Lipid raft interacting galectin 8 regulates primary ciliogenesis.

Primary cilium is a specialized sensory organelle that transmits environmental information into cells. Its length is tightly controlled by various mechanisms such as the frequency or the cargo size of the intraflagellar transport trains which deliver the building materials such as tubulin subunits essential for the growing cilia. Here, we show the sialoglycan interacting galectin 8 regulates the process of primary ciliogenesis. As the epithelia become polarized, there are more galectin 8 being apically secreted and these extracellular galectin 8 molecules apparently bind to a lipid raft enriched domain at the base of the primary cilia through interacting with lipid raft components, such as GD3 ganglioside and scaffold protein caveolin 1. Furthermore, the binding of galectin 8 at this critical region triggers rapid growth of primary cilia by perturbing the barrier function of the transition zone (TZ). Our study also demonstrates the functionality of this barrier depends on intact organization of lipid rafts at the cilia as genetically knockout of Cav1 and pharmacologically inhibition of lipid raft both phenocopy the effect of apical addition of recombinant galectin 8; that is, rapid elongation of primary cilia and redistribution of cilia proteins from TZ to the growing axoneme. Indeed, as cilia elongated, endogenous galectin 8, caveolin 1, and TZ component, TMEM231, also transited from the TZ to the growing axoneme. We also noted that the interaction between caveolin 1 and TMEM231 could be perturbed by exogenous galectin 8. Taken together, we proposed that galectin 8 promoted primary cilia elongation through impeding the barrier function of the TZ by interfering with the interaction between caveolin 1 and TMEM231.

Acetylation regulates the nucleocytoplasmic distribution and oncogenic function of karyopherin alpha 2 in lung adenocarcinoma.

Karyopherin subunit alpha 2 (KPNA2, importin α1) is a nucleoplasmic protein responsible for the nuclear import of proteins with classical nuclear localization signals. Aberrant nuclear accumulation of KPNA2 has been observed in numerous cancer tissues. AMP-activated protein kinase (AMPK) is involved in the phosphorylation and acetylation of KPNA2 in enterocytes. However, the impact of these post-translational modifications on modulating the nucleocytoplasmic distribution of KPNA2 and its oncogenic role remain unclear. Unlike nuclear accumulation of wild-type KPNA2, which promoted lung cancer cell migration, KPNA2 Lys22 acetylation-mimicking mutations (K22Q and K22Q/S105A) prevented nuclear localization of KPNA2 and reduced the cell migration ability. Cytosolic KPNA2 K22Q interacted with and restricted the nuclear entry of E2F transcription factor 1 (E2F1), an oncogenic cargo protein of KPNA2, in lung cancer cells. Intriguingly, the AMPK activator EX229 promoted the nuclear export of KPNA2 S105A. However, the CBP/p300 inhibitor CCS-1477 abolished this phenomenon, suggesting that CBP/p300-mediated acetylation of KPNA2 promoted KPNA2 nuclear export in lung cancer cells. Collectively, our findings suggest that the CBP/p300 positively regulates KPNA2 acetylation, which enhances its cytosolic localization and suppresses its oncogenic activity in lung cancer.

CRNDE acts as an epigenetic modulator of the p300/YY1 complex to promote HCC progression and therapeutic resistance.

BACKGROUND: Hepatocellular carcinoma (HCC) is one of the most common primary liver malignancies worldwide. The long-term prognosis for HCC remains extremely poor, with drug resistance being the major underlying cause of recurrence and mortality. The lncRNA colorectal neoplasia differentially expressed (CRNDE) is an epigenetic mediator and plays an important role to drive proliferation and drug resistance in HCC. However, CRNDE as an epigenetic regulator with influences sorafenib resistance in HCC is unclear. Thus, we explore the potential of targeting the CRNDE/p300/YY1 axis as a novel therapeutic strategy to overcome sorafenib resistance of HCC. METHOD: Detection of the expression level of CRNDE and EGFR in clinical specimens of HCC. CRNDE, EGFR, p300, and YY1expression were altered in HCC cells through transfection with different plasmids, and cell proliferation, migration, invasion, and sorafenib resistance were subsequently observed. Immunoprecipitation, chromatin immunoprecipitation, re-chromatin immunoprecipitation, site-directed mutagenesis, RNA Immunoprecipitation, immune fluorescence, qRT-PCR, and western blotting were performed to uncover the mechanisms of CRNDE regulation. The xenograft nude mice model was used to investigate the tumor growth and sorafenib resistance. RESULTS: In this study, we showed that CRNDE expression is significantly positively correlated with that of epidermal growth factor receptor (EGFR) in clinical specimens of HCC and induces proliferation and sorafenib resistance of HCC via EGFR-mediated signaling. Mechanistically, CRNDE stabilized the p300/YY1 complex at the EGFR promoter and simultaneously enhanced histone H3K9 and H3K27 acetylation, which serve as markers of relaxed chromatin. EGFR was positively upregulated by the epigenetic complex, p300/YY1, in a manner dependent on CRNDE expression, leading to enhanced tumor cell proliferation and sorafenib resistance. Furthermore, C646, a p300 inhibitor, suppressed EGFR transcriptional activity by decreasing chromatin relaxation and YY1 binding, which effectively reduced proliferation/sorafenib resistance and prolonged overall survival. CONCLUSION: Our collective findings support the potential of targeting the CRNDE/p300/YY1 axis as a novel therapeutic strategy to overcome sorafenib resistance of HCC.

Phosphorylation of Arl4A/D promotes their binding by the HYPK chaperone for their stable recruitment to the plasma membrane.

The Arl4 small GTPases participate in a variety of cellular events, including cytoskeleton remodeling, vesicle trafficking, cell migration, and neuronal development. Whereas small GTPases are typically regulated by their GTPase cycle, Arl4 proteins have been found to act independent of this canonical regulatory mechanism. Here, we show that Arl4A and Arl4D (Arl4A/D) are unstable due to proteasomal degradation, but stimulation of cells by fibronectin (FN) inhibits this degradation to promote Arl4A/D stability. Proteomic analysis reveals that FN stimulation induces phosphorylation at S143 of Arl4A and at S144 of Arl4D. We identify Pak1 as the responsible kinase for these phosphorylations. Moreover, these phosphorylations promote the chaperone protein HYPK to bind Arl4A/D, which stabilizes their recruitment to the plasma membrane to promote cell migration. These findings not only advance a major mechanistic understanding of how Arl4 proteins act in cell migration but also achieve a fundamental understanding of how these small GTPases are modulated by revealing that protein stability, rather than the GTPase cycle, acts as a key regulatory mechanism.

Golgin Imh1 and GARP complex cooperate to restore the impaired SNARE recycling transport induced by ER stress.

The accumulation of misfolded proteins in the endoplasmic reticulum (ER) induces the unfolded protein response (UPR), which acts through various mechanisms to reduce ER stress. While the UPR has been well studied for its effects on the ER, its impact on the Golgi is less understood. The Golgi complex receives transport vesicles from the endosome through two types of tethering factors: long coiled-coil golgin and the multisubunit Golgi-associated retrograde protein (GARP) complex. Here, we report that ER stress increases the phosphorylation of golgin Imh1 to maintain the GARP-mediated recycling of the SNAREs Snc1 and Tlg1. We also identify a specific function of the Golgi affected by ER stress and elucidate a homeostatic response to restore this function, which involves both an Ire1-dependent and a MAP kinase Slt2/ERK2-dependent mechanism. Furthermore, our findings advance a general understanding of how two different types of tethers act cooperatively to mediate a transport pathway.

Nuclear accumulation of KPNA2 impacts radioresistance through positive regulation of the PLSCR1-STAT1 loop in lung adenocarcinoma.

Lung adenocarcinoma (ADC) is the predominant histological type of lung cancer, and radiotherapy is one of the current therapeutic strategies for lung cancer treatment. Unfortunately, biological complexity and cancer heterogeneity contribute to radioresistance development. Karyopherin α2 (KPNA2) is a member of the importin α family that mediates the nucleocytoplasmic transport of cargo proteins. KPNA2 overexpression is observed across cancer tissues of diverse origins. However, the role of KPNA2 in lung cancer radioresistance is unclear. Herein, we demonstrated that high expression of KPNA2 is positively correlated with radioresistance and cancer stem cell (CSC) properties in lung ADC cells. Radioresistant cells exhibited nuclear accumulation of KPNA2 and its cargos (OCT4 and c-MYC). Additionally, KPNA2 knockdown regulated CSC-related gene expression in radioresistant cells. Next-generation sequencing and bioinformatic analysis revealed that STAT1 activation and nuclear phospholipid scramblase 1 (PLSCR1) are involved in KPNA2-mediated radioresistance. Endogenous PLSCR1 interacting with KPNA2 and PLSCR1 knockdown suppressed the radioresistance induced by KPNA2 expression. Both STAT1 and PLSCR1 were found to be positively correlated with dysregulated KPNA2 in radioresistant cells and ADC tissues. We further demonstrated a potential positive feedback loop between PLSCR1 and STAT1 in radioresistant cells, and this PLSCR1-STAT1 loop modulates CSC characteristics. In addition, AKT1 knockdown attenuated the nuclear accumulation of KPNA2 in radioresistant lung cancer cells. Our results collectively support a mechanistic understanding of a novel role for KPNA2 in promoting radioresistance in lung ADC cells.

The Pathophysiologic Role of Gelsolin in Chronic Kidney Disease: Focus on Podocytes.

Chronic kidney disease (CKD) is normally related to proteinuria, a common finding in a compromised glomerular filtration barrier (GFB). GFB is a structure composed of glomerular endothelial cells, the basement membrane, and the podocytes. CKD with podocyte damage may be associated with actin cytoskeleton reorganization, resulting in podocyte effacement. Gelsolin plays a critical role in several diseases, including cardiovascular diseases and cancer. Our current study aimed to determine the connection between gelsolin and podocyte, and thus the mechanism underlying podocyte injury in CKD. Experiments were carried out on Drosophila to demonstrate whether gelsolin had a physiological role in maintaining podocyte. Furthermore, the survival rate of gelsolin-knocked down Drosophila larvae was extensively reduced after AgNO3 exposure. Secondly, the in vitro podocytes treated with puromycin aminonucleoside (PAN) enhanced the gelsolin protein expression, as well as small GTPase RhoA and Rac1, which also regulated actin dynamic expression incrementally with the PAN concentrations. Thirdly, we further demonstrated in vivo that GSN was highly expressed inside the glomeruli with mitochondrial dysfunction in a CKD mouse model. Our findings suggest that an excess of gelsolin may contribute to podocytes damage in glomeruli.

ArfGAP1 acts as a GTPase-activating protein for human ADP-ribosylation factor-like 1 protein.

ADP-ribosylation factors (Arfs) and Arf-like (Arl) GTPases are key regulators of intracellular vesicle trafficking and Golgi structure. Both Arf and Arl proteins cycle between active GTP-bound and inactive GDP-bound forms, where guanine nucleotide exchange factors (GEFs) regulate the exchange of GDP for GTP, whereas GTPase-activating proteins (GAPs) promote the hydrolysis of bound GTP. Human Arl1 is located at the trans-Golgi network (TGN) and regulates the function and structure of the Golgi complex. However, neither GEFs nor GAPs for human Arl1 have been identified. Here, we report that ArfGAP1, an Arf1 GAP, can promote GTP hydrolysis of Arl1. We show that ArfGAP1 directly interacts with GTP-bound Arl1 and exhibits GAP activity toward Arl1 in vitro. Exogenous expression of ArfGAP1, but not ArfGAP2 and ArfGAP3, causes dissociation of endogenous Arl1 from the TGN. In addition, GAP activity-deficient ArfGAP1 fails to regulate the Golgi localization of Arl1. Using an activity pull-down assay, we demonstrated that ArfGAP1 regulates the levels of Arl1-GTP in cells expressing ArfGAP1-myc or with ArfGAP1 knockdown. Finally, we observed that, similar to expression of putative active Arl1 (Arl1QL), ArfGAP1 knockdown impairs endosome-to-TGN retrograde transport of the Shiga toxin B-subunit. Thus, our findings support the idea that ArfGAP1 acts as an Arl1 GAP to regulate the function of Arl1 in vesicle trafficking at the TGN.

Integrative Omics Analysis Reveals Soluble Cadherin-3 as a Survival Predictor and an Early Monitoring Marker of EGFR Tyrosine Kinase Inhibitor Therapy in Lung Cancer.

PURPOSE: EGFR tyrosine kinase inhibitors (EGFR-TKI) benefit patients with advanced lung adenocarcinoma (ADC) harboring activating EGFR mutations. We aimed to identify biomarkers to monitor and predict the progression of patients receiving EGFR-TKIs via a comprehensive omic analysis. EXPERIMENTAL DESIGN: We applied quantitative proteomics to generate the TKI resistance-associated pleural effusion (PE) proteome from patients with ADC with or without EGFR-TKI resistance. Candidates were selected from integrated genomic and proteomic datasets. The PE (n = 33) and serum (n = 329) levels of potential biomarkers were validated with ELISAs. Western blotting was applied to detect protein expression in tissues, PEs, and a cell line. Gene knockdown, TKI treatment, and proliferation assays were used to determine EGFR-TKI sensitivity. Progression-free survival (PFS) and overall survival (OS) were assessed to evaluate the prognostic values of the potential biomarkers. RESULTS: Fifteen proteins were identified as potential biomarkers of EGFR-TKI resistance. Cadherin-3 (CDH3) was overexpressed in ADC tissues compared with normal tissues. CDH3 knockdown enhanced EGFR-TKI sensitivity in ADC cells. The PE level of soluble CDH3 (sCDH3) was increased in patients with resistance. The altered sCDH3 serum level reflected the efficacy of EGFR-TKI after 1 month of treatment (n = 43). Baseline sCDH3 was significantly associated with PFS and OS in patients with ADC after EGFR-TKI therapy (n = 76). Moreover, sCDH3 was positively associated with tumor stage in non-small cell lung cancer (n = 272). CONCLUSIONS: We provide useful marker candidates for drug resistance studies. sCDH3 is a survival predictor and real-time indicator of treatment efficacy in patients with ADC treated with EGFR-TKIs.

Cooperative recruitment of Arl4A and Pak1 to the plasma membrane contributes to sustained Pak1 activation for cell migration.

Cell migration requires the coordination of multiple signaling pathways involved in membrane dynamics and cytoskeletal rearrangement. The Arf-like small GTPase Arl4A has been shown to modulate actin cytoskeleton remodeling. However, evidence of the function of Arl4A in cell migration is insufficient. Here, we report that Arl4A acts with the serine/threonine protein kinase Pak1 to modulate cell migration through their cooperative recruitment to the plasma membrane. We first observed that Arl4A and its isoform Arl4D interact with Pak1 and Pak2 and showed that Arl4A recruits Pak1 and Pak2 to the plasma membrane. The fibronectin-induced Pak1 localization at the plasma membrane is reduced in Arl4A-depleted cells. Unexpectedly, we found that Pak1, but not Arl4A-binding-defective Pak1, can recruit a cytoplasmic myristoylation-deficient Arl4A-G2A mutant to the plasma membrane. Furthermore, we found that the Arl4A-Pak1 interaction, which is independent of Rac1 binding to Pak1, is required for Arl4A-induced cell migration. Thus, we infer that there is feedback regulation between Arl4A and Pak1, in which they mutually recruit each other to the plasma membrane for Pak1 activation, thereby modulating cell migration through direct interaction.

Transcriptomic Analysis in Liquid Biopsy Identifies Circulating PCTAIRE-1 mRNA as a Biomarker in NSCLC.

BACKGROUND/AIM: Circulating mRNA can be a useful source of cancer biomarkers. We took advantage of direct transcriptomic analysis in plasma RNA to identify novel mRNA markers for non-small cell lung cancer (NSCLC). PATIENTS AND METHODS: Plasma RNA from NSCLC patients and healthy individuals was profiled with cDNA-mediated annealing, selection, extension and ligation (DASL) microarrays. The microarray results were further validated in plasma RNA. RESULTS: Through RNA profiling and online database mining, four gene transcripts were filtered as candidate markers of NSCLC. After validation, the PCTAIRE-1 transcript was identified as a circulating mRNA marker. The diagnostic potential of PCTAIRE-1 was evaluated by receiver operating characteristic curve analysis, which gave a sensitivity and specificity of 60% and 85%, respectively. In addition, high plasma PCTK1 levels were also correlated with poor progression-free survival (p=0.008). CONCLUSION: Circulating mRNA can be profiled with the DASL assay. From the profile, PCTAIRE-1 RNA in the plasma we discovered as a novel diagnostic/prognostic biomarker and an indicator of poor survival in NSCLC patients.

N-acetylgalactosamine-6-sulfatase (GALNS), Similar to Glycodelin, Is a Potential General Biomarker for Multiple Malignancies.

BACKGROUND/AIM: The aim of this study was to evaluate N-acetylgalactosamine-6-sulfatase (GALNS) as a new biomarker candidate for detecting lung cancer. Glycodelin or PAEP, the serum levels of which are known to be elevated in lung and other cancers, served as a benchmark for comparison. PATIENTS AND METHODS: A total of 170 serum samples from healthy controls and patients with pneumonia, lung cancer, breast cancer, colon cancer, liver cancer, and head and neck cancer were analyzed for the levels of GALNS and PAEP by ELISA. RESULTS: The median serum levels of GALNS and PAEP in all cancer types as well as pneumonia patients were significantly higher than those of the healthy controls. CONCLUSION: In addition to previously known cancers, the median serum levels of PAEP were also found to be higher in liver and head and neck cancer patients. GALNS and PAEP are promising general biomarkers for multiple cancers and deserve further evaluation.

IRF1 Negatively Regulates Oncogenic KPNA2 Expression Under Growth Stimulation and Hypoxia in Lung Cancer Cells.

PURPOSE: Karyopherin alpha 2 (KPNA2) has been reported as an oncogenic protein in numerous human cancers and is currently considered a potential therapeutic target. However, the transcriptional regulation and physiological conditions underlying KPNA2 expression remain unclear. The aim of the present study was to investigate the role and regulation of interferon regulatory factor-1 (IRF1) in modulating KPNA2 expression in lung adenocarcinoma (ADC). MATERIALS AND METHODS: Bioinformatics tools and chromatin immunoprecipitation were used to analyze the transcription factor (TF) binding sites in the KPNA2 promoter region. We searched for a potential role of IRF1 in non-small-cell lung cancer (NSCLC) using Oncomine and Kaplan-Meier Plotter datasets. qRT-PCR was applied to examine the role of IRF1 and signaling involved in regulating KPNA2 transcription. Western blotting was used to determine the effects of extracellular stimulation and intracellular signaling on the modulation of KPNA2-related TF expression. RESULTS: IRF1 was identified as a novel TF that suppresses KPNA2 gene expression. We observed that IRF1 expression was lower in cancerous tissues than in normal lung tissues and that its low expression was correlated with poor prognosis in NSCLC. Notably, both ataxia telangiectasia mutated (ATM) and mechanistic target of rapamycin (mTOR) inhibitors reduced KPNA2 expression, which was accompanied by increased expression of IRF1 but decreased expression of E2F1, a TF that promotes KPNA2 expression in lung ADC cells. IRF1 knockdown restored the reduced levels of KPNA2 in ATM inhibitor-treated cells. We further demonstrated that epidermal growth factor (EGF)-activated mTOR and hypoxia-induced ATM suppressed IRF1 expression but promoted E2F1 expression, which in turn upregulated KPNA2 expression in lung ADC cells. CONCLUSION: IRF1 acts as a potential tumor suppressor in NSCLC. EGF and hypoxia promote KPNA2 expression by simultaneously suppressing IRF1 expression and enhancing E2F1 expression in lung ADC cells. Our study provides new insights into targeted therapy for lung cancer.

Nanoparticle Formulation of Moxifloxacin and Intramuscular Route of Delivery Improve Antibiotic Pharmacokinetics and Treatment of Pneumonic Tularemia in a Mouse Model.

Francisella tularensis causes a serious and often fatal infection, tularemia. We compared the efficacy of moxifloxacin formulated as free drug vs disulfide snap-top mesoporous silica nanoparticles (MSNs) in a mouse model of pneumonic tularemia. We found that MSN-formulated moxifloxacin was more effective than free drug and that the intramuscular and subcutaneous routes were markedly more effective than the intravenous route. Measurement of tissue silica levels and fluorescent flow cytometry assessment of colocalization of MSNs with infected cells revealed that the enhanced efficacy of MSNs and the intramuscular route of delivery was not due to better delivery of MSNs to infected tissues or cells. However, moxifloxacin blood levels demonstrated that the nanoparticle formulation and intramuscular route provided the longest half-life and longest time above the minimal inhibitory concentration. Thus, improved pharmacokinetics are responsible for the greater efficacy of nanoparticle formulation and intramuscular delivery compared with free drug and intravenous delivery.

Glucose intake hampers PKA-regulated HSP90 chaperone activity.

Aging is an intricate phenomenon associated with the gradual loss of physiological functions, and both nutrient sensing and proteostasis control lifespan. Although multiple approaches have facilitated the identification of candidate genes that govern longevity, the molecular mechanisms that link aging pathways are still elusive. Here, we conducted a quantitative mass spectrometry screen and identified all phosphorylation/dephosphorylation sites on yeast proteins that significantly responded to calorie restriction, a well-established approach to extend lifespan. Functional screening of 135 potential regulators uncovered that Ids2 is activated by PP2C under CR and inactivated by PKA under glucose intake. ids2Δ or ids2 phosphomimetic cells displayed heat sensitivity and lifespan shortening. Ids2 serves as a co-chaperone to form a complex with Hsc82 or the redundant Hsp82, and phosphorylation impedes its association with chaperone HSP90. Thus, PP2C and PKA may orchestrate glucose sensing and protein folding to enable cells to maintain protein quality for sustained longevity.

Thyroid hormone negatively regulates tumorigenesis through suppression of BC200.

Thyroid hormone (T3) and its receptor (TR) are involved in cancer progression. While deregulation of long non-coding RNA (lncRNA) expression has been detected in many tumor types, the mechanisms underlying specific involvement of lncRNAs in tumorigenicity remain unclear. Experiments from the current study revealed negative regulation of BC200 expression by T3/TR. BC200 was highly expressed in hepatocellular carcinoma (HCC) and effective as an independent prognostic marker. BC200 promoted cell growth and tumor sphere formation, which was mediated via regulation of cell cycle-related genes and stemness markers. Moreover, BC200 protected cyclin E2 mRNA from degradation. Cell growth ability was repressed by T3, but partially enhanced upon BC200 overexpression. Mechanistically, BC200 directly interacted with cyclin E2 and promoted CDK2-cyclin E2 complex formation. Upregulation of cell cycle-related genes in hepatoma samples was positively correlated with BC200 expression. Our collective findings support the utility of a potential therapeutic strategy involving targeting of BC200 for the treatment of HCC.

Golgi tethering factor golgin-97 suppresses breast cancer cell invasiveness by modulating NF-κB activity.

BACKGROUND: Golgin-97 is a tethering factor in the trans-Golgi network (TGN) and is crucial for vesicular trafficking and maintaining cell polarity. However, the significance of golgin-97 in human diseases such as cancer remains unclear. METHODS: We searched for a potential role of golgin-97 in cancers using Kaplan-Meier Plotter ( http://kmplot.com ) and Oncomine ( www.oncomine.org ) datasets. Specific functions of golgin-97 in migration and invasion were examined in golgin-97-knockdown and golgin-97-overexpressing cells. cDNA microarray, pathway analysis and qPCR were used to identify gene profiles regulated by golgin-97. The role of golgin-97 in NF-κB signaling pathway was examined by using subcellular fractionation, luciferase reporter assay, western blot analysis and immunofluorescence assay (IFA). RESULTS: We found that low expression of golgin-97 correlated with poor overall survival of cancer patients and was associated with invasiveness in breast cancer cells. Golgin-97 knockdown promoted cell migration and invasion, whereas re-expression of golgin-97 restored the above phenotypes in breast cancer cells. Microarray and pathway analyses revealed that golgin-97 knockdown induced the expression of several invasion-promoting genes that were transcriptionally regulated by NF-κB p65. Mechanistically, golgin-97 knockdown significantly reduced IκBα protein levels and activated NF-κB, whereas neither IκBα levels nor NF-κB activity was changed in TGN46- or GCC185-knockdown cells. Conversely, golgin-97 overexpression suppressed NF-κB activity and restored the levels of IκBα in golgin-97-knockdown cells. Interestingly, the results of Golgi-disturbing agent treatment revealed that the loss of Golgi integrity was not involved in the NF-κB activation induced by golgin-97 knockdown. Moreover, both TGN-bound and cytosolic golgin-97 inhibited NF-κB activation, indicating that golgin-97 functions as an NF-κB suppressor regardless of its subcellular localization. CONCLUSION: Our results collectively demonstrate a novel and suppressive role of golgin-97 in cancer invasiveness. We also provide a new avenue for exploring the relationship between the TGN, golgin-97 and NF-κB signaling in tumor progression.

Association of overexpressed karyopherin alpha 2 with poor survival and its contribution to interleukin-1ß-induced matrix metalloproteinase expression in oral cancer.

BACKGROUND: The purpose of this study was to elucidate the clinicopathological associations and molecular mechanisms of karyopherin alpha 2 (KPNA2) in oral cavity squamous cell carcinoma (SCC) progression. METHODS: The KPNA2 expressions were analyzed by immunohistochemistry and enzyme-linked immunosorbent assay in 209 tissues and 181 saliva samples, respectively. The functions of KPNA2 in migration and invasion were examined in KPNA2-knowdown cells. The matrix metalloproteinase (MMP) levels were determined by real-time quantitative polymerase chain reaction (qPCR). The subcellular fraction was used to obtain the nuclear distribution of nuclear factor-kappa B (NF-κB). RESULTS: The KPNA2 overexpression was associated with extranodal extension (P < .05) and poor disease-specific survival in patients with oral cavity SCC (P < .05). The salivary KPNA2 levels were elevated in patients with oral cavity SCC (P < .05). The KPNA2 knockdown reduced cell migration and invasion. This knockdown also suppressed the interleukin (IL)-1ß-induced nuclear import of NF-κB and MMP (MMP-1, MMP-3, and MMP-9) transcription. CONCLUSION: The KPNA2 overexpression is an independent biomarker for poor prognosis of oral cavity SCC and is required for MMP-mediated metastasis.

PARP1 controls KLF4-mediated telomerase expression in stem cells and cancer cells.

Telomerase is highly expressed in cancer and embryonic stem cells (ESCs) and implicated in controlling genome integrity, cancer formation and stemness. Previous studies identified that Krüppel-like transcription factor 4 (KLF4) activates telomerase reverse transcriptase (TERT) expression and contributes to the maintenance of self-renewal in ESCs. However, little is known about how KLF4 regulates TERT expression. Here, we discover poly(ADP-ribose) polymerase 1 (PARP1) as a novel KLF4-interacting partner. Knockdown of PARP1 reduces TERT expression and telomerase activity not only in cancer cells, but also in human and mouse ESCs. Recruitment of KLF4 to TERT promoter is reduced in PARP1-suppressed cells. The poly(ADP-ribose) polymerase activity is dispensable, while the oligo(ADP-ribose) polymerase activity is required for the PARP1- and KLF4-mediated TERT activation. Repression of Parp1 in mouse ESCs decreases expression of pluripotent markers and induces differentiation. These results suggest that PARP1 recruits KLF4 to activate telomerase expression and stem cell pluripotency, indicating a positive regulatory role of the PARP1-KLF4 complex in telomerase expression in cancer and stem cells.

Telomere shortening triggers a feedback loop to enhance end protection.

Telomere homeostasis is controlled by both telomerase machinery and end protection. Telomere shortening induces DNA damage sensing kinases ATM/ATR for telomerase recruitment. Yet, whether telomere shortening also governs end protection is poorly understood. Here we discover that yeast ATM/ATR controls end protection. Rap1 is phosphorylated by Tel1 and Mec1 kinases at serine 731, and this regulation is stimulated by DNA damage and telomere shortening. Compromised Rap1 phosphorylation hampers the interaction between Rap1 and its interacting partner Rif1, which thereby disturbs the end protection. As expected, reduction of Rap1-Rif1 association impairs telomere length regulation and increases telomere-telomere recombination. These results indicate that ATM/ATR DNA damage checkpoint signal contributes to telomere protection by strengthening the Rap1-Rif1 interaction at short telomeres, and the checkpoint signal oversees both telomerase recruitment and end capping pathways to maintain telomere homeostasis.