Cryptic association of B7‐2 molecules and its implication for clustering

Abstract

T‐cell co‐stimulation through CD28/CTLA4:B7‐1/B7‐2 axis is one of the extensively studied pathways that resulted in the discovery of several FDA‐approved drugs for autoimmunity and cancer. However, many aspects of the signaling mechanism remain elusive, including oligomeric association and clustering of B7‐2 on the cell surface. Here, we describe the structure of the IgV domain of B7‐2 and its cryptic association into 1D arrays that appear to represent the pre‐signaling state of B7‐2 on the cell membrane. Super‐resolution microscopy experiments on heterologous cells expressing B7‐2 and B7‐1 suggest, B7‐2 form relatively elongated and larger clusters compared to B7‐1. The sequence and structural comparison of other B7 family members, B7‐1:CTLA4 and B7‐2:CTLA‐4 complex structures, support our view that the observed B7‐2 1D zipper array is physiologically important. This observed 1D zipper‐like array also provides an explanation for its clustering, and upright orientation on the cell surface, and avoidance of spurious signaling.

Characterization of Co-Stimulatory Ligand CD80/86 and Its Effect as a Molecular Adjuvant on DNA Vaccine Against Vibrio anguillarum in Flounder (Paralichthys olivaceus)

“…More B7 family members have been identified in vertebrates ( 3 – 5 ); among them, the interaction between CD80/86 and its ligands is widely recognized as a major T-cell co-stimulatory pathway to regulate the immune response of T cells ( 2 , 6 ). Both B7-1 and B7-2 are type-1 transmembrane glycoproteins that contain two extracellular Ig-like domains ( 7 , 8 ). B7-1 is present as a dimer and is mainly found on activated B cells, activated T cells, and macrophages, while CD86 exists as a monomer and is thought to be more widely expressed at higher levels than CD80, which is constitutively expressed in dendritic cells (DCs), Langerhans cells, peripheral blood DCs, memory B cells, and germinal center B cells ( 9 ).…”