X-ray recordings reveal how a human disease-linked skeletal muscle α-actin mutation leads to contractile dysfunction

J. Ochala, Gina Ravenscroft, Elyshia Mcnamara, Kristen Nowak, H. Iwamoto

Research output: Contribution to journalArticle

4 Citations (Scopus)

Abstract

© 2015 Elsevier Inc. In humans, mutant skeletal muscle α-actin proteins are associated with contractile dysfunction, skeletal muscle weakness and a wide range of primarily skeletal muscle diseases. Despite this knowledge, the exact molecular mechanisms triggering the contractile dysfunction remain unknown. Here, we aimed to unravel these. Hence, we used a transgenic mouse model expressing a well-described D286G mutant skeletal muscle α-actin protein and recapitulating the human condition of contractile deregulation and severe skeletal muscle weakness. We then recorded and analyzed the small-angle X-ray diffraction patterns of isolated membrane-permeabilized myofibers. Results showed that upon addition of Ca2+, the intensity changes of the second (1/19nm-1) and sixth (1/5.9nm-1) actin layer lines and of the first myosin meridional reflection (1/14.3nm-1) were disrupted when the thin-thick filament overlap was optimal (sarcomere length of 2.5-2.6μm). However these reflections were normal when the thin and thick filaments were not interacting (sarcomere length>3.6μm). These findings demonstrate, for the first time, that the replacement of just one amino acid in the skeletal muscle α-actin protein partly prevents actin conformational changes during activation, disrupting the strong binding of myosin molecules. This leads to a limited myosin-related tropomyosin movement over the thin filaments, further affecting the amount of cross-bridges, explaining the contractile dysfunction.
Original languageEnglish
Pages (from-to)331-335
Number of pages5
JournalJournal of Structural Biology
Volume192
Issue number3
Early online date25 Sep 2015
DOIs
Publication statusPublished - Dec 2015

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