Rezniczek GA, Konieczny P, Nikolic B et al.Plectin 1f scaffolding at the sarcolemma of dystrophic (mdx) muscle fibers through multiple interactions with beta-dystroglycan. J Cell Biol 176:965-977

Max F. Perutz Laboratories, Department of Molecular Cell Biology, University of Vienna, A-1030 Vienna, Austria.
The Journal of Cell Biology (Impact Factor: 9.83). 04/2007; 176(7):965-77. DOI: 10.1083/jcb.200604179
Source: PubMed


In skeletal muscle, the cytolinker plectin is prominently expressed at Z-disks and the sarcolemma. Alternative splicing of plectin transcripts gives rise to more than eight protein isoforms differing only in small N-terminal sequences (5-180 residues), four of which (plectins 1, 1b, 1d, and 1f) are found at substantial levels in muscle tissue. Using plectin isoform-specific antibodies and isoform expression constructs, we show the differential regulation of plectin isoforms during myotube differentiation and their localization to different compartments of muscle fibers, identifying plectins 1 and 1f as sarcolemma-associated isoforms, whereas plectin 1d localizes exclusively to Z-disks. Coimmunoprecipitation and in vitro binding assays using recombinant protein fragments revealed the direct binding of plectin to dystrophin (utrophin) and beta-dystroglycan, the key components of the dystrophin-glycoprotein complex. We propose a model in which plectin acts as a universal mediator of desmin intermediate filament anchorage at the sarcolemma and Z-disks. It also explains the plectin phenotype observed in dystrophic skeletal muscle of mdx mice and Duchenne muscular dystrophy patients.

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    • "The importance of the various BPAG1 isoforms is best attested by the dramatic consequences observed in cases of genetic defects of BPAG1. Naturally occurring mutations as well as engineered inactivation of Dst in mice cause dystonia musculorum (dt), a disease characterized by sensory and motor neuron degeneration, and early death [16]–[18]. In humans, a pathogenic mutation affecting the MTBD of BPAG1a/b results in sensory autonomic neuropathy with dysautonomia, severe psychomotor retardation, and early death [19], while disruption of BPAG1a/b due to a chromosome breakpoint in the middle of one of the DST gene copies, is associated with encephalopathy, motor and mental retardation, and visual impairment [20]. "
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    ABSTRACT: BPAG1a and BPAG1b (BPAG1a/b) constitute two major isoforms encoded by the dystonin (Dst) gene and show homology with MACF1a and MACF1b. These proteins are members of the plakin family, giant multi-modular proteins able to connect the intermediate filament, microtubule and microfilament cytoskeletal networks with each other and to distinct cell membrane sites. They also serve as scaffolds for signaling proteins that modulate cytoskeletal dynamics. To gain better insights into the functions of BPAG1a/b, we further characterized their C-terminal region important for their interaction with microtubules and assessed the role of these isoforms in the cytoskeletal organization of C2.7 myoblast cells. Our results show that alternative splicing does not only occur at the 5' end of Dst and Macf1 pre-mRNAs, as previously reported, but also at their 3' end, resulting in expression of additional four mRNA variants of BPAG1 and MACF1. These isoform-specific C-tails were able to bundle microtubules and bound to both EB1 and EB3, two microtubule plus end proteins. In the C2.7 cell line, knockdown of BPAG1a/b had no major effect on the organization of the microtubule and microfilament networks, but negatively affected endocytosis and maintenance of the Golgi apparatus structure, which became dispersed. Finally, knockdown of BPAG1a/b caused a specific decrease in the directness of cell migration, but did not impair initial cell adhesion. These data provide novel insights into the complexity of alternative splicing of Dst pre-mRNAs and into the role of BPAG1a/b in vesicular transport, Golgi apparatus structure as well as in migration in C2.7 myoblasts.
    PLoS ONE 09/2014; 9(9):e107535. DOI:10.1371/journal.pone.0107535 · 3.23 Impact Factor
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    • "However, three plectin isoforms are expressed in the epidermis: plectins 1, 1a, and 1c. They exclusively differ from each other in their N extremities, which confer different tethering properties (Rezniczek et al., 2003; Wilhelmsen et al., 2005; Rezniczek et al., 2007; reviewed in Wiche and Winter, 2011). Plectin 1a seems to be the major variant in hemidesmosomes (Walko et al., 2011). "
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    ABSTRACT: The plakin family consists of giant proteins involved in the cross-linking and organization of the cytoskeleton and adhesion complexes. They further modulate several fundamental biological processes, such as cell adhesion, migration, and polarization or signaling pathways. Inherited and acquired defects of plakins in humans and in animal models potentially lead to dramatic manifestations in the skin, striated muscles, and/or nervous system. These observations unequivocally demonstrate the key role of plakins in the maintenance of tissue integrity. Here we review the characteristics of the mammalian plakin members BPAG1 (bullous pemphigoid antigen 1), desmoplakin, plectin, envoplakin, epiplakin, MACF1 (microtubule-actin cross-linking factor 1), and periplakin, highlighting their role in skin homeostasis and diseases.Journal of Investigative Dermatology advance online publication, 19 December 2013; doi:10.1038/jid.2013.498.
    Journal of Investigative Dermatology 12/2013; 134(4). DOI:10.1038/jid.2013.498 · 7.22 Impact Factor
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    • "According to our results, components of the dystrophin associated proteins DAPs, such as b‐dystroglycan [b‐dg], a‐syntrophin [a‐syn], and a‐dystrobrevin [a‐db] maintain a close relationship with IF and are co‐distributed at the granulomere zone; this interconnection is probably established through plectin, as has been shown for muscle cells [Rezniczek et al., 2007; Hijikata et al., 2008]. IF also possess specialized non‐mechanical functions that participate in the intracellular distribution of organelles and their functioning [Toivola et al., 2005]. "
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    ABSTRACT: The role of platelets in coagulation and the haemostatic process was initially suggested two centuries ago, and under appropriate physiological stimuli, these undergo abrupt morphological changes, attaching and spreading on damaged endothelium, preventing bleeding. During the adhesion process, platelet cytoskeleton reorganizes generating compartments in which actin filaments, microtubules, and associated proteins are arranged in characteristic patterns mediating crucial events, such as centralization of their organelles, secretion of granule contents, aggregation with one another to form a haemostatic plug, and retraction of these aggregates. However, the role of Intermediate filaments during the platelet adhesion process has not been explored. In the present work, we described, by confocal and electron microscopy analysis and Immunoprecipitation assays, the presence of desmin and vimentin and their association with members of the Dystrophin-associated proteins as well as with microfilaments and microtubules through plectin. We have also undertaken a pharmacological approach using Acrylamide and Brefeldin A to evaluate the participation of vimentin and desmin in granule trafficking. Our findings strongly suggest that Microfilaments, Microtubules, and Intermediate filaments modulate platelet membranous system organization. J. Cell. Biochem. © 2013 Wiley Periodicals, Inc.
    Journal of Cellular Biochemistry 09/2013; 114(9). DOI:10.1002/jcb.24546 · 3.26 Impact Factor
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