Singh I N, Sorrentino G, Kanfer J N
Department of Biochemistry and Molecular Biology, University of Manitoba, Faculty of Medicine, Winnipeg, Canada.
Neurochem Res. 1998 Oct;23(10):1225-32. doi: 10.1023/a:1020731813973.
Amyloid beta protein is the major protein component of neuritic plaques found in the brain of Alzheimer's disease. The activation of phospholipase D by amyloid beta protein (25-35), quisqualate and phorbol 12, 13-dibutyrate was investigated in LA-N-2 cells by measuring phosphatidylethanol formation. The activation of phospholipase D by quisqualate and APP (25-35) was calcium-independent. The AbetaP (25-35) and quisqualate activation of phospholipase D appeared to be mediated through a pertussis toxin-sensitive GTP-binding protein. Phospholipase D activation by AbetaP (25-35), quisqualate and phorbol dibutyrate was not blunted by the protein kinase C inhibitors, staurosporine, H-7 and RO-31-8220. However, it was abolished by overnight exposure to phorbol dibutyrate. This activation of phospholipase D was prevented by the tyrosine kinase inhibitor, genistein but not by tyrophostin A. Several excitatory amino acid antagonists were tested for their ability to prevent the phospholipase D activation by quisqualate and AbetaP (25-35). Only NBQX was effective with an IC50 of 75 microM for AbetaP (25-35) and quisqualate. Activation of phospholipase D by AbetaP or quisqualate was absent in LA-N-2 cells previously desensitized by quisqualate or AbetaP (25-35), but the activation by phorbol dibutyrate was unaltered. The responsiveness to AbetaP and quisqualate in previously desensitized cells reappeared subsequent to a period of resensitization. The observations with the antagonist NBQX, and the desensitization and resensitization experiments, are consistent with a receptor occupancy mediated activation of phospholipase D by quisqualate and by AbetaP (25-35).
淀粉样β蛋白是阿尔茨海默病患者大脑中神经炎性斑块的主要蛋白质成分。通过测量磷脂酰乙醇的形成，研究了淀粉样β蛋白（25 - 35）、喹啉酸和佛波酯12,13 - 二丁酸对LA - N - 2细胞中磷脂酶D的激活作用。喹啉酸和APP（25 - 35）对磷脂酶D的激活不依赖于钙。β淀粉样蛋白（25 - 35）和喹啉酸对磷脂酶D的激活似乎是通过百日咳毒素敏感的GTP结合蛋白介导的。蛋白激酶C抑制剂星形孢菌素、H - 7和RO - 31 - 8220不会减弱β淀粉样蛋白（25 - 35）、喹啉酸和佛波酯二丁酸对磷脂酶D的激活作用。然而，过夜暴露于佛波酯二丁酸会使其激活作用消失。酪氨酸激酶抑制剂染料木黄酮可阻止磷脂酶D的这种激活，而酪氨酸磷酸化抑制剂A则不能。测试了几种兴奋性氨基酸拮抗剂阻止喹啉酸和β淀粉样蛋白（25 - 35）激活磷脂酶D的能力。只有NBQX有效，对β淀粉样蛋白（25 - 35）和喹啉酸的IC50为75μM。在先前被喹啉酸或β淀粉样蛋白（25 - 35）脱敏的LA - N - 2细胞中，β淀粉样蛋白或喹啉酸不会激活磷脂酶D，但佛波酯二丁酸的激活作用未改变。在经过一段时间的再敏化后，先前脱敏细胞对β淀粉样蛋白和喹啉酸的反应性重新出现。拮抗剂NBQX的观察结果以及脱敏和再敏化实验结果与喹啉酸和β淀粉样蛋白（25 -
