Nocardia seriolae, a Gram-positive bacterium, is the main pathogen of fish nocardiosis. Protein NlpC/P60 is a cell-wall peptidase and a potential virulence factor of N. seriolae. Subcellular localization research revealed that both NlpC/P60-GFP and NlpC/P60Δsig-GFP fusion proteins were evenly distributed in the whole cell of fathead minnow (FHM) cells. Furthermore, typical apoptotic features, such as nuclear pyrosis and apoptotic bodies, were observed in the transfected FHM cells and grouper spleen cells by the overexpression of protein NlpC/P60. Then, quantitative assays of mitochondrial membrane potential (ΔΨm) value, caspase-3 activity and apoptosis-related gene (Bax, BNIP3, TNF1 and TNF6) mRNA expression were conducted. The results showed that ΔΨm was decreased, caspase-3 was significantly activated, and the mRNA expression of pro-apoptotic genes (Bax and BNIP3) and tumour necrosis factors (TNF1 and TNF6) was up-regulated in NlpC/P60-overexpressed cells. Taken together, the results indicated that the protein NlpC/P60 of N. seriolae might involve in apoptosis regulation. This study may lay the foundation for further study on the function of N. seriolae NlpC/P60 and promote the understanding of the virulence factors and pathogenic mechanism of N. seriolae.

中文翻译：

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鉴定了一种能诱导黑头诺fat鱼细胞凋亡的细胞壁肽酶（NlpC / P60）。

鱼类诺卡氏菌是革兰氏阳性细菌，是鱼类诺卡氏菌病的主要病原体。NlpC / P60蛋白是一种细胞壁肽酶，是一种潜在的毒力因子。亚细胞定位研究表明，NlpC / P60-GFP和NlpC /P60Δsig-GFP融合蛋白均均匀分布在fat鱼（FHM）细胞的整个细胞中。此外，通过蛋白NlpC / P60的过表达，在转染的FHM细胞和石斑鱼脾细胞中观察到典型的凋亡特征，例如核热解和凋亡小体。然后，定量测定线粒体膜电位（ΔΨm）值，caspase-3活性和凋亡相关基因（Bax，BNIP3，TNF1和TNF6）mRNA表达。结果表明，ΔΨm降低，caspase-3被显着激活，NlpC / P60过表达的细胞中促凋亡基因（Bax和BNIP3）和肿瘤坏死因子（TNF1和TNF6）的mRNA表达上调。两者合计，结果表明，N。seriolae NlpC / P60蛋白可能参与细胞凋亡的调控。该研究可为进一步研究N. seriolae NlpC / P60的功能奠定基础，并增进对N. seriolae毒力因子和致病机理的了解。