Identification and function analysis of a novel vascular endothelial growth factor, LvVEGF3, in the Pacific whiteleg shrimp Litopenaeus vannamei

Abstract

VEGF signaling pathway is first discovered in mammals and proved to play important roles in the biological processes of angiogenesis, tumor migration, cell differentiation, apoptosis, host-virus interaction etc. Three members in the VEGF signaling pathway, including LvVEGFR, LvVEGF1 and LvVEGF2 in shrimp have been proved to be related with WSSV infection in our previous studies. Currently, another member of VEGF family, LvVEGF3, was isolated and its function during the WSSV infection of shrimp was studied. The deduced amino acid sequence of LvVEGF3 contained a signal peptide, a typical PDGF/VEGF domain and a cysteine-knot motif (CXCXC). Tissue distribution analysis showed that LvVEGF3 was predominantly expressed in hemocytes. The transcriptional level of LvVEGF3 in hemocytes was apparently up-regulated during WSSV infection. Silencing of LvVEGF3 with double-stranded RNA caused a reduction of the cumulative mortality rate of shrimp during WSSV infection. The expression of LvVEGFR was apparently down-regulated after LvVEGF3 silencing and up-regulated after injection of recombinant LvVEGF3 protein, suggesting an interaction between LvVEGF3 and LvVEGFR. Furthermore, the interaction between LvVEGFR and LvVEGF3 was confirmed using the yeast two-hybrid system. The results provided new insights into understanding the role of VEGF signaling pathway during virus infection.