PDF(Pubmed)
Abstract：
Transient receptor potential (TRP) ion channels are involved in the surveillance or regulation of the acid-base balance. Here, we demonstrate that weak carbonic acids, including acetic acid, lactic acid, and CO2 activate and sensitize TRPV2 through a mechanism requiring permeation through the cell membrane. TRPV2 channels in cell-free inside-out patches maintain weak acid-sensitivity, but protons applied on either side of the membrane do not induce channel activation or sensitization. The involvement of proton modulation sites for weak acid-sensitivity was supported by the identification of titratable extracellular (Glu495, Glu561) and intracellular (His521) residues on a cryo-EM structure of rat TRPV2 (rTRPV2) treated with acetic acid. Molecular dynamics simulations as well as patch clamp experiments on mutant rTRPV2 constructs confirmed that these residues are critical for weak acid-sensitivity. We also demonstrate that the pore residue Glu609 dictates an inhibition of weak acid-induced currents by extracellular calcium. Finally, TRPV2-expression in HEK293 cells is associated with an increased weak acid-induced cytotoxicity. Together, our data provide new insights into weak acids as endogenous modulators of TRPV2.
摘要：
瞬时受体电位（TRP）离子通道参与酸碱平衡的监测或调节。这里,我们证明了弱碳酸，包括乙酸,乳酸,CO2通过需要通过细胞膜渗透的机制激活和敏化TRPV2。TRPV2通道在无细胞内外贴剂中保持弱酸敏感性，但是施加在膜的任一侧的质子不会诱导通道激活或敏化。在用乙酸处理的大鼠TRPV2（rTRPV2）的低温EM结构上，可滴定的细胞外（Glu495，Glu561）和细胞内（His521）残基的鉴定支持了质子调节位点对弱酸敏感性的参与。分子动力学模拟以及对突变rTRPV2构建体的膜片钳实验证实，这些残基对于弱酸敏感性至关重要。我们还证明了孔残基Glu609决定了细胞外钙对弱酸诱导电流的抑制作用。最后,HEK293细胞中的TRPV2表达与弱酸诱导的细胞毒性增加有关。一起,我们的数据为弱酸作为TRPV2的内源性调节剂提供了新的见解。
