Four and a half LIM protein 1 binds myosin-binding protein C and regulates myosin filament formation and sarcomere assembly.
Four and a half LIM protein 1 (FHL1/SLIM1) is highly expressed in skeletal and cardiac muscle; however, the function of FHL1 remains unknown. Yeast two-hybrid screening identified slow type skeletal myosin-binding protein C as an FHL1 binding partner. Myosin-binding protein C is the major myosin-associated protein in striated muscle that ... enhances the lateral association and stabilization of myosin thick filaments and regulates actomyosin interactions. The interaction between FHL1 and myosin-binding protein C was confirmed using co-immunoprecipitation of recombinant and endogenous proteins. Recombinant FHL2 and FHL3 also bound myosin-binding protein C. FHL1 impaired co-sedimentation of myosin-binding protein C with reconstituted myosin filaments, suggesting FHL1 may compete with myosin for binding to myosin-binding protein C. In intact skeletal muscle and isolated myofibrils, FHL1 localized to the I-band, M-line, and sarcolemma, co-localizing with myosin-binding protein C at the sarcolemma in intact skeletal muscle. Furthermore, in isolated myofibrils FHL1 staining at the M-line appeared to extend partially into the C-zone of the A-band, where it co-localized with myosin-binding protein C. Overexpression of FHL1 in differentiating C2C12 cells induced "sac-like" myotube formation (myosac), associated with impaired Z-line and myosin thick filament assembly. This phenotype was rescued by co-expression of myosin-binding protein C. FHL1 knockdown using RNAi resulted in impaired myosin thick filament formation associated with reduced incorporation of myosin-binding protein C into the sarcomere. This study identified FHL1 as a novel regulator of myosin-binding protein C activity and indicates a role for FHL1 in sarcomere assembly.
Mesh Terms:
Actomyosin, Amino Acid Sequence, Animals, Base Sequence, COS Cells, Carrier Proteins, Cell Differentiation, Cell Proliferation, Cercopithecus aethiops, Electrophoresis, Polyacrylamide Gel, Glutathione Transferase, Humans, Immunohistochemistry, Immunoprecipitation, Intracellular Signaling Peptides and Proteins, Mice, Microscopy, Fluorescence, Molecular Sequence Data, Muscle Proteins, Muscle, Skeletal, Myocytes, Cardiac, Myosins, Oligonucleotides, Peptides, Phenotype, Protein Binding, Protein Structure, Tertiary, RNA Interference, Recombinant Proteins, Sarcomeres, Sequence Homology, Amino Acid, Transfection, Two-Hybrid System Techniques
Actomyosin, Amino Acid Sequence, Animals, Base Sequence, COS Cells, Carrier Proteins, Cell Differentiation, Cell Proliferation, Cercopithecus aethiops, Electrophoresis, Polyacrylamide Gel, Glutathione Transferase, Humans, Immunohistochemistry, Immunoprecipitation, Intracellular Signaling Peptides and Proteins, Mice, Microscopy, Fluorescence, Molecular Sequence Data, Muscle Proteins, Muscle, Skeletal, Myocytes, Cardiac, Myosins, Oligonucleotides, Peptides, Phenotype, Protein Binding, Protein Structure, Tertiary, RNA Interference, Recombinant Proteins, Sarcomeres, Sequence Homology, Amino Acid, Transfection, Two-Hybrid System Techniques
J. Biol. Chem.
Date: Mar. 17, 2006
PubMed ID: 16407297
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