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Cyclic AMP-Modulated Phosphorylation of Intermediate Filament Proteins in Cultured Avian Myogenic Cells

Gard, David L. and Lazarides, Elias (1982) Cyclic AMP-Modulated Phosphorylation of Intermediate Filament Proteins in Cultured Avian Myogenic Cells. Molecular and Cellular Biology, 2 (9). pp. 1104-1114. ISSN 0270-7306. PMCID PMC369903. doi:10.1128/MCB.2.9.1104.

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The intermediate filament proteins desmin and vimentin and the muscle tropomyosins were the major protein phosphate acceptors in 8-day-old myotubes incubated for 4 h in medium containing radiolabeled phosphate. The addition of isoproterenol or 8-bromo-cyclic AMP (BrcAMP) resulted in a two- to threefold increase in incorporation of 32PO4 into both desmin and vimentin, whereas no changes in the incorporation of ^(32)PO_4 into tropomyosin or other cellular proteins were observed. The BrcAMP- or hormonally induced increase in ^(32)PO_4 incorporation into desmin and vimentin was independent of protein synthesis and was not caused by stimulation of protein phosphate turnover. In addition, BrcAMP did not induce significant changes in the specific activity of the cellular ATP pool. These data suggest that the observed increase in ^(32)PO_4 incorporation represented an actual increase in phosphorylation of the intermediate filament proteins desmin and vimentin. Two-dimensional tryptic analysis of desmin from 8-day-old myotubes revealed five phosphopeptides of which two showed a 7- to 10-fold increase in ^(32)PO_4 incorporation in BrcAMP-treated myotubes. Four of the phosphopeptides identified in desmin labeled in vivo were also observed in desmin phosphorylated in vitro by bovine heart cAMP-dependent protein kinase. Although phosphorylation of desmin and vimentin was apparent in myogenic cells at all stages of differentiation, BrcAMP- and isoproterenol-induced increases in phosphorylation of these proteins were restricted to mature myotubes. These data strongly suggest that in vivo phosphorylation of the intermediate filament proteins desmin and vimentin is catalyzed by the cAMP-dependent protein kinases and that such phosphorylation may be regulated during muscle differentiation.

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Additional Information:© 1982 American Society for Microbiology. Received 7 April 1982. Accepted 9 June 1982. We thank Clare M. O'Connor for preparing in vitro phosphorylated desmin and the assay for ATP and Ilga Lielausis for assistance in preparing myogenic cell cultures. We also thank Dr. O'Connor, Mary Kennedy, Bruce L. Granger, and Chung Wang for helpful discussion during the course of this research and preparation of this manuscript. This work was supported by Public Health Service grant no. GM 06965 from the National Institutes of Health, grants from the National Science Foundation and Muscular Dystrophy Association of America, and a Biomedical Research Support Grant to the Division of Biology, California Institute of Technology. D.L.G. was also supported by Predoctoral Training grant no. OM 07616 and E.L. is the recipient of a Research Career Development Award, both from the National Institutes of Health.
Funding AgencyGrant Number
NIHGM 06965
Muscular Dystrophy Association of AmericaUNSPECIFIED
Caltech Biomedical Research Support GrantUNSPECIFIED
NIH Predoctoral FellowshipGM 07616
Issue or Number:9
PubMed Central ID:PMC369903
Record Number:CaltechAUTHORS:20120717-091559709
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Official Citation:Cyclic AMP-modulated phosphorylation of intermediate filament proteins in cultured avian myogenic cells. D L Gard and E Lazarides Mol. Cell. Biol. September 1982 2:1104-1114; doi:10.1128/MCB.2.9.1104
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:32503
Deposited By: Ruth Sustaita
Deposited On:17 Jul 2012 17:06
Last Modified:09 Nov 2021 21:27

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