The complete gene sequence of titin, expression of an unusual approximately 700-kDa titin isoform, and its interaction with obscurin identify a novel Z-line to I-band linking system
| Autor: | Christian Witt, Mark McNabb, Thomas Centner, Siegfried Labeit, Dietmar Labeit, Adam J. Geach, Friderike Fornoff, Carol C. Gregorio, Michael Gotthardt, Marie Louise Bang, Henk Granzier |
|---|---|
| Rok vydání: | 2001 |
| Předmět: |
Sarcomeres
animal structures Physiology Macromolecular Substances Immunoelectron microscopy Molecular Sequence Data Muscle Proteins Obscurin macromolecular substances Biology Protein Serine-Threonine Kinases Polyadenylation Sarcomere ANK1 Gene Duplication Myotilin Animals Guanine Nucleotide Exchange Factors Humans Protein Isoforms Connectin RNA Messenger Cloning Molecular Muscle Skeletal Cells Cultured Base Sequence Myocardium Exons musculoskeletal system Molecular biology Cell biology Rats Actinin alpha 2 biology.protein Titin Cardiology and Cardiovascular Medicine Myofibril tissues Protein Kinases Rho Guanine Nucleotide Exchange Factors |
| Zdroj: | Circulation research. 89(11) |
| ISSN: | 1524-4571 |
| Popis: | Titin is a giant vertebrate striated muscle protein with critical importance for myofibril elasticity and structural integrity. We show here that the complete sequence of the human titin gene contains 363 exons, which together code for 38 138 residues (4200 kDa). In its central I-band region, 47 novel PEVK exons were found, which contribute to titin’s extensible spring properties. Additionally, 3 unique I-band titin exons were identified (named novex-1 to -3). Novex-3 functions as an alternative titin C-terminus. The novex-3 titin isoform is ≈700 kDa in size and spans from Z1-Z2 (titin’s N-terminus) to novex-3 (C-terminal exon). Novex-3 titin specifically interacts with obscurin, a 721-kDa myofibrillar protein composed of 57 Ig/FN3 domains, followed by one IQ, SH3, DH, and a PH domain at its C-terminus. The obscurin domains Ig48/Ig49 bind to novex-3 titin and target to the Z-line region when expressed as a GFP fusion protein in live cardiac myocytes. Immunoelectron microscopy detected the C-terminal Ig48/Ig49 obscurin epitope near the Z-line edge. The distance from the Z-line varied with sarcomere length, suggesting that the novex-3 titin/obscurin complex forms an elastic Z-disc to I-band linking system. This system could link together calcium-dependent, SH3-, and GTPase-regulated signaling pathways in close proximity to the Z-disc, a structure increasingly implicated in the restructuring of sarcomeres during cardiomyopathies. |
| Databáze: | OpenAIRE |
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