Ayala-Lujan Jorge Luis, Vijayakumar Vidhya, Gong Mei, Smith Rachel, Santiago Araceli E, Ruiz-Perez Fernando
Department of Pediatrics, University of Virginia School of Medicine, Charlottesville, Virginia, United States of America; Unidad Academica de Ciencias Quimicas, Universidad Autonoma de Zacatecas, Zacatecas, Mexico.
Department of Pediatrics, University of Virginia School of Medicine, Charlottesville, Virginia, United States of America; Department of Immunology and Microbiology, University of Maryland at Baltimore, Baltimore, Maryland, United States of America.
PLoS One. 2014 Sep 24;9(9):e107920. doi: 10.1371/journal.pone.0107920. eCollection 2014.
The serine protease autotransporter from Enterobacteriaceae (SPATE) family, which number more than 25 proteases with apparent diverse functions, have been phylogenetically divided into two distinct classes, designated 1 and 2. We recently demonstrated that Pic and Tsh, two members of the class-2 SPATE family produced by intestinal and extraintestinal pathogenic E. coli, were able to cleave a number of O-glycosylated proteins on neutrophils and lymphocytes resulting in impaired leukocyte functions. Here we show that most members of the class-2 SPATE family have lectin-like properties and exhibit differential protease activity reliant on glycoprotein type and cell lineage. Protease activity was seen in virtually all tested O-glycosylated proteins including CD34, CD55, CD164, TIM1, TIM3, TIM4 and C1-INH. We also show that although SPATE proteins bound and cleaved glycoproteins more efficiently on granulocytes and monocytes, they also targeted glycoproteins on B, T and natural killer lymphocytes. Finally, we found that the characteristic domain-2 of class-2 SPATEs is not required for glycoprotease activity, but single amino acid mutations in Pic domain-1 to those residues naturally occurring in domain-1 of SepA, were sufficient to hamper Pic glycoprotease activity. This study shows that most class-2 SPATEs have redundant activities and suggest that they may function as immunomodulators at several levels of the immune system.
来自肠杆菌科的丝氨酸蛋白酶自转运体（SPATE）家族有超过25种蛋白酶，其功能明显多样，在系统发育上已被分为两个不同的类别，即1类和2类。我们最近证明，由肠道和肠道外致病性大肠杆菌产生的2类SPATE家族的两个成员Pic和Tsh，能够切割中性粒细胞和淋巴细胞上的一些O-糖基化蛋白，导致白细胞功能受损。在这里，我们表明2类SPATE家族的大多数成员具有凝集素样特性，并表现出依赖于糖蛋白类型和细胞谱系的差异蛋白酶活性。在几乎所有测试的O-糖基化蛋白中都观察到了蛋白酶活性，包括CD34、CD55、CD164、TIM1、TIM3、TIM4和C1-INH。我们还表明，尽管SPATE蛋白在粒细胞和单核细胞上结合和切割糖蛋白的效率更高，但它们也靶向B、T和自然杀伤淋巴细胞上的糖蛋白。最后，我们发现2类SPATEs的特征性结构域2对于糖蛋白酶活性不是必需的，但Pic结构域1中的单个氨基酸突变为SepA结构域1中天然存在的那些残基，就足以阻碍Pic糖蛋白酶活性。这项研究表明，大多数2类SPATEs具有冗余活性，并表明它们可能在免疫系统的多个层面上作为免疫调节剂发挥作用。
