title: Contractility-dependent actin dynamics in cardiomyocyte sarcomeres.
abstract: In contrast to the highly dynamic actin cytoskeleton in non-muscle cells, actin filaments in muscle sarcomeres are thought to be relatively stable and undergo dynamics only at their ends. However, many proteins that promote rapid actin dynamics are also expressed in striated muscles. We show that a subset of actin filaments in cardiomyocyte sarcomeres displays rapid turnover. Importantly, we found that turnover of these filaments depends on contractility of the cardiomyocytes. Studies using an actin-polymerization inhibitor suggest that the pool of dynamic actin filaments is composed of filaments that do not contribute to contractility. Furthermore, we provide evidence that ADF/cofilins, together with myosin-induced contractility, are required to disassemble non-productive filaments in developing cardiomyocytes. These data indicate that an excess of actin filaments is produced during sarcomere assembly, and that contractility is applied to recognize non-productive filaments that are subsequently destined for depolymerization. Consequently, contractility-induced actin dynamics plays an important role in sarcomere maturation.
authors.affiliation: Institute of Biotechnology, PO Box 56, 00014, University of Helsinki, Finland.
authors.forename: Aneta
authors.initials: A
authors.lastname: Skwarek-Maruszewska
authors.forename: Pirta
authors.initials: P
authors.lastname: Hotulainen
authors.forename: Pieta K
authors.initials: PK
authors.lastname: Mattila
authors.forename: Pekka
authors.initials: P
authors.lastname: Lappalainen
mesh_terms: D008841:Actin Cytoskeleton / Q000378:metabolism / Q000502:physiology; D051339:Actin Depolymerizing Factors / Q000502:physiology; D000199:Actins / Q000378:metabolism*; D000818:Animals; D000831:Animals, Newborn; D002478:Cells, Cultured; D051345:Destrin / Q000502:physiology; D007700:Kinetics; D009200:Myocardial Contraction / Q000502:physiology*; D032383:Myocytes, Cardiac / Q000378:metabolism* / Q000502:physiology; D055503:Protein Multimerization / Q000502:physiology; D021381:Protein Transport; D051381:Rats; D017208:Rats, Wistar; D012518:Sarcomeres / Q000378:metabolism* / Q000502:physiology
chemical_list: D051339:Actin Depolymerizing Factors; D000199:Actins; D051345:Destrin