Analysis of the interaction between desmosomal proteins: Desmoplakin and Plakophilins-1/2

Abstract

[Background]: Desmosomes are intercellular junctions that anchor cytoskeletal intermediate filaments to the plasma membrane providing strong cell-cell adhesion. Desmoplakin (DP), a member of the plakin family, is a component of the desmosomes. DP contains at the N-terminus a Plakin Domain (DP-PD) (~1000 residues), the N-terminal half of the DP-PD is important for localization at the desmosomes and mediates the interaction with other desmosomal proteins including the armadillo proteins plakophilins (PKPs). [Observations]: We have made a systematic analysis of the interaction between PKPs and the DP-PD, a region that consists of eight spectrin repeats (SR2-SR9) and a SH3 domain. Co-immunoprecipitation experiments using PKP-1 and a collection of structure-based DP fragments co-expressed in COS cells, suggest that the DP-PD harbors more than one interaction site for PKP-1 and that the PKP-1-interactions sites correspond to multi-domain regions. FRET and FLIM assays have been used to further map the PKP-1-binding site within the N-terminal half of DP-PD. Four fragments of the SR2-SR5 region, each one containing one to three SRs, show interaction with PKP-1. A similar binding site-pattern has been observed for the interaction of DP with PKP-2. Additionally, we are studying the sub-cellular distribution of DP-PD fragments in co-transfections with PKP-1 and/or PKP-2. [Conclusions]: The interaction of DP with PKP-1 and PKP-2 involves multiple regions of the DP-PD, and binding occurs at several of the PD sub-domains.