognostic factor for lung cancer (HR = 1.122 for OS, P < 0.001 and HR = 1.894 for DFS, P < 0.001). Subsequently, the results revealed that a high Ki-67 level was significantly associated with clinical parameters of lung cancer including age (odd ratio, OR = 1.246 for older patients, P = 0.018), gender (OR = 1.874 for males, P < 0.001) and smoking status (OR = 3.087 for smokers, P < 0.001). Additionally, significant positive correlations were found between Ki-67 overexpression and poorer differentiation (OR = 1.993, P = 0.003), larger tumor size (OR = 1.436, P = 0.003), and higher pathologic stages (OR = 1.867 for III-IV, P < 0.001). Furthermore, high expression of Ki-67 was found to be a valuable predictive factor for lymph node metastasis positive (OR = 1.653, P < 0.001) and advanced TNM stages (OR = 1.497 for stage III-IV, P = 0.024). Finally, no publication bias was detected in any of the analyses.

Conclusions

This study highlights that the high expression of Ki-67 is clinically relevant in terms of the prognostic and clinicopathological characteristics for lung cancer. Nevertheless, more prospective well-designed studies are warranted to validate these findings.

Electronic supplementary material

The online version of this article (10.1186/s12931-018-0843-7) contains supplementary material, which is available to authorized users.

Downregulated Expression of PTPN9 Contributes to Human Hepatocellular Carcinoma Growth and Progression

Human hepatocellular carcinoma (HCC) is one of the most common malignant cancers, whose molecular mechanisms is remains largely. PTPN9 has recently been reported to play a critical role in breast cancer development. However, the role of PTPN9 in human HCC remains elusive. The present study aimed at investigating the potential role of PTPN9 in HCC. Western blot and immunohistochemistry were used to examine the expression of PTPN9 protein in HCC and adjacent non-tumorous tissues in 45 patients. Furthermore, Cell Counting Kit-8, flow cytometry and RNA interference experiments were performed to analyze the role of PTPN9 in the regulation of HCC cell proliferation. We showed that the expression level of PTPN9 was significantly reduced in HCC, compared with adjacent non-tumorous tissues. PTPN9 expression was inversely associated with Tumor size (P = 0.014), serum AFP level (P = 0.004) and Ki-67 expression. Low expression of PTPN9 predicted poor survival in HCC patients. Moreover, PTPN9 interference assay that PTPN9 inhibited cell proliferation in HepG2 cells. Cell apoptosis assay revealed that, silencing of PTPN9 expression significantly reduced cell apoptosis, compared with control ShRNA treatment group. Our results suggested that PTPN9 expression was down-regulated in HCC tumor tissues, and reduced PTPN9 expression was associated with worsened overall survival in HCC patients. Depletion of PTPN9 inhibits the apoptosis and promotes the proliferation of HCC cells.

Proteomic profile and in silico analysis in metastatic melanoma with and without BRAF mutation

INTRODUCTION

Selective inhibitors of BRAF, vemurafenib and dabrafenib are the standard of care for metastatic melanoma patients with BRAF V600, while chemotherapy continued to be widely used in BRAF wild type patients.

MATERIALS AND METHODS

In order to discover novel candidate biomarkers predictive to treatment, serum of 39 metastatic melanoma vemurafenib (n = 19) or chemotherapy (n = 20) treated patients at baseline, at disease control and at progression, were analyzed using SELDI-TOF technology. In silico analysis was used to identify more significant peaks.

RESULTS

In patients with different BRAF status, we found 5 peptides significantly deregulated, with the down-regulation of the m/z 9176 peak strongly associated with BRAF mutation. At baseline as predictive biomarkers we identified 2 peptides - m/z 6411, 4075 - as significantly up-regulated in responders to chemotherapy and 4 peaks - m/z 5900, 12544, 49124 and 11724 - significantly up-regulated in longer vs shorter responders to vemurafenib. After response, 3 peptides (m/z 4658, 18639, and 9307) resulted significantly down regulated while 3 peptides m/z 9292, 7765 and 9176 appeared up-regulated respectively in chemotherapy and vemurafenib responder patients. In vemurafenib treated patients, 16 peaks appeared deregulated at progression compared to baseline time. In silico analysis identified proteins involved in invasiveness (SLAIN1) and resistance (ABCC12) as well as in the pathway of detoxification (NQO1) and apoptosis (RBM10, TOX3, MTEFD1, TSPO2). Proteins associated with the modulation of neuronal plasticity (RIN1) and regulatory activity factors of gene transcription (KLF17, ZBTB44) were also highlighted.

CONCLUSION

Our exploratory study highlighted some factors that deserve to be further investigated in order to provide a framework for improving melanoma treatment management through the development of biomarkers which could act as the strongest surrogates of the key biological events in stage IV melanoma.

Solution structure of the SGTA dimerisation domain and investigation of its interactions with the ubiquitin-like domains of BAG6 and UBL4A

Background

The BAG6 complex resides in the cytosol and acts as a sorting point to target diverse hydrophobic protein substrates along their appropriate paths, including proteasomal degradation and ER membrane insertion. Composed of a trimeric complex of BAG6, TRC35 and UBL4A, the BAG6 complex is closely associated with SGTA, a co-chaperone from which it can obtain hydrophobic substrates.

Methodology and Principal Findings

SGTA consists of an N-terminal dimerisation domain (SGTA_NT), a central tetratricopeptide repeat (TPR) domain, and a glutamine rich region towards the C-terminus. Here we solve a solution structure of the SGTA dimerisation domain and use biophysical techniques to investigate its interaction with two different UBL domains from the BAG6 complex. The SGTA_NT structure is a dimer with a tight hydrophobic interface connecting two sets of four alpha helices. Using a combination of NMR chemical shift perturbation, isothermal titration calorimetry (ITC) and microscale thermophoresis (MST) experiments we have biochemically characterised the interactions of SGTA with components of the BAG6 complex, the ubiquitin-like domain (UBL) containing proteins UBL4A and BAG6. We demonstrate that the UBL domains from UBL4A and BAG6 directly compete for binding to SGTA at the same site. Using a combination of structural and interaction data we have implemented the HADDOCK protein-protein interaction docking tool to generate models of the SGTA-UBL complexes.

Significance

This atomic level information contributes to our understanding of the way in which hydrophobic proteins have their fate decided by the collaboration between SGTA and the BAG6 complex.

SGTA regulates the cytosolic quality control of hydrophobic substrates

Hydrophobic amino acids are normally shielded from the cytosol and their exposure is often used as an indicator of protein misfolding to enable the chaperone-mediated recognition and quality control of aberrant polypeptides. Mislocalised membrane proteins (MLPs) represent a particular challenge to cellular quality control, and, in this study, membrane protein fragments have been exploited to study a specialised pathway that underlies the efficient detection and proteasomal degradation of MLPs. Our data show that the BAG6 complex and SGTA compete for cytosolic MLPs by recognition of their exposed hydrophobicity, and the data suggest that SGTA acts to maintain these substrates in a non-ubiquitylated state. Hence, SGTA might counter the actions of BAG6 to delay the ubiquitylation of specific precursors and thereby increase their opportunity for successful post-translational delivery to the endoplasmic reticulum. However, when SGTA is overexpressed, the normally efficient removal of aberrant MLPs is delayed, increasing their steady-state level and promoting aggregation. Our data suggest that SGTA regulates the cellular fate of a range of hydrophobic polypeptides should they become exposed to the cytosol.

Upregulation of SYF2 in esophageal squamous cell carcinoma promotes tumor cell proliferation and predicts poor prognosis

SYF2, also known as CCNDBP1-interactor or p29, is reported in pre-mRNA splicing and cell cycle progression. However, the role of SYF2 in esophageal squamous cell carcinoma (ESCC) development remains elusive. In the present study, Western blot and immunohistochemistry assays demonstrated that SYF2 was overexpressed in ESCC tumor tissues and cell lines. In addition, immunohistochemistry analysis revealed that SYF2 expression was positively correlated with tumor grade and predicted poor prognosis of ESCC. In vitro studies using serum starvation-refeeding experiment and SYF2-siRNA transfection assay demonstrated that SYF2 expression promoted proliferation of ESCC cells, while SYF2 knockdown led to decreased cell growth rate and colony formation resulted from growth arrest of cell cycle at G0/G1 phase. Furthermore, our results indicated that SYF2 can down-regulate the sensitivity of ESCC cells for cisplatin. Our findings for the first time supported that SYF2 might play an important role in the regulation of ESCC proliferation and would provide a novel therapeutic strategy against human ESCC.

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

Small glutamine-rich tetratricopeptide repeat-containing protein alpha (SGTA) was reported to be implicated in various cellular processes and involved in control of cell cycle regulation and transcription. It may play a critical role in oncogenesis. In this study, to investigate the potential roles of SGTA in breast cancer, expression patterns, interaction and the correlation with clinical/prognostic factors of SGTA and Ki-67 were examined among patients with breast cancer. Immunohistochemistry and Western blot analysis were performed for SGTA in 100 breast carcinoma samples. The data were correlated with clinicopathological features. The univariate and multivariate survival analyses were also performed to determine the prognostic significance. We found that SGTA was overexpressed in breast carcinoma compared with the adjacent normal tissues. High expression of SGTA was positively associated with histological grade (P = 0.002) and Ki-67 (P = 0.001). Univariate analysis showed that SGTA expression was associated with a poor prognosis (P = 0.002). Kaplan-Meier survival curves of the study population showed that high expression level of SGTA significantly correlated with short-term survival. While in vitro, SGTA depletion by small interfering RNA inhibited cell proliferation and cell cycle in breast cancer cell lines. Western blot analyses showed that SGTA depletion decreased cyclin A, cyclin B and CDK2, whereas increased p27 levels. Additionally, treatment of phosphatidylinositol 3-kinase inhibitor LY294002 could arrest cells growth and diminish SGTA expression. These results suggested that SGTA overexpression was involved in the pathogenesis of breast cancer which might serve as a future target for novel treatment in breast cancer.

Expression of small glutamine-rich TPR-containing protein A (SGTA) in Non-Hodgkin's Lymphomas promotes tumor proliferation and reverses cell adhesion-mediated drug resistance (CAM-DR)

The expression and biologic function of SGTA in Non-Hodgkin's Lymphomas (NHL) was investigated in this study. Clinically, by immunohistochemistry analysis we detected SGTA expression in both reactive lymphoid tissues and NHL tissues. In addition, we also correlated high expression of SGTA with poor prognosis. Functionally, SGTA expression was positively related with cell proliferation and negative related with cell adhesion. Finally, SGTA knockdown induced adhesion-mediated drug resistance. Our finding supports a role of SGTA in NHL cell proliferation, adhesion and drug resistance, and it may pave the way for a novel therapeutic approach for CAM-DR in NHL.

Knocking down the expression of adenylate cyclase-associated protein 1 inhibits the proliferation and migration of breast cancer cells

Adenylate cyclase-associated protein 1 (CAP1) is a conserved protein that was found to be up-regulated in breast cancer and related to the migration of breast cancer. We verified its roles in breast cancer specimens and cell lines. In our results, 71 of 100 specimens of breast cancer showed high levels of CAP1 by immunohistochemistry. Associated with statistical analysis, we saw that CAP1 was related to the grade of breast cancer. In MDA-MB-231, the expression of CAP1 was the highest and by knocking down the expression of CAP1 in MDA-MB-231, its ability for proliferating and migrating apparently decreased and induced changes in morphology, which were related to the arrangement of F-actin. Therefore, CAP1 might be a potential molecular targeted therapy for surgery and immune treatment.