Ahmed Musaab, Elvira Bernat, Almilaji Ahmad, Bock C-Thomas, Kandolf Reinhard, Lang Florian
Department of Physiology, University of Tübingen, Gmelinstr. 5, 72076, Tübingen, Germany.
J Membr Biol. 2015 Apr;248(2):223-9. doi: 10.1007/s00232-014-9762-9. Epub 2014 Dec 9.
Parvovirus B19 (B19V) has previously been shown to cause endothelial dysfunction. B19V capsid protein VP1 harbors a lysophosphatidylcholine producing phospholipase A2 (PLA2). Lysophosphatidylcholine inhibits Na(+)/K(+) ATPase, which in turn may impact on the activity of inwardly rectifying K(+) channels. The present study explored whether VP1 modifies the activity of Kir2.1 K(+) channels. cRNA encoding Kir2.1 was injected into Xenopus oocytes without or with cRNA encoding VP1 isolated from a patient suffering from fatal B19V-induced inflammatory cardiomyopathy or the VP1 mutant (H153A)VP1 lacking a functional PLA2 activity. K(+) channel activity was determined by dual electrode voltage clamp. In addition, Na(+)/K(+)-ATPase activity was estimated from K(+)-induced pump current (I(pump)) and ouabain-inhibited current (I(ouabain)). Injection of cRNA encoding Kir2.1 into Xenopus oocytes was followed by appearance of inwardly rectifying K(+) channel activity (I(K)), which was significantly decreased by additional injection of cRNA encoding VP1, but not by additional injection of cRNA encoding (H153A)VP1. The effect of VP1 on I K was mimicked by lysophosphatidylcholine (1 μg/ml) and by inhibition of Na(+)/K(+)-ATPase with 0.1 mM ouabain. In the presence of lysophosphatidylcholine, I K was not further decreased by additional treatment with ouabain. The B19V capsid protein VP1 thus inhibits Kir2.1 channels, an effect at least partially due to PLA2-dependent formation of lysophosphatidylcholine with subsequent inhibition of Na(+)/K(+)-ATPase activity.
细小病毒B19（B19V）先前已被证明可导致内皮功能障碍。B19V衣壳蛋白VP1含有一种产生溶血磷脂酰胆碱的磷脂酶A2（PLA2）。溶血磷脂酰胆碱抑制钠钾ATP酶，这反过来可能会影响内向整流钾通道的活性。本研究探讨了VP1是否会改变Kir2.1钾通道的活性。将编码Kir2.1的cRNA注射到非洲爪蟾卵母细胞中，分别注射或不注射从一名死于B19V诱导的炎症性心肌病患者分离出的编码VP1的cRNA，或缺乏功能性PLA2活性的VP1突变体（H153A）VP1。通过双电极电压钳测定钾通道活性。此外，根据钾诱导的泵电流（I(pump)）和哇巴因抑制电流（I(ouabain)）估算钠钾ATP酶活性。将编码Kir2.1的cRNA注射到非洲爪蟾卵母细胞后，出现内向整流钾通道活性（I(K)），额外注射编码VP1的cRNA可使其显著降低，但额外注射编码（H153A）VP1的cRNA则不会。溶血磷脂酰胆碱（1μg/ml）和用0.1mM哇巴因抑制钠钾ATP酶可模拟VP1对I K的作用。在存在溶血磷脂酰胆碱的情况下，用哇巴因进一步处理不会使I K进一步降低。因此，B19V衣壳蛋白VP1抑制Kir2.1通道，这种作用至少部分是由于PLA2依赖性形成溶血磷脂酰胆碱，随后抑制钠钾ATP酶活性。
