Abstract

Integrins are evolutionarily conserved adhesion receptors that play pivotal roles in phagocytosis across metazoans, yet the specific αβ heterodimers involved in crustacean cellular immunity remain poorly defined. In this study, we identified and characterized an integrin α subunit, designated integrin αPS3 ( Es ITGAPS3), from the economically important Chinese mitten crab, Eriocheir sinensis . Bioinformatic analyses revealed that Es ITGAPS3 shares structural similarity with arthropod integrin αPS3/αPS4/αPS5 subfamily members but exhibits low sequence conservation across distant taxa. EsITGAPS3 was ubiquitously expressed in crab tissues, with the highest levels in immune-relevant organs, including hemocytes, hepatopancreas, and gills. Its transcription was significantly induced in hemocytes following in vitro challenge with Vibrio parahaemolyticus . Functional knockdown of EsITGAPS3 via RNA interference markedly impaired hemocyte phagocytosis of FITC-labeled bacteria, demonstrating its important role in antibacterial cellular immunity. Using AlphaFold-based structural prediction, we identified integrin βPS-like subunit integrin βPS1 ( Es ITGBPS1) as the top-ranked candidate β partner for Es ITGAPS3, and co-immunoprecipitation confirmed their physical interaction and heterodimer formation. Importantly, RNAi-mediated silencing of Es ITGBPS1 similarly compromised bacterial phagocytosis, indicating that the integrin αPS3βPS1 ( Es ITGAPS3- Es ITGBPS1) heterodimer functions as a key receptor complex in crab hemocytes. Our findings define a specific integrin αPS3βPS1 pair required for efficient phagocytosis in E. sinensis , providing mechanistic insight into integrin-mediated immune adaptation in crustaceans and highlighting a potential target for enhancing disease resistance in aquaculture.