I-band titin in cardiac muscle is a three-element molecular spring and is critical for maintaining thin filament structure

Wolfgang A. Linke, Diane E. Rudy, Thomas Centner, Mathias Gautel, Christian Witt, Siegfried Labeit, Carol Gregorio

Research output: Contribution to journalArticle

176 Citations (Scopus)

Abstract

In cardiac muscle, the giant protein titin exists in different length isoforms expressed in the molecule's I-band region. Both isoforms, termed N2- A and N2-B, comprise stretches of Ig-like modules separated by the PEVK domain. Central I-band titin also contains isoform-specific Ig-motifs and nonmodular sequences, notably a longer insertion in N2-B. We investigates file elastic behavior of the I-band isoforms by using single-myofibril mechanics, immunofluorescence microscopy, and immunoelectron microscopy of rabbit cardiac sarcomeres stained with sequence-assigned antibodies. Moreover, we overexpressed constructs from the N2-B region in chick cardiac cells to search for possible structural properties of this cardiac-specific segment. We found that cardiac titin contains three distinct elastic elements: poly-Ig regions, the PEVK domain, and the N2-B sequence insertion, which extends ~60 nm at high physiological stretch. Recruitment of all three elements allows cardiac titin to extend fully reversibly at physiological sarcomere lengths, without the need to unfold Ig domains. Overexpressing the entire N2-B region or its NH2 terminus in cardiac myocytes greatly disrupted thin filament, but not thick filament structure. Our results strongly suggest that the NH2-terminal N2-B domains are necessary to stabilize thin filament integrity. N2-B-titin emerges as a unique region critical for both reversible extensibility and structural maintenance of cardiac myofibrils.

Original languageEnglish (US)
Pages (from-to)631-644
Number of pages14
JournalJournal of Cell Biology
Volume146
Issue number3
DOIs
StatePublished - Aug 9 1999

Fingerprint

Connectin
Myocardium
Protein Isoforms
Sarcomeres
Myofibrils
Immunoelectron Microscopy
Insertional Mutagenesis
Mechanics
Fluorescence Microscopy
Cardiac Myocytes
Maintenance
Rabbits
Antibodies
Proteins

Keywords

  • Connectin
  • Elasticity
  • Heart muscle
  • Sarcomere
  • Transfection

ASJC Scopus subject areas

  • Cell Biology

Cite this

I-band titin in cardiac muscle is a three-element molecular spring and is critical for maintaining thin filament structure. / Linke, Wolfgang A.; Rudy, Diane E.; Centner, Thomas; Gautel, Mathias; Witt, Christian; Labeit, Siegfried; Gregorio, Carol.

In: Journal of Cell Biology, Vol. 146, No. 3, 09.08.1999, p. 631-644.

Research output: Contribution to journalArticle

Linke, Wolfgang A. ; Rudy, Diane E. ; Centner, Thomas ; Gautel, Mathias ; Witt, Christian ; Labeit, Siegfried ; Gregorio, Carol. / I-band titin in cardiac muscle is a three-element molecular spring and is critical for maintaining thin filament structure. In: Journal of Cell Biology. 1999 ; Vol. 146, No. 3. pp. 631-644.
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