Expression, purification, and characterization of the histidine kinase CarS from Fusobacterium nucleatum / 生物工程学报

Fusobacterium nucleatum is an opportunistic pathogenic bacterium that can be enriched in colorectal cancer tissues, affecting multiple stages of colorectal cancer development. The two-component system plays an important role in the regulation and expression of genes related to pathogenic resistance and pathogenicity. In this paper, we focused on the CarRS two-component system of F. nucleatum, and the histidine kinase protein CarS was recombinantly expressed and characterized. Several online software such as SMART, CCTOP and AlphaFold2 were used to predict the secondary and tertiary structure of the CarS protein. The results showed that CarS is a membrane protein with two transmembrane helices and contains 9 α-helices and 12 β-folds. CarS protein is composed of two domains, one is the N-terminal transmembrane domain (amino acids 1-170), the other is the C-terminal intracellular domain. The latter is composed of a signal receiving domain (histidine kinases, adenylyl cyclases, methyl-accepting proteins, prokaryotic signaling proteins, HAMP), a phosphate receptor domain (histidine kinase domain, HisKA), and a histidine kinase catalytic domain (histidine kinase-like ATPase catalytic domain, HATPase_c). Since the full-length CarS protein could not be expressed in host cells, a fusion expression vector pET-28a(+)-MBP-TEV-CarScyto was constructed based on the characteristics of secondary and tertiary structures, and overexpressed in Escherichia coli BL21-Codonplus(DE3)RIL. CarScyto-MBP protein was purified by affinity chromatography, ion-exchange chromatography, and gel filtration chromatography with a final concentration of 20 mg/ml. CarScyto-MBP protein showed both protein kinase and phosphotransferase activities, and the MBP tag had no effect on the function of CarScyto protein. The above results provide a basis for in-depth analysis of the biological function of the CarRS two-component system in F. nucleatum.

Effect of dendritic cells on immune function regulated by programmed cell death-1/programmed cell death-ligand 1 in sepsis / 中华危重病急救医学

Objective:To study the effect of programmed cell death-1/programmed cell death-ligand 1 (PD-1/PD-L1) regulating dendritic cells (DC) on the immune status of sepsis, and analyze the effect of PD-1/PD-L1 on prognosis.Methods:Twenty-five patients with sepsis in the intensive care unit (ICU) of the Affiliated Hospital of Zunyi Medical University from October 2018 to September 2019 were collected and followed up for 28 days. According to the 28-day survival of patients, patients were divided into survival group and death group. Among them, 10 cases were in the survival group and 15 cases were in the death group. Simultaneously, 20 healthy subjects in our hospital during the same period served as the healthy control group. Peripheral blood of patients with sepsis was taken within 24 hours after diagnosis, and the healthy control group was taken at the time of enrollment. Flow cytometry was used to detect the proportion of CD4 +T and CD8 +T cells, the ratio of T cell subsets (CD4/CD8), the expression of PD-1 on CD4 +T and CD8 +T cells, and the expression of PD-L1 and CD86 in DC. Enzyme linked immunosorbent assay (ELISA) was used to detect the levels of interleukin-10 (IL-10) and tumor necrosis factor-α(TNF-α) in serum. Spearman correlation analysis was used to analyze the correlation between CD11c +PD-L1 and CD4 +PD-1, CD8 +PD-1, TNF-α, DC, CD11c +CD86, T cell subpopulation ratio, CD4 +T cells, CD8 +T cells, and IL-10. Binary Logistic regression was used to analyze the risk factors affecting the death of patients with sepsis, and receiver operator characteristic curve (ROC curve) was drawn to evaluate the predictive value of independent risk factors on the prognosis of patients. Results:The scores of acute physiology and chronic health evaluationⅡ (APACHEⅡ) and sequential organ failure assessment (SOFA) in the death group were higher than that in the survival group (APACHEⅡ score: 27.0±7.3 vs. 17.0±3.9, SOFA score: 15.1±4.1 vs. 10.7±2.7, both P < 0.05). The ratio of T cell subsets in the survival group and the death group was less than 1, the death group was lower than that in the survival group (CD4/CD8: 0.54±0.15 vs. 0.79±0.09, P < 0.05), and the ratio of T cell subsets in the healthy control group was greater than 1. Compared with healthy control group, the levels of CD4 +T cells, CD8 +T cells, CD11c +DC, CD11c +CD86, IL-10 and TNF-α in survival group and death group were significantly decreased, the level of CD4 +PD-1, CD8 +PD-1, CD11c +PD-L1 were significantly increased, and the changes in the above indicators in the death group were significant compared with the survival group [CD4 +T cells: 0.14±0.07 vs. 0.22±0.08, CD8 +T cells: 0.24±0.07 vs. 0.28±0.10, CD11c +DC: 0.84±0.14 vs. 0.93±0.03, CD11c +CD86: (58.83±20.77)% vs. (78.24±9.39)%, IL-10 (ng/L): 34.22±13.98 vs. 18.49±5.55, TNF-α(ng/L): 95.30±29.33 vs. 67.00±20.16, CD4 +PD-1: (39.58±10.08)% vs. (27.03±6.35)%, CD8 +PD-1: (38.77±11.91)% vs. (29.15±8.37)%, CD11c +PD-L1: (21.13±11.54)% vs. (12.11± 8.34)%, all P < 0.05]. Spearman correlation analysis showed that CD11c +PD-L1 was positively correlated with CD4 +PD-1, CD8 +PD-1, and IL-10 ( r values were 0.748, 0.713, 0.898, all P < 0.05), while was negatively correlated with DC, CD11c +CD86, T cell subpopulation ratio, CD4 +T cells, CD8 +T cells, and TNF-α( r values were -0.587, -0.906, -0.840, -0.706, -0.513, -0.820, all P < 0.05). Multivariate binary Logistic regression analysis showed that CD4 +T PD-1 was an independent risk factor for the prognosis of sepsis patients [odds ratio ( OR) = 1.463, 95% confidence interval (95% CI) = 1.032-2.074, P = 0.033]. ROC curve analysis showed that CD4 +TPD-1 had certain predictive value for the prognosis of patients with sepsis [area under ROC curve (AUC) = 0.857, 95% CI was 0.709-1.000, P < 0.01). When the best predictive value was 34.48%, the sensitivity, specificity, and accuracy were 66.7%, 90.0%, and 85.7% respectively. Conclusions:Up-regulation of PD-1/PD-L1 in peripheral blood could inhibit the activation and proliferation of DC, affect the activation of T cells, and induce immunosuppressive state. PD-1/PD-L1 can reflect the immune status of patients with sepsis. The expression of PD-1 on CD4 +T cells may have important significance for the evaluation of prognosis.