Traynor A E, Weitzman S A, Gordon L I
Department of Medicine, Northwestern University Medical School, Chicago, Illinois 60611.
Cell Immunol. 1993 Dec;152(2):582-93. doi: 10.1006/cimm.1993.1314.
Bacterial phosphatidylcholine-preferring phospholipase C (PC-PLC) has been recognized as a virulence factor and is implicated in the hemolytic and dermonecrotic properties associated with certain organisms. Moreover, recent data suggest that PC-PLC may be an important component in the signal transduction cascade by contributing to diacylglycerol (DAG) mass via the hydrolysis of phosphatidylcholine (PC). We have previously shown that PC-PLC can inhibit superoxide generation in human polymorphonuclear leukocytes (PMN). We now extend these observations and show that the mechanism of PC-PLC inhibition of superoxide generation is reversible inhibition of the membrane component of the NADPH oxidase (in a cell-free system) accompanied by expected generation of DAG and phosphorylcholine. Addition of PC reversed the effects of the enzyme. Surprisingly, we also found that phosphatidic acid (PA), the hydrolysis product of phospholipase D, was also produced in intact PMN following PC-PLC exposure. Subsequent addition of the agonist N-formylmethionyl-phenylalanine resulted in further PA production. Restoration of PA in cell-free preparations partially restored superoxide generating capability. We conclude that PC-PLC may enhance bacterial virulence by inhibiting superoxide generation by human PMN, and that this effect is due to direct inhibition of the membrane component of the NADPH oxidase.
细菌磷脂酰胆碱偏好性磷脂酶C（PC-PLC）已被公认为一种毒力因子，与某些生物体的溶血和皮肤坏死特性有关。此外，最近的数据表明，PC-PLC可能是信号转导级联反应中的一个重要组成部分，通过磷脂酰胆碱（PC）的水解增加二酰基甘油（DAG）的量。我们之前已经表明，PC-PLC可以抑制人多形核白细胞（PMN）中超氧化物的产生。现在我们扩展这些观察结果，并表明PC-PLC抑制超氧化物产生的机制是对NADPH氧化酶膜成分的可逆抑制（在无细胞系统中），同时伴随着预期的DAG和磷酸胆碱的产生。添加PC可逆转该酶的作用。令人惊讶的是，我们还发现，磷脂酶D的水解产物磷脂酸（PA）在PC-PLC作用于完整的PMN后也会产生。随后添加激动剂N-甲酰甲硫氨酰-苯丙氨酸会导致PA进一步产生。在无细胞制剂中恢复PA可部分恢复超氧化物产生能力。我们得出结论，PC-PLC可能通过抑制人PMN中超氧化物的产生来增强细菌毒力，并且这种作用是由于对NADPH氧化酶膜成分的直接抑制。
