Capra Valérie, Accomazzo Maria Rosa, Ravasi Saula, Parenti Marco, Macchia Marco, Nicosia Simonetta, Rovati G Enrico
Laboratory of Molecular Pharmacology, Department of Pharmacological Sciences, University of Milan, Via Balzaretti 9, 20133 Milan, Italy.
Prostaglandins Other Lipid Mediat. 2003 Jul;71(3-4):235-51. doi: 10.1016/s1098-8823(03)00045-5.
We investigated signal transduction pathways for LTD4 in the human promonocytic cell line U937 known, upon differentiation, to express CysLT1 receptors. We confirmed the presence of high-affinity binding sites for 3H-LTD4, which, in functional studies, displayed the features of CysLT1 receptor. In fact, three potent and selective CysLT1 receptor antagonists were able to completely inhibit LTD4-induced response. In turn, cytosolic Ca2+ ([Ca2+]i) increase (EC50 = 3.4 nM +/- 27% CV) was only partially sensitive to pertussis toxin (PTx) as well as to the prenylation inhibitor fluvastatin and to the specific geranylgeranylation and farnesylation inhibitors BAL 9504 and FPT II. Finally, Clostridium sordellii lethal toxin, inhibitor of the Ras family of GTPases, and FTS, a potent methyltransferase inhibitor, were both able to partially inhibit LTD4-induced [Ca2+] increase, suggesting a role for a Ras family member in [Ca2+]i regulation. In conclusion, in dU937 LTD4 signal transduction involves: (a) at least two pathways, one sensitive and one insensitive to PTx; (b) isoprenylated proteins, such as betagamma subunits and, possibly, a small G protein of the Ras family.
我们研究了白三烯D4（LTD4）在人早幼粒细胞系U937中的信号转导途径，已知该细胞系在分化时会表达半胱氨酰白三烯1（CysLT1）受体。我们证实了存在3H-LTD4的高亲和力结合位点，在功能研究中，这些位点表现出CysLT1受体的特征。事实上，三种强效且选择性的CysLT1受体拮抗剂能够完全抑制LTD4诱导的反应。相应地，胞质Ca2+（[Ca2+]i）升高（EC50 = 3.4 nM ± 27%变异系数）仅部分受百日咳毒素（PTx）、异戊二烯化抑制剂氟伐他汀以及特异性香叶基香叶基化和法尼基化抑制剂BAL 9504和FPT II的影响。最后，梭状芽孢杆菌致死毒素（一种GTP酶Ras家族的抑制剂）和FTS（一种强效甲基转移酶抑制剂）都能够部分抑制LTD4诱导的[Ca2+]升高，这表明Ras家族成员在[Ca2+]i调节中发挥作用。总之，在分化的U937细胞中，LTD4信号转导涉及：（a）至少两条途径，一条对PTx敏感，一条不敏感；（b）异戊二烯化蛋白，如βγ亚基，以及可能的Ras家族小G蛋白。
