Expression and Characterization of a Variant of TACI (CRD2-shortTACIFc) in Pichia pastoris

Rui      Wang; Shiliang      Zhou; Xiaomin      Peng; Xin-Wen      Zhou; Zhi-Qun      Xie; Yuxiong      Wang; Wei      Mo; Min      Yu

doi:10.2174/092986612799363136

Abstract

TACI is a member of the tumor necrosis factor receptor superfamily and serves as a key regulator of B cell function. The extracellular domain of a typical TNFR contains multiple copies of CRD, which bind in the monomermonomer interfaces of a trimeric ligand. TACI binds to two ligands, APRIL and BAFF, with high affinity and contains two CRD in its extracellular regions, while BCMA and BR3, contain a single or partial CRD for binding the two ligands. However, TACI can be classified as a single CRD receptor because the amino-terminal CRD1 doesnt contribute to ligand binding. To obtain a new variant of TACI possessing higher affinities for binding, we fused a repeat sequence of CRD2 to the N-terminus of the short form of TACI. The new APRIL antagonist peptide, CRD2-shortTACI-Fc, was designed based on the modeling 3-D complex structure of TACI and APRIL. As expected, the purified recombinant CRD2-shortTACI-Fc fusion protein could bind to APRIL in vitro and demonstrated dose-dependent inhibition of APRIL-induced proliferative activity in Raji cells. We found that CRD2-shortTACI-Fc, has a higher affinity for binding to ligands than short-TACI-Fc, which contains a single CRD2.

Keywords: TACI, CRD2, BAFF, APRIL, affinity, autoimmune disorders, Novagen, DNA ligase, homology modeling, Pichia pastoris