Investigating the interaction between integrin αL cytoplasmic domain and CD45 full-length cytoplasmic domain.

Abstract

The cell adhesion molecule integrin αLβ2 and the phosphatase CD45 are important molecules in maintaining a functional immune system. Both molecules are transmembrane proteins. CD45 has a large cytoplasmic domain that comprises two subdomains known as D1 and D2. Integrin αLβ2 has two short cytoplasmic tails. In a previous NMR study, it has been shown that the αL cytoplasmic tail has a compact tri-helical fold with an acidic solvent-exposed surface, which may serve as a docking site for cytoplasmic protein. It has also been reported that αL cytoplasmic tail interacts with the CD45 D1 domain. In this study, we aim to further characterize the interaction of αL cytoplasmic tail and CD45 cytoplasmic domain. To this end, the full-length cytoplasmic domains of CD45 and αL were expressed and purified from E. coli using affinity, size-exclusion and reverse-phase chromatography methods. Pull-down assays were performed using purified CD45 cytoplasmic domain and protein A beads with or without immobilized αL cytoplasmic tail. CD45 precipitated with beads containing αL cytoplasmic tail, but not with the control beads. Because of time limitation, further characterization of this interaction was not performed.