The surface protein GroEl of lactic acid bacteria mediates its modulation of the intestinal barrier in Penaeus vannamei.

The molecular chaperone GroEL, commonly found in various bacterial species, exhibits heightened expression levels in response to high temperatures and increased levels of oxygen free radicals. Limited literature currently exists on the probiotic role of GroEL in invertebrates. This study sought to explore how the surface protein GroEL from Lactobacillus plantarum Ep-M17 impacts the intestinal barrier function of Penaeus vannamei. Through pull-down and immunofluorescence assays, the interaction between GroEL and Act1 in the gastrointestinal tract of P. vannamei was confirmed. Results from bacterial binding assays demonstrated that rGroEL can bind to pathogens like Vibrio parahaemolyticus E1 (V. p-E1). In vitro experiments revealed that the administration of rGroEL significantly decreased the levels of inflammatory cytokines induced by pathogens while preserving the integrity of tight junctions between intestinal epithelial cells and reducing bacteria-induced apoptosis. Additionally, rGroEL notably lessened the intestinal loading of V. p-E1 in P. vannamei, downregulated immune-related gene expression, and upregulated BCL/BAX expression in the intestines following V. p-E1 challenge. Mechanistic investigations further showed that rGroEL treatment effectively suppressed the expression and phosphorylation of proteins involved in the NF-κB and PI3K-AKT-mTOR signalling pathways in the intestines of bacteria-infected P. vannamei. Furthermore, GroEL reinforces protection against bacterial infections by enhancing the phagocytic and anti-apoptotic capabilities of P. vannamei hemocytes. These results suggest that GroEL may impede the interaction between pathogens and the intestinal mucosa through its competitive binding characteristics, ultimately reducing bacterial infections.