Quantitative proteomic analyses provide insights into the hyalinocytes and granulocytes phagocytic killing of ivory shell Babylonia areolata in vitro

Abstract The molecular mechanisms underlying the phagocytosis of haemocytes remain unclear in Babylonia areolata. In this study, the phagocytic activities of hyalinocytes and granulocytes in B. areolata were examined by flow cytometry combined with electron microscopy and proteomics analyses in vitro. The ultrastructural features of haemocytes that internalised and engulfed Vibrio parahaemolyticus were revealed by electron microscopy. The results of V. parahaemolyticus challenge using electron microscopy showed a process during phagosome formation in hyalinocytes. The phagocytic rates of hyalinocytes and granulocytes that ingested fluorescent microspheres were approximately 31.19 ± 4.79% and 10.66 ± 1.18%, respectively. The phagocytosis rate of hyalinocytes to V. parahaemolyticus was 44.99 ± 5.03%, and that of granulocytes was 49.67 ± 4.06%. After V. parahaemolyticus challenge, differentially expressed proteins were identified by label-free quantitative proteomic analysis. The identified proteins included cathepsins, clathrin, heat shock protein 90 kDa, molecular chaperone HtpG, integrin, collagen, laminin, protein kinase A, Ras-related C3 botulinum toxin substrate 1, Ras-related protein, GTPase, V-type H + -transporting ATPase, and Rab-7A, which were involved in different signalling pathways. Some immune-related KEGG pathways were significantly up-regulated or down-regulated after V. parahaemolyticus challenge, including lysosome, proteasome, NOD-like receptor, PI3K-Akt, JAK-STAT, and Wnt signalling pathways. The results suggest that there are differences in the phagocytotic abilities between hyalinocytes and granulocytes of B. areolata based on changes in morphological, functional, and molecular features.