Determination of the intracellular aqueous/lipid interface of integrin alpha 2b in vivo

Abstract

Integrins are a family of cell adhesion receptors that mediate cell migration, extracellular matrix assembly and platelet aggregation. They are heterodimeric proteins composed of alpha and beta subunits. Integrins exist in a default low affinity state in the cell membrane. The highly conserved intracellular memebrane proximal region of the alpha subunit is considered to play a critical role in constraining the receptor in the low affinity state, however, the location of this region in the cellular environment remains controversial. In this study, we explored the location of the membrane proximal region of integrin alpha 2b by substituted cysteine accessibility method (SCAM). Residues in the membrane proximal region of integrin alpha 2b were individually substituted with cysteines and subjected to in situ chemical probing with a cysteine specific reagent, biotin maleimide. Results showed that Lys‐994 marks the first aqueous exposed residue in the region, consistent with the in vitro findings. Further functional analysis with a flow cytometry assay revealed that all the mutant receptors were active. On the basis of the results, we conclude that the in vitro determined aqueous/lipid interface of integrin alpha 2b represents the active state of the receptor.Source of Research Support: UCLA Nephrology Research Fund