In situ tip-recordings found no evidence for an Orco-based ionotropic mechanism of pheromone-transduction in Manduca sexta.
In situ tip-recordings found no evidence for an Orco-based ionotropic mechanism of pheromone-transduction in Manduca sexta.
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DOI：
10.1371/journal.pone.0062648
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发表时间：
2013
期刊：
影响因子：
3.7
通讯作者：
Stengl M
中科院分区：
文献类型：
--
作者：
Nolte A;Funk NW;Mukunda L;Gawalek P;Werckenthin A;Hansson BS;Wicher D;Stengl M
昆虫气味信号转导的机制仍存在争议。昆虫气味受体（ORs）是一类膜拓扑结构倒置的7 TM受体。它们与具有分子伴侣和离子通道功能的保守辅助受体（Orco）共定位。一些研究表明，昆虫采用专门的离子型气味转导通过OR-Orco异源聚体。其他研究提供了不同的代谢性气味转导级联的证据，其中采用第二信使门控离子通道家族的气味转导。天蛾Manduca sexta是昆虫嗅觉研究的模式生物，这也是由于天蛾特异性信息素与其主要成分家蚕醛混合的可用性。以前的膜片钳研究对原代细胞培养的M。Sexta嗅觉受体神经元提供了磷脂酶Cβ的信息素依赖性激活的证据。信息素的应用引起了一个快速的，显然IP 3依赖的，瞬态和两个较慢的Ca 2+依赖性内向电流的序列。它仍然是未知的，是否额外的离子型信息素转导机制。如果OR-Orco离子通道复合物确实是离子型机制的基础，则OR-Orco通道孔的Orco激动剂依赖性开放应加起来为信息素依赖性孔开放。在这里，在提示记录完整的信息素敏感的感受器，灌注与Orco激动剂VUAA 1没有增加信息素的反应在第一个1000毫秒。然而，VUAA 1增加自发活动的嗅觉受体神经元Zeitgebertime和剂量依赖性。我们的结论是，我们没有发现证据的Orco依赖的离子型信息素转导级联M。六。相反，在M. sexta Orco似乎是一个较慢的第二信使依赖性起搏通道，通过细胞内Ca 2+基线浓度的变化影响动力学和信息素检测阈值。
The mechanisms of insect odor transduction are still controversial. Insect odorant receptors (ORs) are 7TM receptors with inverted membrane topology. They colocalize with a conserved coreceptor (Orco) with chaperone and ion channel function. Some studies suggest that insects employ exclusively ionotropic odor transduction via OR-Orco heteromers. Other studies provide evidence for different metabotropic odor transduction cascades, which employ second messenger-gated ion channel families for odor transduction. The hawkmoth Manduca sexta is an established model organism for studies of insect olfaction, also due to the availability of the hawkmoth-specific pheromone blend with its main component bombykal. Previous patch-clamp studies on primary cell cultures of M. sexta olfactory receptor neurons provided evidence for a pheromone-dependent activation of a phospholipase Cβ. Pheromone application elicited a sequence of one rapid, apparently IP3-dependent, transient and two slower Ca2+-dependent inward currents. It remains unknown whether additionally an ionotropic pheromone-transduction mechanism is employed. If indeed an OR-Orco ion channel complex underlies an ionotropic mechanism, then Orco agonist-dependent opening of the OR-Orco channel pore should add up to pheromone-dependent opening of the pore. Here, in tip-recordings from intact pheromone-sensitive sensilla, perfusion with the Orco agonist VUAA1 did not increase pheromone-responses within the first 1000 ms. However, VUAA1 increased spontaneous activity of olfactory receptor neurons Zeitgebertime- and dose-dependently. We conclude that we find no evidence for an Orco-dependent ionotropic pheromone transduction cascade in M. sexta. Instead, in M. sexta Orco appears to be a slower, second messenger-dependent pacemaker channel which affects kinetics and threshold of pheromone-detection via changes of intracellular Ca2+ baseline concentrations.
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