eEF1Bγ is a positive regulator of NF-кB signaling pathway

Function of eEF-1γ in the nucleus in response to insulin in hepatocellular carcinoma cells

Insulin promotes HepG2 cell proliferation by inducing phosphorylation of the pyruvate dehydrogenase E1α (PDHA1) subunit at Ser293, a mechanism distinct from normal liver tissue. This study investigates how phosphorylated PDHA1 drives hepatocellular carcinoma cell proliferation. We identified eukaryotic elongation factor-1γ (eEF-1γ) as a key binding protein interacting with p-PDHA1 in response to insulin, facilitating their nuclear translocation. Silencing eEF-1γ (si-eEF-1γ) significantly reduced p-PDHA1 and PKM2 levels, highlighting eEF-1γ's role in stabilizing these proteins. Additionally, eEF-1γ interacts with ATP-citrate lyase (ACL) and p300 acetyltransferase, and its knockdown decreased histone acetylation at H3K9/14, H3K18, and H3K27, along with RBP4 expression. Chromatin immunoprecipitation PCR (ChIP-PCR) confirmed eEF-1γ association with RBP4 promoter. Functionally, si-eEF-1γ reduced cell proliferation and deceased c-Myc and cyclin D1 protein levels. It also suppressed migration, and altered epithelial-mesenchymal transition (EMT) markers, increasing E-cadherin while reducing ZEB1, snail1, vimentin, and N-cadherin levels. Similarly, RBP4 knockdown with siRNA diminished cell proliferation and migration. In vivo, eEF-1γ knockdown in 4T1 xenografts using siRNA led to reduced tumor mass. These findings highlight eEF-1γ as a crucial driver of insulin-induced tumor progression and suggest its potential as a therapeutic target in hepatocellular carcinoma.

RNF8 induces autophagy and reduces inflammation by promoting AKT degradation via ubiquitination in ulcerative colitis mice

RING finger protein 8 (RNF8) is an E3 ligase that is pivotal for DNA repair. However, the role of RNF8 in ulcerative colitis (UC) remains unclear. The aim of this study is to investigate the effect and the mechanism of RNF8 on UC model induced by trinitrobenzene sulfonic acid (TNBS) in mice. Lentiviruses overexpressing RNF8 were injected into mice after the induction of UC. The histopathological changes in colon tissues were assessed by haematoxylin and eosin staining. The mRNA level of RNF8 was detected by real-time quantitative polymerase chain reaction. The protein levels of RNF8, autophagy-related proteins (LC3 and P62) and AKT/mammalian target of rapamycin (mTOR) signalling-related proteins were measured by Western blot. The pro-inflammatory cytokines (tumour necrosis factor-α and interleukin-1β) were examined by immunohistochemical analysis. Immunoprecipitation was performed to analyse the interaction between RNF8 and AKT1. The TNBS-induced UC mice exhibited colonic damage and inflammation, accompanied by decreased RNF8 expression, impaired autophagy and increased phosphorylation levels of AKT and mTOR in the colon. However, these alterations were reversed by RNF8 overexpression. Furthermore, RNF8 bound to AKT1 and mediated its ubiquitination. Collectively, RNF8 overexpression protects against TNBS-induced UC, which might be due to its enhancement of autophagy by suppressing the AKT/mTOR signalling via AKT1 ubiquitination.

Oxidized glutathione promotes association between eukaryotic translation elongation factor 1Bγ and Ure2p glutathione transferase from Phanerochaete chrysosporium

The eukaryotic translation elongation factor 1Bγ (eEF1Bγ) is an atypical member of the glutathione transferase (GST) superfamily. Contrary to more classical GSTs having a role in toxic compound detoxification, eEF1Bγ is suggested to act as a scaffold protein, anchoring the elongation factor complex EF1B to the endoplasmic reticulum. In this study, we show that eEF1Bγ from the basidiomycete Phanerochaete chrysosporium is fully active as a glutathione transferase in vitro and undergoes conformational changes upon binding of oxidized glutathione. Using real-time analyses of biomolecular interactions, we show that GSSG allows eEF1Bγ to physically interact with other GSTs from the Ure2p class, opening new perspectives for a better understanding of the role of eEF1Bγ in cellular oxidative stress response.

ApoL1 induces kidney inflammation through RIG-I/NF-κB activation

The genetic variations of the apolipoprotein L1 (APOL1) gene are associated with non-diabetic kidney diseases. However, very little is known about the role of ApoL1 in glomerular damage. Here, we aimed to identify the function and mechanism of ApoL1 in glomerular damage. The mice were randomly divided into two groups: one group was intraperitoneally injected with phosphate buffer saline (PBS), while the other group was intraperitoneally injected with recombinant ApoL1 every other day for 3 months. Hematoxylin and eosin (HE) and periodic acid Schiff (PAS) staining were used to demonstrate the effects of ApoL1 on kidney inflammation and injury. Furthermore, quantitative real-time polymerase chain reaction (qRT-PCR) and enzyme-linked immunosorbent assay (ELISA) analyses revealed that ApoL1-treated mice exhibited enhanced expression of various inflammation markers in the kidney and serum compared to the PBS-treated mice. Immunofluorescence staining revealed that ApoL1 accumulated in kidney podocytes. Treatment with ApoL1 dose-dependently increased the expression of inflammation markers and apoptotic markers. The abnormal gene expression associated with ApoL1-mediated podocyte inflammation was evaluated using microarray analysis. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses revealed that the upregulated genes were enriched in the inflammation-related processes, such as the RIG-I/NF-κB signaling pathway. Consistently, the knockdown of RIG-I significantly mitigated the ApoL1-induced upregulation of inflammatory and apoptotic markers in the human podocytes. Additionally, the ApoL1-induced glomerular damage was attenuated in AAV-shRIG-I mice. Therefore, the effects of ApoL1 on glomerular damage may be, at least partially, through inducing abnormal expression of inflammatory molecules, which may have important implications for treatment of kidney diseases.

Non-translational Connections of eEF1B in the Cytoplasm and Nucleus of Cancer Cells

The human translation machinery includes three types of supramolecular complexes involved in elongation of the polypeptide chain: the ribosome, complex of elongation factors eEF1B and multienzyme aminoacyl-tRNA synthetase complex. Of the above, eEF1B is the least investigated assembly. Recently, a number of studies provided some insights into the structure of different eEF1B subunits and changes in their expression in cancer and other diseases. There is increasing agreement that possible disease-related functions of eEF1B are not necessarily related to its role in translation. This mini-review focuses on structural and functional features of the eEF1B complex while paying special attention to possible non-canonical functions of its subunits in cancer cells.

RNF8 negatively regulates NF-kappaB signaling by targeting IkappaB kinase: implications for the regulation of inflammation signaling

Persistent or excess activation of NF-κB leads to cancer, autoimmune and inflammatory diseases. Therefore, activated NF-κB needs to be terminated after induction, which highlights the physiological significance of NF-κB-negative regulators. However, the molecular mechanisms that negatively regulate NF-κB are not well understood. Here, we report that Ring Finger Protein 8 (RNF8), an E3 ubiquitin ligase, inhibits TNFα-mediated NF-κB activation by targeting IκB kinase (IKK). Upon TNFα stimulation, RNF8 binds to the catalytic subunits of IKK complex, resulting in inhibition of IKKα/β phosphorylation and subsequent NF-κB activation. RNF8 targets the IKK complex in a manner independent of its RING domain. We further provide evidence that the silencing of RNF8 results in enhanced TNFα-induced IKK activation, and an increase expression of NF-κB-induced inflammatory cytokine IL-8. Our study identifies a previously unrecognized role for RNF8 in the negative regulation of NF-κB activation by targeting and deactivating the IKK complex.

eEF1Bγ binds the Che-1 and TP53 gene promoters and their transcripts

Background

We have previously shown that the eukaryotic elongation factor subunit 1B gamma (eEF1Bγ) interacts with the RNA polymerase II (pol II) alpha-like subunit “C” (POLR2C), alone or complexed, in the pol II enzyme. Moreover, we demonstrated that eEF1Bγ binds the promoter region and the 3’ UTR mRNA of the vimentin gene. These events contribute to localize the vimentin transcript and consequentially its translation, promoting a proper mitochondrial network.

Methods

With the intent of identifying additional transcripts that complex with the eEF1Bγ protein, we performed a series of ribonucleoprotein immunoprecipitation (RIP) assays using a mitochondria-enriched heavy membrane (HM) fraction.

Results

Among the eEF1Bγ complexed transcripts, we found the mRNA encoding the Che-1/AATF multifunctional protein. As reported by other research groups, we found the tumor suppressor p53 transcript complexed with the eEF1Bγ protein. Here, we show for the first time that eEF1Bγ binds not only Che-1 and p53 transcripts but also their promoters. Remarkably, we demonstrate that both the Che-1 transcript and its translated product localize also to the mitochondria and that eEF1Bγ depletion strongly perturbs the mitochondrial network and the correct localization of Che-1. In a doxorubicin (Dox)-induced DNA damage assay we show that eEF1Bγ depletion significantly decreases p53 protein accumulation and slightly impacts on Che-1 accumulation. Importantly, Che-1 and p53 proteins are components of the DNA damage response machinery that maintains genome integrity and prevents tumorigenesis.

Conclusions

Our data support the notion that eEF1Bγ, besides its canonical role in translation, is an RNA-binding protein and a key player in cellular stress responses. We suggest for eEF1Bγ a role as primordial transcription/translation factor that links fundamental steps from transcription control to local translation.

Electronic supplementary material

The online version of this article (doi:10.1186/s13046-016-0424-x) contains supplementary material, which is available to authorized users.

Human rhinovirus-induced inflammatory responses are inhibited by phosphatidylserine containing liposomes

Human rhinovirus (HRV) infections are major contributors to the healthcare burden associated with acute exacerbations of chronic airway disease, such as chronic obstructive pulmonary disease and asthma. Cellular responses to HRV are mediated through pattern recognition receptors that may in part signal from membrane microdomains. We previously found Toll-like receptor signaling is reduced, by targeting membrane microdomains with a specific liposomal phosphatidylserine species, 1-stearoyl-2-arachidonoyl-sn-glycero-3-phospho-L-serine (SAPS). Here we explored the ability of this approach to target a clinically important pathogen. We determined the biochemical and biophysical properties and stability of SAPS liposomes and studied their ability to modulate rhinovirus-induced inflammation, measured by cytokine production, and rhinovirus replication in both immortalized and normal primary bronchial epithelial cells. SAPS liposomes rapidly partitioned throughout the plasma membrane and internal cellular membranes of epithelial cells. Uptake of liposomes did not cause cell death, but was associated with markedly reduced inflammatory responses to rhinovirus, at the expense of only modest non-significant increases in viral replication, and without impairment of interferon receptor signaling. Thus using liposomes of phosphatidylserine to target membrane microdomains is a feasible mechanism for modulating rhinovirus-induced signaling, and potentially a prototypic new therapy for viral-mediated inflammation.

Independent overexpression of the subunits of translation elongation factor complex eEF1H in human lung cancer

BACKGROUND

The constituents of stable multiprotein complexes are known to dissociate from the complex to play independent regulatory roles. The components of translation elongation complex eEF1H (eEF1A, eEF1Bα, eEF1Bβ, eEF1Bγ) were found overexpressed in different cancers. To gain the knowledge about novel cancer-related translational mechanisms we intended to reveal whether eEF1H exists as a single unit or independent subunits in different human cancers.

METHODS

The changes in the expression level of every subunit of eEF1H in the human non-small-cell lung cancer tissues were examined. The localization of eEF1H subunits was assessed by immunohistochemistry methods, subcellular fractionation and confocal microscopy. The possibility of the interaction between the subunits was estimated by co-immunoprecipitation.

RESULTS

The level of eEF1Bβ expression was increased more than two-fold in 36%, eEF1Bγ in 28%, eEF1A in 20% and eEF1Bα in 8% of tumor specimens. The cancer-induced alterations in the subunits level were found to be uncoordinated, therefore the increase in the level of at least one subunit of eEF1H was observed in 52% of samples. Nuclear localization of eEF1Bβ in the cancer rather than distal normal looking tissues was found. In cancer tissue, eEF1A and eEF1Bα were not found in nuclei while all four subunits of eEF1H demonstrated both cytoplasmic and nuclear appearance in the lung carcinoma cell line A549. Unexpectedly, in the A549 nuclear fraction eEF1A lost the ability to interact with the eEF1B complex.

CONCLUSIONS

The results suggest independent functioning of some fraction of the eEF1H subunits in human tumors. The absence of eEF1A and eEF1B interplay in nuclei of A549 cells is a first evidence for non-translational role of nuclear-localized subunits of eEF1B. We conclude the appearance of the individual eEF1B subunits in tumors is a more general phenomenon than appreciated before and thus is a novel signal of cancer-related changes in translation apparatus.