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This Article Full Text Full Text (PDF) All Versions of this Article: 290/3/C711    most recent 00217.2005v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via ISI Web of Science (4) Citing Articles via Google Scholar Google Scholar Articles by Bortoloso, E. Articles by Volpe, P. Search for Related Content PubMed PubMed Citation Articles by Bortoloso, E. Articles by Volpe, P.

MUSCLE CELL BIOLOGY AND CELL MOTILITY

Transition of Homer isoforms during skeletal muscle regeneration

¹Dipartimento di Scienze Biomediche Sperimentali dell'Università di Padova, ²Istituto Interuniversitario di Miologia, and ³Dipartimento di Anatomia e Fisiologia Umana dell'Università di Padova, Padova, Italy

Submitted 6 May 2005 ; accepted in final form 11 October 2005

Homer represents a new and diversified family of proteins that includes several isoforms, Homer 1, 2, and 3; some of these isoforms have been reported to be present in striated muscles. In this study, the presence of Homer isoforms 1a, 1b/c/d, 2b, and 3 was thoroughly investigated in rat skeletal muscles under resting conditions. Transition in Homer isoforms compositon was studied under experimental conditions of short-term and long-term adaptation, e.g., fatigue and regeneration, respectively. First, we show that Homer 1a was constitutively expressed and was transiently upregulated during regeneration. In C₂C₁₂ cell cultures, Homer 1a was also upregulated during formation of myotubes. No change of Homer 1a was observed in fatigue. Second, Homer 1b/c/d and Homer 2b were positively and linearly related to muscle mass change during regeneration, and third, Homer 3 was not detectable under resting conditions but was transiently expressed during regeneration although with a temporal pattern distinct from that of Homer 1a. Thus a switch in Homer isoforms is associated to muscle differentiation and regeneration. Homers may play a role not only in signal transduction of skeletal muscle, in particular regulation of Ca²⁺ release from sarcoplasmic reticulum (Ward CW, Feng W, Tu J, Pessah IN, Worley PF, and Schneider MF. Homer protein increases activation of Ca²⁺ sparks in permeabilized skeletal muscle. J Biol Chem 279: 5781–5787, 2004), but also in adaptation.

fatigue; immediate early gene; muscle adaptation; myogenesis