α-Actinin 4 potentiates nuclear factor κ-light-chain-enhancer of activated B-cell (NF-κB) activity in podocytes independent of its cytoplasmic actin binding function

Proteomic profiling of laser capture microdissection kidneys from diabetic nephropathy patients

Diabetic nephropathy (DN) remains the primary cause of end-stage renal disease (ESRD), warranting equal attention and separate analysis of glomerular, tubular, and interstitial lesions in its diagnosis and intervention. This study aims to identify the specific proteomics characteristics of DN, and assess changes in the biological processes associated with DN. 5 patients with DN and 5 healthy kidney transplant donor control individuals were selected for analysis. The proteomic characteristics of glomeruli, renal tubules, and renal interstitial tissue obtained through laser capture microscopy (LCM) were studied using high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). Significantly, the expression of multiple heat shock proteins (HSPs), tubulins, and heterogeneous nuclear ribonucleoproteins (hnRNPs) in glomeruli and tubules was significantly reduced. Differentially expressed proteins (DEPs) in the glomerulus showed significant enrichment in pathways related to cell junctions and cell movement, including the regulation of actin cytoskeleton and tight junction. DEPs in renal tubules were significantly enriched in glucose metabolism-related pathways, such as glucose metabolism, glycolysis/gluconeogenesis, and the citric acid cycle. Moreover, the glycolysis/gluconeogenesis pathway was a co-enrichment pathway in both DN glomeruli and tubules. Notably, ACTB emerged as the most crucial protein in the protein-protein interaction (PPI) analysis of DEPs in both glomeruli and renal tubules. In this study, we delve into the unique proteomic characteristics of each sub-region of renal tissue. This enhances our understanding of the potential pathophysiological changes in DN, particularly the potential involvement of glycolysis metabolic disorder, glomerular cytoskeleton and cell junctions. These insights are crucial for further research into the identification of disease biomarkers and the pathogenesis of DN.

GDF-15 alleviates diabetic nephropathy via inhibiting NEDD4L-mediated IKK/NF-κB signalling pathways

Podocyte inflammatory injury has been indicated to play a pivotal role in the occurrence and development of diabetic nephropathy (DN). However, the pathogenesis of inflammation remains unclear. Recent researches have shown that GDF-15, a member of the transforming growth factor-β superfamily, were elevated under pathological conditions, such as myocardial ischemia, cancer, as well as inflammation. Here, we demonstrated that GDF-15 could alleviate podocyte inflammatory injury by modulating the NF-κB pathway. GDF-15 and other pro-inflammatory factors, such as TNF-α, IL-1β, and IL-6 were upregulated in the serum of HFD/STZ rat models. GDF-15 was also elevated in diabetic glomeruli and hyperglycemic stimuli treated-podocytes. The silence of GDF-15 in HG-stimulated podocytes further augmented inflammation and podocyte injury, while overexpression of GDF-15 significantly reduced the inflammatory response in podocytes. Mechanistically, we demonstrated that GDF-15 could inhibit the nuclear translocation of NF-κB through IKK and IκBα by interaction with ubiquitin ligase NEDD4L. Taken together, our data suggested a protective mechanism of elevated GDF-15 in DN through obstruction of ubiquitin degradation of IKK by inhibiting NEDD4L expression, thus decreasing the activation of NF-κB and relieving the inflammation. GDF-15 could serve as a potential therapeutic target for DN.

Protein tyrosine phosphatase 1B is a regulator of alpha-actinin4 in the glomerular podocyte

Glomerular podocytes are instrumental for the barrier function of the kidney, and podocyte injury contributes to proteinuria and the deterioration of renal function. Protein tyrosine phosphatase 1B (PTP1B) is an established metabolic regulator, and the inactivation of this phosphatase mitigates podocyte injury. However, there is a paucity of data regarding the substrates that mediate PTP1B actions in podocytes. This study aims to uncover novel substrates of PTP1B in podocytes and validate a leading candidate. To this end, using substrate-trapping and mass spectroscopy, we identified putative substrates of this phosphatase and investigated the actin cross-linking cytoskeletal protein alpha-actinin4. PTP1B and alpha-actinin4 co-localized in murine and human glomeruli and transiently transfected E11 podocyte cells. Additionally, podocyte PTP1B deficiency in vivo and culture was associated with elevated tyrosine phosphorylation of alpha-actinin4. Conversely, reconstitution of the knockdown cells with PTP1B attenuated alpha-actinin4 tyrosine phosphorylation. We demonstrated co-association between alpha-actinin4 and the PTP1B substrate-trapping mutant, which was enhanced upon insulin stimulation and disrupted by vanadate, consistent with an enzyme-substrate interaction. Moreover, we identified alpha-actinin4 tandem tyrosine residues 486/487 as mediators of its interaction with PTP1B. Furthermore, knockdown studies in E11 cells suggest that PTP1B and alpha-actinin4 are modulators of podocyte motility. These observations indicate that PTP1B and alpha-actinin4 are likely interacting partners in a signaling node that modulates podocyte function. Targeting PTP1B and plausibly this one of its substrates may represent a new therapeutic approach for podocyte injury that warrants additional investigation.

NF-κB signaling in neoplastic transition from epithelial to mesenchymal phenotype

NF-κB transcription factors are critical regulators of innate and adaptive immunity and major mediators of inflammatory signaling. The NF-κB signaling is dysregulated in a significant number of cancers and drives malignant transformation through maintenance of constitutive pro-survival signaling and downregulation of apoptosis. Overactive NF-κB signaling results in overexpression of pro-inflammatory cytokines, chemokines and/or growth factors leading to accumulation of proliferative signals together with activation of innate and select adaptive immune cells. This state of chronic inflammation is now thought to be linked to induction of malignant transformation, angiogenesis, metastasis, subversion of adaptive immunity, and therapy resistance. Moreover, accumulating evidence indicates the involvement of NF-κB signaling in induction and maintenance of invasive phenotypes linked to epithelial to mesenchymal transition (EMT) and metastasis. In this review we summarize reported links of NF-κB signaling to sequential steps of transition from epithelial to mesenchymal phenotypes. Understanding the involvement of NF-κB in EMT regulation may contribute to formulating optimized therapeutic strategies in cancer. Video Abstract.

Induction of filopodia formation by α-Actinin-2 via RelA with a feedforward activation loop promoting overt bone marrow metastasis of gastric cancer

BACKGROUND

Bone marrow metastasis (BMM) is underestimated in gastric cancer (GC). GC with BMM frequently complicate critical hematological abnormalities like diffused intravascular coagulation and microangiopathic hemolytic anemia, which constitute a highly aggressive GC (HAGC) subtype. HAGC present a very poor prognosis with peculiar clinical and pathological features when compared with not otherwise specified advanced GC (NAGC). But the molecular mechanisms underlying BMM from GC remain rudimentary.

METHODS

The transcriptomic difference between HAGC and NAGC were analyzed. Genes that were specifically upregulated in HAGC were identified, and their effect on cell migration and invasion was studied. The function of ACTN2 gene were confirmed by GC cell lines, bone-metastatic animal model and patients' tissues. Furthermore, the molecular mechanism of ACTN2 derived-BMM was explored by multiple immunofluorescence staining, western blot, chromatin immunoprecipitation, and luciferase reporter assays.

RESULTS

We elucidated the key mechanisms of BMM depending on the transcriptomic difference between HAGC and NAGC. Five genes specifically upregulated in HAGC were assessed their effect on cell migration and invasion. The ACTN2 gene encoding protein α-Actinin-2 was detected enhanced the metastatic capability and induced BMM of GC cells in mouse models. Mechanically, α-Actinin-2 was involved in filopodia formation where it promoted the Actin filament cross-linking by replacing α-Actinin-1 to form α-Actinin-2:α-Actinin-4 complexes in GC cells. Moreover, NF-κB subunit RelA and α-Actinin-2 formed heterotrimers in the nuclei of GC cells. As a direct target of RelA:α-Actinin-2 heterotrimers, the ACTN2 gene was a positive auto-regulatory loop for α-Actinin-2 expression.

CONCLUSIONS

We demonstrated a link between filopodia, BMM and ACTN2 activation, where a feedforward activation loop between ACTN2 and RelA is established via actin in response to distant metastasis. Given the novel filopodia formation function and the new mechanism of BMM in GC, we propose ACTN2 as a druggable molecular vulnerability that may provide potential therapeutic benefit against BMM of GC.

Liver Proteome Alterations in Red Deer (Cervus elaphus) Infected by the Giant Liver Fluke Fascioloides magna

Liver fluke infections are recognised as diseases with worldwide distribution and considerable veterinary and public health importance. The giant liver fluke, Fascioloides magna, is an important non-native parasite which has been introduced to Europe, posing a threat to the survival of local wildlife populations such as red deer (Cervus elaphus). The aim of the study was to analyse differences in liver proteomes between F. magna-infected and control red deer groups using a label-based high-throughput quantitative proteomics approach. The proteomics analysis identified 234 proteins with differential abundance between the control and infected groups. Our findings showed that F. magna infection in this definitive host is associated with changes in the metabolism of proteins and fatty acids, oxidative stress, fibrosis, and signaling pathways. The identified proteins and associated biological pathways represent a valuable contribution to the understanding of host-parasite interactions and the pathogenesis of liver fluke infection.

Alpha-actnin-4 (ACTN4) selectively affects the DNA double-strand breaks repair in non-small lung carcinoma cells

BACKGROUND

ACTN4 is an actin-binding protein involved in many cellular processes, including cancer development. High ACTN4 expression is often associated with a poor prognosis. However, it has been identified as a positive marker for platinum-based adjuvant chemotherapy for non-small cell lung cancer (NSCLC). The goal of our study was to investigate the involvement of ACTN4 in the NSCLC cells' response to the genotoxic drugs.

RESULTS

We generated H1299 cells with the ACTN4 gene knock-out (ACTN4 KO), using the CRISPR/Cas9 system. The resistance of the cells to the cisplatin and etoposide was analyzed with the MTT assay. We were also able to estimate the efficiency of DNA repair through the DNA comet assay and gamma-H2AX staining. Possible ACTN4 effects on the non-homologous end joining (NHEJ) and homologous recombination (HR) were investigated using pathway-specific reporter plasmids and through the immunostaining of the key proteins. We found that the H1299 cells with the ACTN4 gene knock-out did not show cisplatin-resistance, but did display a higher resistance to the topoisomerase II inhibitors etoposide and doxorubicin, suggesting that ACTN4 might be somehow involved in the repair of DNA strand breaks. Indeed, the H1299 ACTN4 KO cells repaired etoposide- and doxorubicin-induced DNA breaks more effectively than the control cells. Moreover, the ACTN4 gene knock-out enhanced NHEJ and suppressed HR efficiency. Supporting the data, the depletion of ACTN4 resulted in the faster assembly of the 53BP1 foci with a lower number of the phospho-BRCA1 foci after the etoposide treatment.

CONCLUSIONS

Thus, we are the first to demonstrate that ACTN4 may influence the resistance of cancer cells to the topoisomerase II inhibitors, and affect the efficiency of the DNA double strand breaks repair. We hypothesize that ACTN4 interferes with the assembly of the NHEJ and HR complexes, and hence regulates balance between these DNA repair pathways.

Modeling of ACTN4-Based Podocytopathy Using Drosophila Nephrocytes

Introduction

Genetic disorders are among the most prevalent causes leading to progressive glomerular disease and, ultimately, end-stage renal disease (ESRD) in children and adolescents. Identification of underlying genetic causes is indispensable for targeted treatment strategies and counseling of affected patients and their families.

Methods

Here, we report on a boy who presented at 4 years of age with proteinuria and biopsy-proven focal segmental glomerulosclerosis (FSGS) that was temporarily responsive to treatment with ciclosporin A. Molecular genetic testing identified a novel mutation in alpha-actinin-4 (p.M240T). We describe a feasible and efficient experimental approach to test its pathogenicity by combining in silico, in vitro, and in vivo analyses.

Results

The de novo p.M240T mutation led to decreased alpha-actinin-4 stability as well as protein mislocalization and actin cytoskeleton rearrangements. Transgenic expression of wild-type human alpha-actinin-4 in Drosophila melanogaster nephrocytes was able to ameliorate phenotypes associated with the knockdown of endogenous actinin. In contrast, p.M240T, as well as other established disease variants p.W59R and p.K255E, failed to rescue these phenotypes, underlining the pathogenicity of the novel alpha-actinin-4 variant.

Conclusion

Our data highlight that the newly identified alpha-actinin-4 mutation indeed encodes for a disease-causing variant of the protein and promote the Drosophila model as a simple and convenient tool to study monogenic kidney disease in vivo.

Benefits from Adjuvant Chemotherapy in Patients with Resected Non-Small Cell Lung Cancer: Possibility of Stratification by Gene Amplification of ACTN4 According to Evaluation of Metastatic Ability

Surgical treatment is the best curative treatment option for patients with non-small cell lung cancer (NSCLC), but some patients have recurrence beyond the surgical margin even after receiving curative surgery. Therefore, therapies with anti-cancer agents also play an important role perioperatively. In this paper, we review the current status of adjuvant chemotherapy in NSCLC and describe promising perioperative therapies, including molecularly targeted therapies and immune checkpoint inhibitors. Previously reported biomarkers of adjuvant chemotherapy for NSCLC are discussed along with their limitations. Adjuvant chemotherapy after resective surgery was most effective in patients with metastatic lesions located just outside the surgical margin; in addition, these metastatic lesions were the most sensitive to adjuvant chemotherapy. Thus, the first step in predicting patients who have sensitivity to adjuvant therapies is to perform a qualified evaluation of metastatic ability using markers such as actinin-4 (ACTN4). In this review, we discuss the potential use of biomarkers in patient stratification for effective adjuvant chemotherapy and, in particular, the use of ACTN4 as a possible biomarker for NSCLC.

Development of biomarkers for predicting recurrence by determining the metastatic ability of cancer cells

Adjuvant chemotherapy has been carried out for patients with cancer who underwent curative resection, but it is basically not needed for patients without micro-metastatic lesions who undergo a perfectly curative surgical operation. The patients who need adjuvant chemotherapy are defined as those whose micro-metastases cannot be detected by imaging modalities in the other sites of the resective areas, despite curative resection for the primary sites. If biomarkers to efficiently evaluate the metastatic potential of each patient could be developed, we may be able to provide personalized adjuvant chemotherapy in the clinical setting. Actinin-4 (ACTN4, gene name ACTN4) is an actin-bundling protein that we identified in 1998 as a novel molecule involved in cancer invasion and metastasis. Protein overexpression of actinin-4 in cancer cells leads to the invasive phenotype, and patients with gene amplification of ACTN4 have a worse prognosis than patients with a normal copy number in some cancers, including pancreas, lung, and salivary gland cancers. In this review, the biological roles of actinin-4 for cancer invasion and metastasis are summarized, and the potential usefulness of actinin-4 as a biomarker for evaluation of metastatic ability is examined.

Complementary liver and serum protein profile in wild boars infected by the giant liver fluke Fascioloides magna using tandem mass tags quantitative approach

Liver fluke, Fascioloides magna, is an important non-native parasite introduced to Europe, posing a threat to survival of local wildlife populations. The aim of this study was to assess the serum and liver protein profile of control and F. magna infected wild boars, by means of shotgun tandem mass tag - based quantitative high resolution proteomics approach. In serum, 4 differentially abundant proteins were found out of total 1073 identified, while in liver from 3520 identified proteins, 116 were differentially abundant between healthy and F. magna infected wild boars. Pathway analysis revealed that most of the proteins differing in abundance are involved in metabolism, biological oxidations, cellular responses to stimuli, fatty acid metabolism, and others. Validation of proteomic results was performed for paraoxonase-1, ceruloplasmin, glutathione S-transferase and liver enzymes by ELISA and automated assays. Complementary analysis of liver and serum in F. magna infection enabled insight into changes of proteome profile of the host at local and sistemic level. Our findings showed that chronic infection with F. magna is associated with immune response in host, oxidative stress and metabolomic changes in liver. SIGNIFICANCE: Liver fluke infections are recognised as worldwide neglected diseases with considerable veterinary and public health importance. Pathological changes, clinical signs and outcome of F. magna infection are strongly related to the type of final hosts and their different tolerance to infection. In order to gain insight into host-parasite interactions in wild boars, dead-end host for F. magna, we assessed proteomics profile of serum and liver of control animals and those infected with F. magna. Proteomics analysis of serum and liver in parallel showed as advantageous and beneficial, demonstrating protein alterations mainly at local level. Bioinformatics analysis enabled elucidation of molecular pathways associated with F. magna infection. Identification and validation of proteins associated with infection may have added value to current tools for efficient liver fluke control.

Adiponectin protects obesity-related glomerulopathy by inhibiting ROS/NF-κB/NLRP3 inflammation pathway

BACKGROUND

Adiponectin is an adipocytokine that plays a key regulatory role in glucose and lipid metabolism in obesity. The prevalence of obesity has led to an increase in the incidence of obesity-related glomerulopathy (ORG). This study aimed to identify the protective role of adiponectin in ORG.

METHODS

Small-interfering RNA (siRNA) against the gene encoding adiponectin was transfected into podocytes. The oxidative stress level was determined using a fluorometric assay. Apoptosis was analyzed by flow cytometry. The expressions of podocyte markers and pyrin domain containing protein 3 (NLRP3) inflammasome-related proteins were measured by qRT-PCR, immunohistochemistry, and Western blot.

RESULTS

Podocytes treated with palmitic acid (PA) showed downregulated expressions of podocyte markers, increased apoptosis, upregulated levels of NLRP3 inflammasome-related proteins, increased production of inflammatory cytokines (IL-18 and IL-1β), and induced activation of NF-κB as compared to the vehicle-treated controls. Decreased adiponectin expression was observed in the serum samples from high fat diet (HFD)-fed mice. Decreased podocin expression and upregulated NLRP3 expression were observed in the kidney samples from high fat diet (HFD)-fed mice. Treatment with adiponectin or the NLRP3 inflammasome inhibitor, MCC950, protected cultured podocytes against podocyte apoptosis and inflammation. Treatment with adiponectin protected mouse kidney tissues against decreased podocin expression and upregulated NLRP3 expression. The knockout of adiponectin gene by siRNA increased ROS production, resulting in the activation of NLRP3 inflammasome and the phosphorylation of NF-κB in podocytes. Pyrrolidine dithiocarbamate, an NF-κB inhibitor, prevented adiponectin from ameliorating FFA-induced podocyte injury and NLRP3 activation.

CONCLUSIONS

Our study showed that adiponectin ameliorated PA-induced podocyte injury in vitro and HFD-induced injury in vivo via inhibiting the ROS/NF-κB/NLRP3 pathway. These data suggest the potential use of adiponectin for the prevention and treatment of ORG.

Changes in the levels of α-actinin-4 in differentiating human myeloid leukemia cells induced by retinoic acid

Retinoic acid (RA) induces granulocytic differentiation and inhibits the growth of human promyelocytic leukemia HL60 cells. α-Actinin-4 is a member of the α-actinin family, which exhibits unique mechanosensory regulation. Herein, we elucidated the effects of RA on α-actinin-4 expression during cell differentiation. RA increased the levels of α-actinin-4 protein significantly, while mRNA expression remained unchanged. In addition, RA treatment altered the intracellular localization of α-actinin-4 from the nucleus to the cytoplasm. Cells pretreated with RA, maintained α-actinin-4 protein levels after cycloheximide treatment as compared with control cells. The amount of ubiquitylated α-actinin-4 protein in RA-treated cells was less than in control cells. These results indicate that RA may inhibit nuclei transport and proteasomal degradation of α-actinin-4 protein. α-Actinin-4 may play a significant role in RA-induced differentiation, including the promotion of cytomorphology changes.

Expression correlation attenuates within and between key signaling pathways in chronic kidney disease

Background

Compared to the conventional differential expression approach, differential coexpression analysis represents a different yet complementary perspective into diseased transcriptomes. In particular, global loss of transcriptome correlation was previously observed in aging mice, and a most recent study found genetic and environmental perturbations on human subjects tended to cause universal attenuation of transcriptome coherence. While methodological progresses surrounding differential coexpression have helped with research on several human diseases, there has not been an investigation of coexpression disruptions in chronic kidney disease (CKD) yet.

Methods

RNA-seq was performed on total RNAs of kidney tissue samples from 140 CKD patients. A combination of differential coexpression methods were employed to analyze the transcriptome transition in CKD from the early, mild phase to the late, severe kidney damage phase.

Results

We discovered a global expression correlation attenuation in CKD progression, with pathway Regulation of nuclear SMAD2/3 signaling demonstrating the most remarkable intra-pathway correlation rewiring. Moreover, the pathway Signaling events mediated by focal adhesion kinase displayed significantly weakened crosstalk with seven pathways, including Regulation of nuclear SMAD2/3 signaling. Well-known relevant genes, such as ACTN4, were characterized with widespread correlation disassociation with partners from a wide array of signaling pathways.

Conclusions

Altogether, our analysis reported a global expression correlation attenuation within and between key signaling pathways in chronic kidney disease, and presented a list of vanishing hub genes and disrupted correlations within and between key signaling pathways, illuminating on the pathophysiological mechanisms of CKD progression.

Connectivity mapping of glomerular proteins identifies dimethylaminoparthenolide as a new inhibitor of diabetic kidney disease

While blocking the renin angiotensin aldosterone system (RAAS) has been the main therapeutic strategy to control diabetic kidney disease (DKD) for many years, 25-30% of diabetic patients still develop the disease. In the present work we adopted a systems biology strategy to analyze glomerular protein signatures to identify drugs with potential therapeutic properties in DKD acting through a RAAS-independent mechanism. Glomeruli were isolated from wild type and type 1 diabetic (Ins2Akita) mice treated or not with the angiotensin-converting enzyme inhibitor (ACEi) ramipril. Ramipril efficiently reduced the urinary albumin/creatine ratio (ACR) of Ins2Akita mice without modifying DKD-associated renal-injuries. Large scale quantitative proteomics was used to identify the DKD-associated glomerular proteins (DKD-GPs) that were ramipril-insensitive (RI-DKD-GPs). The raw data are publicly available via ProteomeXchange with identifier PXD018728. We then applied an in silico drug repurposing approach using a pattern-matching algorithm (Connectivity Mapping) to compare the RI-DKD-GPs's signature with a collection of thousands of transcriptional signatures of bioactive compounds. The sesquiterpene lactone parthenolide was identified as one of the top compounds predicted to reverse the RI-DKD-GPs's signature. Oral treatment of 2 months old Ins2Akita mice with dimethylaminoparthenolide (DMAPT, a water-soluble analogue of parthenolide) for two months at 10 mg/kg/d by gavage significantly reduced urinary ACR. However, in contrast to ramipril, DMAPT also significantly reduced glomerulosclerosis and tubulointerstitial fibrosis. Using a system biology approach, we identified DMAPT, as a compound with a potential add-on value to standard-of-care ACEi-treatment in DKD.

Serum Actinin-4 Levels as a Potential Diagnostic and Prognostic Marker in Cervical Cancer

Purpose

The present study was aimed at determining the serum levels of actinin-4 (ACTN4) in cervical cancer (CC) and investigating the diagnostic and prognostic value of serum ACTN4 in CC.

Materials and Methods

We included 93 CC patients, 52 cervical intraepithelial neoplasia (CIN) patients, and 70 healthy women. Serum ACTN4 levels were assessed using an ELISA method. A receiver operating characteristic (ROC) curve was performed to evaluate the diagnostic value of serum ACTN4. The survival curves were used to display the overall survival distributions.

Results

Serum ACTN4 levels in CC patients were 48.39 ± 13.98 pg/mL which is significantly higher than those in CIN patients (32.72 ± 9.44 pg/mL; P < 0.001) and those in healthy controls (30.84 ± 8.08 pg/mL; P < 0.001). The ROC analysis demonstrated that the area under the curve (AUC) of ACTN4 was 0.852 (95%CI = 0.796-0.908), with sensitivity of 76.3% and specificity of 87.7%. Serum ACTN4 levels were associated with the FIGO stage, lymph node metastasis, and lymphovascular space invasion of CC (all P < 0.05). The survival curve suggested that high serum ACTN4 levels were related to poor prognosis.

Conclusion

Our findings suggest that serum ACTN4 levels may be valuable diagnostic and prognostic biomarkers for CC.

Prognostic impact of ACTN4 gene copy number alteration in hormone receptor-positive, HER2-negative, node-negative invasive breast carcinoma

BACKGROUND

Most patients with hormone receptor (HR)-positive, human epidermal growth factor receptor type 2 (HER2)-negative breast cancer can be cured by surgery and endocrine therapy, but a significant proportion suffer recurrences. Actinin-4 is associated with cancer invasion and metastasis, and its genetic alteration may be used for breast cancer prognostication.

METHODS

The copy number of the actinin-4 (ACTN4) gene was determined by fluorescence in situ hybridisation (FISH) in two independent cohorts totalling 597 patients (336 from Japan and 261 from the USA) with HR-positive, HER2-negative, node-negative breast cancer.

RESULTS

In the Japanese cohort, multivariate analysis revealed that a copy number increase (CNI) of ACTN4 was an independent factor associated with high risks of recurrence (P = 0.01; hazard ratio (HR), 2.95) and breast cancer death (P = 0.014; HR, 4.27). The prognostic significance of ACTN4 CNI was validated in the US cohort, where it was the sole prognostic factor significantly associated with high risks of recurrence (P = 0.04; HR, 2.73) and death (P = 0.016; HR, 4.01).

CONCLUSIONS

Copy number analysis of a single gene, ACTN4, can identify early-stage luminal breast cancer patients with a distinct outcome. Such high-risk patients may benefit from adjuvant chemotherapy.

Kidney podocyte-associated gene polymorphisms affect tacrolimus concentration in pediatric patients with refractory nephrotic syndrome

Few studies have investigated the correlation between pharmacogenomics and tacrolimus pharmacokinetics in patients with nephrotic syndrome (NS). This study evaluated the influences of genetic polymorphisms of metabolic enzymes, transporters, and podocyte-associated proteins on tacrolimus concentration in Chinese pediatric patients with refractory NS. A total of 167 pediatric patients with refractory NS were included from July 2013 to December 2017. Age of onset was restricted to <14 years of age. Dose-adjusted tacrolimus trough concentration (C₀/D) on the third month was calculated, and 20 single-nucleotide polymorphisms in sixteen genes were genotyped. Age was correlated with tacrolimus C₀/D (p = 0.006, r = 0.213). Tacrolimus C₀/D was higher in CYP3A5 nonexpressers than in CYP3A5 expressers (p = 0.003). ACTN4 rs62121818, MYH9 rs2239781, CYP3A5*3, and age explained 20.5% interindividual variability of tacrolimus concentration in the total cohort. In CYP3A5 nonexpressers, ACTN4 rs62121818 and MYH9 rs2239781 together explained 14.6% variation of tacrolimus C₀/D. MYH9 rs2239781, LAMB2 rs62119873 and age together explained 22.3% variability of tacrolimus level in CYP3A5 expressers. CYP3A5*3 was still an important factor affecting tacrolimus concentration in patients with NS. Podocyte-associated gene polymorphisms, especially ACTN4 rs62121818 and MYH9 rs2239781, were the other most important biomarkers for tacrolimus whole blood levels. Genotyping of CYP3A5, ACTN4, and MYH9 polymorphisms may be helpful for better guiding tacrolimus dosing in pediatric patients with refractory NS.

Role of ACTN4 in Tumorigenesis, Metastasis, and EMT

The actin-binding protein ACTN4 belongs to a family of actin-binding proteins and is a non-muscle alpha-actinin that has long been associated with cancer development. Numerous clinical studies showed that changes in ACTN4 gene expression are correlated with aggressiveness, invasion, and metastasis in certain tumors. Amplification of the 19q chromosomal region where the gene is located has also been reported. Experimental manipulations with ACTN4 expression further confirmed its involvement in cell proliferation, motility, and epithelial-mesenchymal transition (EMT). However, both clinical and experimental data suggest that the effects of ACTN4 up- or down-regulation may vary a lot between different types of tumors. Functional studies demonstrated its engagement in a number of cytoplasmic and nuclear processes, ranging from cytoskeleton reorganization to regulation of different signaling pathways. Such a variety of functions may be the reason behind cell type and cell line specific responses. Herein, we will review research progress and controversies regarding the prognostic and functional significance of ACTN4 for tumorigenesis.

Anti-Inflammatory Effects of Canavalia gladiata in Macrophage Cells and DSS-Induced Colitis Mouse Model

Canavalia gladiata, known as sword bean, has been used as a Chinese traditional medicine for anti-inflammatory effects. However, the action mechanisms of sword bean have not yet been clearly defined. In the present study, the whole parts of a ripened sword bean (RSB) and the green sword bean (GSB) containing bean pod were extracted with ethanol by reflux extraction. The two crude extracts (RSBE and GSBE) from RSB and GSB were validated by a liquid chromatography-tandem mass spectrometry (LC/MS/MS) analysis of gallic acid as a reference chemical. The anti-inflammatory effects of two sword bean extracts were extensively investigated using LPS-stimulated macrophage cells. First, RSBE and GSBE significantly inhibited the production of pro-inflammatory mediators, such as tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), prostaglandinE₂ (PGE₂), and nitric oxide (NO) in LPS-induced RAW264.7 cells. RSBE and GSBE showed no cytotoxicity to RAW264.7 cells and mouse peritoneal macrophage cells. In addition, the overexpression of cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS) induced by LPS in RAW264.7 cells was significantly decreased by RSBE and GSBE. Western blotting and immunostaining analysis showed that RSBE and GSBE inhibited the nuclear translocation of NF-κB subunits, which correlated with the inhibitory effects on inhibitor kappa B (IκB) degradation. In dextran sulfated sodium (DSS)-induced colitis mice model, RSBE restored body weight, colon length, and the levels of pro-inflammatory cytokines, such as TNF-α, IL-6, interleukin-1β (IL-1β), and interferon-γ (IFN-γ). In addition, RSBE significantly suppressed the expression of COX-2, iNOS, and NF-κB.

Actinin-4 as a Diagnostic Biomarker in Serum of Breast Cancer Patients

Background

α-actinin-4 (Actinin-4 or ACTN4), originally identified as an actin-binding protein associated with the biological function of cancer cells, appears to be highly expressed in numerous human epithelial carcinomas, including breast cancer (BC). In the present study we assessed the role of serum ACTN4 as a biomarker for BC diagnosis, as well as the association between ACTN4 levels and clinicopathological features.

Material/Methods

ACTN4 expression level was measured with quantitative real-time PCR (qRT-PCR) analysis in serum specimens of 128 BC patients and 96 healthy volunteers. χ² testing was conducted to explore the association of ACTN4 levels with clinicopathologic factors. Moreover, the diagnostic value of ACTN4 was analyzed using receiver operating characteristic (ROC) curves.

Results

Serum ACTN4 level was obviously upregulated in patients with BC compared with healthy controls (P<0.05). High ACTN4 expression was significantly associated with clinical stage (P=0.000), tumor grade (P=0.004), and lymph node status (P=0.024). However, no association was found between ACTN4 expression and age, tumor size, ER status, PR status, or HER-2 status (all P>0.05). The ROC analysis showed that the area under the curve (AUC) of ACTN4 was 0.887 (95%CI: 0.843–0.931), with sensitivity of 80.5% and specificity of 84.4%, and the cutoff value was 1.050.

Conclusions

ACTN4 in serum can serve as a clinical predictor in the diagnosis or prediction of clinical outcomes of patients with BC.

ACTN4 regulates the stability of RIPK1 in melanoma

The actin crosslinking protein α-actinin-4 (ACTN4) is emerging as an important contributor to the pathogenesis of cancer. This has largely been attributed to its role in regulating cytoskeleton organization and its involvement in transcriptional regulation of gene expression. Here we report a novel function of ACTN4 as a scaffold necessary for stabilization of receptor-interacting protein kinase 1 (RIPK1) that we have recently found to be an oncogenic driver in melanoma. ACTN4 bound to RIPK1 and cellular inhibitor of apoptosis protein 1 (cIAP1) with its actin-binding domain at the N-terminus and the CaM-like domain at the C-terminus, respectively. This facilitated the physical association between RIPK1 and cIAP1 and was critical for stabilization of RIPK1 that in turn activated NF-κB. Functional investigations showed that silencing of ACTN4 suppressed melanoma cell proliferation and retarded melanoma xenograft growth. In contrast, overexpression of ACTN4 promoted melanocyte and melanoma cell proliferation and moreover, prompted melanocyte anchorage-independent growth. Of note, the expression of ACTN4 was transcriptionally activated by NF-κB. Taken together, our findings identify ACTN4 as an oncogenic regulator through driving a feedforward signaling axis of ACTN4-RIPK1-NF-κB, with potential implications for targeting ACTN4 in the treatment of melanoma.

Co-expression of RelA/p65 and ACTN4 induces apoptosis in non-small lung carcinoma cells

Alpha-actinin 4 (ACTN4) is an actin-binding protein of the spectrin superfamily. ACTN4 is found both in the cytoplasm and nucleus of eukaryotic cells. The main function of cytoplasmic ACTN4 is stabilization of actin filaments and their binding to focal contacts. Nuclear ACTN4 takes part in the regulation of gene expression following by activation of certain transcription factors, but the mechanisms of regulation are not completely understood. Our previous studies have demonstrated the interaction of ACTN4 with the RelA/p65 subunit of NF-kappaB factor and the effect on its transcriptional activity in A431 and HEK293T cells. In the present work, we investigated changes in the composition of nuclear ACTN4-interacting proteins in non-small cell lung cancer cells H1299 upon stable RELA overexpression. We showed that ACTN4 was present in the nuclei of H1299 cells, regardless of the RELA expression level. The presence of ectopic RelA/p65 in H1299 cells increased the number of proteins interacting with nuclear ACTN4. Stable expression of RELA in these cells suppressed cell proliferation, which was further affected by simultaneous ACTN4 overexpression. We detected no significant effect on cell cycle but the apoptosis rate was increased in cells with a double RELA/ACTN4 overexpression. Interestingly, when expressed individually ACTN4 promoted proliferation of lung cancer cells. Furthermore, the bioinformatics analysis of gene expression in lung cancer patients suggested that overexpression of ACTN4 correlated with poor survival prognosis. We hypothesize that the effect of RELA on proliferation and apoptosis of H1299 cells can be mediated via affecting the interactome of ACTN4.

Functions of nuclear actin-binding proteins in human cancer

Nuclear actin-binding proteins (ABPs) perform distinguishable functions compared with their cytoplasmic counterparts in extensive activities of living cells. In addition to the ability to regulate actin cytoskeleton dynamics, nuclear ABPs are associated with multiple nuclear biological processes, including chromatin remodeling, gene transcriptional regulation, DNA damage response, nucleocytoplasmic trafficking and nuclear structure maintenance. The nuclear translocation of ABPs is affected by numerous intracellular or extracellular stimuli, which may lead to developmental malformation, tumor initiation, tumor progression and metastasis. Abnormal expression of certain ABPs have been reported in different types of cancer. This review focuses on the newly identified roles of nuclear ABPs in the pathological processes associated with cancer.

α-Actinin-4 promotes metastasis in gastric cancer

Metastasis increases the mortality rate of gastric cancer, which is the third leading cause of cancer-associated deaths worldwide. This study aims to identify the genes promoting metastasis of gastric cancer (GC). A human cell motility PCR array was used to analyze a pair of tumor and non-tumor tissue samples from a patient with stage IV GC (T3N3M1). Expression of the dysregulated genes was then evaluated in GC tissue samples (n=10) and cell lines (n=6) via qPCR. Expression of α-actinin-4 (ACTN4) was validated in a larger sample size (n=47) by qPCR, western blot and immunohistochemistry. Knockdown of ACTN4 with specific siRNAs was performed in GC cells, and adhesion assays, transwell invasion assays and migration assays were used to evaluate the function of these cells. Expression of potential targets of ACTN4 were then evaluated by qPCR. Thirty upregulated genes (greater than twofold) were revealed by the PCR array. We focused on ACTN4 because it was upregulated in 6 out of 10 pairs of tissue samples and 5 out of 6 GC cell lines. Further study indicated that ACTN4 was upregulated in 22/32 pairs of tissue samples at stage III &IV (P=0.0069). Knockdown of ACTN4 in GC cells showed no significant effect on cell proliferation, but significantly increased cell-matrix adhesion, as well as reduced migration and invasion of AGS, MKN7 and NCI-N87 cells. We found that NF-κB was downregulated in GC with the knockdown of ACTN4. In conclusion, this is the first study to indicate that ACTN4 is significantly upregulated in patients with metastatic GC. ACTN4 reduces cell adhesion and enhances migration and invasion of GC cells and may therefore be a novel therapeutic target for GC.

The Evolving Complexity of the Podocyte Cytoskeleton

Podocytes exhibit a unique cytoskeletal architecture that is fundamentally linked to their function in maintaining the kidney filtration barrier. The cytoskeleton regulates podocyte shape, structure, stability, slit diaphragm insertion, adhesion, plasticity, and dynamic response to environmental stimuli. Genetic mutations demonstrate that even slight impairment of the podocyte cytoskeletal apparatus results in proteinuria and glomerular disease. Moreover, mechanisms underpinning all acquired glomerular pathologies converge on disruption of the cytoskeleton, suggesting that this subcellular structure could be targeted for therapeutic purposes. This review summarizes our current understanding of the function of the cytoskeleton in podocytes and the associated implications for pathophysiology.

α Actinin 4 (ACTN4) Regulates Glucocorticoid Receptor-mediated Transactivation and Transrepression in Podocytes

Glucocorticoids are a general class of steroids that possess renoprotective activity in glomeruli through their interaction with the glucocorticoid receptor. However, the mechanisms by which glucocorticoids ameliorate proteinuria and glomerular disease are not well understood. In this study, we demonstrated that α actinin 4 (ACTN4), an actin-cross-linking protein known to coordinate cytoskeletal organization, interacts with the glucocorticoid receptor (GR) in the nucleus of human podocytes (HPCs), a key cell type in the glomerulus critical for kidney filtration function. The GR-ACTN4 complex enhances glucocorticoid response element (GRE)-driven reporter activity. Stable knockdown of ACTN4 by shRNA in HPCs significantly reduces dexamethasone-mediated induction of GR target genes and GRE-driven reporter activity without disrupting dexamethasone-induced nuclear translocation of GR. Synonymous mutations or protein expression losses in ACTN4 are associated with kidney diseases, including focal segmental glomerulosclerosis, characterized by proteinuria and podocyte injury. We found that focal segmental glomerulosclerosis-linked ACTN4 mutants lose their ability to bind liganded GR and support GRE-mediated transcriptional activity. Mechanistically, GR and ACTN4 interact in the nucleus of HPCs. Furthermore, disruption of the LXXLL nuclear receptor-interacting motif present in ACTN4 results in reduced GR interaction and dexamethasone-mediated transactivation of a GRE reporter while still maintaining its actin-binding activity. In contrast, an ACTN4 isoform, ACTN4 (Iso), that loses its actin-binding domain is still capable of potentiating a GRE reporter. Dexamethasone induces the recruitment of ACTN4 and GR to putative GREs in dexamethasone-transactivated promoters, SERPINE1, ANGPLT4, CCL20, and SAA1 as well as the NF-κB (p65) binding sites on GR-transrepressed promoters such as IL-1β, IL-6, and IL-8 Taken together, our data establish ACTN4 as a transcriptional co-regulator that modulates both dexamethasone-transactivated and -transrepressed genes in podocytes.

Adenosine A2B Receptor: From Cell Biology to Human Diseases

Extracellular adenosine is a ubiquitous signaling molecule that modulates a wide array of biological processes. Recently, significant advances have been made in our understanding of A2B adenosine receptor (A2BAR). In this review, we first summarize some of the general characteristics of A2BAR, and then we describe the multiple binding partners of the receptor, such as newly identified α-actinin-1 and p105, and discuss how these associated proteins could modulate A2BAR's functions, including certain seemingly paradoxical functions of the receptor. Growing evidence indicates a critical role of A2BAR in cancer, renal disease, and diabetes, in addition to its importance in the regulation of vascular diseases, and lung disease. Here, we also discuss the role of A2BAR in cancer, renal disease, and diabetes and the potential of the receptor as a target for treating these three diseases.

The cytoskeleton as a novel target for treatment of renal fibrosis

The incidence of chronic kidney disease (CKD) is increasing, with an estimated prevalence of 12% in the United States (Synder et al., 2009). While CKD may progress to end-stage renal disease (ESRD), which necessitates renal replacement therapy, i.e. dialysis or transplantation, most CKD patients never reach ESRD due to the increased risk of death from cardiovascular disease. It is well-established that regardless of the initiating insult - most often diabetes or hypertension - fibrosis is the common pathogenic pathway that leads to progressive injury and organ dysfunction (Eddy, 2014; Duffield, 2014). As such, there has been extensive research into the molecular and cellular mechanisms of renal fibrosis; however, translation to effective therapeutic strategies has been limited. While a role for the disruption of the cytoskeleton, most notably the actin network, has been established in acute kidney injury over the past two decades, a role in regulating renal fibrosis and CKD is only recently emerging. This review will focus on the role of the cytoskeleton in regulating pro-fibrotic pathways in the kidney, as well as data suggesting that these pathways represent novel therapeutic targets to manage fibrosis and ultimately CKD.

Introducing STRaNDs: shuttling transcriptional regulators that are non-DNA binding

Many proteins originally identified as cytoplasmic - including many associated with the cytoskeleton or cell junctions - are increasingly being found in the nucleus, where they have specific functions. Here, we focus on proteins that translocate from the cytoplasm to the nucleus in response to external signals and regulate transcription without binding to DNA directly (for example, through interaction with transcription factors). We propose that proteins with such characteristics are classified as a distinct group of extracellular signalling effectors, and we suggest the term STRaND (shuttling transcriptional regulators and non-DNA binding) to refer to this group. Crucial roles of STRaNDs include linking cell morphology and adhesion with changes in transcriptional programmes in response to signals such as mechanical stresses.

Actinin-1 binds to the C-terminus of A2B adenosine receptor (A2BAR) and enhances A2BAR cell-surface expression

A2BAR (A2B adenosine receptor) has been implicated in several physiological conditions, such as allergic or inflammatory disorders, vasodilation, cell growth and epithelial electrolyte secretion. For mediating the protein-protein interactions of A2BAR, the receptor's C-terminus is recognized to be crucial. In the present study, we unexpectedly found that two point mutations in the A2BAR C-terminus (F297A and R298A) drastically impaired the expression of A2BAR protein by accelerating its degradation. Thus we tested the hypothesis that these two point mutations disrupt A2BAR's interaction with a protein essential for A2BAR stability. Our results show that both mutations disrupted the interaction of A2BAR with actinin-1, an actin-associated protein. Furthermore, actinin-1 binding stabilized the global and cell-surface expression of A2BAR. By contrast, actinin-4, another non-muscle actinin isoform, did not bind to A2BAR. Thus our findings reveal a previously unidentified regulatory mechanism of A2BAR abundance.

Three-layered proteomic characterization of a novel ACTN4 mutation unravels its pathogenic potential in FSGS

Genetic diseases constitute the most important cause for end-stage renal disease in children and adolescents. Mutations in the ACTN4 gene, encoding the actin-binding protein α-actinin-4, are a rare cause of autosomal dominant familial focal segmental glomerulosclerosis (FSGS). Here, we report the identification of a novel, disease-causing ACTN4 mutation (p.G195D, de novo) in a sporadic case of childhood FSGS using next generation sequencing. Proteome analysis by quantitative mass spectrometry (MS) of patient-derived urinary epithelial cells indicated that ACTN4 levels were significantly decreased when compared with healthy controls. By resolving the peptide bearing the mutated residue, we could proof that the mutant protein is less abundant when compared with the wild-type protein. Further analyses revealed that the decreased stability of p.G195D is associated with increased ubiquitylation in the vicinity of the mutation site. We next defined the ACTN4 interactome, which was predominantly composed of cytoskeletal modulators and LIM domain-containing proteins. Interestingly, this entire group of proteins, including several highly specific ACTN4 interactors, was globally decreased in the patient-derived cells. Taken together, these data suggest a mechanistic link between ACTN4 instability and proteome perturbations of the ACTN4 interactome. Our findings advance the understanding of dominant effects exerted by ACTN4 mutations in FSGS. This study illustrates the potential of genomics and complementary, high-resolution proteomics analyses to study the pathogenicity of rare gene variants.

The biological role of actinin-4 (ACTN4) in malignant phenotypes of cancer

Invasion and metastasis are malignant phenotypes in cancer that lead to patient death. Cell motility is involved in these processes. In 1998, we identified overexpression of the actin-bundling protein actinin-4 in several types of cancer. Protein expression of actinin-4 is closely associated with the invasive phenotypes of cancers. Actinin-4 is predominantly expressed in the cellular protrusions that stimulate the invasive phenotype in cancer cells and is essential for formation of cellular protrusions such as filopodia and lamellipodia. ACTN4 (gene name encoding actinin-4 protein) is located on human chromosome 19q. ACTN4 amplification is frequently observed in patients with carcinomas of the pancreas, ovary, lung, and salivary gland, and patients with ACTN4 amplifications have worse outcomes than patients without amplification. In addition, nuclear distribution of actinin-4 is frequently observed in small cell lung, breast, and ovarian cancer. Actinin-4, when expressed in cancer cell nuclei, functions as a transcriptional co-activator. In this review, we summarize recent developments regarding the biological roles of actinin-4 in cancer invasion.

The role of alpha-actinin-4 in human kidney disease

Mutations in the Alpha-actinin-4 gene (ACTN4) cause a rare form of familial focal segmental glomerulosclerosis in humans. Individuals with kidney disease-associated ACTN4 mutations tend to have mild to moderate proteinuria, with many developing decreased kidney function progressing to end stage kidney disease. All of the disease-causing ACTN4 mutations identified to date are located within the actin-binding domain of the encoded protein, increasing its binding affinity to F-actin and leading to abnormal actin rich cellular aggregates. The identification of ACTN4 mutations as a cause of human kidney disease demonstrates a key cellular pathway by which alterations in cytoskeletal behavior can mediate kidney disease. Here we review the studies relevant to ACTN4 and its role in mediating kidney disease.

The role of Merkel cell polyomavirus and other human polyomaviruses in emerging hallmarks of cancer

Polyomaviruses are non-enveloped, dsDNA viruses that are common in mammals, including humans. All polyomaviruses encode the large T-antigen and small t-antigen proteins that share conserved functional domains, comprising binding motifs for the tumor suppressors pRb and p53, and for protein phosphatase 2A, respectively. At present, 13 different human polyomaviruses are known, and for some of them their large T-antigen and small t-antigen have been shown to possess oncogenic properties in cell culture and animal models, while similar functions are assumed for the large T- and small t-antigen of other human polyomaviruses. However, so far the Merkel cell polyomavirus seems to be the only human polyomavirus associated with cancer. The large T- and small t-antigen exert their tumorigenic effects through classical hallmarks of cancer: inhibiting tumor suppressors, activating tumor promoters, preventing apoptosis, inducing angiogenesis and stimulating metastasis. This review elaborates on the putative roles of human polyomaviruses in some of the emerging hallmarks of cancer. The reciprocal interactions between human polyomaviruses and the immune system response are discussed, a plausible role of polyomavirus-encoded and polyomavirus-induced microRNA in cancer is described, and the effect of polyomaviruses on energy homeostasis and exosomes is explored. Therapeutic strategies against these emerging hallmarks of cancer are also suggested.