A putative insulin receptor involved in immune response of Chinese mitten crab Eriocheir sinensis

Insulin plays important roles in metabolic homeostasis during environmental challenges. The insulin receptor is a key molecule to receive and transduce insulin signals. In the present study, a novel insulin receptor was identified from the Chinese mitten crab Eriocheir sinensis (designated as EsIR). The coding region of EsIR gene was 3573 bp in length and encoded 1190 amino acids with all the functional domains of mammal insulin receptors, including furin-like domain, receptor L domain, transmembrane domain, and tyrosine kinase domain. Phylogenetic analysis showed that the EsIR shared the closest evolutionary relationship with the insulin receptor from Macrobrachium rosenbergii. Cell transfection experiments confirmed that EsIR proteins were localized on the cytomembrane. The mRNA transcripts of EsIR were widely distributed in various tissues with higher abundance in hepatopancreas and eyestalk of E. sinensis. After Aeromonas hydrophila stimulation, the expression level of EsIR mRNA decreased from 3 h to 6 h, and then increased at 12 h. The conserved structure and subcellular localization of EsIR together with its sensitivity to A. hydrophila stimulation implied that EsIR was probably involved in immune response of E. sinensis. The present study provided clues for the further investigation about the evolution and function of the insulin signaling pathway in invertebrates.