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Skeletal muscle Ca(2+)-independent kinase activity increases during either hypertrophy or runningSpikes in free Ca(2+) initiate contractions in skeletal muscle cells, but whether and how they might signal to transcription factors in skeletal muscles of living animals is unknown. Since previous studies in non-muscle cells have shown that serum response factor (SRF) protein, a transcription factor, is phosphorylated rapidly by Ca(2+)/calmodulin (CaM)-dependent protein kinase after rises in intracellular Ca(2+), we measured enzymatic activity that phosphorylates SRF (designated SRF kinase activity). Homogenates from 7-day-hypertrophied anterior latissimus dorsi muscles of roosters had more Ca(2+)-independent SRF kinase activity than their respective control muscles. However, no differences were noted in Ca(2+)/CaM-dependent SRF kinase activity between control and trained muscles. To determine whether the Ca(2+)-independent and Ca(2+)/CaM-dependent forms of Ca(2+)/CaM-dependent protein kinase II (CaMKII) might contribute to some of the SRF kinase activity, autocamtide-3, a synthetic substrate that is specific for CaMKII, was employed. While the Ca(2+)-independent form of CaMKII was increased, like the Ca(2+)-independent form of SRF kinase, no alteration in CaMKII occurred at 7 days of stretch overload. These observations suggest that some of SRF phosphorylation by skeletal muscle extracts could be due to CaMKII. To determine whether this adaptation was specific to the exercise type (i.e., hypertrophy), similar measurements were made in the white vastus lateralis muscle of rats that had completed 2 wk of voluntary running. Although Ca(2+)-independent SRF kinase was increased, no alteration occurred in Ca(2+)/CaM-dependent SRF kinase activity. Thus any role of Ca(2+)-independent SRF kinase signaling has downstream modulators specific to the exercise phenotype.
Document ID
20040141694
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Fluck, M.
(University of Texas Medical School Houston, Texas 77030, United States)
Waxham, M. N.
Hamilton, M. T.
Booth, F. W.
Date Acquired
August 22, 2013
Publication Date
January 1, 2000
Publication Information
Publication: Journal of applied physiology (Bethesda, Md. : 1985)
Volume: 88
Issue: 1
ISSN: 8750-7587
Subject Category
Life Sciences (General)
Funding Number(s)
CONTRACT_GRANT: AR19393
CONTRACT_GRANT: HL57367
Distribution Limits
Public
Copyright
Other
Keywords
NASA Program Fundamental Space Biology
Non-NASA Center
NASA Discipline Musculoskeletal

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