Ras suppression potentiates rear actomyosin contractility-driven cell polarization and migration.

Ras has been extensively studied as a promoter of cell proliferation, whereas few studies have explored its role in migration. To investigate the direct and immediate effects of Ras activity on cell motility or polarity, we focused on RasGAPs, C2GAPB in Dictyostelium amoebae and RASAL3 in HL-60 neutrophils and macrophages. In both cellular systems, optically recruiting the respective RasGAP to the cell front extinguished pre-existing protrusions and changed migration direction. However, when these respective RasGAPs were recruited uniformly to the membrane, cells polarized and moved more rapidly, whereas targeting to the back exaggerated these effects. These unexpected outcomes of attenuating Ras activity naturally had strong, context-dependent consequences for chemotaxis. The RasGAP-mediated polarization depended critically on myosin II activity and commenced with contraction at the cell rear, followed by sustained mTORC2-dependent actin polymerization at the front. These experimental results were captured by computational simulations in which Ras levels control front- and back-promoting feedback loops. The discovery that inhibiting Ras activity can produce counterintuitive effects on cell migration has important implications for future drug-design strategies targeting oncogenic Ras.

Ras-mediated homeostatic control of front-back signaling dictates cell polarity.

Studies in the model systems, Dictyostelium amoebae and HL-60 neutrophils, have shown that local Ras activity directly regulates cell motility or polarity. Localized Ras activation on the membrane is spatiotemporally regulated by its activators, RasGEFs, and inhibitors, RasGAPs, which might be expected to create a stable 'front' and 'back', respectively, in migrating cells. Focusing on C2GAPB in amoebae and RASAL3 in neutrophils, we investigated how Ras activity along the cortex controls polarity. Since existing gene knockout and overexpression studies can be circumvented, we chose optogenetic approaches to assess the immediate, local effects of these Ras regulators on the cell cortex. In both cellular systems, optically targeting the respective RasGAPs to the cell front extinguished existing protrusions and changed the direction of migration, as might be expected. However, when the expression of C2GAPB was induced globally, amoebae polarized within hours. Furthermore, within minutes of globally recruiting either C2GAPB in amoebae or RASAL3 in neutrophils, each cell type polarized and moved more rapidly. Targeting the RasGAPs to the cell backs exaggerated these effects on migration and polarity. Overall, in both cell types, RasGAP-mediated polarization was brought about by increased actomyosin contractility at the back and sustained, localized F-actin polymerization at the front. These experimental results were accurately captured by computational simulations in which Ras levels control front and back feedback loops. The discovery that context-dependent Ras activity on the cell cortex has counterintuitive, unanticipated effects on cell polarity can have important implications for future drug-design strategies targeting oncogenic Ras.

Role of the TSLP-DC-OX40L pathway in asthma pathogenesis and airway inflammation in mice.

This study aimed to explore the effect of the TSLP-DC-OX40L pathway in asthma pathogenesis and airway inflammation in mice. For this, 65 male BALF/c mice were distributed among the control, asthma, immunoglobulin G (IgG) + asthma (IgG, 500 µg/500 µL, intratracheal injection of 50 µL each time), LY294002 (OX40L inhibitor) + asthma (intratracheal injection of 2 mg/kg LY294002), and anti-TSLP + asthma (intratracheal injection of 500 µg/500 µL TSLP antibody, 50 µL each time) groups. ELISA was applied to measure the serum levels of immunoglobulin E (IgE), ovalbumin (OVA)-sIgE, interleukin-4 (IL-4), IL-5, IL-13, and interferon-γ (IFN-γ); flow cytometry was employed to detect Treg cells and dendritic cell (DC) and lymphopoiesis. RT-qPCR and Western blot assays were used to measure the levels of TSLP, OX40L, T-bet, GATA-3, NF-κB, p38, and ERK. Treatment with LY294002 and anti-TSLP resulted in increases in the numbers of total cells, eosinophils, neutrophils, and lymphocytes in the bronchoalveolar lavage fluid; total serum levels of IgE, OVA-sIgE, IL-4, IL-5, and IL-13; levels of DC cells; lymphopoiesis; and levels of TSLP, OX40L, GATA-3, NF-κB, p38, and ERK, whereas there were decreases in the levels of IFN-γ and CD4+CD25+Treg cells; CD4+Foxp3+Treg cells; and T-bet. The TSLP-DC-OX40L pathway may contribute to asthma pathogenesis and airway inflammation by modulating the levels of CD4+CD25+Treg cells and inflammatory cytokines.

Time and energy-efficient homogeneous transesterification of cellulose under mild reaction conditions.

In this research, cellulose aliphatic esters (CEs) were synthesized efficiently in an N, N-dimethylacetamide/lithium chloride system (DMAc/LiCl) with vinyl esters (VEs, number of carbon atoms ranging from 4 to 12) as acylation reagent and 1,8-diazabicyclo[5,4,0]undec-7-ene (DBU) as catalyst. The structures and properties of the products have been characterized by various analytical techniques. The key concept in this cellulose modification was the achievement the degree of substitution (DS) >2.75 at much milder temperature and shorter reaction time (under 30°C within 15min-30min), other than previous research. Generally, the DS of obtained CEs showed a reverse trend with the length of the aliphatic chain increasing. The priority of reactions in three positions of the CEs followed the same order of C6>C2>C3 for a homogeneous conversion. There was no decrease of molecule weight under this mild reaction. This research provides a novel homogeneous technology to synthesize various CEs efficiently.