Direct interaction between the intracellular domains of bullous pemphigoid antigen 2 (BP180) and beta 4 integrin, hemidesmosomal components of basal keratinocytes.

Bullous pemphigoid antigen 2 (BPAG2/BP180, also known as type XVII collagen) and alpha 6 beta 4 integrin are both transmembrane proteins and hemidesmosomal components of basal keratinocytes. In this study, using yeast two-hybrid system, we demonstrate direct protein-protein interaction between the intracellular domains of BP180 and the beta 4 integrin subunit. Detailed analysis revealed that a bait construct spanning amino acids 13-89 of BP180 contained sufficient information for the protein protein interaction, but further deletion of 13 amino-terminal amino acids, which eliminates a predicted beta-sheet, abolished the interaction. The intracellular domain of the beta 4 integrin subunit contains two pairs of fibronectin type III (FNIII) repeats separated by a connecting segment. Series of expression constructs, sequentially deleting each domain, revealed that the connecting segment, the second pair of FNIII repeats and the tail region of the beta 4 integrin subunit were necessary for the interaction with BP180 in yeast two-hybrid system.