The sigma 54 genes rpoN1 and rpoN2 of Xanthomonas citri subsp. citri play different roles in virulence, nutrient utilization and cell motility

The sigma factor 54（σ^（54）） controls the expression of many genes in response to nutritional and environmental conditions. There are two σ^（54） genes, rpo N1（XAC1969） and rpo N2（XAC2972）, in Xanthomonas citri subsp. citri. To investigate their functions, the deletion mutants ΔrpoN1, ΔrpoN2 and ΔrpoN1N2 were constructed in this study. All the mutants delayed canker development in low concentration inoculation in citrus plants. The bacterial growth of mutants was retarded in the medium supplemented with nitrogen and carbon resources. Under either condition, the influence degree caused by deletion of rpoN 2 was larger than the deletion of rpoN 1. Remarkably, the mutant ΔrpoN 1 showed a reduction in cell motility, while the mutant Δrpo N2 increased cell motility. Our data suggested that the rpoN 1 and rpoN 2 play diverse roles in X. citri subsp. citri.

PRR11 induces filopodia formation and promotes cell motility via recruiting ARP2/3 complex in non-small cell lung cancer cells

Filopodia, a finger-like structure and actin-rich plasma-membrane protrusion at the leading edge of the cell, has important roles in cell motility. However, the mechanisms of filopodia generation are not well-understood via the actin-related protein 2/3 (ARP2/3) complex in Non-Small Cell Lung Cancer (NSCLC) cells. We previously have demonstrated that PRR11 associates with the ARP2/3 complex to regulate cytoskeleton-nucleoskeleton assembly and chromatin remodeling. In this study, we further demonstrate that PRR11 involves in filopodia formation, focal adhesion turnover and cell motility through ARP2/3 complex. Cell phenotype assays revealed that the silencing of PRR11 increased cellular size and inhibited cell motility in NSCLC cells. Mechanistically, PRR11 recruited and co-localized with Arp2 at the membrane protrusion to promote filopodia formation but not lamellipodia formation. Notably, PRR11 mutant deletion of the proline-rich region 2 (amino acid residues 185–200) abrogated the effect of filopodia formation. In addition, PRR11-depletion inhibited filopodial actin filaments assembly and increased the level of active integrin β1 in the cell surface, whereas reduced the phosphorylation level of focal adhesion kinase (FAKY397) to repress focal adhesion turnover and cell motility in NSCLC cells. Taken together, our findings indicate that PRR11 has critical roles in controlling filopodia formation, focal adhesion turnover and cell motility by recruiting ARP2/3 complex, thus dysregualted expression of PRR11 potentially facilitates tumor metastasis in NSCLC cells.

Catechu Inhibiting Cathepsin B Activity and Motility of HT1080 Cells

We reported that Catechu extract has a significant inhibitory effect on cathepsin B activity. The IC50 value for the Catechu extract against cathepsin B was 7.6 μg/mL. In addition, we showed that HT1080 human fibrosarcoma cells express cathepsin B and Catechu modulate the invasion and motility of these cells. These data may provide molecular mechanisms for the therapeutic effects of Catechu.

Cell adhesion molecules regulate contractile ring-indepen- dent cytokinesis in Dictyostelium discoideum

To investigate the roles of substrate adhesion in cytokinesis, we established cell lines lacking paxillin （PAXB） or vineulin （VINA）, and those expressing the respective GFP fusion proteins in Dictyostelium discoideum. As in mammalian cells, GFP-PAXB and GFP-VINA formed focal adhesion-like complexes on the cell bottom, paxB^- cells in suspension grew normally, but on substrates, often failed to divide after regression of the furrow. The efficient cytokinesis of paxB^- cells in suspension is not because of shear forces to assist abscission, as they divided normally in static suspension culture as well. Double knockout strains lacking mhcA, which codes for myosin II, and paxB or vinA displayed more severe cytokinetic defects than each single knockout strain. In mitotic wild-type cells, GFP-PAXB was diffusely distributed on the basal membrane, hut was strikingly condensed along the polar edges in mitotic mhcA^- cells. These results are consistent with our idea that Dictyostelium displays two forms of cytokinesis, one that is contractile ringdependent and adhesion-independent, and the other that is contractile ring-independent and adhesion-dependent, and that the latter requires PAXB and VINA. Furthermore, thatpaxB- cells fail to divide normally in the presence of substrate adhesion suggests that this adhesion molecule may play additional signaling roles.

Histone deacetylase 6 and cytoplasmic linker protein 170 function together to regulate the motility of pancreatic cancer cells

Pancreatic cancer is a devastating disease with the worst prognosis among all the major human malignancies. The propensity to rapidly metastasize contributes signifi- cantly to the highly aggressive feature of pancreatic cancer. The molecular mechanisms underlying this remain elusive, and proteins involved in the control of pancreatic cancer cell motility are not fully characterized. In this study, we find that histone deacetylase 6 （HDAC6）, a member of the class II HDAC family, is highly expres- sed at both protein and mRNA levels in human pancre- atic cancer tissues. HDAC6 does not obviously affect pancreatic cancer cell proliferation or cell cycle pro- gression. Instead, it significantly promotes the motility of pancreatic cancer cells. Further studies reveal that HDAC6 interacts with cytoplasmic linker protein 170 （CLIP-170） and that these two proteins function together to stimulate the migration of pancreatic cancer cells. These findings provide mechanistic insight into the progression of pancreatic cancer and suggest HDAC6 as a potential target for the management of this malignancy.

Modeling cells spreading,motility,and receptors dynamics:a general framework

The response of cells during spreading and motility is dictated by several multi-physics events,which are triggered by extracellular cues and occur at different time-scales.For this sake,it is not completely appropriate to provide a cell with classical notions of the mechanics of materials,as for“rheology”or“mechanical response”.Rather,a cell is an alive system with constituents that show a reproducible response,as for the contractility for single stress fibers or for the mechanical response of a biopolymer actin network,but that reorganize in response to external cues in a non-exactly-predictable and reproducible way.Aware of such complexity,in this note we aim at formulating a multi-physics framework for modeling cells spreading and motility,accounting for the relocation of proteins on advecting lipid membranes.

Differential thymosin β10 expression levels and actin filament organization in tumor cell lines with different metastatic potential

Background To investigate the differential expression levels of thymosin β10 (Tβ10) and the corresponding changes of actin filament organization in human tumor cell lines with different metastatic potential.Methods Four groups of nine human tumor cell lines with different metastatic potential were analyzed for the amount of Tβ10 mRNAs by Northern blot and for their peptide expression levels by immunohistochemistry. The filamentous actin (F-actin) was observed by staining of TRITC-phalloidin to detect changes in actin organization.Results In comparison with non-/weakly metastatic counterparts, Tβ10 was upregulated in highly metastatic human lung cancer, malignant melanoma and breast cancer cell lines. Staining of TRITC-phalloidin revealed less actin bundles, a fuzzy network of shorter filaments and some F-actin aggregates in the highly metastatic tumor cells. Meanwhile, the actin filaments were robust and orderly arranged in the non-/weakly metastatic cancer cell lines.Conclusion Tβ10 levels correlate positively with the metastatic capacity in human tumors currently examined. The increasing metastatic potential of tumor cells is accompanied by a loss of F-actin, poorly arranged actin skeleton organizations and presence of F-actin aggregates. There is a consistent correlation between the elevated Tβ10 expression and the disrupted actin skeleton.

Active bleb formation is abated in Lytechinus variegatus red spherule coelomocytes after disruption of acto-myosin contractility

Red spherule coelomocytes are immune cells in the sea urchin Lytechinus variegatus that have been characterizedas motile O2 transport cells. Video microscopy of living red spherule coelomocytes reveals a constitutive, dynamicarray of cellular morphologies and movements. Cells continuously send out and retract membrane blebs all over thecell surface as part of their normal cellular physiology. Disruption of microtubules by perfusion with either nocodazoleor taxol had no effect on bleb formation or motility. Perfusion with cytochalasin B abated bleb formation andrevealed cells that exhibited multiple small spheres attached by short membrane extensions. Attenuation of blebbingand intracellular organelle motility were restored by washing out with cytochalasin B. Treatment with phalloidinalso abated bleb formation and revealed a smooth, spherical cellular morphology. The effects of phalloidin werecompletely reversible after washout. Red spherule coelomocytes treated with blebbistatin rounded up with anirreversible retraction of blebs into surface blebs that were greatly reduced in size, number and motility. Normal cellsurface bleb formation and intracellular organelle motility were not restored after washout of the drug. These resultsindicate that the acto-myosin contractile mechanism contributes to the dynamics of constitutive cell surface membraneblebbing in invertebrate immune cells.

The activating effect of IFN-y on monocytes/macrophages is regulated by the LIF-trophoblast-lL-lO axis via Statl inhibition and Stat3 activation

Interferon gamma （IFN-7） and leukemia inhibitory factor （LIF） are key gestational factors that may differentially affect leukocyte function during gestation. Because IFN-,/induces a pro-inflammatory phenotype in macrophages and because trophoblast cells are principal targets of LIF in the placenta, we investigated whether and how soluble factors from trophoblast cells regulate the effects of IFN-7 on macrophage activation. IFN-7 reduces macrophage motility, but enhances Statl activation, pro-inflammatory gene expression and cytotoxic functions. Soluble factors from villous cytotrophoblasts （vCT＋LIF cells） and BeWo cells （BW/ST＋LIF cells） that were differentiated in the presence of LIF inhibit macrophage Statl activation but inversely sustain Stat3 activation in response to IFN-7. vCT＋LIF cells produce soluble factors that induce Stat3 activation; this effect is partially abrogated in the presence of neutralizing anti-interleukin 10 （IL-IO） antibodies. Moreover, soluble factors from BW/ST＋LIF cells reduce cell proliferation but enhance the migratory responses of monocytes. In addition, these factors reverse the inhibitory effect of IFN-y on monocyte/macrophage motility. BW/ST＋LIF cells also generate IFN-y-activated macrophages with enhanced IL-IO expression, but reduced tumor-necrosis factor alpha （TNF-cd, CD14 and CD40 expression as well as impaired cytotoxic function. Additional assays performed in the presence of neutralizing anti-lL-lO antibodies and exogenous IL-IO demonstrate that reduced macrophage cytotoxicity and proliferation, but increased cell motility result from the ability of trophoblast IL-IO to sustain Star3 activation and suppress IFN-y-induced Star1 activation. These in vitro studies are the first to describe the regulatory role of the LIF-trophoblast-lL- 10 axis in the process of macrophage activation in response to pro-inflammatory cytokines.