Department of Medicine, Division of Gastroenterology & Hepatology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
Department of Internal Medicine, Division of Gastroenterology & Hepatology, University of New Mexico, Albuquerque, NM 87131, USA.
Toxins (Basel). 2018 Sep 1;10(9):351. doi: 10.3390/toxins10090351.
One of the characteristic manifestations of Shiga-toxin-producing () infection in humans, including EHEC and O104:H4, is watery diarrhea. However, neither Shiga toxin nor numerous components of the type-3 secretion system have been found to independently elicit fluid secretion. We used the adult stem-cell-derived human colonoid monolayers (HCM) to test whether EHEC-secreted extracellular serine protease P (EspP), a member of the serine protease family broadly expressed by diarrheagenic can act as an enterotoxin. We applied the Ussing chamber/voltage clamp technique to determine whether EspP stimulates electrogenic ion transport indicated by a change in short-circuit current (Isc). EspP stimulates Isc in HCM. The EspP-stimulated Isc does not require protease activity, is not cystic fibrosis transmembrane conductance regulator (CFTR)-mediated, but is partially Ca-dependent. EspP neutralization with a specific antibody reduces its potency in stimulating Isc. Serine Protease A, secreted by , also stimulates Isc in HCM, but this current is CFTR-dependent. In conclusion, EspP stimulates colonic CFTR-independent active ion transport and may be involved in the pathophysiology of EHEC diarrhea. Serine protease toxins from pathogens appear to serve as enterotoxins, potentially significantly contributing to watery diarrhea.
产志贺毒素大肠杆菌（STEC）感染的一个特征性表现是水样腹泻，包括肠出血性大肠杆菌（EHEC）和 O104:H4。然而，无论是志贺毒素还是 III 型分泌系统的许多成分，都没有被发现能够独立地引起液体分泌。我们使用成人干细胞衍生的人结肠类器官单层（HCM）来测试肠致病性大肠杆菌分泌的细胞外丝氨酸蛋白酶 P（EspP）是否可以作为肠毒素，EspP 是广泛表达于致泻性大肠杆菌的丝氨酸蛋白酶家族的成员。我们应用 Ussing 室/电压钳技术来确定 EspP 是否刺激电致离子转运，表现为短路电流（Isc）的变化。EspP 刺激 HCM 中的 Isc。EspP 刺激的 Isc 不需要蛋白酶活性，不依赖于囊性纤维化跨膜电导调节剂（CFTR），但部分依赖于 Ca2+。用特异性抗体中和 EspP 会降低其刺激 Isc 的效力。大肠杆菌分泌的丝氨酸蛋白酶 A 也刺激 HCM 中的 Isc，但这种电流依赖于 CFTR。总之，EspP 刺激结肠 CFTR 非依赖性主动离子转运，可能参与 EHEC 腹泻的病理生理学。来自致病性大肠杆菌的丝氨酸蛋白酶毒素似乎作为肠毒素发挥作用，可能对水样腹泻有重要贡献。
