Abstract
Desmoplakin (DP) is a cytoskeletal linker protein that connects the desmosomal cadherin/plakoglobin/plakophilin complex to intermediate filaments (IFs). The C-terminal region of DP (DPCT) mediates IF binding, and contains three plakin repeat domains (PRDs), termed PRD-A, PRD-B and PRD-C. Previous crystal structures of PRDs B and C revealed that each is formed by 4.5 copies of a plakin repeat (PR) and has a conserved positively charged groove on its surface. Although PRDs A and B are linked by just four amino acids, B and C are separated by a 154 residue flexible linker, which has hindered crystallographic analysis of the full DPCT. Here we present the crystal structure of a DPCT fragment spanning PRDs A and B, and elucidate the overall architecture of DPCT by small angle X-ray scattering (SAXS) analysis. The structure of PRD-A is similar to that of PRD-B, and the two domains are arranged in a quasi-linear arrangement, and separated by a 4 amino acid linker. Analysis of the B-C linker region using secondary structure prediction and the crystal structure of a homologous linker from the cytolinker periplakin suggests that the N-terminal ~100 amino acids of the linker form two PR-like motifs. SAXS analysis of DPCT indicates an elongated but non-linear shape with Rg = 51.5 Å and Dmax = 178 Å. These data provide the first structural insights into an IF binding protein containing multiple PRDs and provide a foundation for studying the molecular basis of DP-IF interactions.
Highlights
Desmosomes are intercellular junctions that confer structural integrity to tissues by linking the intermediate filament cytoskeletons of adjacent cells
DPCT consists of three plakin repeat domains (PRDs), PRD-A, PRD-B, and PRD-C, of which crystal structures of PRD-B and PRD-C were previously determined [10]
PRD-A is expected to form a similar PRD structure based on sequence similarity, no direct structural data have been available
Summary
Desmosomes are intercellular junctions that confer structural integrity to tissues by linking the intermediate filament cytoskeletons of adjacent cells. Desmosomes contain the desmosomal cadherins (desmogleins and desmocollins), whose extracellular regions to form the adhesive bond between cells, and whose cytoplasmic regions link to intermediate filaments. The cytosolic armadillo proteins plakoglobin and plakophilins interact with desmosomal cadherins and with desmoplakin (DP), a member of the plakin family of cytolinkers [1, 2]. The N-terminal domain of plakophilin has been shown to interact with desmosomal cadherins and DP [3]. Human DP (Uniprot ID P15924) contains 2871 amino acids and contains three distinct regions. The N-terminal 1056-residue domain contains an N-terminal 175 residue domain of PLOS ONE | DOI:10.1371/journal.pone.0147641. The N-terminal 1056-residue domain contains an N-terminal 175 residue domain of PLOS ONE | DOI:10.1371/journal.pone.0147641 January 25, 2016
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