Chlamydia psittaci SINC protein inhibits host cell apoptosis through activating MAPK/ERK signaling pathway / 中华微生物学和免疫学杂志

Objective:To investigate the effects of SINC, a novel secreted protein of Chlamydia psittaci, on the apoptosis of host cells and the regulatory role of mitogen-activated protein kinase/extracellular signal-regulated kinase (MAPK/ERK) signaling pathway in it. Methods:HeLa cells were treated with recombinant SINC. The expression of Bax and Bcl-2 at protein level and the phosphorylation of ERK1/2 were analyzed by Western blot. Hoechst 33258 staining was used to detect the apoptosis of HeLa cells after SINC stimulation. Moreover, HeLa cells were pretreated with MEK1/2 inhibitor U0126 (50 μmol/L), and then stimulated with different concentrations of SINC for different time. Flow cytometry was used to detect the changes in cell apoptosis rates and Western blot was performed to detect the expression of Bax and Bcl-2 at protein level.Results:Treating HeLa cells with 10 μg/ml of SINC for 18 h resulted in down-regulated Bax and up-regulated Bcl-2 at protein level. Besides, the ratio of Bax/Bcl-2 was the lowest and a significant increase in the ratio of phosphorylated ERK1/2 (p-ERK1/2) to ERK1/2 was observed. Hoechst 33258 staining showed that the number of apoptotic bodies decreased significantly after stimulating HeLa cells with 5, 10 and 15 μg/ml of SINC. In the presence of MEK1/2 inhibitor U0126, the expression of Bcl-2 at protein level was down-regulated, while the expression of cleaved PARP was significantly up-regulated. Flow cytometry showed a significantly enhanced apoptosis of HeLa cells.Conclusions:SINC can inhibit the apoptosis of HeLa cells through activating the MAPK/ERK signaling pathway.

Type III secretory protein SINC of Chlamydia psittaci promotes host cell autophagy by activating the MAPK/ERK signaling pathway / 南方医科大学学报

OBJECTIVE@#To investigate the effects of SINC, a secreted protein of Chlamydia psittaci, on autophagy of host cells and the role of MAPK/ERK signaling pathway in mediating SINC-induced autophagy.@*METHODS@#RAW 264.7 cells treated with recombinant SINC were examined for changes in expression levels of LC3-II, Beclin-1, phosphorylated and total ERK1/2 using Western blotting. The expression level of LC3 in the treated cells was detected using immunofluorescence analysis, and the formation of autophagosomes and autolysosomes was observed with transmission electron microscopy (TEM). The effect of pretreatment with U0126 (a specific ERK inhibitor) on the expression levels of LC3-II and Beclin-1 in RAW 264.7 cells exposed to different concentrations of SINC was examined using Western blotting, and LC3 puncta in the cells was detected with immunofluorescence analysis.@*RESULTS@#The expression levels of LC3-II and Beclin-1 were the highest in RAW 264.7 cells treated with 2 μg/mL SINC for 12h. Immunofluorescence analysis showed exposure to SINC significantly increased the number of cells containing LC3 puncta, where the presence of autophagosomes and autolysosomes was detected. Exposure to 2 μg/mL SINC for 15 min resulted in the most significant increase of the ratios of p-ERK1/2/ERK1/2 in RAW 264.7 cells. Pretreatment of the cells with U0126 prior to SINC exposure significantly decreased the ratio of p-ERK1/2/ERK1/2, lowered the expression levels of LC3-II and Beclin-1, and decreased LC3 aggregation in the cells.@*CONCLUSIONS@#SINC exposure can induce autophagy in RAW 264.7 cells by activating the MAPK/ERK signaling pathway.

A New Tailored Sinc Pulse and Its Use for Multiband Pulse Design

PURPOSE: Among RF pulses, a sinc pulse is typically used for slice selection due to its frequency-selective feature. When a sinc pulse is implemented in practice, it needs to be apodized to avoid truncation artifacts at the expense of broadening the transition region of the excited-band profile. Here a sinc pulse tailored by a new apodization function is proposed that produces a sharper transition region with well suppression of truncation artifacts in comparison with conventional tailored sinc pulses. A multiband pulse designed using this newly apodized sinc pulse is also suggested inheriting the better performance of the newly apodized sinc pulse. MATERIALS AND METHODS: A new apodization function is introduced to taper a sinc pulse, playing a role to slightly shift the first zero-crossing of a tailored sinc pulse from the peak of the main lobe and thereby producing a narrower bandwidth as well as a sharper pass-band in the excitation profile. The newly apodized sinc pulse was also utilized to design a multiband pulse which inherits the performance of its constituent. Performances of the proposed sinc pulse and the multiband pulse generated with it were demonstrated by Bloch simulation and phantom imaging. RESULTS: In both simulations and experiments, the newly apodized sinc pulse yielded a narrower bandwidth and a sharper transition of the pass-band profile with a desirable degree of side-lobe suppression than the commonly used Hanning-windowed sinc pulse. The multiband pulse designed using the newly apodized sinc pulse also showed the better performance in multi-slice excitation than the one designed with the Hanning-windowed sinc pulse. CONCLUSION: The new tailored sinc pulse proposed here provides a better performance in slice (or slab) selection than conventional tailored sinc pulses. Thanks to the availability of analytical expression, it can also be utilized for multiband pulse design with great flexibility and readiness in implementation, transferring its better performance.