Acidic and basic troponin T isoforms in mature fast-twitch skeletal muscle and effect on contractility

Ozgur Ogut, Henk Granzier, Jian Ping Jin

Research output: Contribution to journalArticle

70 Scopus citations

Abstract

Developmentally regulated alternative RNA splicing generates distinct classes of acidic and basic troponin T (TnT) isoforms. In fast-twitch skeletal muscles, an acidic-to-basic TnT isoform switch ensures basic isoform expression in the adult. As an exception, an acidic segment in the NH2- terminal variable region of adult chicken breast muscle TnT isoforms is responsible for the unique exclusive expression of acidic TnTs in this muscle (O. Ogut and J.-P. Jin. J. Biol. Chem. 273: 27858-27866, 1998). To understand the relationship between acidic vs. basic TnT isoform expression and muscle contraction, the contractile properties of fibers from adult chicken breast muscle were compared with those of the levator coccygeus muscle, which expresses solely basic TnT isoforms. With use of Triton X-100-skinned muscle fibers, the force and stiffness responses to Ca2+ were measured. Relative to the levator coccygeus muscle, the breast muscle fibers showed significantly increased sensitivity to Ca2+ of force and stiffness with a shift of ~0.15 in the pCa at which force or stiffness was 50% of maximal. The expression of tropomyosin, troponin I, and troponin C isoforms was also determined to delineate their contribution to thin-filament regulation. The data indicate that TnT isoforms differing in their NH2-terminal charge are able to alter the sensitivity of the myofibrillar contractile apparatus to Ca2+. These results provide evidence linking the regulated expression of distinct acidic and basic TnT isoform classes to the contractility of striated muscle.

Original languageEnglish (US)
Pages (from-to)C1162-C1170
JournalAmerican Journal of Physiology - Cell Physiology
Volume276
Issue number5 45-5
StatePublished - Jun 5 1999
Externally publishedYes

Keywords

  • Activation of force and stiffness
  • Alternative ribonucleic acid splicing
  • Calcium
  • Developmental regulation
  • Tropomyosin

ASJC Scopus subject areas

  • Physiology
  • Cell Biology

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