P21 activated kinase 4 binds translation elongation factor eEF1A1 to promote gastric cancer cell migration and invasion

UCHL3 promotes hepatocellular carcinoma progression by stabilizing EEF1A1 through deubiquitination

BACKGROUND

Hepatocellular carcinoma (HCC) ranks as the second leading cause of global cancer-related deaths and is characterized by a poor prognosis. Eukaryotic translation elongation factor 1 alpha 1 (EEF1A1) have been proved to play important roles in various human cancers, whereas the deubiquitination of EEF1A1 was poorly understood.

METHODS

The binding and regulatory relationship between Ubiquitin carboxyl-terminal hydrolase L3 (UCHL3) and EEF1A1 was validated using clinical tissue samples, reverse transcription quantitative real-time fluorescence quantitative PCR (RT-qPCR), Western blotting, co-immunoprecipitation, and immunofluorescence, as well as ubiquitin detection and cyclohexamide tracking experiments. Finally, the impact of the UCHL3/EEF1A1 axis on HCC malignant behavior was analyzed through functional experiments and nude mouse models.

RESULTS

UCHL3 was found to have a high expression level in HCC tissues. Tissue samples from 60 HCC patients were used to evaluate the correlation between UCHL3 and EEF1A1. UCHL3 binds to EEF1A1 through the lysine site, which reduces the ubiquitination level of EEF1A1. Functional experiments and nude mouse models have demonstrated that the UCHL3/EEF1A1 axis promotes the migration, stemness, and drug resistance of HCC cells. Reducing the expression of EEF1A1 can reverse the effect of UCHL3 on the malignant behavior of HCC cells.

CONCLUSION

Our findings revealed that UCHL3 binds and stabilizes EEF1A1 through deubiquitination. UCHL3 and EEF1A1 formed a functional axis in facilitating the malignant progression of HCC, proving new insights for the anti-tumor targeted therapy for HCC.

The eEF1A protein in cancer: Clinical significance, oncogenic mechanisms, and targeted therapeutic strategies

Eukaryotic elongation factor 1A (eEF1A) is among the most abundant proteins in eukaryotic cells. Evolutionarily conserved across species, eEF1A is in charge of translation elongation for protein biosynthesis as well as a plethora of non-translational moonlighting functions for cellular homeostasis. In malignant cells, however, eEF1A becomes a pleiotropic driver of cancer progression via a broad diversity of pathways, which are not limited to hyperactive translational output. In the past decades, mounting studies have demonstrated the causal link between eEF1A and carcinogenesis, gaining deeper insights into its multifaceted mechanisms and corroborating its value as a prognostic marker in various cancers. On the other hand, an increasing number of natural and synthetic compounds were discovered as anticancer eEF1A-targeting inhibitors. Among them, plitidepsin was approved for the treatment of multiple myeloma whereas metarrestin was currently under clinical development. Despite significant achievements in these two interrelated fields, hitherto there lacks a systematic examination of the eEF1A protein in the context of cancer research. Therefore, the present work aims to delineate its clinical implications, molecular oncogenic mechanisms, and targeted therapeutic strategies as reflected in the ever expanding body of literature, so as to deepen mechanistic understanding of eEF1A-involved tumorigenesis and inspire the development of eEF1A-targeted chemotherapeutics and biologics.

Translational regulation of cell invasion through extracellular matrix-an emerging role for ribosomes

Many developmental and physiological processes require cells to invade and migrate through extracellular matrix barriers. This specialized cellular behavior is also misregulated in many diseases, such as immune disorders and cancer. Cell invasive activity is driven by pro-invasive transcriptional networks that activate the expression of genes encoding numerous different proteins that expand and regulate the cytoskeleton, endomembrane system, cell adhesion, signaling pathways, and metabolic networks. While detailed mechanistic studies have uncovered crucial insights into pro-invasive transcriptional networks and the distinct cell biological attributes of invasive cells, less is known about how invasive cells modulate mRNA translation to meet the robust, dynamic, and unique protein production needs of cell invasion. In this review we outline known modes of translation regulation promoting cell invasion and focus on recent studies revealing elegant mechanisms that expand ribosome biogenesis within invasive cells to meet the increased protein production requirements to invade and migrate through extracellular matrix barriers.

TOPK promotes the growth of esophageal cancer in vitro and in vivo by enhancing YB1/eEF1A1 signal pathway

T-LAK-originated protein kinase (TOPK), a dual specificity serine/threonine kinase, is up-regulated and related to poor prognosis in many types of cancers. Y-box binding protein 1 (YB1) is a DNA/RNA binding protein and serves important roles in multiple cellular processes. Here, we reported that TOPK and YB1 were both highly expressed in esophageal cancer (EC) and correlated with poor prognosis. TOPK knockout effectively suppressed EC cell proliferation and these effects were reversible by rescuing YB1 expression. Notably, TOPK phosphorylated YB1 at Thr 89 (T89) and Ser 209 (S209) amino acid residues, then the phosphorylated YB1 bound with the promoter of the eukaryotic translation elongation factor 1 alpha 1 (eEF1A1) to activate its transcription. Consequently, the AKT/mTOR signal pathway was activated by up-regulated eEF1A1 protein. Importantly, TOPK inhibitor HI-TOPK-032 suppressed the EC cell proliferation and tumor growth by TOPK/YB1/eEF1A1 signal pathway in vitro and in vivo. Taken together, our study reveals that TOPK and YB1 are essential for the growth of EC, and TOPK inhibitors may be applied to retard cell proliferation in EC. This study highlights the promising therapeutic potential of TOPK as a target for treatment of EC.

Dynamic regulation of eEF1A1 acetylation affects colorectal carcinogenesis

The dysregulation of the translation elongation factor families which are responsible for reprogramming of mRNA translation has been shown to contribute to tumor progression. Here, we report that the acetylation of eukaryotic Elongation Factor 1 Alpha 1 (eEF1A1/EF1A1) is required for genotoxic stress response and maintaining the malignancy of colorectal cancer (CRC) cells. The evolutionarily conserved site K439 is identified as the key acetylation site. Tissue expression analysis demonstrates that the acetylation level of eEF1A1 K439 is higher than paired normal tissues. Most importantly, hyperacetylation of eEF1A1 at K439 negatively correlates with CRC patient survival. Mechanistically, CBP and SIRT1 are the major acetyltransferase and deacetylase of eEF1A1. Hyperacetylation of eEF1A1 at K439 shows a significant tumor-promoting effect by increasing the capacity of proliferation, migration, and invasion of CRC cells. Our findings identify the altered post-translational modification at the translation machines as a critical factor in stress response and susceptibility to colorectal carcinogenesis.

Identification of COVID-19-Specific Immune Markers Using a Machine Learning Method

Notably, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has a tight relationship with the immune system. Human resistance to COVID-19 infection comprises two stages. The first stage is immune defense, while the second stage is extensive inflammation. This process is further divided into innate and adaptive immunity during the immune defense phase. These two stages involve various immune cells, including CD4⁺ T cells, CD8⁺ T cells, monocytes, dendritic cells, B cells, and natural killer cells. Various immune cells are involved and make up the complex and unique immune system response to COVID-19, providing characteristics that set it apart from other respiratory infectious diseases. In the present study, we identified cell markers for differentiating COVID-19 from common inflammatory responses, non-COVID-19 severe respiratory diseases, and healthy populations based on single-cell profiling of the gene expression of six immune cell types by using Boruta and mRMR feature selection methods. Some features such as IFI44L in B cells, S100A8 in monocytes, and NCR2 in natural killer cells are involved in the innate immune response of COVID-19. Other features such as ZFP36L2 in CD4⁺ T cells can regulate the inflammatory process of COVID-19. Subsequently, the IFS method was used to determine the best feature subsets and classifiers in the six immune cell types for two classification algorithms. Furthermore, we established the quantitative rules used to distinguish the disease status. The results of this study can provide theoretical support for a more in-depth investigation of COVID-19 pathogenesis and intervention strategies.

Tissue-Based Proteomic Profiling in Patients with Hyperplasia and Endometrial Cancer

Uterine cancers are among the most prevalent gynecological malignancies, and endometrial cancer (EC) is the most common in this group. This study used tissue-based proteomic profiling analysis in patients with endometrial cancer and hyperplasia, and control patients. Conventional 2D gel electrophoresis, followed by a mass spectrometry approach with bioinformatics, including a network pathway analysis pipeline, was used to identify differentially expressed proteins and associated metabolic pathways between the study groups. Thirty-six patients (twelve with endometrial cancer, twelve with hyperplasia, and twelve controls) were enrolled in this study. The mean age of the participants was 46–75 years. Eighty-seven proteins were significantly differentially expressed between the study groups, of which fifty-three were significantly differentially regulated (twenty-eight upregulated and twenty-five downregulated) in the tissue samples of EC patients compared to the control (Ctrl). Furthermore, 26 proteins were significantly dysregulated (8 upregulated and 18 downregulated) in tissue samples of hyperplasia (HY) patients compared to Ctrl. Thirty-two proteins (nineteen upregulated and thirteen downregulated) including desmin, peptidyl prolyl cis-trans isomerase A, and zinc finger protein 844 were downregulated in the EC group compared to the HY group. Additionally, fructose bisphosphate aldolase A, alpha enolase, and keratin type 1 cytoskeletal 10 were upregulated in the EC group compared to those in the HY group. The proteins identified in this study were known to regulate cellular processes (36%), followed by biological regulation (16%). Ingenuity pathway analysis found that proteins that are differentially expressed between EC and HY are linked to AKT, ACTA2, and other signaling pathways. The panels of protein markers identified in this study could be used as potential biomarkers for distinguishing between EC and HY and early diagnosis and progression of EC from hyperplasia and normal patients.

The significance of PAK4 in signaling and clinicopathology: A review

P21-activated protein kinases (PAKs) are thought to be at the center of tumor signaling pathways. As a representative member of the group II PAK family, P21-activated protein kinase 4 (PAK4) plays an important role in the development of tumors, with several biological functions such as participating in oncogenic transformation, promoting cell division, resisting aging and apoptosis, regulating cytoskeleton and adhesion, as well as suppressing antitumor immune responses. PAK4 is also crucial in biological processes, including the occurrence, proliferation, survival, migration, invasion, drug resistance, and immune escape of tumor cells. It is closely related to poor prognosis and tumor-related pathological indicators, which have significant clinical and pathological significance. Therefore, this article offers a review of the structure, activation, and biological functions of PAK4 and its clinical and pathological importance. This overview should be of assistance for future research on PAK4 and tumors and provide new ideas for tumor treatment and prognostic evaluation of patients.

eEF1A1 promotes colorectal cancer progression and predicts poor prognosis of patients

Colorectal cancer (CRC) is a major leading cause of cancer mortality worldwide in which dysregulated protein synthesis plays an etiologic role. The eukaryotic elongation factor 1 A1 (eEF1A1) exerts significant effects on protein synthesis by contributing to peptide chain extension. Whereas its role in CRC remains to be investigated. In this study, we found that the mRNA and protein levels of eEF1A1 were significantly upregulated in CRC cell lines and tissues. Elevated expression of eEF1A1 was correlated with shorter overall survival in 94 CRC patients. The inhibition of proliferation and cell cycle block were observed in CRC cells after eEF1A1 downregulation. Mechanistically, weighted gene correlation network analysis and further Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis suggested that mitogen-activated protein kinases (MAPKs) signaling pathways were significantly enriched in high-eEF1A1 expression group, and the levels of phosphorylated p38/JNK/ERK MAPK were dramatically decreased after eEF1A1 downregulation. Overexpression of eEF1A1 in CRC correlated with a poor prognosis. Collectively, this study determined the oncogenic role of eEF1A1 in CRC proliferation and tumorigenesis. eEF1A1 might be a promising therapeutic target and prognostic biomarker in CRC.

A novel 3'tRNA-derived fragment tRF-Val promotes proliferation and inhibits apoptosis by targeting EEF1A1 in gastric cancer

At present, it is commonly believed that tRFs and tiRNAs are formed by the specific and selective shear of tRNAs under certain pressure stimulation, rather than by random degradation of tRNA. tRFs and tiRNAs have been reported to contribute to the biological process of a variety of human cancers. However, the evidence for the mechanisms of tRFs and tiRNAs in the occurrence and development of gastric cancer (GC) is still insufficient. Here, we aimed to explore the carcinogenic roles of tRFs and tiRNAs in GC with RNA-sequencing technique, and found a novel 3'tRNA-derived fragment tRF-Val was significantly upregulated in GC tissues and cell lines. tRF-Val expression was positively correlated with tumor size and the depth of tumor invasion in GC tissues. Functionally, tRF-Val promoted proliferation and invasion, and inhibited apoptosis in GC cells. Mechanistically, tRF-Val directly bound to the chaperone molecule EEF1A1, mediated its transport into the nucleus and promoted its interaction with MDM2 (a specific p53 E3 ubiquitin ligase), thus inhibiting the downstream molecular pathway of p53 and promoting GC progression. These findings provided a new potential therapeutic target for GC and a new explanation for the occurrence of GC.

OUP accepted manuscript

Background

The glioblastoma-amplified sequence (GBAS) is a newly identified gene that is amplified in approximately 40% of glioblastomas. This article probes into the expression, prognostic significance, and possible pathways of GBAS in ovarian cancer (OC).

Method

Immunohistochemical methods were used to evaluate the expression level of GBAS in OC and its relationship with clinicopathological characteristics and prognosis. Glioblastoma-amplified sequence shRNA was designed to transfect into OC cell lines to silence GBAS expression, then detect the proliferation, apoptosis, and migration ability of the cell. Furthermore, an in vitro tumor formation experiment in mice was constructed to prove the effect of GBAS expression on the growth of OC in vivo. To further study the regulation mechanism of GBAS, we performed co-immunoprecipitation (Co-IP) and shotgun LC-MS mass spectrometry identification.

Results

Immunohistochemistry indicated that GBAS was markedly overexpressed in OC compared with normal ovarian tissue and was associated with lymph node metastasis. Inhibition of GBAS expression can significantly reduce OC cell proliferation, colony formation, promote cell apoptosis, and reduce the ability of cell migration and invasion. In vivo tumor formation experiments showed that the size and weight of tumors in mice after GBAS expression knockdown was significantly smaller. Glioblastoma-amplified sequence may be combined with elongation factor 1 alpha 1 (eEF1A1) to achieve its regulation in OC. Bioinformatics analysis data indicate that GBAS may be a key regulator of mitochondria-associated pathways, therefore controlling cancer progression. MicroRNA-27b, MicroRNA-23a, and MicroRNA-590 may directly targeting GBAS affects the biological behavior of OC cells.

Conclusion

The glioblastoma-amplified sequence may regulate the proliferation and metastasis of OC cells by combining with eEF1A1.

Gastric Cancer: Identification of microRNAs Inhibiting Druggable Targets and Mediating Efficacy in Preclinical In Vivo Models

In addition to chemotherapy, targeted therapies have been approved for treatment of locally advanced and metastatic gastric cancer. The therapeutic benefit is significant but more durable responses and improvement of survival should be achieved. Therefore, the identification of new targets and new approaches for clinical treatment are of paramount importance. In this review, we searched the literature for down-regulated microRNAs which interfere with druggable targets and exhibit efficacy in preclinical in vivo efficacy models. As druggable targets, we selected transmembrane receptors, secreted factors and enzymes. We identified 38 microRNAs corresponding to the criteria as outlined. A total of 13 miRs target transmembrane receptors, nine inhibit secreted proteins and 16 attenuate enzymes. These microRNAs are targets for reconstitution therapy of gastric cancer. Further target validation experiments are mandatory for all of the identified microRNAs.

Expression of Long Non-coding RNA RGD1566344 in the Brain Cortex of Male Mice After Focal Cerebral Ischemia-Reperfusion and the Neuroprotective Effect of a Non-coding RNA RGD1566344 Inhibitor

Ischemic stroke (IS) remains a major cause of disability and death. The changes in long non-coding RNA (lncRNA) RGD1566344 expression in the mouse cerebral cortex, including the infarct and penumbra regions after IS, are not clear. Less is known about the impact and underlying mechanisms of RGD1566344 in IS. In this study, we found that RGD1566344 levels were elevated in the ischemic infarct and penumbra regions 12 h after middle cerebral artery occlusion/reperfusion (MCAO/R) in male mice and in PC12 cells with oxygen glucose deprivation/reperfusion (OGD/R). The inhibition of RGD1566344 by small interference RNA (siRNA) significantly alleviated apoptosis in OGD/R PC12 cells. In cell transfection, quantitative real-time PCR, and Western blot experiments, we demonstrated the possible interaction of non-POU domain-containing octamer-binding protein (NONO) with RGD1566344. The NONO level in OGD/R PC12 cells was obviously increased after inhibiting the RGD1566344 treatment; subsequently the protein kinase B (AKT)/mammalian target of rapamycin (mTOR) signaling pathway was activated. This demonstrated the effect of the RGD1566344-NONO-AKT axis on neural protection after IS. These results revealed a new molecular mechanism of lncRNA RGD1566344 inhibitors through targeting NONO/AKT/mTOR signaling to protect against ischemic neuronal injury, providing strong evidence for the development of promising therapeutic strategies against IS.

Unmasking Intra-tumoral Heterogeneity and Clonal Evolution in NF1-MPNST

Sarcomas are highly aggressive cancers that have a high propensity for metastasis, fail to respond to conventional therapies, and carry a poor 5-year survival rate. This is particularly true for patients with neurofibromatosis type 1 (NF1), in which 8%–13% of affected individuals will develop a malignant peripheral nerve sheath tumor (MPNST). Despite continued research, no effective therapies have emerged from recent clinical trials based on preclinical work. One explanation for these failures could be the lack of attention to intra-tumoral heterogeneity. Prior studies have relied on a single sample from these tumors, which may not be representative of all subclones present within the tumor. In the current study, samples were taken from three distinct areas within a single tumor from a patient with an NF1-MPNST. Whole exome sequencing, RNA sequencing, and copy number analysis were performed on each sample. A blood sample was obtained as a germline DNA control. Distinct mutational signatures were identified in different areas of the tumor as well as significant differences in gene expression among the spatially distinct areas, leading to an understanding of the clonal evolution within this patient. These data suggest that multi-regional sampling may be important for driver gene identification and biomarker development in the future.

Long noncoding RNA LINC00657 enhances the malignancy of pancreatic ductal adenocarcinoma by acting as a competing endogenous RNA on microRNA-433 to increase PAK4 expression

A long noncoding RNAs (lncRNA) called LINC00657 is dysregulated and contributes to tumor progression in a number of human cancer types. However, there is limited information on the expression profile and functions of LINC00657 in pancreatic ductal adenocarcinoma (PDAC). The expression profile of LINC00657 in PDAC was estimated by reverse-transcription quantitative polymerase chain reaction (RT-qPCR). The effects of LINC00657 upregulation on PDAC cell proliferation, apoptosis, migration, and invasion in vitro and tumor growth in vivo were explored using CCK-8, flow cytometry, Transwell migration and invasion assays, and a xenograft tumor formation experiment, respectively. The results revealed that LINC00657 was evidently upregulated in the PDAC tumors and cell lines. High LINC00657 expression significantly correlated with the pathological T stage, lymph node metastasis, and shorter overall survival. Functional analysis demonstrated that LINC00657 knockdown inhibited the proliferation, migration, and invasion while promoted the apoptosis of PDAC cells. In addition, LINC00657 knockdown markedly suppressed tumor growth of these cells in vivo. In terms of the mechanism, LINC00657 could directly interact with microRNA-433 (miR-433) and effectively worked as an miR-433 sponge, thus decreasing the competitive binding of miR-433 to PAK4 mRNA and ultimately increasing PAK4 expression. The actions of LINC00657 knockdown on malignant phenotype of PDAC cells were strongly attenuated by miR-433 inhibition and PAK4 restoration. These results indicate that LINC00657 promotes PDAC progression by increasing the output of the miR-433-PAK4 regulatory loop, thus highlighting the importance of the LINC00657-miR-433-PAK4 network in PDAC pathogenesis.

Expression of EEF1A1 Is Associated with Prognosis of Patients with Colon Adenocarcinoma

Background: The prognostic role of the translational factor, elongation factor-1 alpha 1 (EEF1A1), in colon cancer is unclear. Objectives: The present study aimed to investigate the expression of EEF1A in tissues obtained from patients with stage II and III colon cancer and analyze its association with patient prognosis. Methods: A total of 281 patients with colon cancer who underwent curative resection were analyzed according to EEF1A1 expression. Results: The five-year overall survival in the high-EEF1A1 group was 87.7%, whereas it was 65.6% in the low-EEF1A1 expression group (hazard ratio (HR) 2.47, 95% confidence interval (CI) 1.38–4.44, p = 0.002). The five-year disease-free survival of patients with high EEF1A1 expression was 82.5%, which was longer than the rate of 55.4% observed for patients with low EEF1A1 expression (HR 2.94, 95% CI 1.72–5.04, p < 0.001). Univariate Cox regression analysis indicated that age, preoperative carcinoembryonic antigen level, adjuvant treatment, total number of metastatic lymph nodes, and EEF1A1 expression level were significant prognostic factors for death. In multivariate analysis, expression of EEF1A1 was an independent prognostic factor associated with death (HR 3.01, 95% CI 1.636–5.543, p < 0.001). EEF1A1 expression was also an independent prognostic factor for disease-free survival in multivariate analysis (HR 2.54, 95% CI 1.459–4.434, p < 0.001). Conclusions: Our study demonstrated that high expression of EEF1A1 has a favorable prognostic effect on patients with colon adenocarcinoma.

Translation elongation factor eEF1Bα is identified as a novel prognostic marker of gastric cancer

Gastric cancer (GC) is a common cancer in humans. Although overexpression of eukaryotic translation elongation factor eEF1Bα is associated with cancer onset and progression, little is known about its expression in GC and its prognostic significance. Here we used immunohistochemistry to analyze eEF1Bα expression in the following tissue types: GC, normal gastric, chronic gastritis, intestinal metaplasia, and intraepithelial neoplasia. These data were correlated with patients' clinical information. eEF1Bα was expressed at levels approximately three times higher in GC tissues compared with normal gastric tissues. High expression of eEF1Bα was significantly associated with histological type, TNM stage, tumor size, and distant metastases. GC patients with high eEF1Bα expression experienced significantly shorter overall survival. Bioinformatics analysis indicated that eEF1Bα may be associated with protein synthesis, energy metabolism, cell cycle, and the p53 signaling pathway. We identified the products of RPL10A and RPS13 as critical components of a network comprising eEF1Bα. We concluded that high eEF1Bα expression is associated with poor overall survival and may serve as an independent prognostic factor of GC. Further, we proposed that eEF1Bα likely mediates the development of GC through the cell cycle and p53 signaling pathway. Together, our findings suggest that eEF1Bα could be an effective prognostic biomarker for GC.

[Eukaryotic translation elongation factor 1A1 positively regulates NOB1 expression to promote invasion and metastasis of hepatocellular carcinoma cells in vitro]

OBJECTIVE

To explore the role of eukaryotic translation elongation factor 1A1 (eEF1A1) in regulating the invasion and metastasis of hepatocellular carcinoma (HCC) cells and the possible mechanism.

METHODS

qRT-PCR and Western blotting were used to detect the mRNA and protein expression of eEF1A1 and NOB1 in different HCC cell lines and normal liver cells. The invasion and migration abilities of HCC cells with eEF1A1 knockdown or overexpression were examined using Transwell chamber assay and RTCA assay, and the changes in NOB1 mRNA and protein expressions in the cells were detected. The effects of increasing NOB1 expression in HCCLM3-sheEF1A1 cells and decreasing NOB1 expression in eEF1A1-overexpressing MHCC97h cells on eEF1A1 expression and cell invasion and migration abilities were analyzed using Western blotting, Transwell chamber assay and RTCA assay.

RESULTS

The expressions of eEF1A1 and NOB1 were significantly increased in positive correlation in HCC cells as compared with normal hepatocytes. Knockdown of eEF1A1 significantly decreased the invasion and migration of HCC cells and reduced the mRNA and protein expression of NOB1 (P &lt; 0.01). Overexpression of eEF1A1 significantly enhanced invasion and migration of HCC cells and increased NOB1 mRNA and protein expressions (P &lt; 0.01). Increasing NOB1 expression in HCCLM3-sheEF1A1 cells led to the restoration of NOB1 expression and cell invasion and migration abilities (P &lt; 0.01), whereas decreasing NOB1 in MHCC97h-eEF1A1 cells resulted in inhibition of NOB1 expression and cell invasion and migration (P &lt; 0.01).

CONCLUSIONS

eEF1A1 positively regulates the expression of NOB1 to promote the invasion and migration of HCC cells in vitro.

P21-activated kinase 4 in pancreatic acinar cells is activated by numerous gastrointestinal hormones/neurotransmitters and growth factors by novel signaling, and its activation stimulates secretory/growth cascades

p21-activated kinases (PAKs) are highly conserved serine/threonine protein kinases, which are divided into two groups: group-I (PAKs1-3) and group-II (PAKs4-6). In various tissues, Group-II PAKs play important roles in cytoskeletal dynamics and cell growth as well as neoplastic development/progression. However, little is known about Group-II PAK's role in a number of physiological events, including their ability to be activated by gastrointestinal (GI) hormones/neurotransmitters/growth factors (GFs). We used rat pancreatic acini to explore the ability of GI hormones/neurotransmitters/GFs to activate Group-II-PAKs and the signaling cascades involved. Only PAK4 was detected in pancreatic acini. PAK4 was activated by endothelin, secretagogues-stimulating phospholipase C (bombesin, CCK-8, and carbachol), by pancreatic GFs (insulin, insulin-like growth factor 1, hepatocyte growth factor, epidermal growth factor, basic fibroblast growth factor, and platelet-derived growth factor), and by postreceptor stimulants (12-O-tetradecanoylphobol-13-acetate and A23187 ). CCK-8 activation of PAK4 required both high- and low-affinity CCK1-receptor state activation. It was reduced by PKC-, Src-, p44/42-, or p38-inhibition but not with phosphatidylinositol 3-kinase-inhibitors and only minimally by thapsigargin. A protein kinase D (PKD)-inhibitor completely inhibited CCK-8-stimulated PKD-activation; however, stimulated PAK4 phosphorylation was only inhibited by 60%, demonstrating that it is both PKD-dependent and PKD-independent. PF-3758309 and LCH-7749944, inhibitors of PAK4, decreased CCK-8-stimulated PAK4 activation but not PAK2 activation. Each inhibited ERK1/2 activation and amylase release induced by CCK-8 or bombesin. These results show that PAK4 has an important role in modulating signal cascades activated by a number of GI hormones/neurotransmitters/GFs that have been shown to mediate both physiological/pathological responses in acinar cells. Therefore, in addition to the extensive studies on PAK4 in pancreatic cancer, PAK4 should also be considered an important signaling molecule for pancreatic acinar physiological responses and, in the future, should be investigated for a possible role in pancreatic acinar pathophysiological responses, such as in pancreatitis. NEW & NOTEWORTHY This study demonstrates that the only Group-II p21-activated kinase (PAK) in rat pancreatic acinar cells is PAK4, and thus differs from islets/pancreatic cancer. Both gastrointestinal hormones/neurotransmitters stimulating PLC and pancreatic growth factors activate PAK4. With cholecystokinin (CCK), activation is PKC-dependent/-independent, requires both CCK1-R affinity states, Src, p42/44, and p38 activation. PAK4 activation is required for CCK-mediated p42/44 activation/amylase release. These results show PAK4 plays an important role in mediating CCK physiological signal cascades and suggest it may be a target in pancreatic acinar diseases besides cancer.

eEF1A1 Overexpression Enhances Tumor Progression and Indicates Poor Prognosis in Hepatocellular Carcinoma

Liver is a major contributor of protein production physiologically. The aberrant state of protein synthesis leads to tumor progression. Eukaryotic elongation factor 1 alpha 1 (eEF1A1) is a major member of the eukaryotic elongation factor family that regulates protein synthesis. Although eEF1A1 plays an essential role in controlling the cell fate, its clinical significance in tumor development and progression has not been reported. Here, we aimed to uncover the expression and prognostic significance of eEF1A1 in hepatocellular carcinoma (HCC). Our data indicated that eEF1A1 expression was elevated in HCC cell lines and clinical samples at both the mRNA and protein levels. Immunohistochemistry revealed that eEF1A1 expression was upregulated in HCC samples compared with corresponding non-tumorous tissues. In 50 HCC cases with portal vein embolus, higher eEF1A1 immunoreactivity was detected in tumor metastases compared with the primary lesions. Kaplan–Meier analysis indicated that increased eEF1A1 expression was closely associated with unfavorable post-surgical overall and disease-free survival in 453 HCC patients. Moreover, multivariate analysis indicated eEF1A1 as an independent predictor for overall and disease-free survival. Collectively, our study suggests eEF1A1 as a novel prognostic biomarker and potential therapeutic target for HCC patients.

Identification of the PAK4 interactome reveals PAK4 phosphorylation of N-WASP and promotion of Arp2/3-dependent actin polymerization

p21-activated kinase 4 (PAK4) regulates cell proliferation, apoptosis, cell motility and F-actin remodeling, but the PAK4 interactome has not been systematically analyzed. Here, we comprehensively characterized the human PAK4 interactome by iTRAQ quantitative mass spectrometry of PAK4-immunoprecipitations. Consistent with its multiple reported functions, the PAK4 interactome was enriched in diverse protein networks, including the 14-3-3, proteasome, replication fork, CCT and Arp2/3 complexes. Because PAK4 co-immunoprecipitated most subunits of the Arp2/3 complex, we hypothesized that PAK4 may play a role in Arp2/3 dependent actin regulation. Indeed, we found that PAK4 interacts with and phosphorylates the nucleation promoting factor N-WASP at Ser484/Ser485 and promotes Arp2/3-dependent actin polymerization in vitro. Also, PAK4 ablation in vivo reduced N-WASP Ser484/Ser485 phosphorylation and altered the cellular balance between G- and F-actin as well as the actin organization. By presenting the PAK4 interactome, we here provide a powerful resource for further investigations and as proof of principle, we also indicate a novel mechanism by which PAK4 regulates actin cytoskeleton remodeling.