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The carboxyl‐terminal ahnak domain induces actin bundling and stabilizes muscle contraction
Author(s) -
Haase Hannelore,
Pagel Ines,
Khalina Yana,
Zacharzowsky Udo,
Person Veronika,
Lutsch Gudrun,
Petzhold Daria,
Kott Monika,
Schaper Jutta,
Morano Ingo
Publication year - 2004
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fj.03-0446fje
Subject(s) - myofibril , actin , biophysics , chemistry , skeletal muscle , microbiology and biotechnology , myosin , contraction (grammar) , protein filament , muscle contraction , myocyte , contractility , biochemistry , biology , anatomy , endocrinology
Ahnak, a 700 kDa protein, is expressed in a variety of cells and has been implicated in different cell‐type‐specific functions. In the human heart, we observed an endogenous carboxyl‐terminal 72 kDa ahnak fragment that copurified with myofibrillar proteins. Immunocytochemistry combined with confocal microscopy localized this fragment to the intercalated discs and close to the Z‐line of cardiomyocytes. No endogenous myofibrillar ahnak fragment was observed in the skeletal muscle. We elucidated the role of the recombinant carboxyl‐terminal ahnak fragment (ahnak‐C2) in actin filament organization and in the function of muscle fibers. Addition of ahnak‐C2 to actin filaments induced filament bundling into paracrystalline‐like structures as revealed by electron microscopy. Incubation of demembranated skeletal muscle fibers with ahnak‐C2 attenuated the decline in isometric force development upon repeated contraction–relaxation cycles. Our results suggest that the carboxyl‐terminal ahnak domain exerts a stabilizing effect on muscle contractility via its interaction with actin of thin filaments.