Na+-stimulated phosphate uptake system in Synechocystis sp. PCC 6803 with Pst1 as a main transporter

<p>Abstract</p> <p>Background</p> <p>Most living cells uptake phosphate, an indispensable nutrient for growth from their natural environment. In <it>Synechocystis </it>sp. PCC 6803, the cells lack phosphate-inorganic transport (Pit) system but contain two phosphate-specific transport (Pst) systems, Pst1 and Pst2. We investigated the kinetics of Pi uptake of these two Pst systems by constructing the two mutants, ΔPst1 and ΔPst2, and comparing their kinetic properties with those of the wild-type cells under both Pi-sufficient and deficient conditions. The effects of pH and Na⁺on the uptake of phosphate in <it>Synechocystis </it>were also studied.</p> <p>Results</p> <p>Growth rates of the two mutants and wild type were similar either under phosphate-sufficient or deficient condition. The <it>K_m</it>for phosphate uptake was 6.09 μM in wild type and this was reduced to 0.13 μM in ΔPst1 cells and 5.16 μM in the ΔPst2 strain. The <it>V_max</it>values of 2.48, 0.22, and 2.17 μmol • (min • mg of chlorophyll <it>a</it>)^-1were obtained for wild type, the ΔPst1 and ΔPst2 strains, respectively. A monophasic phosphate uptake was observed in wild-type cells. The uptake of phosphate was energy and pH-dependent with a broad pH optimum between pH 7-10. Osmolality imposed by NaCl stimulated phosphate uptake whereas that imposed by sorbitol decreased uptake, suggesting stimulation of uptake was dependent upon ionic effects.</p> <p>Conclusion</p> <p>The data demonstrate that Pst2 system of <it>Synechocystis </it>has higher affinity toward phosphate with lower <it>V_max</it>than Pst1 system. The Pst1 system had similar <it>K_m</it>and <it>V_max</it>values to those of the wild type suggesting that Pst1 is the main phosphate transporter in <it>Synechocystis </it>sp. PCC 6803. The <it>K_m</it>of Pst1 of <it>Synechocystis </it>is closer to that of Pit system than to that of the Pst system of <it>E. coli</it>, suggesting that <it>Synechocystis </it>Pst1 is rather a medium/low affinity transporter whereas Pst2 is a high affinity transporter.</p

Fcγ Receptors in Solid Organ Transplantation.

In the current era, one of the major factors limiting graft survival is chronic antibody-mediated rejection (ABMR), whilst patient survival is impacted by the effects of immunosuppression on susceptibility to infection, malignancy and atherosclerosis. IgG antibodies play a role in all of these processes, and many of their cellular effects are mediated by Fc gamma receptors (FcγRs). These surface receptors are expressed by most immune cells, including B cells, natural killer cells, dendritic cells and macrophages. Genetic variation in FCGR genes is likely to affect susceptibility to ABMR and to modulate the physiological functions of IgG. In this review, we discuss the potential role played by FcγRs in determining outcomes in solid organ transplantation, and how genetic polymorphisms in these receptors may contribute to variations in transplant outcome.MRC is supported by the NIHR Cambridge BRC, the NIHR Blood and Transplant Research Unit (Cambridge) and by a Medical Research Council New Investigator Grant (MR/N024907/1).This is the final version of the article. It first appeared from Springer via https://doi.org/10.1007/s40472-016-0116-

Heat shock protein 27 and its autoantibodies in atherogenesis

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Heat Shock Protein 27 and its Autoantibodies in Atherogenesis.

Atherosclerosis is a chronic inflammatory disease and autoimmune mechanisms may contribute to its pathogenesis. Hsp27, a member of the small heat shock protein family, has been found to be expressed in atherosclerotic lesions. The aim of this study was to investigate whether Hsp27 may be involved in atherogenesis. In vitro, Hsp27 treatment of the J774. 2 murine macrophage cell line was associated with a significant decrease in macrophage interleukin (IL)-10 secretion (p<0.05). This effect was reduced when cells were pretreated with anti-toll like receptor-2 (TLR2) blocking antibodies. Also, a significant increase in macrophage TLR-2 surface expression was observed following treatment with Hsp27 (p<0.05). In patients with an acute myocardial infarction, Hsp27 concentrations were lower in samples taken 12 hours post-infarction compared to samples taken on admission (p=0.02). There was also a concomitant decrease in the levels of anti-Hsp27 immunoglobulin (Ig)M antibodies (p=0.02) and complement C3 in the 12 hour samples compared to samples taken on admission (p=0.02). In a study group of young healthy controls and gymnasts, for the healthy controls only, there was a divergent association between Hsp27 antibody levels with physical activity, with Hsp27 IgM positively correlated (r=0.42, p<0.05) and the Hsp27 IgG negatively correlated (r=-0.43, p<0.05) with physical activity. In patients with glucose intolerance (GI) and established cardiovascular disease (CVD) there was a significantly higher serum Hsp27 (p=0.02) concentration, and a significantly lower anti-Hsp27 IgM antibody level (p=0.02), compared to levels in healthy controls and a borderline significantly higher anti-Hsp27 IgG antibody levels compared to levels in GI patients without CVD. Serum anti-Hsp27 IgG antibody levels were positively correlated with levels of the inflammatory marker, intercellular adhesion molecule (ICAM)-1, r=0.28, p=0.03. The pattern of high serum Hsp27, low IgM and high IgG autoantibodies in patients with cardiovascular disease and the association of the Hsp27 IgG antibodies with the inflammatory marker ICAM-1 suggest involvement of Hsp27 in atherogenesis. One way it may support lesion development is via its inhibitory action on macrophage production of the inflammatory cytokine, IL-10