The human solute carrier family 11 member 1 protein (SLC11A1): linking infections, autoimmunity and cancer?

SLC11A1 is known to link infections, autoimmunity and cancers. A review is presented of the mechanisms by which a balance is maintained between infections caused by pathogens (viral, bacterial and protozoan; intracellular and extracellular) and disorders resulting from (acute or chronic) inflammation, and of the interactions that determine how the initial innate immune system directs subsequent acquired immune responses in human populations.     

LIM domain protein FHL1B interacts with PP2A catalytic β subunit--a novel cell cycle regulatory pathway

Four-and-a-half LIM domain protein 1B (FHL1B) is an alternatively-spliced isoform of FHL1. In this study, FHL1B was demonstrated to interact with the β catalytic subunit (Cβ) of a type 2A protein phosphatase (PP2A) by yeast two-hybrid screening. Domain studies using a small-scale yeast two-hybrid interaction assay revealed the mediation of protein-protein interaction by FHL1B’s C-terminus. Interaction between FHL1B and PP2A was further verified by co-immunoprecipitation. FHL1B was also shown to shuttle between nucleus and cytoplasm at different phases of the cell cycle. These data suggest that the FHL1B/PP2A_Cβ interaction may illustrate a novel cell-cycle regulatory pathway.

Structured summary

MINT-8044739: FHL1B (uniprotkb:Q13642-2) physically interacts (MI:0915) with PP2Acbeta (uniprotkb:P62714) by two hybrid (MI:0018)MINT-8044769, MINT-8044778: FHL1B (uniprotkb:Q13642-2) physically interacts (MI:0915) with PP2Acbeta (uniprotkb:P62714) by anti bait coimmunoprecipitation (MI:0006)     

Regulation of cell adhesion to collagen via β1 integrins is dependent on interactions of filamin A with vimentin and protein kinase C epsilon

Cell adhesion and spreading on collagen, which are essential processes for development and wound healing in mammals, are mediated by β1 integrins and the actin and intermediate filament cytoskeletons. The mechanisms by which these separate cytoskeletal systems interact to regulate β1 integrins and cell spreading are poorly defined. We previously reported that the actin cross-linking protein filamin A binds the intermediate filament protein vimentin and that these two proteins co-regulate cell spreading. Here we used deletional mutants of filamin A to define filamin A-vimentin interactions and the subsequent phosphorylation and re-distribution of vimentin during cell spreading on collagen. Imaging of fixed and live cell preparations showed that phosphorylated vimentin is translocated to the cell membrane during spreading. Knockdown of filamin A inhibited cell spreading and the phosphorylation and re-distribution of vimentin. Knockdown of filamin A and/or vimentin reduced the cell surface expression and activation of β1 integrins, as indicated by immunoblotting of plasma membrane-associated proteins and shear force assays. In vitro pull-down assays using filamin A mutants showed that both vimentin and protein kinase C? bind to repeats 1-8 of filamin A. Reconstitution of filamin-A-deficient cells with full-length filamin A or filamin A repeats 1-8 restored cell spreading, vimentin phosphorylation, and the cell surface expression of β1 integrins. We conclude that the binding of filamin A to vimentin and protein kinase Cε is an essential regulatory step for the trafficking and activation of β1 integrins and cell spreading on collagen.     

A geminivirus betasatellite encoded βC1 protein interacts with PsbP and subverts PsbP-mediated antiviral defence in plants

Geminivirus disease complexes potentially interfere with plants physiology and cause disastrous effects on a wide range of economically important crops throughout the world. Diverse geminivirus betasatellite associations exacerbate the epidemic threat for global food security. Our previous study showed that βC1, the pathogenicity determinant of geminivirus betasatellites induce symptom development by disrupting the ultrastructure and function of chloroplasts. Here we explored the betasatellite-virus-chloroplast interaction in the scope of viral pathogenesis as well as plant defence responses, using Nicotiana benthamiana—Radish leaf curl betasatellite (RaLCB) as the model system. We have shown an interaction between RaLCB-encoded βC1 and one of the extrinsic subunit proteins of oxygen-evolving complex of photosystem II both in vitro and in vivo. Further, we demonstrate a novel function of the Nicotiana benthamiana oxygen-evolving enhancer protein 2 (PsbP), in that it binds DNA, including geminivirus DNA. Transient silencing of PsbP in N. benthamiana plants enhances pathogenicity and viral DNA accumulation. Overexpression of PsbP impedes disease development during the early phase of infection, suggesting that PsbP is involved in generation of defence response during geminivirus infection. In addition, βC1-PsbP interaction hampers non-specific binding of PsbP to the geminivirus DNA. Our findings suggest that betasatellite-encoded βC1 protein accomplishes counter-defence by physical interaction with PsbP reducing the ability of PsbP to bind geminivirus DNA to establish infection.     

Berberine inhibits human colon cancer cell migration via AMP-activated protein kinase-mediated downregulation of integrin β1 signaling

Colon cancer is associated with a poor prognosis, motivating strategies to prevent its development. An encouraging preventative strategy is the use of nutraceuticals; however, scientific verification of therapeutic functions and mechanisms of biological activity are necessary for the acceptance of dietary supplements in cancer treatment. Berberine is a benzylisoquinoline alkaloid extracted from many kinds of medicinal plants that has been extensively used as a Chinese traditional medicine. Recently, berberine has been reported to possess antitumoral activities. Among the various cellular targets of berberine is AMP-activated protein kinase (AMPK), which regulates tumor progression and metastasis. However, the specific role of berberine-induced AMPK activation and its effects on the metastatic potential of colon cancer remain largely unknown. The present study investigated berberine-induced activation of AMPK and its effects on colon cancer cell migration. Berberine decreased the migration of SW480 and HCT116 cells. We found that berberine activated AMPK in human colon cancer cell lines. Notably, berberine-induced activation of AMPK reduced the integrin β1 protein levels and decreased the phosphorylation of integrin β1 signaling targets. Knockdown of AMPKα1 subunits using small interfering RNA significantly attenuated berberine-induced downregulation of integrin β1 and inhibition of tumor cell migration. Collectively, our results suggest that berberine-induced AMPK activation inhibits the metastatic potential of colon cancer cells by decreasing integrin β1 protein levels and downstream signaling.     

The β-glucan receptor Dectin-1 activates the integrin Mac-1 in neutrophils via Vav protein signaling to promote Candida albicans clearance

Resistance to fungal infections is attributed to engagement of host pattern-recognition receptors, notably the β-glucan receptor Dectin-1 and the integrin Mac-1, which induce phagocytosis and antifungal immunity. However, the mechanisms by which these receptors coordinate fungal clearance are unknown. We show that upon ligand binding, Dectin-1 activates Mac-1 to also recognize fungal components, and this stepwise process is critical for neutrophil cytotoxic responses. Both Mac-1 activation and Dectin-1- and Mac-1-induced neutrophil effector functions require Vav1 and Vav3, exchange factors for RhoGTPases. Mac-1- or Vav1,3-deficient mice have increased susceptibility to systemic candidiasis that is not due to impaired neutrophil recruitment but defective intracellular killing of C.?albicans yeast forms, and Mac-1 or Vav1,3 reconstitution in hematopoietic cells restores resistance. Our results demonstrate that antifungal immunity depends on Dectin-1-induced activation of Mac-1 functions that is coordinated by Vav proteins, a pathway that may localize cytotoxic responses of circulating neutrophils to infected tissues.     

KCTD11 inhibits progression of lung cancer by binding to β-catenin to regulate the activity of the Wnt and Hippo pathways

KCTD11 has been reported to be a potential tumour suppressor in several tumour types. However, the expression of KCTD11 and its role has not been reported in human non-small cell lung cancer (NSCLC). Whether its potential molecular mechanism is related to its BTB domain is also unknown. The expression of KCTD11 in 139 NSCLC tissue samples was detected by immunohistochemistry, and its correlation with clinicopathological factors was analysed. The effect of KCTD11 on the biological behaviour of lung cancer cells was verified in vitro and in vivo. Its effect on the epithelial-mesenchymal transition(EMT)process and the Wnt/β-catenin and Hippo/YAP pathways were observed by Western blot, dual-luciferase assay, RT-qPCR, immunofluorescence and immunoprecipitation. KCTD11 is under-expressed in lung cancer tissues and cells and was negatively correlated with the degree of differentiation, tumour-node-metastasis (TNM) stage and lymph node metastasis. Low KCTD11 expression was associated with poor prognosis. KCTD11 overexpression inhibited the proliferation and migration of lung cancer cells. Further studies indicated that KCTD11 inhibited the Wnt pathway, activated the Hippo pathway and inhibited EMT processes by inhibiting the nuclear translocation of β-catenin and YAP. KCTD11 lost its stimulatory effect on the Hippo pathway after knock down of β-catenin. These findings confirm that KCTD11 inhibits β-catenin and YAP nuclear translocation as well as the malignant phenotype of lung cancer cells by interacting with β-catenin. This provides an important experimental basis for the interaction between KCTD11, β-catenin and YAP, further revealing the link between the Wnt and Hippo pathways.     

Isolation and characterization of BetaM protein encoded by ATP1B4--a unique member of the Na,K-ATPase β-subunit gene family

ATP1B4 genes represent a rare instance of the orthologous gene co-option that radically changed functions of encoded BetaM proteins during vertebrate evolution. In lower vertebrates, this protein is a β-subunit of Na,K-ATPase located in the cell membrane. In placental mammals, BetaM completely lost its ancestral role and through acquisition of two extended Glu-rich clusters into the N-terminal domain gained entirely new properties as a muscle-specific protein of the inner nuclear membrane possessing the ability to regulate gene expression. Strict temporal regulation of BetaM expression, which is the highest in late fetal and early postnatal myocytes, indicates that it plays an essential role in perinatal development. Here we report the first structural characterization of the native eutherian BetaM protein. It should be noted that, in contrast to structurally related Na,K-ATPase β-subunits, the polypeptide chain of BetaM is highly sensitive to endogenous proteases that greatly complicated its isolation. Nevertheless, using a complex of protease inhibitors, a sample of authentic BetaM was isolated from pig neonatal skeletal muscle by a combination of ion-exchange and lectin-affinity chromatography followed by SDS–PAGE. Results of the analysis of the BetaM tryptic digest using MALDI-TOF and ESI-MS/MS mass spectrometry have demonstrated that native BetaM in neonatal skeletal muscle is a product of alternative splice mRNA variant B and comprised of 351 amino acid residues. Isolated BetaM protein was also characterized by SELDI-TOF mass spectrometry before and after deglycosylation. This allowed us to determine that the carbohydrate moiety of BetaM has molecular mass 5.9 kDa and consists of short high-mannose type N-glycans. The results of direct analysis of the purified native eutherian BetaM protein provide first insights into structural properties underlying its entirely new evolutionarily acquired functions.     

Association of single nucleotide autophagy-related protein 5 gene polymorphism rs2245214 with susceptibility to non–small cell lung cancer

Introduction : Autophagy is a mechanism that is involved in the regulation of cellular life, apoptosis, and stemness while its intervening genes play important functions in various cancers including lung cancer. ATG5 is one of the key genes for the regulation of the autophagy pathway. In this study, our team has investigated the potential relationship between ATG5 gene polymorphism rs2245214 with non–small cell lung cancer (NSCLC) in a subpopulation of patients from southern Iran. In this study, 34 patients with NSCLC (20 males and 14 females [mean age: 12.86 ± 60.47 years]) and 50 healthy subjects (30 males and 20 females [mean age: 13.09 ± 56.62 years]) were studied in terms of the genotype of the ATG5 gene. We used restriction fragment length polymorphism and analyzed the results using SPSS software (v.23). The results revealed that subjects harboring the guanine/cytosine (GC) genotype of the rs2245214 ATG5 gene polymorphism had suffered less from NSCLC, whereas the prevalence of the C-allele of this polymorphism was significantly higher in patients with NSCLC ( P < 0.05). On the basis of the results of logistic regression, the presence of this C-allele may predict the risk of lung cancer ( P value = 0.011; OR, 3.52; 95% CI, 1.33-9.26). This study concludes that the C-allele of the rs2245214 ATG5 gene polymorphism is associated with increased susceptibility to NSCLC, whereas the GC genotype of this polymorphism is associated with decreased risk and might therefore have a protective role in the development of NSCLC.     

Characterization of a cDNA encoding a protein with limited similarity to β1, 3-N-acetylglucosaminyltransferase

Glycosyltransferases constitute a large group of enzymes that are involved in a wide range of functions in all living organisms. By large-scale sequencing analysis of a human fetal brain cDNA library, we isolated a novel human putative glycosyltransferase gene named beta3GnTL1. Its cDNA is 1372 base pair in length, encoding a predicted protein with 361 amino acid residues. The human beta3GnTL1 is located to chromosome 17q25.3 by comparison of its cDNA with human gemome database. RT-PCR result shows the beta3GnTL1 is expressed at various levels in most of tissues examined.     

Regulation of tubulin polypeptides and microtubule function: Rki1p interacts with the β-tubulin binding protein Rbl2p

Genetic analysis of microtubule functions in the yeast Saccharomyces cerevisiae suggests that cells manage the levels and activities of the tubulin polypeptides. These reactions may be involved in protein folding, formation of the heterodimer, and maintenance of the appropriate balance between α- and β-tubulin. One protein involved in these functions is Rbl2p, which forms a complex with β-tubulin. Here we describe the identification of a novel yeast gene, RKI1, that interacts genetically with RBL2. Deletion of rki1 causes conditional defects in microtubule assembly and cell growth. Rki1p can be isolated in a complex containing Rbl2p. The results support the existence of cellular mechanisms for regulating microtubule function through the tubulin polypeptides. Received: 8 August 1998 / Accepted: 13 September 1998     

Activation of p53-p21 is closely associated with the acquisition of resistance to apoptosis caused by β1-integrin silencing in head and neck cancer cells

The issue of whether aberrant expression of β1-integrin is associated with cancer progression and development of resistance to cytotoxic therapy is of considerable interest. Studies to date have shown that the anchorage-independent survival of cancer is attributed, in part, to epithelial-to-mesenchymal transition (EMT). Here, we have reported a novel alternative mechanism of anchorage-independent survival of cancer cells. Cell lines derived from head and neck cancer patients (AMC-HN-3 and AMC-HN-9) and the well-known EMT cancer cell line, MDA-MB231, were examined. The EMT features of AMC-HN-9 cells were comparable to those of MDA-MB231, whereas AMC-HN-3 cells showed no EMT characteristics. Although the pattern and degree of β1-integrin expression were similar in all three cell lines, sensitivities of the cells to β1-integrin knockdown with small interfering RNA (siRNA) were different. Cancer cells with no EMT features underwent cell death to a more significant extent following β1-integrin silencing than those with EMT. Intriguingly, we observed reactive activation of the p53-p21 pathway after β1-integrin silencing in AMC-HN-9 cells lacking an apparent cell death response. Simultaneous knockdown of wild-type p53 and β1-integrin in this cell line promoted cell death. Our data collectively indicate that β1-integrin-related cell death is closely associated with EMT phenotypes and activation of the p53-p21 pathway is partly involved in the acquisition of resistance to apoptosis induced by β1-integrin silencing. Further clarification of the mechanisms underlying p53 integration with β1-integrin signaling may facilitate the development of novel anti-cancer strategies.     

Modulation of membrane properties of lung cancer cells by azurin enhances the sensitivity to EGFR-targeted therapy and decreased β1 integrin-mediated adhesion

In lung cancer, the Epidermal Growth Factor Receptor (EGFR) is one of the main targets for clinical management of this disease. The effectiveness of therapies toward this receptor has already been linked to the expression of integrin receptor subunit β₁ in NSCLC A549 cells. In this work we demonstrate that azurin, an anticancer therapeutic protein originated from bacterial cells, controls the levels of integrin β₁ and its appropriate membrane localization, impairing the intracellular signaling cascades downstream these receptors and the invasiveness of cells. We show evidences that azurin when combined with gefitinib and erlotinib, tyrosine kinase inhibitors which targets specifically the EGFR, enhances the sensitivity of these lung cancer cells to these molecules. The broad effect of azurin at the cell surface level was examined by Atomic Force Microscopy. The Young 's module (E) shows that the stiffness of A549 lung cancer cells decreased with exposure to azurin and also gefitinib, suggesting that the alterations in the membrane properties may be the basis of the broad anticancer activity of this protein. Overall, these results show that azurin may be relevant as an adjuvant to improve the effects of other anticancer agents already in clinical use, to which patients often develop resistance hampering its full therapeutic response