Fatty acid binding protein FABP3 from Chinese mitten crab Eriocheir sinensis participates in antimicrobial responses

• The full-length sequence of a new Eriocheir sinensis FABP (Es-FABP3) was cloned.
• Es-FABP3 mRNA is highly abundant in primary immune tissues.
• Temporal expression of Es-FABP3 in E. sinensis was analyzed after PAMP challenge.
• Recombinant Es-FABP3 binds to a wide spectrum of microorganisms.

Intracellular fatty acid-binding proteins (FABPs) are members of the lipid-binding protein superfamily. Aside from the main functions of FABPs in the uptake and transport of fatty acids, they are also critical in innate immunology. In this work, the full-length cDNA for a Chinese mitten crab Eriocheir sinensis FABP (Es-FABP3) was cloned with an open reading frame of 402 bp encoding a 133 amino acid polypeptide. Analysis using quantitative real-time PCR (qPCR) revealed that Es-FABP3 transcripts were widely distributed in gills, muscle, intestine, hepatopancreas, eyestalk, heart, stomach, brain, thoracic ganglia and hemocytes. After challenge with pathogen associated molecular pattern molecules (PAMPs), the relative mRNA expression levels of Es-FABP3 increased in hepatopancreas, gills and hemocytes. Moreover, the mature recombinant Es-FABP3 protein exhibited different binding activities to bacteria and fungus and inhibited the growth of different microbes. These collective results demonstrated the role of Es-FABP3 in the immunoreactions of E. sinensis to PAMPs.