CD63 Promotes Hemocyte-Mediated Phagocytosis in the Clam,Paphia undulata

As one of the surface membrane proteins of tetraspanin family,cd63 plays a crucial role in cellular trafficking and endocytosis,which also is associated with activation of a wide variety of immune cells. here,the homolog of cd63 was characterized from one marine mollusk,paphia undulata,which is designated as pu-cd63. the complete cdna of pu-cd63 is 1,738 bp in length with an open reading frame (orf) of 849 bp,encoding a 282 amino acid protein with four putative hydrophobic transmembrane helixes. bioinformatic analysis revealed that pu-cd63 contains one putative yxxø consensus motif of 110-yvii-113 and one n-glycosylation site 155-ngt-157 within the large extracellular loop (lel) region,supporting its conserved function in plasma membrane and endosomal/lysosomal trafficking. moreover,temporal expression profile analysis demonstrates a drastic induction in the expression of cd63 in hemocytes after pathogenic challenge with either v. parahaemolyticus or v. alginolyticus. by performing dsrna-mediate rnai knockdowns of cd63,a dramatic reduction in hemocytes phagocytic activity to pathogenic vibrio is recorded by flow cytometry,revealing the definite role of pu-cd63 in promoting hemocyte-mediated phagocytosis. therefore,our work has greatly enhanced our understanding about primitive character of innate immunity in marine mollusk. © 2016 mingjia yu et al.