PMID: 21285457 , Related PDB id: 3QD6

Authors:

An HJ, Kim YJ, Song DH, Park BS, Kim HM, Lee JD, Paik SG, Lee JO, Lee H

Title:

Crystallographic and mutational analysis of the CD40-CD154 complex and its implications for receptor activation.

Journal:

J Biol Chem. 2011 Apr 1;286(13):11226-35. Epub 2011 Feb 1.

Abstract:

CD40 is a tumor necrosis factor receptor (TNFR) family protein that plays an important role in B cell development. CD154/CD40L is the physiological ligand of CD40. We have determined the crystal structure of the CD40-CD154 complex at 3.5 A resolution. The binding site of CD40 is located in a crevice formed between two CD154 subunits. Charge complementarity plays a critical role in the CD40-CD154 interaction. Some of the missense mutations found in hereditary hyper-IgM syndrome can be mapped to the CD40-CD154 interface. The CD40 interaction area of one of the CD154 subunits is twice as large as that of the other subunit forming the binding crevice. This is because cysteine-rich domain 3 (CRD3) of CD40 has a disulfide bridge in an unusual position that alters the direction of the ladder-like structure of CD40. The Ser(132) loop of CD154 is not involved in CD40 binding but its substitution significantly reduces p38- and ERK-dependent signaling by CD40, whereas JNK-dependent signaling is not affected. These findings suggest that ligand-induced di- or trimerization is necessary but not sufficient for complete activation of CD40.