The serine protease homolog spheroide is involved in sensing of pathogenic Gram-positive bacteria

In Drosophila, recognition of pathogens such as Gram-positive bacteria and fungi triggers the activation of proteolytic cascades and the subsequent activation of the Toll pathway. This response can be achieved by either detection of pathogen associated molecular patterns or by sensing microbial proteolytic activities (“danger signals”). Previous data suggested that certain serine protease homologs (serine protease folds that lack an active catalytic triad) could be involved in the pathway. We generated a null mutant of the serine protease homolog spheroide (sphe). These mutant flies are susceptible to Enterococcus faecalis infection and unable to fully activate the Toll pathway. Sphe is required to activate the Toll pathway after challenge with pathogenic Gram-Positive bacteria. Sphe functions in the danger signal pathway, downstream or at the level of Persephone.

在果蝇中，对诸如革兰氏阳性细菌和真菌等病原体的识别会引发蛋白酶级联反应的激活，进而触发Toll途径的激活。此反应可通过病原体相关分子模式（PAMPs）的检测或通过感知微生物蛋白酶活性（即‘危险信号’）来实现。先前的研究数据表明，某些丝氨酸蛋白酶同源物（缺乏活性催化三联体的丝氨酸蛋白酶折叠）可能参与该途径。我们生成了丝氨酸蛋白酶同源物spheroide（sphe）的null突变体。这些突变果蝇对粪肠球菌感染敏感，且无法完全激活Toll途径。在挑战革兰氏阳性病原菌后，Sphe对于激活Toll途径是必需的。Sphe在危险信号途径中发挥作用，位于Persephone下游或同一水平。