Characterization of P2X7R and Its Function in the Macrophages of ayu, Plecoglossus altivelis

Abstract

P2X purinoceptor 7 (P2X7R), an ATP-gated ion channel, plays an important role during the innate immune response in mammals. However, relatively little is known about the role of P2X7R in the fish immune system. Here, we cloned a cDNA sequence encoding ayu (Plecoglossus altivelis) P2X7R (aP2X7R). The predicted protein was composed of 574 amino acid residues with a P2X family signature, two transmembrane domains, and a long C-terminal. aP2X7R transcripts were mainly distributed in ayu immune tissues and significantly increased in all tested tissues and in macrophages after Listonella anguillarum infection. The aP2X7R protein was upregulated significantly in macrophages upon bacterial challenge. An antibody against the ectodomain of aP2X7R (aEPAb) and an antagonist (oATP) were used to block aP2X7R. aP2X7R siRNA was also used to knockdown the receptor expression in ayu macrophages. Cell death induced by ATP was significantly inhibited in ayu macrophages after aEPAb, oATP, or siRNA treatment. Moreover, aP2X7R ablation also resulted in suppression of phagocytic activity and ATP-induced bacterial killing in ayu macrophages. Our results indicated that aP2X7R was upregulated after infection and mediated cell death, phagocytosis, and bacterial killing of ayu macrophages.

B Cell Functions Can Be Modulated by Antimicrobial Peptides in Rainbow Trout Oncorhynchus mykiss: Novel Insights into the Innate Nature of B Cells in Fish

“…In this study, we found that trout B cells could also express P2X 7 R, with the expression level in the IgT + B cells higher than that in the IgM + B cells. In addition, we found that the expression level of trout P2X 7 R in phagocytic IgM + and IgT + B cells was significantly higher than that of non-phagocytic B cells, indicating that P2X 7 R might play a role in the phagocytosis of fish B cells, which has been proven in fish macrophages (47). However, whether the immunomodulatory effect of fish cathelicidin peptides on B cells is also mediated by P2X 7 R needs to be further clarified.…”

“…In human, P2X 7 R has been proven to mediate the stimulating effects of LL-37 on the bactericidal, ROS, and lysosome formation activities of macrophages (25). In ayu ( Plecoglossus altivelis ), knockdown of P2X 7 R significantly reduced the stimulating effects of cathelicidin peptide CATH on the phagocytic, bactericidal, and ROS activities of monocytes/macrophages (39, 47). In this study, we found that trout B cells could also express P2X 7 R, with the expression level in the IgT + B cells higher than that in the IgM + B cells.…”

Crucial Role of P2X7Receptor in Regulating Exocytosis of Single-Walled Carbon Nanotubes in Macrophages

“…Upon ATP stimulation, the fast and reversible opening of P2X 7 R channel could lead to calcium ion influx in cells, which has also been documented in macrophages in response to stimulations . As a second messenger, the rise of intracellular calcium ion concentration ([Ca 2+ ] i ) appears to be important in both normal physiology as well as pathophysiological processes in a variety of cell types including T cells, smooth muscle cell, and macrophages .…”

Evolutionary Origin of the P2X7 C-ter Region: Capture of an Ancient Ballast Domain by a P2X4-Like Gene in Ancient Jawed Vertebrates

“…Little is known about the function of P2X7 in non-mammalian species. However, P2X7 identified in Ayu (Plecoglossus altivelis, an Asian salmoniform), is induced by infection and is involved in ATP dependent cell death, phagocytosis, and bactericidal activity of macrophages (37,38). Importantly, after transfection in HEK293 cells, seabream or zebrafish P2X7 receptors were unable to induce the maturation and secretion of human or fish IL-1β.…”