Desmoplakin

thumb|350px|Cell adhesion in desmosomes Desmoplakin is a protein in humans that is encoded by the DSP gene. Desmoplakin is a critical component of desmosome structures in cardiac muscle and epidermal cells, which function to maintain the structural integrity at adjacent cell contacts. In cardiac muscle, desmoplakin is localized to intercalated discs which mechanically couple cardiac cells to function in a coordinated syncytial structure. Mutations in desmoplakin have been shown to play a role in dilated cardiomyopathy and arrhythmogenic right ventricular cardiomyopathy, where it may present with acute myocardial injury; striate palmoplantar keratoderma, Carvajal syndrome and paraneoplastic pemphigus.

==Structure== Desmoplakin exists as two predominant isoforms; the first, known as "DPII", has molecular weight 260.0 kDa (2272 amino acids) and the second, known as "DPI", has molecular weight 332.0 kDa (2871 amino acids). These isoforms are identical except for the shorter rod domain in DPII. DPI is the predominant isoform expressed in cardiac muscle. The DSP gene is located on chromosome 6p24.3, containing 24 exons and spanning approximately 45 kDa of genomic DNA. Desmoplakin is a large desmosomal plaque protein that homodimerizes and adopts a dumbbell-shaped conformation. The N-terminal globular head domain of desmoplakin is composed of a series of alpha helical bundles, and is required for both the localization to the desmosome and interaction with the N-terminal region of plakophilin 1 and plakoglobin as well as desmocollin and desmoglein. This is further sub divided into a region called the "Plakin domain" made up of six spectrin repeat domains separated by SH3 domain. A crystal structure of part of the plakin domain has been resolved, while the entire plakin domain has been elucidated using small angle X-ray scattering which revealed a non-linear structure, an unexpected result considering spectrin repeats are observed in linear orientations. The C-terminal region of desmoplakin is composed of three plakin repeat domains, termed A, B and C, which are essential for coalignment and binding of intermediate filaments. Located at the most distal C-terminus of desmoplakin is a region rich in glycine–serine–arginine; it has been demonstrated that serine phosphorylation of this domain may modify desmoplakin-intermediate filament interactions. In the mid-region of desmoplakin, a coiled-coil rod domain is responsible for homodimerization.