Molecular structure, expression analysis and functional characterization of APRIL (TNFSF13) gene in bat (Vespertilio superans Thomas)

Abstract

A proliferation-inducing ligand (APRIL) is a novel member of the tumor necrosis factor (TNF) superfamily, which is involved in immune regulation. In the present study, the full-length cDNA of APRIL (designated bAPRIL) from bat was cloned using RT-PCR and its biological activities have been characterized. The open reading frame (ORF) of this cDNA consists of 753 bases, encoding a protein of 250 amino acids. This protein was found to contain a predicted transmembrane domain, a putative furin protease cleavage site, and a typical TNF homology domain corresponding to other, known APRIL homologs. Real-time quantitative PCR (qPCR) analysis indicated that bAPRIL mRNA was predominantly expressed in bat lymphoid tissue spleen. The SUMO–bsAPRIL was efficiently expressed in Escherichia coli BL21 (DE3) and confirmed by SDS-PAGE and Western blot analysis. Laser scanning confocal microscopy analysis showed that bsAPRIL could bind to its receptors on B cells. In vitro, MTT assays indicated that bsAPRIL could promote the survival/proliferation of mouse splenic B cells grown with anti-mouse IgM. These findings indicate that bsAPRIL plays an important role in the survival and proliferation of B cells and has functional cross-reactivity among mammalians. The present findings may provide valuable information for research into the immune system of the bat.