Activation of EGL-47, a Gαo-coupled receptor, inhibits function of hermaphrodite-specific motor neurons to regulate Caenorhabditis elegans egg-laying behavior
Activation of EGL-47, a Gαo-coupled receptor, inhibits function of hermaphrodite-specific motor neurons to regulate Caenorhabditis elegans egg-laying behavior
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DOI：
10.1523/jneurosci.1915-04.2004
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发表时间：
2004-09-29
影响因子：
5.3
通讯作者：
Koelle, MR
中科院分区：
文献类型：
--
作者：
Moresco, JJ;Koelle, MR
秀丽隐杆线虫的产卵行为受到通过神经G蛋白Galalpha（o）的神经递质信号的抑制，并作为分析Galalpha（o）信号的模型。改变产卵频率的突变已经确定了编码许多与Galalpha（o）起作用的信号蛋白的基因，但激活Galalpha（o）的受体仍然没有被鉴定。为了进一步分析Galalpha（o）信号传导，我们克隆了egl-47基因，该基因通过两个严重抑制产卵的显性突变来鉴定。egl-47编码两种孤儿G蛋白偶联受体同种型，它们共享所有七个跨膜结构域，但具有不同的胞外N末端。两种显性突变都将第六跨膜结构域中的相同丙氨酸改变为缬氨酸，导致组成型激活受体。egl-47基因的缺失没有引起可检测到的产卵缺陷，这表明EGL-47的功能是冗余的，或者它在尚未确定的特定情况下抑制产卵。使用启动子：通过绿色荧光蛋白转基因，我们发现EGL-47在许多神经元中表达，包括支配产蛋肌以刺激收缩的两性特异性神经元（HSN）。特异性在HSN中转基因表达组成型活性EGL-47或组成型活性Galalpha（o）足以抑制产卵行为。我们的研究结果表明，EGL-47通过激活HSN运动神经元中的Galalpha（o）来抑制其活性，从而调节产卵。由于几种神经递质通过Ga（o）抑制HSN功能，因此似乎任何一种受体（如EGL-47）的缺失都只会导致轻度缺陷。Galalpha（o）显然整合了HSN中多种受体（包括EGL-47）的信号，以设定产卵行为的频率。
Caenorhabditis elegans egg-laying behavior is inhibited by neurotransmitter signaling through the neural G-protein Galpha(o) and serves as a model for analyzing Galpha(o) signaling. Mutations that alter egg-laying frequency have identified genes encoding a number of signaling proteins that act with Galpha(o), but the receptors that activate Galpha(o) remain mostly uncharacterized. To further analyze Galpha(o) signaling, we cloned the egl-47 gene, which was identified by two dominant mutations that severely inhibit egg laying. egl-47 encodes two orphan G-protein-coupled receptor isoforms, which share all seven transmembrane domains but have different extracellular N termini. Both dominant mutations change the same alanine to valine in the sixth transmembrane domain, resulting in constitutively activated receptors. Deletion of the egl-47 gene caused no detectable egg-laying defects, suggesting that EGL-47 functions redundantly, or it inhibits egg laying under specific circumstances as yet unidentified. Using promoter:: green fluorescent protein transgenes, we found that EGL-47 is expressed in a number of neurons, including the hermaphrodite-specific neurons (HSNs) that innervate the egg-laying muscles to stimulate contraction. Transgenic expression of constitutively active EGL-47 or constitutively active Galpha(o) specifically in the HSNs was sufficient to inhibit egg-laying behavior. Our results suggest that EGL-47 regulates egg laying by activating Galpha(o) in the HSN motor neurons to inhibit their activity. Because several neurotransmitters act through Galpha(o) to inhibit HSN function, it appears that loss of any one receptor, such as EGL-47, causes only mild defects. Galpha(o) apparently integrates signaling from multiple receptors in the HSNs, including EGL-47, to set the frequency of egg-laying behavior.