苦受体 hTAS2R46 的激动剂苦艾素揭示了内质网到线粒体的 Ca2+穿梭事件。

Absinthin, an agonist of the bitter taste receptor hTAS2R46, uncovers an ER-to-mitochondria Ca-shuttling event.

机构信息

Department of Health Sciences, School of Medicine, University of Piemonte Orientale, Via Solaroli, 17-28100 Novara, Italy.

Department of Pharmaceutical Sciences, University of Piemonte Orientale, Via Bovio, 6-28100 Novara, Italy.

出版信息

J Biol Chem. 2019 Aug 16;294(33):12472-12482. doi: 10.1074/jbc.RA119.007763. Epub 2019 Jun 27.

Abstract

Type 2 taste receptors (TAS2R) are G protein-coupled receptors first described in the gustatory system, but have also been shown to have extraoral localizations, including airway smooth muscle (ASM) cells, in which TAS2R have been reported to induce relaxation. TAS2R46 is an unexplored subtype that responds to its highly specific agonist absinthin. Here, we first demonstrate that, unlike other bitter-taste receptor agonists, absinthin alone (1 μm) in ASM cells does not induce Ca signals but reduces histamine-induced cytosolic Ca increases. To investigate this mechanism, we introduced into ASM cells aequorin-based Ca probes targeted to the cytosol, subplasma membrane domain, or the mitochondrial matrix. We show that absinthin reduces cytosolic histamine-induced Ca rises and simultaneously increases Ca influx into mitochondria. We found that this effect is inhibited by the potent human TAS2R46 (hTAS2R46) antagonist 3β-hydroxydihydrocostunolide and is no longer evident in hTAS2R46-silenced ASM cells, indicating that it is hTAS2R46-dependent. Furthermore, these changes were sensitive to the mitochondrial uncoupler carbonyl cyanide -(trifluoromethoxy)phenyl-hydrazone (FCCP); the mitochondrial calcium uniporter inhibitor KB-R7943 (carbamimidothioic acid); the cytoskeletal disrupter latrunculin; and an inhibitor of the exchange protein directly activated by cAMP (EPAC), ESI-09. Similarly, the β2 agonist salbutamol also could induce Ca shuttling from cytoplasm to mitochondria, suggesting that this new mechanism might be generalizable. Moreover, forskolin and an EPAC activator mimicked this effect in HeLa cells. Our findings support the hypothesis that plasma membrane receptors can positively regulate mitochondrial Ca uptake, adding a further facet to the ability of cells to encode complex Ca signals.

摘要

2 型味觉受体 (TAS2R) 是最初在味觉系统中描述的 G 蛋白偶联受体,但也已被证明具有口腔外的定位,包括气道平滑肌 (ASM) 细胞,据报道 TAS2R 在其中诱导松弛。TAS2R46 是一种未被探索的亚型,对其高度特异性激动剂苦艾素产生反应。在这里,我们首先证明,与其他苦味受体激动剂不同,ASM 细胞中单独的苦艾素(1 μm)不会诱导 Ca 信号,但会减少组胺诱导的细胞浆 Ca 增加。为了研究这种机制,我们将基于水母发光蛋白的 Ca 探针引入 ASM 细胞,该探针靶向细胞质、亚质膜域或线粒体基质。我们表明,苦艾素可降低细胞浆中组胺诱导的 Ca 上升,同时增加 Ca 流入线粒体。我们发现,这种效应被强效人 TAS2R46 (hTAS2R46) 拮抗剂 3β-羟基二氢缬草醇内酯抑制,并且在 hTAS2R46 沉默的 ASM 细胞中不再明显,表明它是 hTAS2R46 依赖性的。此外,这些变化对线粒体解偶联剂羰基氰化物-(三氟甲氧基)苯腙 (FCCP)、线粒体钙单向转运体抑制剂 KB-R7943 (氨基甲硫基噻唑酸)、细胞骨架破坏剂拉曲库林和 cAMP 直接激活的交换蛋白抑制剂 (EPAC) ESI-09 敏感。同样,β2 激动剂沙丁胺醇也能诱导 Ca 从细胞质穿梭到线粒体,表明这种新机制可能具有普遍性。此外, forskolin 和 EPAC 激活剂在 HeLa 细胞中模拟了这种效应。我们的发现支持了这样一种假设,即质膜受体可以正向调节线粒体 Ca 摄取,为细胞编码复杂 Ca 信号增加了另一个方面。

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