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J. Cell Biol.,
Volume 142, Number 1, July 13, 1998 241-250
* Department of Molecular, Cellular and Developmental Biology, University of Colorado, Boulder, Colorado 80309, and the
Walther Cancer Institute, Indianapolis, Indiana 47238; Ligand-stimulated activation of FGF receptors (FGFRs) in skeletal muscle cells represses terminal
myogenic differentiation. Skeletal muscle cell lines and
subsets of primary cells are dependent on FGFs to repress myogenesis and maintain growth. To understand the intracellular events that transduce these signals,
MM14 skeletal muscle cells were transfected with expression vectors encoding chimeric receptors. The
chimeras are comprised of the PDGF Department of Biological Sciences, § Department of Basic Medical
Sciences, and Department of Biochemistry, Purdue University, West Lafayette, Indiana 47907
receptor (PDGFR) extracellular domain, the FGFR-1 intracellular domain, and either the PDGFR or FGFR-1
transmembrane domain. The chimeric receptors were
autophosphorylated upon PDGF-BB stimulation and are capable of stimulating mitogen-activated protein kinase activity. Activation of the tyrosine kinase domain
of either chimera repressed myogenesis, suggesting intracellular responses regulating skeletal muscle differentiation are transduced by activation of the FGFR-1 tyrosine kinase. Unexpectedly, we found that activation
of either chimeric receptor failed to stimulate cellular
proliferation. Thus, it appears that regulation of skeletal
muscle differentiation by FGFs requires only activation
of the FGFR tyrosine kinase. In contrast, stimulation of
proliferation may require additional, as yet unidentified,
signals involving the receptor ectodomain, the FGF
ligand, and heparan sulfate either alone, or in combination.
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