Benedikt Jan, Teisinger Jan, Vyklicky Ladislav, Vlachova Viktorie
Department of Cellular Neurophysiology, Institute of Physiology, Academy of Sciences of the Czech Republic, Prague, Czech Republic.
J Neurochem. 2007 Jan;100(1):211-24. doi: 10.1111/j.1471-4159.2006.04192.x. Epub 2006 Oct 27.
Ethanol has opposite effects on two members of the transient receptor potential (TRP) family of ion channels: it inhibits the cold-menthol receptor TRPM8, whereas it potentiates the activity of the heat- and capsaicin-gated vanilloid receptor TRPV1. Both thermosensitive cation channels are critically regulated by the membrane lipid, phosphatidylinositol 4,5-bisphosphate (PIP(2)). The effects of this phospholipid on TRPM8 and TRPV1 are also functionally opposite: PIP(2) is necessary for the activation of TRPM8 but it constitutively inhibits TRPV1. This parallel led us to investigate the possible role of PIP(2) in the ethanol-induced modulation of rat TRPM8, heterologously expressed in HEK293T cells. In this study, we characterize the effects of ethanol (0.1-10%) on whole-cell currents produced by menthol and by low temperature (< 17 degrees C). We show that the inclusion of PIP(2) in the intracellular solution results in a strong reduction in the ethanol-induced inhibition of menthol-evoked responses. Conversely, intracellular dialysis with anti-PIP(2) antibody or with the PIP(2) scavenger, poly L-lysine, enhanced the ethanol-induced inhibition of TRPM8. A 20 min pre-incubation with wortmannin caused a modest decrease in inhibition produced by 1% ethanol, indicating that the ethanol-induced inhibition is not mediated by lipid kinases. These findings suggest that ethanol inhibits TRPM8 by weakening the PIP(2)-TRPM8 channel interaction; a similar mechanism may contribute to the ethanol-mediated modulation of some other PIP(2)-sensitive TRP channels.
乙醇对瞬时受体电位（TRP）离子通道家族的两个成员具有相反的作用：它抑制冷-薄荷醇受体TRPM8，而增强热和辣椒素门控的香草酸受体TRPV1的活性。这两种热敏阳离子通道均受到膜脂磷脂酰肌醇4,5-二磷酸（PIP₂）的严格调控。这种磷脂对TRPM8和TRPV1的作用在功能上也是相反的：PIP₂是TRPM8激活所必需的，但它对TRPV1具有组成性抑制作用。这种相似性促使我们研究PIP₂在乙醇诱导的对在HEK293T细胞中异源表达的大鼠TRPM8的调节中可能发挥的作用。在本研究中，我们描述了乙醇（0.1 - 10%）对薄荷醇和低温（<17℃）产生的全细胞电流的影响。我们发现，在细胞内溶液中加入PIP₂会导致乙醇诱导的对薄荷醇诱发反应的抑制作用大幅降低。相反，用抗PIP₂抗体或PIP₂清除剂聚L-赖氨酸进行细胞内透析可增强乙醇诱导的对TRPM8的抑制作用。用渥曼青霉素预孵育20分钟会使1%乙醇产生的抑制作用适度降低，这表明乙醇诱导的抑制作用不是由脂质激酶介导的。这些发现表明，乙醇通过减弱PIP₂ - TRPM8通道相互作用来抑制TRPM8；类似的机制可能有助于乙醇对其他一些PIP₂敏感的TRP通道的介导调节。
