Zhu Xiaojing, Zhang Lei, Jiang Linlong, Chen Huaqing, Tang Yu, Yang Xiaoyun, Bao Pengkun, Liao Chenghong, Li Jianyong, Vavricka Christopher J, Ren Delin, Chen Zhaohui, Guo Yingying, Han Qian
Laboratory of Tropical Veterinary Medicine and Vector Biology, School of Life and Health Sciences, Hainan Province Key Laboratory of One Health, Collaborative Innovation Center of One Health, Hainan University, Haikou, Hainan 570228, China.
Hainan International One Health Institute, Hainan University, Haikou, Hainan 570228, China.
Proc Natl Acad Sci U S A. 2025 Jan 21;122(3):e2413131122. doi: 10.1073/pnas.2413131122. Epub 2025 Jan 14.
Insect phenoloxidase, presented as an inactive precursor prophenoloxidase (PPO) in hemolymph, catalyzes melanin formation, which is involved in wound healing, pathogen killing, reversible oxygen collection during insect respiration, and cuticle and eggshell formation. Mosquitoes possess 9 to 16 PPO members across different genera, a number that is more than that found in other dipteran insects. However, the reasons for the redundancy of these PPOs and whether they have distinct biochemical properties and physiological functions remain unclear. Phylogenetic analysis confirmed that PPO6 (Aea-PPO6) is an ortholog to PPOs in other insect species, classified as the classical insect type, while other Aea-PPOs are unique to Diptera, herein referred to as the dipteran type here. We characterized two Aea-PPO members, Aea-PPO6, the classical insect type, and Aea-PPO10, a dipteran type, which exhibit distinct substrate specificities. By resolving Aea-PPO6's crystal structure and creating a chimera protein (Aea-PPO6-cm) with Motif 1 (GDGPDSVVR) from Aea-PPO10, we identified the motif that determines PPO substrate specificity. In vivo, loss of Aea-PPO6 led to larval lethality, while Aea-PPO10 was involved in development, pigmentation, and immunity. Our results enhance the understanding of the functional diversification of mosquito PPOs.
昆虫酚氧化酶在血淋巴中以无活性的前体酚氧化酶原（PPO）形式存在，催化黑色素形成，这一过程参与伤口愈合、病原体杀灭、昆虫呼吸过程中的可逆性氧气收集以及表皮和卵壳形成。不同属的蚊子拥有9至16个PPO成员，这一数量多于其他双翅目昆虫中的PPO数量。然而，这些PPO冗余的原因以及它们是否具有不同的生化特性和生理功能仍不清楚。系统发育分析证实，PPO6（埃及伊蚊PPO6，Aea-PPO6）是其他昆虫物种中PPO的直系同源物，属于经典昆虫类型，而其他埃及伊蚊PPO是双翅目特有的，在此称为双翅目类型。我们对两个埃及伊蚊PPO成员进行了表征，即经典昆虫类型的Aea-PPO6和双翅目类型的Aea-PPO10，它们表现出不同的底物特异性。通过解析Aea-PPO6的晶体结构，并利用来自Aea-PPO10的基序1（GDGPDSVVR）创建嵌合蛋白（Aea-PPO6-cm），我们确定了决定PPO底物特异性的基序。在体内，Aea-PPO6缺失导致幼虫致死，而Aea-PPO10参与发育、色素沉着和免疫。我们的结果增进了对蚊子PPO功能多样性的理解。
