The activated beta-integrin (Cg beta V) enhances RGD-binding and phagocytic capabilities of hemocytes in Crassostrea gigas

• Published in: Fish & Shellfish Immunology
• Main Authors: Lv, Zhao, Qiu, Limei, Jia, Zhihao, Wang, Weilin, Liu, Zhaoqun, Wang, Lingling, Song, Linsheng
• Format: Report
• Language: English
• Published: ACADEMIC PRESS LTD- ELSEVIER SCIENCE LTD 2019
• Subjects: C. gigas; RGD-Binding; Integrin activation; Integrin-mediated phagocytosis; Fisheries; Immunology; Marine & Freshwater Biology; Veterinary Sciences; Pacific; Crassostrea gigas; Pacific oyster
• Online Access: http://ir.qdio.ac.cn/handle/337002/161137; http://ir.qdio.ac.cn/handle/337002/161138; https://doi.org/10.1016/j.fsi.2019.01.047

Integrins are an important family of cell receptors that can bind foreign particles and promote cell phagocytosis after they are activated. In the present study, a novel beta integrin was identified from pacific oyster Crassostrea gigas with an extracellular domain, a single transmembrane segment, and a short cytoplasmic domain. It was phylogenetically clustered with phagocytosis-related insecta beta V, and designated as Cg beta V. Cg beta V shared a conserved NPX[Y/F] motif related to integrin activation with other phagocytosis-related beta integrins. The mRNA transcripts of Cg beta V were widely detected in oyster tissues including hemocytes, gonad, adductor muscle, mantle, gill, and hepatopancreas, and the expression level in hemocytes was significantly up-regulated at 12 h after lipopolysaccharide (LPS) stimulation (p < 0.05), which was 2.29-fold higher than that in the control group. Cg beta V proteins were mainly observed on the hemocytes surface. The oyster hemocytes were found to bind fluorescein isothiocyanate (FITC)-labeled Arg-Gly-Asp-containing peptides (RGDCPs), and the binding capability was significantly up-regulated with the peak percentage of 37.6% at 12 h post LPS stimulation, which was higher than that in the control group (8.8%, p < 0.05), suggesting the activation of RGD-binding integrins on oyster hemocytes surface. The label-free RGDCPs and anti-Cg beta V antibody inhibited the binding capability of hemocytes towards FITC-labeled RGDCPs, which were significant lower in RGD blocking group (7.4%, p < 0.05) and anti-Cg beta V blocking group (22.1%, p < 0.05) than that in the control group (37.6%), indicating that Cg beta V could be a RGD-binding integrin. Phagocytosis assay demonstrated that LPS could enhance the phagocytosis of hemocytes towards Escherichia cob and fluorescent beads with the phagocytic rate (PR) of 18.3% and 17.4%, and phagocytic index (PI) of 5.29 and 37.71, respectively, which were significant higher than that in the control group (11.0% and 3.65 for E. coli, ...