Plectin is a giantprotein found in nearly allmammaliancells which acts as a link between the three main components of thecytoskeleton:actin microfilaments,microtubules andintermediate filaments.[5] In addition, plectin links the cytoskeleton to junctions found in theplasma membrane that structurally connect different cells. By holding these different networks together, plectin plays an important role in maintaining the mechanical integrity andviscoelastic properties oftissues.[6]
Plectin can exist in cells as several alternatively-spliced isoforms, all around 500 kDa and >4000 amino acids.[7][8] The structure of plectin is thought to be adimer consisting of a centralcoiled coil ofalpha helices connecting two large globular domains (one at each terminus). These globular domains are responsible for connecting plectin to its various cytoskeletal targets. The carboxy-terminal domain is made of 6 highly homologous repeating regions. The subdomain between regions five and six of this domain is known to connect to the intermediate filamentscytokeratin andvimentin. At the opposite end of the protein, in the N-terminal domain, a region has been defined as responsible for binding toactin.[9] In 2004, the exact crystal structure of thisactin-binding domain (ABD) was determined in mice and shown to be composed of twocalponin homology (CH) domains.[10] Plectin is expressed in nearly all mammalian tissues. Incardiac muscle andskeletal muscle, plectin is localized to specialized entities known asZ-discs.[11] Plectin binds several proteins, includingvinculin,DES,[12]actin,[6][13] fodrin,[6][13] microtubule-associating proteins,[6][13] nuclear laminin B,[6][13]SPTAN1,[14][15]vimentin[14][15][16] andITGB4.[6][13]
Studies employing a plectinknockout mouse have shed light on the functions of plectin. Pups died 2–3 days after birth, and these mice exhibited marked skin abnormalities, including degeneration ofkeratinocytes. Skeletal and cardiac muscle tissues were also significantly affected. Cardiacintercalated discs were disintegrated and sarcomeres were irregularly shapen, and intracellular accumulation of aberrant isolated myofibrillar bundles andZ-disc components was also observed. Expression ofvinculin in muscle cells was strikingly down-regulated.[17] Through the use of gold-immunoelectron microscopy,immunoblotting andimmunofluorescence experiments plectin has been found to associate with all three major components of the cytoskeleton. In muscle, plectin binds to the periphery of Z-discs,[12] and along with the intermediate filament proteindesmin, may form lateral linkages among neighboring Z-discs. This interaction between plectin and desmin intermediate filaments also appears to facilitate the close association of myofibrils and mitochondria, both at Z-discs and along the remainder thesarcomere.[18] Plectin also functions to link cytoskeleton to intercellular junctions, such asdesmosomes andhemidesmosomes, which link intermediate filament networks between cells. Plectin has been revealed to localize to the desmosomes and in vitro studies have shown that it can form bridges between the desmosome protein,desmoplakin and intermediate filaments.[19] In hemidesmosomes plectin has been shown to interact with theintegrin β4 subunits of the hemidesmosome plaque and function in a clamp-like manner to link the intermediate filamentcytokeratin to the junction.[20]
Mutations inPLEC have been associated with epidermolysis bullosa simplex with muscular dystrophy.[21] A missense variant of PLEC has been recently proposed as a cause of atrial fibrillation in some populations.[22] Isolated left ventricular non-compaction accompanying epidermolysis bullosa simplex with muscular dystrophy was also noted.[23]Plectin has been proposed as abiomarker forpancreatic cancer.[24][25] Although normally acytoplasmic protein, plectin is expressed on the cell membrane inpancreatic ductal adenocarcinoma (PDAC) and can therefore be used to target PDAC cells.[24]
^abcdefWiche G (September 1998). "Role of plectin in cytoskeleton organization and dynamics".Journal of Cell Science.111 (17):2477–2486.doi:10.1242/jcs.111.17.2477.PMID9701547.
^Zernig G, Wiche G (July 1985). "Morphological integrity of single adult cardiac myocytes isolated by collagenase treatment: immunolocalization of tubulin, microtubule-associated proteins 1 and 2, plectin, vimentin, and vinculin".European Journal of Cell Biology.38 (1):113–122.PMID2992982.
^abHijikata T, Murakami T, Imamura M, Fujimaki N, Ishikawa H (March 1999). "Plectin is a linker of intermediate filaments to Z-discs in skeletal muscle fibers".Journal of Cell Science.112 (6):867–876.doi:10.1242/jcs.112.6.867.PMID10036236.
^Favre B, Schneider Y, Lingasamy P, Bouameur JE, Begré N, Gontier Y, et al. (May 2011). "Plectin interacts with the rod domain of type III intermediate filament proteins desmin and vimentin".European Journal of Cell Biology.90 (5):390–400.doi:10.1016/j.ejcb.2010.11.013.PMID21296452.
^Reipert S, Steinböck F, Fischer I, Bittner RE, Zeöld A, Wiche G (November 1999). "Association of mitochondria with plectin and desmin intermediate filaments in striated muscle".Experimental Cell Research.252 (2):479–491.doi:10.1006/excr.1999.4626.PMID10527638.
^Bardhan A, Bruckner-Tuderman L, Chapple IL, Fine JD, Harper N, Has C, et al. (September 2020). "Epidermolysis bullosa".Nature Reviews. Disease Primers.6 (1): 78.doi:10.1038/s41572-020-0210-0.PMID32973163.S2CID221861310.
