Department of Chemistry, University of Nebraska-Lincoln, Lincoln, NE 68588.
The Nebraska Center for Integrated Biomolecular Communication, University of Nebraska-Lincoln, Lincoln, NE 68588.
Proc Natl Acad Sci U S A. 2023 Mar 14;120(11):e2217604120. doi: 10.1073/pnas.2217604120. Epub 2023 Mar 6.
The l- to d-amino acid residue isomerization of neuropeptides is an understudied post-translational modification found in animals across several phyla. Despite its physiological importance, little information is available regarding the impact of endogenous peptide isomerization on receptor recognition and activation. As a result, the full roles peptide isomerization play in biology are not well understood. Here, we identify that the allatotropin-related peptide (ATRP) signaling system utilizes l- to d-residue isomerization of one amino acid residue in the neuropeptide ligand to modulate selectivity between two distinct G protein-coupled receptors (GPCRs). We first identified a novel receptor for ATRP that is selective for the D2-ATRP form, which bears a single d-phenylalanine residue at position 2. Using cell-based receptor activation experiments, we then characterized the stereoselectivity of the two known ATRP receptors for both endogenous ATRP diastereomers, as well as for homologous toxin peptides from a carnivorous predator. We found that the ATRP system displayed dual signaling through both the Gα and Gα pathways, and each receptor was selectively activated by one naturally occurring ligand diastereomer over the other. Overall, our results provide insights into an unexplored mechanism by which nature regulates intercellular communication. Given the challenges in detecting l- to d-residue isomerization from complex mixtures de novo and in identifying receptors for novel neuropeptides, it is likely that other neuropeptide-receptor systems may also utilize changes in stereochemistry to modulate receptor selectivity in a manner similar to that discovered here.
神经肽的 l-到 d-氨基酸残基异构化是一种在几个门的动物中都存在的研究不足的翻译后修饰。尽管它具有重要的生理学意义，但关于内源性肽异构化对受体识别和激活的影响的信息很少。因此，肽异构化在生物学中所扮演的全部角色还不是很清楚。在这里，我们发现，促前胸腺激素相关肽（ATRP）信号系统利用神经肽配体中一个氨基酸残基的 l-到 d-残基异构化来调节两种不同 G 蛋白偶联受体（GPCR）之间的选择性。我们首先鉴定了一种新型的 ATRP 受体，它对 D2-ATRP 形式具有选择性，该形式在位置 2 上带有一个单一的 d-苯丙氨酸残基。然后，我们使用基于细胞的受体激活实验，对两种已知的 ATRP 受体对两种内源性 ATRP 对映体以及来自肉食性捕食者的同源毒素肽的立体选择性进行了特征描述。我们发现，ATRP 系统通过 Gα 和 Gα 两种途径进行双重信号传递，并且每种受体都被一种天然存在的配体对映体选择性激活，而另一种则被激活。总的来说，我们的结果提供了对自然界调节细胞间通讯的一种未知机制的深入了解。鉴于从复杂混合物中从头检测 l-到 d-残基异构化以及鉴定新型神经肽受体的挑战，其他神经肽-受体系统也可能利用立体化学的变化以类似于这里发现的方式调节受体选择性。
