BioMAP, UMR ISP 1282 INRAe, Université de Tours, 37200 Tours, France.
Department of Pharmacology, University of Gezira, Wad Madani 21111, Sudan.
Genes (Basel). 2024 Jun 27;15(7):844. doi: 10.3390/genes15070844.
The human louse () is an obligatory blood feeding ectoparasite with two ecotypes: the human body louse (), a competent vector of several bacterial pathogens, and the human head louse (), responsible for pediculosis and affecting millions of people around the globe. GABA (γ-aminobutyric acid) receptors, members of the cys-loop ligand gated ion channel superfamily, are among the main pharmacological targets for insecticides. In insects, there are four subunits of GABA receptors: resistant-to-dieldrin (RDL), glycin-like receptor of drosophila (GRD), ligand-gated chloride channel homologue3 (LCCH3), and 8916 are well described and form distinct phylogenetic clades revealing orthologous relationships. Our previous studies in the human body louse confirmed that subunits Phh-RDL, Phh-GRD, and Phh-LCCH3 are well clustered in their corresponding clades. In the present work, we cloned and characterized a putative new GABA receptor subunit in the human body louse that we named HoCas, for Homologous to Cys-loop α like subunit. Extending our analysis to arthropods, HoCas was found to be conserved and clustered in a new (fifth) phylogenetic clade. Interestingly, the gene encoding this subunit is ancestral and has been lost in some insect orders. Compared to the other studied GABA receptor subunits, HoCas exhibited a relatively higher expression level in all development stages and in different tissues of human body louse. These findings improved our understanding of the complex nature of GABA receptors in and more generally in arthropods.
人体虱（）是一种专性吸血的外寄生虫，有两种生态型：人体虱（），是几种细菌病原体的有效传播媒介，和人头虱（），引起头虱病，影响着全球数百万人。γ-氨基丁酸（GABA）受体是 cys-环配体门控离子通道超家族的成员之一，是杀虫剂的主要药理靶点之一。在昆虫中，有四种 GABA 受体亚基：对滴滴涕（Dieldrin）有抗性（RDL）、果蝇甘氨酸样受体（GRD）、配体门控氯离子通道同源物 3（LCCH3），以及 8916 已被很好地描述并形成独特的系统发育分支，显示出同源关系。我们以前在人体虱中的研究证实，Phh-RDL、Phh-GRD 和 Phh-LCCH3 亚基很好地聚类在它们各自的分支中。在本工作中，我们克隆并鉴定了人体虱中一个假定的新 GABA 受体亚基，我们将其命名为 HoCas，代表与 cys-环α样亚基同源。将我们的分析扩展到节肢动物，发现 HoCas 保守并聚类在一个新的（第五）系统发育分支中。有趣的是，编码这个亚基的基因是祖先的，在一些昆虫目中已经丢失。与其他研究的 GABA 受体亚基相比，HoCas 在人体虱的所有发育阶段和不同组织中的表达水平相对较高。这些发现提高了我们对 GABA 受体在 中的复杂性质的理解，更广泛地说，在节肢动物中也是如此。
