Defective regulation of contractile function in muscle fibres carrying an E41K beta-tropomyosin mutation
2008 (English)In: Journal of Physiology, ISSN 0022-3751, E-ISSN 1469-7793, Vol. 586, no 12, 2993-3004 p.Article in journal (Refereed) Published
A novel E41K beta-tropomyosin (beta-Tm) mutation, associated with congenital myopathy and muscle weakness, was recently identified in a woman and her daughter. In both patients, muscle weakness was coupled with muscle fibre atrophy. It remains unknown, however, whether the E41K beta-Tm mutation directly affects regulation of muscle contraction, contributing to the muscle weakness. To address this question, we studied a broad range of contractile characteristics in skinned muscle fibres from the two patients and eight healthy controls. Results showed decreases (i) in speed of contraction at saturated Ca2+ concentration (apparent rate constant of force redevelopment (k(tr)) and unloaded shortening speed (V-0)); and (ii) in contraction sensitivity to Ca2+ concentration, in fibres from patients compared with controls, suggesting that the mutation has a negative effect on contractile function, contributing to the muscle weakness. To investigate whether these negative impacts are reversible, we exposed skinned muscle fibres to the Ca2+ sensitizer EMD 57033. In fibres from patients, 30 mu m of EMD 57033 (i) had no effect on speed of contraction (k(tr) and V-0) at saturated Ca2+ concentration but (ii) increased Ca2+ sensitivity of contraction, suggesting a potential therapeutic approach in patients carrying the E41K beta-Tm mutation.
Place, publisher, year, edition, pages
2008. Vol. 586, no 12, 2993-3004 p.
Medical and Health Sciences
IdentifiersURN: urn:nbn:se:uu:diva-17511DOI: 10.1113/jphysiol.2008.153650ISI: 000256733700017PubMedID: 18420702OAI: oai:DiVA.org:uu-17511DiVA: diva2:45282