Catisti R, Uyemura S A, Docampo R, Vercesi A E
Department of Pathobiology, University of Illinois at Urbana-Champaign, Urbana 61802, USA.
Mol Biochem Parasitol. 2000 Feb 5;105(2):261-71. doi: 10.1016/s0166-6851(99)00186-3.
A recent report (Eintracht J, Maathai R, Mellors A, Ruben L. Calcium entry in Trypanosoma brucei is regulated by phospholipase A, and arachidonic acid, Biochem J 1998:336:659-66) provided evidence that calcium entry in Trypanosoma brucei bloodstream trypomastigotes is regulated via a signaling pathway involving phospholipase A2-mediated generation of arachidonic acid and stimulation of a plasma membrane-located calcium channel. Here we show that Ca2+ influx in T. brucei procyclic trypomastigotes, Leishmania donovani promastigotes and T. cruzi amastigotes was also stimulated in a dose-dependent manner (50-400 nM) by the amphiphilic peptide melittin. This effect was blocked by the phospholipase A, inhibitor 3-(4-octadecyl)-benzoylacrylic acid. The unsaturated fatty acid arachidonic acid, in the range of 10-75 microM, induced Ca2+ entry by a mechanism sensitive to LaCl3. However, both melittin and arachidonic acid induced an increase in [Ca2+]i in T. brucei procyclic trypomastigotes incubated in Ca2+-free medium implying Ca2+ mobilization from intracellular stores. This hypothesis was supported by experiments showing that arachidonic acid promoted Ca2+ release from the acidocalcisomes of these cells. The results showing changes in mitochondrial membrane potential, release of acridine orange and Ca2+ from the acidocalcisomes and Ca2+ transport across the plasma membrane suggest that in addition to the possible stimulation of a Ca2+ channel-mediated process, arachidonic acid, in the range of concentrations used here, have other nonspecific effects on the trypanosomatids membranes.
最近的一份报告（Eintracht J、Maathai R、Mellors A、Ruben L.《布氏锥虫中的钙内流受磷脂酶A和花生四烯酸调节》，《生物化学杂志》1998年：336：659 - 66）提供了证据，表明布氏锥虫血流型锥鞭毛体中的钙内流是通过一条信号通路来调节的，该信号通路涉及磷脂酶A2介导的花生四烯酸生成以及对位于质膜上的钙通道的刺激。在此我们表明，两亲性肽蜂毒素也以剂量依赖的方式（50 - 400 nM）刺激了布氏锥虫前循环型锥鞭毛体、杜氏利什曼原虫前鞭毛体和克氏锥虫无鞭毛体中的Ca2+内流。这种效应被磷脂酶A抑制剂3 -（4 - 十八烷基）- 苯甲酰丙烯酸阻断。10 - 75 microM范围内的不饱和脂肪酸花生四烯酸通过一种对LaCl3敏感的机制诱导Ca2+内流。然而，蜂毒素和花生四烯酸在无Ca2+培养基中培养的布氏锥虫前循环型锥鞭毛体中均诱导了[Ca2+]i升高，这意味着Ca2+从细胞内储存库中动员出来。该假说得到了实验的支持，这些实验表明花生四烯酸促进了这些细胞酸性钙小体中的Ca2+释放。显示线粒体膜电位变化、吖啶橙从酸性钙小体中释放以及Ca2+从酸性钙小体中释放以及Ca2+跨质膜转运的结果表明，除了可能刺激Ca2+通道介导的过程外，此处所用浓度范围内的花生四烯酸对锥虫细胞膜还有其他非特异性作用。
