Iron–sulfur clusters are essential cofactors found in all kingdoms of life and play essential roles in fundamental processes, including but not limited to respiration, photosynthesis, and nitrogen fixation. The chemistry of iron–sulfur clusters makes them ideal for sensing various redox environmental signals, while the physics of iron–sulfur clusters and its host proteins have been long overlooked. One such protein, MagR, has been proposed as a putative animal magnetoreceptor. It forms a rod-like complex with cryptochromes (Cry) and possesses intrinsic magnetic moment. However, the magnetism modulation of MagR remains unknown. Here in this study, iron–sulfur cluster binding in MagR has been characterized. Three conserved cysteines of MagR play different roles in iron–sulfur cluster binding. Two forms of iron–sulfur clusters binding have been identified in pigeon MagR and showed different magnetic properties: [3Fe–4S]-MagR appears to be superparamagnetic and has saturation magnetization at 5 K but [2Fe–2S]-MagR is paramagnetic. While at 300 K, [2Fe–2S]-MagR is diamagnetic but [3Fe–4S]-MagR is paramagnetic. Together, the different types of iron–sulfur cluster binding in MagR attribute distinguished magnetic properties, which may provide a fascinating mechanism for animals to modulate the sensitivity in magnetic sensing.
Background:Systemic lupus erythematosus (SLE) is an autoimmune disease with disturbance of lymphocyte subpopulations1. Growing experimental and clinical evidence suggests that chronic inflammatory response induced by gut microbiome critically contribute to the development of SLE2 3.Objectives:To investigate the characteristics of gut microbiome and the associations between flora and peripheral lymphocyte subpopulations in SLE patients.Methods:A total of 19 SLE patients who fulfilled the 2019 American college of Rheumatology (ACR) and European League Against Rheumatism (EULAR) classification criteria and 16 age- and sex- matched healthy controls (HC) were enrolled in this study. The peripheral T lymphocyte subsets of these participants were assessed by flow cytometry and the gut microbiota were investigated via 16s rRNA. Indicators of disease activity such as erythrocyte sedimentation rate (ESR), complement C3 and C4 were recorded at the same time. Mann-Whitney U test was applied to compare T lymphocyte subsets between SLE patients and HC. Spearman analysis was used for calculating correlation between T subsets and highly expressed differential flora as well as their correlation with disease activity indicators. All P-values reported herein were two-tailed and P-value<0.05 was taken as statistically significant.Results:SLE patients had higher proportions of Th17 cells (P=0.020) and γδT cells (P=0.018) but lower levels of Treg cells (P=0.001), Tfh cells (P=0.018) and Naïve CD4+T cells (P=0.004) (Figure 1a-e). The diversity and relative abundance of intestinal flora in patients with SLE were significantly different from those in HCs. Detailly, the α-diversity was decreased in SLE (P<0.05) (Figure 2a-c). Compared with HC, 11 species of flora were discovered to be distinctly different(P<0.05) (Figure 2d-e). Moreover, there was a significant positive correlation between Treg levels and Ruminococcus2 (P=0.042), Th17 and Megamonas (P=0.009), γδT and Streptococcus (P=0.004) as well as Megamonas (P=0.003), Tfh and Bacteroides (P=0.040). Whereas Th1 levels and Bifidobacterium were negatively correlated in these participants (P=0.005). As for clinical disease measures, there were negative correlations not only between ESR and Treg cells (P=0.031) but also C4 and the amount of Unclassified Ruminococcaceae (P=0.032).Conclusion:Abnormality of T cell subsets, especially the level of Naïve CD4+T, γδT, Tfh, Treg, and Th17 cells contributes to the occurrence and progression of SLE, which may be related to the disturbance of gut microbiota. Therefore it is necessary to attach importance to the alteration of gut microbiota to prevent the outbreak of inflammation and maybe they can be identified as biomarkers predicting disease activity.References:[1]Katsuyama T, Tsokos GC, Moulton VR. Aberrant T Cell Signaling and Subsets in Systemic Lupus Erythematosus. Front Immunol 2018;9:1088. doi: 10.3389/fimmu.2018.01088 [published Online First: 2018/06/06][2]López P, de Paz B, Rodríguez-Carrio J, et al. Th17 responses and natural IgM antibodies are related to gut microbiota composition in systemic lupus erythematosus patients. Sci Rep 2016;6:24072. doi: 10.1038/srep24072 [published Online First: 2016/04/06][3]Esmaeili SA, Mahmoudi M, Momtazi AA, et al. Tolerogenic probiotics: potential immunoregulators in Systemic Lupus Erythematosus. J Cell Physiol 2017;232(8):1994-2007. doi: 10.1002/jcp.25748 [published Online First: 2016/12/21]Acknowledgements:This project was supported by National Science Foundation of China (82001740), Open Fund from the Key Laboratory of Cellular Physiology (Shanxi Medical University) (KLCP2019) and Innovation Plan for Postgraduate Education in Shanxi Province (2020BY078).Disclosure of Interests:None declared.
The nucleotide binding protein 35 (Nbp35)/cytosolic Fe‐S cluster deficient 1 (Cfd1)/alternative pyrimidine biosynthetic protein C (ApbC) protein homologs have been identified in all three domains of life. In eukaryotes, the Nbp35/Cfd1 heterocomplex is an essential Fe‐S cluster assembly scaffold required for the maturation of Fe‐S proteins in the cytosol and nucleus, whereas the bacterial ApbC is an Fe‐S cluster transfer protein only involved in the maturation of a specific target protein. Here, we show that the Nbp35/ApbC homolog MMP0704 purified from its native archaeal host Methanococcus maripaludis contains a [4Fe‐4S] cluster that can be transferred to a [4Fe‐4S] apoprotein. Deletion of mmp0704 from M. maripaludis does not cause growth deficiency under our tested conditions. Our data indicate that Nbp35/ApbC is a nonessential [4Fe‐4S] cluster transfer protein in methanogenic archaea.
For robust DNA-based gut microbiome analysis, all cells in the stool samples need to be lysed. However, no standards have been developed to evaluate a DNA extraction protocol's capability of lysing all cells and its sensitivity on detecting microbial structural differences among samples. In this study, we incrementally increased the intensity of mechanical lysis and integrated lysozyme pretreatment to Protocol Q (PQ), which was recommended as the best from 21 protocols. A new protocol (LPQ) was optimized when DNA yield, Gram-positive bacteria ratio, and beta diversity all reached to a plateau with no further significant changes, indicating the achievement of saturated lysing. LPQ detected significant differences among three groups of fiber-treated human stool samples and identified 64 responsive ASVs, while a commercial kit failed to detect any significant treatment effects and PQ only detected 17 responsive ASVs. Therefore, saturated lysing as defined in this study should be adopted for evaluating microbiome DNA extraction protocols.
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