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).[10][11] These isoforms are identical except for the shorter rod domain in DPII. DPI is the predominant isoform expressed in cardiac muscle.[12] The DSP gene is located on chromosome 6p24.3, containing 24 exons and spanning approximately 45 kDa of genomic DNA.[13] Desmoplakin is a large desmosomal plaque protein that homodimerizes and adopts a dumbbell-shaped conformation.[13] 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.[14] This is further sub divided into a region called the "Plakin domain" made up of six spectrin repeat domains separated by SH3 domain.[15] A crystal structure of part of the plakin domain has been resolved,[16] 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.[17] 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.[14][18][19] Located at the most distal C-terminus of desmoplakin is a region rich in glycine–serine–arginine; it has been demonstrated that serinephosphorylation of this domain may modify desmoplakin-intermediate filamentinteractions.[20] In the mid-region of desmoplakin, a coiled-coil rod domain is responsible for homodimerization.[21]
Function
Desmosomes are intercellular junctions that tightly link adjacent cells. Desmoplakin is an obligate component of functional desmosomes that anchors intermediate filaments to desmosomal plaques. In cardiomyocytes, desmoplakin forms desmosomal plaques with the intermediate filamentdesmin, whereas in endothelial cellscytokeratin type intermediate filaments are recruited, and vimentin in arachnoid and follicular dendritic cell types.[21][22] Both types of intermediate filaments attach in a lateral fashion to desmoplakin to form the plaque.[23] In cardiac muscle, desmoplakin is localized to desmosomes in intercalated discs. Desmoplakin isoform DPI is highly expressed and is thought to play a role in both the assembly and stabilization of desmosomes; its role is critical, as desmoplakin knockout mice display embryonic lethality.[24] In mice overexpressing a C-terminal mutated desmoplakin protein, desmoplakin binding to desmin is disrupted in cardiac muscle and hearts display abnormal intercalated disc formation and structure.[25] Much has been learned regarding desmoplakin function from mutations in patients with arrhythmogenic right ventricular cardiomyopathy, where mutations in specific binding domains alter desmoplakin binding to plakoglobin or desmin and result in cell death and dysfunction.[26]
^ abAl-Jassar C, Knowles T, Jeeves M, Kami K, Behr E, Bikker H, Overduin M, Chidgey M (2011). "The nonlinear structure of the desmoplakin plakin domain and the effects of cardiomyopathy-linked mutations". J. Mol. Biol. 411 (5): 1049–61. doi:10.1016/j.jmb.2011.06.047. PMID21756917.
^Choi HJ, Park-Snyder S, Pascoe LT, Green KJ, Weis WI (Aug 2002). "Structures of two intermediate filament-binding fragments of desmoplakin reveal a unique repeat motif structure". Nature Structural Biology. 9 (8): 612–20. doi:10.1038/nsb818. PMID12101406. S2CID10611026.
^Carvajal-Huerta L (Sep 1998). "Epidermolytic palmoplantar keratoderma with woolly hair and dilated cardiomyopathy". Journal of the American Academy of Dermatology. 39 (3): 418–21. doi:10.1016/s0190-9622(98)70317-2. PMID9738775.
^Carvajal-Huerta L (Sep 1998). "Epidermolytic palmoplantar keratoderma with woolly hair and dilated cardiomyopathy". Journal of the American Academy of Dermatology. 39 (3): 418–21. doi:10.1016/s0190-9622(98)70317-2. PMID9738775.
^Papagerakis S, Shabana AH, Pollock BH, Papagerakis P, Depondt J, Berdal A (Sep 2009). "Altered desmoplakin expression at transcriptional and protein levels provides prognostic information in human oropharyngeal cancer". Human Pathology. 40 (9): 1320–9. doi:10.1016/j.humpath.2009.02.002. PMID19386346.
^Hofmann I, Mertens C, Brettel M, Nimmrich V, Schnölzer M, Herrmann H (July 2000). "Interaction of plakophilins with desmoplakin and intermediate filament proteins: an in vitro analysis". J. Cell Sci. 113 (13): 2471–83. doi:10.1242/jcs.113.13.2471. PMID10852826.
^Kowalczyk AP, Navarro P, Dejana E, Bornslaeger EA, Green KJ, Kopp DS, Borgwardt JE (October 1998). "VE-cadherin and desmoplakin are assembled into dermal microvascular endothelial intercellular junctions: a pivotal role for plakoglobin in the recruitment of desmoplakin to intercellular junctions". J. Cell Sci. 111 (20): 3045–57. doi:10.1242/jcs.111.20.3045. PMID9739078.
Presland RB, Dale BA (2000). "Epithelial structural proteins of the skin and oral cavity: function in health and disease". Crit. Rev. Oral Biol. Med. 11 (4): 383–408. doi:10.1177/10454411000110040101. PMID11132762.