APRIL

APRIL (a proliferation inducing ligand), also known as TNFSF13, TALL2, and TRDL1, is a member of the TNF ligand superfamily. It is synthesized as a 32 kDa type II transmembrane protein which is cleaved by furin in the Golgi to release a 17 kDa soluble molecule. Secreted APRIL consists almost entirely of a single TNF homology domain. Little or no transmembrane APRIL is expressed on the cell surface. Alternate splicing generates isoforms with short deletions at the Nor C-terminus. Both APRIL and the closely related protein BAFF signal through the TNF superfamily receptors TACI and BCMA to promote cellular proliferation and protect from apoptosis. APRIL can form bioactive heterotrimers with BAFF. A bioactive cell surface-expressed protein known as TWEPRIL consists of the intracellular domain, transmembrane segment, and stalk region of TWEAK fused to the TNF homology domain of APRIL. Human APRIL shares 85% amino acid sequence identity with mouse and rat APRIL.