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MAdCAM-1 binds to integrin α4β7, which mediates the rolling and arrest of circulating lymphocytes upon the vascular endothelia during lymphocytic homing. The calcium response by adhered lymphocytes is a critical event for lymphocyte activation and subsequent arrest and migration under flow. However, whether the interaction of integrin α4β7 /MAdCAM-1 can effectively trigger the calcium response of lymphocytes remains unclear, as well as whether the fluid force affects the calcium response. In this study, we explore the mechanical regulation of integrin α4β7-induced calcium signaling under flow. Flou-4 AM was used to examine the calcium response under real-time fluorescence microscopy when cells were firmly adhered to a parallel plate flow chamber. The interaction between integrin α4β7 and MAdCAM-1 was found to effectively trigger calcium signaling in firmly adhered RPMI 8226 cells. Meanwhile, increasing fluid shear stress accelerated the cytosolic calcium response and enhanced signaling intensity. Additionally, the calcium signaling of RPMI 8226 activated by integrin α4β7 originated from extracellular calcium influx instead of cytoplasmic calcium release, and the signaling transduction of integrin α4β7 was involved in Kindlin-3. These findings shed new light on the mechano-chemical mechanism of calcium signaling in RPMI 8226 cells induced by integrin α4β7. [ABSTRACT FROM AUTHOR]

Simple Summary: The integrin αvβ3-RGD motif interaction plays a key role in the progression of malignant tumor. Although two typical cyclic and linear RGD short peptides have been widely used in tumor diagnosis and therapy, little is known about the internal dynamic mechanism for different configurations of RGD peptides with different affinities interacting with the integrin αvβ3. Our results showed that the cyclic RGD peptide had a more stable configuration in binding to integrins αvβ3, which depended on the higher binding energy and higher static electrical energy, especially in the interaction between AspRGD-MIDAS. The steered molecular dynamics simulation showed a stronger interaction for the cyclic RGD-integrin αvβ3 system than the linear one, with a larger dissociation force (average peak force) and more time to dissociate. Our findings provide insights into the dynamics of integrin αvβ3 interactions with linear and cyclic RGD ligands and offer some new therapeutic approaches for the design and development of novel antitumor drugs. Integrin αvβ3 interacting with the short Arg-Gly-Asp (RGD) motif plays a critical role in the progression of several types of tumors. However, the effects of the RGD structure (cyclic or linear) with integrin αvβ3 at the atomic level remain poorly understood. Here, we performed association and dissociation dynamic simulations for integrin αvβ3 in complex with a linear or cyclic pentapeptide by steered molecular dynamics simulations. Compared with cyclic RGD, the linear RGD peptide triggers instability of the configurational changes, mainly resting with the RGD domain due to its flexibility. The main interaction energy between Mg2+ and cyclic RGD is much stronger than that of the linear RGD system by the well shield to lessen attacks by free water molecules. The force-dependent dissociation results show that it is easier for linear RGD peptides to leave the active site and much quicker than the cyclic RGD ligand, whereas it is harder to enter the appropriate active binding site in linear RGD. The Ser123-AspRGD bond may play a critical role in the allosteric pathway. Our findings provide insights into the dynamics of αvβ3 interactions with linear and cyclic RGD ligands and contribute to the application of RGD-based strategies in preclinical therapy. [ABSTRACT FROM AUTHOR]

Activation of integrins is crucial for recruitment of flowing leukocytes to inflammatory or injured vascular sites, but their spatiotemporal characteristics are incompletely understood. We discovered that β 2 -integrin activation over the entire surface of neutrophils on immobilized P-selectin occurred via mitogen-activated protein kinase (MAPK) or non-MAPK signaling with a minute-level timescale in a force-dependent manner. In flow, MAPK signaling required intracellular Ca 2+ release to activate integrin within 2 min. Integrin activation via non-MAPK signaling occurred first locally in the vicinity of ligated P-selectin glycoprotein ligand-1 (PSGL-1) within sub-seconds, and then over the entire cell surface within 1 min in an extracellular Ca 2+ influx-dependent manner. The transition from a local (but rapid) to global (but slow) activation mode was triggered by ligating the freshly activated integrin. Lipid rafts, moesin, actin, and talin were involved in non-MAPK signaling. Fluid loads had a slight effect on local integrin activation with a second-level timescale, but served as enhancers of global integrin activation., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Sun, Huang, Pan, Fang, Wang, Ji, Ling, Guo, Lin, Li, Fang and Wu.)

We in this study measured the site density of E-selectin in order to explore the practical pliability using radionuclide labeling method and γ-imaging of single photon emission computer tomography (SPECT). This method required labeling of antibody with 125 I using Indogen method and binding of the labeled antibody to E-selectin. Labeled E-selectin was separated and purified in a Sephadex G25 column. The different fractions of the eluants were imaged, analyzed and quantified with SPECT method. For measuring the saturation curve of E-selectin, 130 μL of E-selectin solution with different concentrations were added in a 48-well plate and incubated overnight at 4℃. After incubation, 130 μL of labeled antibody solution were added and kept incubated for 30 min. The resulted mixture was washed, and the radioactivity in each sample was detected by SPECT. The levels of radioactivity were translated to site densities, and were used to plot a standard curve. The labeled product was quantitatively analyzed with SPECT. The labeling rate of E-selectin was 78%. The saturation curve of different concentration samples showed that when the concentration was in the concentration range of 0-1 mg/mL, the standard curve was y =6 045.7 x -51.166, R 2 =0.997 9. Based on this finding, it could be concluded that γ-imaging is an important tool for analysis of radiolabeled product and determination of site density.

Tumor hypoxia is an independent prognostic indicator of tumor malignant progression and poor patient survival. Therefore, eradication of hypoxic tumor cells is of paramount importance for successful disease control. In this study, we have made a new discovery that nifurtimox, a clinically approved drug to treat Chagas disease caused by the parasitic protozoan trypanosomes, can function as a hypoxia-activated cytotoxin. We have found that nifurtimox preferentially kill clonogenic tumor cells especially under the hypoxic conditions of ≤0.1% O 2 . Mechanistically, nifurtimox becomes activated after tumor cells enter into a fully hypoxic state, as shown by the stabilization of the Hypoxia-Inducible Factor 1α (HIF-1α). Nifurtimox specifically induces the formation of 53BP1 foci, a hallmark of DNA double-stranded breaks, in hypoxic tumor cells. Hypoxia-dependent activation of nifurtimox involves P450 (cytochrome) oxidoreductase. The anti-protozoan drug nifurtimox holds promise as a new hypoxia-activated cytotoxin with the potential to preferentially eliminates severely hypoxic tumor cells., Competing Interests: None.

Atherosclerosis is a complex disease characterized by lipid accumulation in the vascular wall and influenced by multiple genetic and environmental factors. To understand the mechanisms of molecular regulation related to atherosclerosis better, a protein interaction network was constructed in the present study. Genes were collected in nucleotide database and interactions were downloaded from Biomolecular Object Network Database (BOND). The interactional data were imported into the software Cytoscape to construct the interaction network, and then the degree characteristics of the network were analyzed for Hub proteins. Statistical significance pathways and diseases were figured out by inputting Hub proteins to KOBAS2. 0. The complete pathway network related to atherosclerosis was constructed. The results identified a series of key genes related to atherosclerosis, which would be the potential promising drug targets for effective prevention.

Endogenous viral elements (EVEs) are widely distributed throughout eukaryotic genomes, and their evolution and potential function have attracted a lot of interest. Draft genome sequences for Schistosoma mansoni, Schistosoma japonicum and Schistosoma haematobium are now available; however, information about EVEs in blood flukes of the genus schistosoma is scanty. Here, genome-wide survey into the putative EVE sequences of the three key schistosome genomes were present. Totally 4, 117 gene sequences were identified, including retrovirus-like gypsy elements, RNA viruses and dsDNA viruses. Compared with S. japonicum and S. haematobium, S. mansoni appeared to greatly out numbered by gypsy members. Phylogenetic analysis revealed one novel endogenous retrovirus element in S. mansoni. This initial characterization of schistosomes showed that schistosomes harbour distinct EVEs that may have played an important evolutionary role. Studies of schistosomes' endogenous viruses helped us to glance at an earlier viral event in the class Trematoda, greatly broadening the field of palaeovirology.