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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Available from: Branislav Nikolic
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    • "Plectin of approximately 530 kDa is a key linker molecule that maintains interactions within the cytoskeletal network consisting of actin filaments, microtubules and intermediate filaments. It was shown to tether desmin-containing intermediate filaments to dystrophin and vinculin, thus playing a central role in the stabilization of the subsarcolemmal region during excitation-contraction-relaxation cycles545556. On the extracellular site, the dystrophin complex interacts with the small leucine-rich repeat proteoglycan biglycan of the matrisome. "
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    ABSTRACT: The development of advanced mass spectrometric methodology has decisively enhanced the analytical capabilities for studies into the composition and dynamics of multi-subunit protein complexes and their associated components. Large-scale complexome profiling is an approach that combines the systematic isolation and enrichment of protein assemblies with sophisticated mass spectrometry-based identification methods. In skeletal muscles, the membrane cytoskeletal protein dystrophin of 427kDa forms tight interactions with a variety of sarcolemmal, cytosolic and extracellular proteins, which in turn associate with key components of the extracellular matrix and the intracellular cytoskeleton. A major function of this enormous assembly of proteins, including dystroglycans, sarcoglycans, syntrophins, dystrobrevins, sarcospan, laminin and cortical actin, is postulated to stabilize muscle fibres during the physical tensions of continuous excitation-contraction-relaxation cycles. This article reviews the evidence from recent proteomic studies that have focused on the characterization of the dystrophin-glycoprotein complex and its central role in the establishment of the cytoskeleton-sarcolemma-matrisome axis. Proteomic findings suggest a close linkage of the core dystrophin complex with a variety of protein species, including tubulin, vimentin, desmin, annexin, proteoglycans and collagens. Since the almost complete absence of dystrophin is the underlying cause for X-linked muscular dystrophy, a more detailed understanding of the composition, structure and plasticity of the dystrophin complexome may have considerable biomedical implications.
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    • "The third domain coded by exons 62 to 69 is the Cys-rich domain composed of a WW domain, two EF hands and a ZZ domain[36] [37]. This domain binds to the most important partner of dystrophin i.e. the membrane protein β-dystroglycan [38] [39] and to several other proteins such as plectin[40], ankyrin [41] and the intermediate filament protein synemin[25]. The C-terminal domain of dystrophin coded by exons 69 to 79 binds to the two cytoplasmic proteins syntrophin and dystrobrevin[42] [43]. "
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    ABSTRACT: Mutations of the dystrophin DMD gene, essentially deletions of one or several exons, are the cause of two devastating and to date incurable diseases, Duchenne (DMD) and Becker (BMD) muscular dystrophies. Depending upon the preservation or not of the reading frame, dystrophin is completely absent in DMD, or present in either a mutated or a truncated form in BMD. DMD is a severe disease which leads to a premature death of the patients. Therapy approaches are evolving with the aim to transform the severe DMD in the BMD form of the disease by restoring the expression of a mutated or truncated dystrophin. These therapies are based on the assumption that BMD is a mild disease. However, this is not completely true as BMD patients are more or less severely affected and no molecular basis of this heterogeneity of the BMD form of the disease is yet understood. The aim of this review is to report for the correlation between dystrophin structures in BMD deletions in view of this heterogeneity and to emphasize that examining BMD patients in details is highly relevant to anticipate for DMD therapy effects.
    Preview · Article · Aug 2015 · Bosnian journal of basic medical sciences / Udruzenje basicnih mediciniskih znanosti = Association of Basic Medical Sciences
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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.
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