Molecular and Clinical Hematology Branch, National Heart, Lung, and Blood Institute, Bethesda, MD 20892, USA.
J Immunol. 2012 Sep 1;189(5):2460-7. doi: 10.4049/jimmunol.1103179. Epub 2012 Jul 27.
Neutrophils kill bacteria generally through oxidative and nonoxidative mechanisms. Whereas much research has focused on the enzymes essential for neutrophil killing, little is known about the regulatory molecules responsible for such killing. In this study, we investigated the role of olfactomedin 4 (OLFM4), an olfactomedin-related glycoprotein, in neutrophil bactericidal capability and host innate immunity. Neutrophils from OLFM4⁻/⁻ mice have increased intracellular killing of Staphylococcus aureus and Escherichia coli in vitro. The OLFM4⁻/⁻ mice have enhanced in vivo bacterial clearance and are more resistant to sepsis when challenged with S. aureus or E. coli by i.p. injection. OLFM4 was found to interact with cathepsin C, a cysteine protease that plays an important role in bacterial killing and immune regulation. We demonstrated that OLFM4 inhibited cathepsin C activity in vitro and in vivo. The cathepsin C activity in neutrophils from OLFM4⁻/⁻ mice was significantly higher than that in neutrophils from wild-type littermate mice. The activities of three serine proteases (neutrophil elastase, cathepsin G, and proteinase 3), which require cathepsin C activity for processing and maturity, were also significantly higher in OLFM4⁻/⁻ neutrophils. The bacterial killing and clearance capabilities observed in OLFM4⁻/⁻ mice that were enhanced relative to wild-type mice were significantly compromised by the additional loss of cathepsin C in mice with OLFM4 and cathepsin C double deficiency. These results indicate that OLFM4 is an important negative regulator of neutrophil bactericidal activity by restricting cathepsin C activity and its downstream granule-associated serine proteases.
中性粒细胞通常通过氧化和非氧化机制杀死细菌。虽然许多研究都集中在对中性粒细胞杀伤至关重要的酶上，但对于负责这种杀伤的调节分子知之甚少。在这项研究中，我们研究了嗅觉钙黏蛋白 4（OLFM4）在中性粒细胞杀菌能力和宿主先天免疫中的作用。OLFM4⁻/⁻小鼠的中性粒细胞在体外对金黄色葡萄球菌和大肠杆菌的细胞内杀伤能力增强。OLFM4⁻/⁻小鼠具有增强的体内细菌清除能力，并且在用金黄色葡萄球菌或大肠杆菌通过腹腔注射挑战时对败血症的抵抗力更强。发现 OLFM4 与组织蛋白酶 C 相互作用，组织蛋白酶 C 是一种半胱氨酸蛋白酶，在细菌杀伤和免疫调节中起重要作用。我们证明 OLFM4 在体外和体内抑制组织蛋白酶 C 活性。OLFM4⁻/⁻小鼠中性粒细胞中的组织蛋白酶 C 活性明显高于野生型同窝小鼠中性粒细胞中的组织蛋白酶 C 活性。三种丝氨酸蛋白酶（中性粒细胞弹性蛋白酶、组织蛋白酶 G 和蛋白酶 3）的活性也明显更高，这三种丝氨酸蛋白酶的加工和成熟都需要组织蛋白酶 C 活性。OLFM4 和组织蛋白酶 C 双重缺陷小鼠中组织蛋白酶 C 的额外缺失显著削弱了 OLFM4⁻/⁻小鼠相对于野生型小鼠观察到的增强的细菌杀伤和清除能力。这些结果表明，OLFM4 通过限制组织蛋白酶 C 活性及其下游颗粒相关丝氨酸蛋白酶来调节中性粒细胞的杀菌活性，是一种重要的负调控因子。
