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| Identifiers | |||||||||||||||||||||||||||||||||||||||||||||||||||
| Aliases | FLNC , ABP-280, ABP280A, ABPA, ABPL, FLN2, MFM5, MPD4, filamin C, RCM5, CMH26 | ||||||||||||||||||||||||||||||||||||||||||||||||||
| External IDs | OMIM: 102565 MGI: 95557 HomoloGene: 37481 GeneCards: FLNC | ||||||||||||||||||||||||||||||||||||||||||||||||||
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Filamin-C (FLN-C) also known as actin-binding-like protein (ABPL) or filamin-2 (FLN2) is a protein that in humans is encoded by the FLNC gene. [5] [6] [7] Filamin-C is mainly expressed in cardiac and skeletal muscles, and functions at Z-discs and in subsarcolemmal regions.
Filamin-C is a 290.8 kDa protein composed of 2725 amino acids. [8] [9] Filamin-C, like the ubiquitously-expressed isoform Filamin-A, have an N-terminal filamentous actin-binding domain, followed by a lengthy C-terminal self-association domain containing a series of immunoglobulin-like domains, and a membrane glycoprotein-binding domain. [10] Filamin-C interacts with γ-sarcoglycan and δ-sarcoglycan at the sarcolemma; [11] [12] myotilin and FATZ/calsarcin/myozenin at Z-lines, [13] [14] [15] [16] as well as LL5β. [17] Filamin-C has also been shown to interact with INPPL1, [18] KCND2, [19] and MAP2K4. [20]
The family of Filamin proteins crosslink actin filaments into orthogonal networks in cortical cytoplasm and participate in the anchoring of membrane proteins for the actin cytoskeleton. However, the precise function of the Filamin-C isoform is still under investigation. As Filamin-C is localized mainly to striated muscle, its functions are likely specific to the specialized sarcomeric cytoskeleton present in muscle. As Filamin-C is found at both subsarcolemmal regions and at Z-lines, one plausible function of Filamin-C would be to act as a mode of communication between the membrane and the sarcomere. In skeletal muscle, Filamin-C is found at sites of core formation in skeletal myopathies, [21] and alterations in subcellular localization of Filamin-C have been exhibited in limb-girdle muscular dystrophy and Duchenne muscular dystrophy. [22]
Mutations in Filamin C have been associated with human hypertrophic cardiomyopathy, dilated cardiomyopathy [23] restrictive cardiomyopathy [24] and a higher incidence of sudden cardiac death. [25] Expression of mutant protein in rat cardiac cells demonstrated that mutant Filamin C forms aggregates, which may provide a mechanistic link to the observed cardiac dysfunction. [25] Deficiency of this protein has been associated with muscle weakness. [26]
In mammalian cells, vinculin is a membrane-cytoskeletal protein in focal adhesion plaques that is involved in linkage of integrin adhesion molecules to the actin cytoskeleton. Vinculin is a cytoskeletal protein associated with cell-cell and cell-matrix junctions, where it is thought to function as one of several interacting proteins involved in anchoring F-actin to the membrane.
Plakoglobin, also known as junction plakoglobin or gamma-catenin, is a protein that in humans is encoded by the JUP gene. Plakoglobin is a member of the catenin protein family and homologous to β-catenin. Plakoglobin is a cytoplasmic component of desmosomes and adherens junctions structures located within intercalated discs of cardiac muscle that function to anchor sarcomeres and join adjacent cells in cardiac muscle. Mutations in plakoglobin are associated with arrhythmogenic right ventricular dysplasia.
Utrophin is a protein that in humans is encoded by the UTRN gene. The name is a short form for ubiquitous dystrophin.
Paxillin is a protein that in humans is encoded by the PXN gene. Paxillin is expressed at focal adhesions of non-striated cells and at costameres of striated muscle cells, and it functions to adhere cells to the extracellular matrix. Mutations in PXN as well as abnormal expression of paxillin protein has been implicated in the progression of various cancers.
The costamere is a structural-functional component of striated muscle cells which connects the sarcomere of the muscle to the cell membrane.
Integrin beta-1 (ITGB1), also known as CD29, is a cell surface receptor that in humans is encoded by the ITGB1 gene. This integrin associates with integrin alpha 1 and integrin alpha 2 to form integrin complexes which function as collagen receptors. It also forms dimers with integrin alpha 3 to form integrin receptors for netrin 1 and reelin. These and other integrin beta 1 complexes have been historically known as very late activation (VLA) antigens.
Dystrobrevin is a protein that binds to dystrophin in the costamere of skeletal muscle cells. In humans, there are at least two isoforms of dystrobrevin, dystrobrevin alpha and dystrobrevin beta.
Actin, cytoplasmic 2, or gamma-actin is a protein that in humans is encoded by the ACTG1 gene. Gamma-actin is widely expressed in cellular cytoskeletons of many tissues; in adult striated muscle cells, gamma-actin is localized to Z-discs and costamere structures, which are responsible for force transduction and transmission in muscle cells. Mutations in ACTG1 have been associated with nonsyndromic hearing loss and Baraitser-Winter syndrome, as well as susceptibility of adolescent patients to vincristine toxicity.
Alpha-actinin-3, also known as alpha-actinin skeletal muscle isoform 3 or F-actin cross-linking protein, is a protein that in humans is encoded by the ACTN3 gene located on chromosome 11. All people have two copies (alleles) of this gene.
Alpha-actinin-2 is a protein which in humans is encoded by the ACTN2 gene. This gene encodes an alpha-actinin isoform that is expressed in both skeletal and cardiac muscles and functions to anchor myofibrillar actin thin filaments and titin to Z-discs.
Telethonin, also known as Tcap, is a protein that in humans is encoded by the TCAP gene. Telethonin is expressed in cardiac and skeletal muscle at Z-discs and functions to regulate sarcomere assembly, T-tubule function and apoptosis. Telethonin has been implicated in several diseases, including limb-girdle muscular dystrophy, hypertrophic cardiomyopathy, dilated cardiomyopathy and idiopathic cardiomyopathy.
Filamin B, beta (FLNB), also known as Filamin B, beta , is a cytoplasmic protein which in humans is encoded by the FLNB gene.
Delta-sarcoglycan is a protein that in humans is encoded by the SGCD gene.
Alpha-sarcoglycan is a protein that in humans is encoded by the SGCA gene.
Gamma-sarcoglycan is a protein that in humans is encoded by the SGCG gene. The α to δ-sarcoglycans are expressed predominantly (β) or exclusively in striated muscle. A mutation in any of the sarcoglycan genes may lead to a secondary deficiency of the other sarcoglycan proteins, presumably due to destabilisation of the sarcoglycan complex. The disease-causing mutations in the α to δ genes cause disruptions within the dystrophin-associated protein (DAP) complex in the muscle cell membrane. The transmembrane components of the DAP complex link the cytoskeleton to the extracellular matrix in adult muscle fibres, and are essential for the preservation of the integrity of the muscle cell membrane.
Myozenin-2, also referred to as Calsarcin-1, is a protein that in humans is encoded by the MYOZ2 gene. The Calsarcin-1 isoform is a muscle protein expressed in cardiac muscle and slow-twitch skeletal muscle, which functions to tether calcineurin to alpha-actinin at Z-discs, and inhibit the pathological cardiac hypertrophic response. This differs from the fast-skeletal muscle isoform, calsarcin-2.
LIM domain binding 3 (LDB3), also known as Z-band alternatively spliced PDZ-motif (ZASP), is a protein which in humans is encoded by the LDB3 gene. ZASP belongs to the Enigma subfamily of proteins and stabilizes the sarcomere during contraction, through interactions with actin in cardiac and skeletal muscles. Mutations in the ZASP gene has been associated with several muscular diseases.
Myozenin-1 is a protein that in humans is encoded by the MYOZ1 gene.
Talin-1 is a protein that in humans is encoded by the TLN1 gene. Talin-1 is ubiquitously expressed, and is localized to costamere structures in cardiac and skeletal muscle cells, and to focal adhesions in smooth muscle and non-muscle cells. Talin-1 functions to mediate cell-cell adhesion via the linkage of integrins to the actin cytoskeleton and in the activation of integrins. Altered expression of talin-1 has been observed in patients with heart failure, however no mutations in TLN1 have been linked with specific diseases.
Filamins are a class of proteins that hold two actin filaments at large angles. Filamin protein in mammals is made up of an actin-binding domain at its N-terminus that is followed by 24 immunoglobulin-like repeat modules of roughly 95 amino acids. There are two hinge regions; between repeats 15-16 and 23-24. Filamin gets cleaved at these hinge regions to generate smaller fragments of the protein. Filamin has two actin-binding sites with a V-linkage between them, so that it cross-links actin filaments into a network with the filaments orientated almost at right angles to one another.
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