Abstract
Vascular endothelial growth factor (VEGF) signaling pathway is known to play key roles in endothelial cell proliferation, migration, angiogenesis, vascular permeability, inhibition of apoptosis, and virus infection. In the present study, a novel VEGFR gene (LvVEGFR2) was identified and characterized from Litopenaeus vannamei. The deduced amino acid sequence of LvVEGFR2 possessed typical features of VEGFRs reported in other species, including six IG-like domains, a transmembrane motif, a protein kinase (PK) domain, and one tyrosine-PK active site. The transcripts of LvVEGFR2 were mainly detected in hemocytes and lymphoid organ (Oka). Subcellular localization analysis showed that LvVEGFR2 was a membrane protein. Its expression level was obviously upregulated in hemocytes and Oka of the shrimp after white spot syndrome virus (WSSV) infection. Knockdown of LvVEGFR2 gene expression by double-strand RNA mediated interference could lead to a decrease of virus copy number in WSSV-infected shrimp. The interaction between LvVEGFR2 and different LvVEGFs (LvVEGF1, LvVEGF2, and LvVEGF3) in shrimp was analyzed at the transcription level and protein level, respectively. Knockdown of LvVEGF2 or LvVEGF3 could downregulate the expression level of LvVEGFR2, and injection of the recombinant LvVEGF2 or LvVEGF3 could upregulate the expression level of LvVEGFR2. Yeast two-hybrid analysis showed that LvVEGFR2 could interact with LvVEGF2 and LvVEGF3 directly. The study improved our understanding on the VEGF signaling pathway of shrimp and its role during WSSV infection.
Highlights
The vascular endothelial growth factor (VEGF) signaling pathway plays crucial roles in promoting cell proliferation, cell migration, increasing the vasopermeability, and promoting angiogenesis [1]
Phylogenetic analysis showed that LvVEGFR2 was first clustered together with LvVEGFR1 and with VEGFR members from insects, while VEGFRs from vertebrates were clustered into another branch (Figure 2)
We characterized a VEGFR gene (LvVEGFR1) and three Vascular endothelial growth factor (VEGF) genes in L. vannamei and data showed that they were all involved in white spot syndrome virus (WSSV) infection [16,17,18]
Summary
The vascular endothelial growth factor (VEGF) signaling pathway plays crucial roles in promoting cell proliferation, cell migration, increasing the vasopermeability, and promoting angiogenesis [1]. VEGFs and their receptors, VEGFRs, are primary members of the VEGF signaling pathway. The VEGF signaling pathway could be activated through binding of VEGF ligands to their receptors. A Novel VEGFR Participates in WSSV Infection high-affinity binding of VEGF ligands [3, 4]. Different VEGFRs play various functions through binding to different VEGF ligands. VEGFR1 plays roles in recruitment of hematopoietic stem cells, migration of monocytes and macrophages as well as in cellular energy metabolism by binding to VEGF-A and VEGF-B [5, 6]. VEGFR3 was considered to be involved in lymphangiogenesis and maintenance of the lymphatic endothelium by interacting with VEGF-C and VEGF-D [8, 9]
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