Heterogeneity in ess transcriptional organization and variable contribution of the Ess/Type VII protein secretion system to virulence across closely related Staphylocccus aureus strains.

The Type VII protein secretion system, found in Gram-positive bacteria, secretes small proteins, containing a conserved W-x-G amino acid sequence motif, to the growth medium. Staphylococcus aureus has a conserved Type VII secretion system, termed Ess, which is dispensable for laboratory growth but required for virulence. In this study we show that there are unexpected differences in the organization of the ess gene cluster between closely related strains of S. aureus. We further show that in laboratory growth medium different strains of S. aureus secrete the EsxA and EsxC substrate proteins at different growth points, and that the Ess system in strain Newman is inactive under these conditions. Systematic deletion analysis in S. aureus RN6390 is consistent with the EsaA, EsaB, EssA, EssB, EssC and EsxA proteins comprising core components of the secretion machinery in this strain. Finally we demonstrate that the Ess secretion machinery of two S. aureus strains, RN6390 and COL, is important for nasal colonization and virulence in the murine lung pneumonia model. Surprisingly, however, the secretion system plays no role in the virulence of strain SA113 under the same conditions.

[Effect of neuropeptide NAP on cultured neuroepithelial cells from rabbit retina].

OBJECTIVE: With the rabbit iris pigment epithelial cells (IPECs), which were containing the NT4-NAP fusion gene, taken as the substituting secreting cells producing the neuropeptide NAP, the effect of neuropeptide NAP on the growth status of retinal neuroepithelial cells of rabbit was examined and explored. METHODS: The iris pigment epithelial cells and retinal neuroepithelial cells of rabbit were cultured; rAAV-GFP and rAAV-NAP (containing NT4-NAP fusion gene) were constructed; the rabbit IPECs were infected with rAAV-GFP and rAAV-NAP; the infections of viruses were detected by GFP fluorescence expression; the supernatant of culture from rabbit IPECs with NAP was collected and added into the culture medium of rabbit retinal neuroepithelial cells, and the growth state of retinal neuroepithelial cell was observed. RESULTS: Compared to control cells, the rabbit IPECs could express the GFP fluorescence. The rabbit retinal neuroepithelial cells with NAP supernatant could survive more, and the survival cells showed longer and stronger axons. On 14's day of cell culture, the mean axon length of NAP group was (14. 6+/-1. 1) microm, while that of control group was only (3. 1+/-0. 6) mircom. Obviously, a significant difference existed between two groups (P<0. 05). CONCLUSION: The rabbit IPECs with NT4-NAP fusion gene can secrete NAP, and the NAP can promise the growth of rabbit retinal

[The effect of NT4-NAP fusion gene transfection on photoprotection of rabbit iris pigment epithelium cells].

OBJECTIVE: To investigate the effect of infection with adeno-associated virus (AAV) vector containing NT4-NAP fusion gene on photoprotection of rabbit iris pigment epithelium cells (IPECs). METHODS: rAAV-GFP and rAAV-NAP (containing NT4-NAP fusion gene) were constructed; rabbit IPECs were cultured and infected with rAAV-GFP and rAAV-NAP; transfection of viruses was detected by GFP fluorescence expression; NAP protect rabbit iris pigment epithelium from light stimulation was evaluated by MTT and flow cytometry. RESULTS: Rabbit IPECs expressed the GFP fluorescence; comparing with control cells, IPECs transfected with rAAV-NAP remained normal proliferation and showed lower apoptosis percentage after ultra-violet stimulation. CONCLUSION: rAAV-NAP constructed in the study can infect rabbit IPECs, and NAP may protect rabbit IPECs from ultra-violet damage.

Transcriptional activation function of hepatitis B virus Pre S1 protein in yeast.

OBJECTIVE: To explore the feasibility of cloning of the hepatocyte receptor interacting with the Pre S1 protein of HBV by two-hybrid system. METHODS: Yeast expression plasmids encoding fusion proteins of full length or portions of Pre S1 of HBV and DNA binding domain of yeast protein GAL4 were constructed and used to transform yeast reporter strain SFY526. Reporter gene product beta-galactosidase activity was assayed as a measure of transcriptional activation in yeast. Mammalian expression plasmid encoding fusion proteins of full length Pre S1 and DNA binding domain of GAL4 was constructed and used to cotransfect hepatoma cell line Huh-7 together with CAT reporter plasmid. Cell extracts were assayed for CAT activity by thin-layer chromatography. RESULTS: The fusion proteins of full length Pre S1 protein and GAL4 DNA binding domain presented transcriptional activation function in yeast. The transcription activating sequence was localized to the 21 to 47 amino acids of Pre S1 protein. Fusion proteins of full length Pre S1 and GAL4 DNA binding domain did not show transcriptional activation function in mammalian cells. CONCLUSIONS: The transcription activating sequence of HBV Pre S1 protein in yeast overlaps the hepatocyte receptor binding site. The transcriptional activation function of HBV Pre S1 protein in yeast may prevent researchers from using yeast two-hybrid system to clone HBV receptor interacting with Pre S1 protein. However, the Pre S1 protein does not show transcriptional activation function in mammalian cells. Mammalian two-hybrid system may be a practical method to clone the HBV hepatocyte receptor interacting with Pre S1 protein.

[Effects of bradykinin on the proliferation, apoptosis and differentiation of human keratinocytes].

OBJECTIVE: To investigate the effects of bradykinin (BK) on the proliferation, apoptosis and differentiation of human keratinocyte (HKC) and the underlying mechanisms. METHODS: HKCs were cultured together with 1 x 10(-4) - 1 x 10(-9) mol/L of BK. With methyl thiotetrazole (MTT) and trypan blue staining it was shown that the BK in dose of 1 x 10(-4) mol/L possessed most powerful inhibitory effect, and the survival rate of HKC was 69.3%. Therefore, BK was employed in the dose of 1 x 10(-4) mol/L in the following studies. When the growth of HKCs reached the logarithmic phase, BK in the concentration of 1 x 10(-4) mol/L was added, and it was categorized as the test group (E). HKCs without BK served as the control group (C). The cell cycle and apoptosis were detected by flow cytometry after being cultured for 24 and 48 hours. The change in intracellular calcium [Ca(2+)](i) was determined by means of laser scanning confocal microscopy with calcium fluorescence probe Fluo-3/AM technique. The expression of HKC differentiation labeling protein keratin10 (K10) and involucrin were detected with Strept Avidin-Biotin Complex (SABC) immunocytochemical assay. RESULTS: The cell ratio in G0/G1 phase in E group increased by 34.57% while in S phase decreased by 58.91% in reference to that in C group. The G1/S phase switching of HKCs was obviously inhibited by BK, and apoptosis was stimulated (apoptotic rate of 15.34% in E group vs 5.60% in C group, P < 0.05). The [Ca(2+)](i) increased transiently in HKCs by 163.0% in E group after 3 minutes of BK activation and decreased thereafter in reference to that in C group. The K10 expression in HKC was down-regulated in E group with positive cell rate of 2.20%, which was lower than that of C group (6.89%, P < 0.05). CONCLUSION: The cell cycle process of HKC could be inhibited by high concentration of BK with increased apoptosis and an increase in [Ca(2+)](i), which might be the mechanism of inhibition of growth of HKC in vitro. Furthermore, the epithelial regeneration and HKC differentiation can also be inhibited by BK.