Regulation of avian fibroblast growth factor receptor 1 (FGFR-1) gene expression during skeletal muscle differentiation

ABSTRACT Heparan sulfate proteoglycans (HSPGs) are critical modulators of growth factor activities. Skeletal muscle differentiation is strongly inhibited by fibroblast growth factor 2 (FGF-2). We have shown that HSPGs present at the plasma membrane are expressed in myoblasts and are downregulated during muscle differentiation. An exception is glypican-1, which is present throughout the myogenic process. Myoblasts that do not express glypican-1 exhibit defective differentiation, with an increase in the receptor binding of FGF-2, concomitant with increased signaling. Glypican-1-deficient myoblasts show decreased expression of myogenin, the master gene that controls myogenesis, myosin, and the myoblast fusion index. Reversion of these defects was induced by expression of rat glypican-1. Glypican-1 is the only HSPG localized in lipid raft domains in myoblasts, resulting in the sequestration of FGF-2 away from FGF-2 receptors (FGFRs) located in nonraft domains. A chimeric glypican-1, containing syndecan-1 transmembrane and cytoplasmic domains, is located in nonraft domains interacting with FGFR-IV- and enhanced FGF-2-dependent signaling. Thus, glypican-1 acts as a positive regulator of muscle differentiation by sequestering FGF-2 in lipid rafts and preventing its binding and dependent signaling.

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A Competitive PCR-Based Method to Measure Human Fibroblast Growth Factor Receptor 1–4 (FGFR1–4) Gene Expression

DNA and Cell Biology ◽

10.1089/10445490152122488 ◽

2001 ◽

Vol 20 (6) ◽

pp. 367-379 ◽

Cited By ~ 13

Author(s):

Marco Tartaglia ◽

Alessandra Fragale ◽

Piero A. Battaglia

Keyword(s):

Gene Expression ◽

Growth Factor ◽

Fibroblast Growth Factor ◽

Human Fibroblast ◽

Fibroblast Growth Factor Receptor ◽

Growth Factor Receptor ◽

Fibroblast Growth ◽

Competitive Pcr

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Cell surface fibroblast growth factor and epidermal growth factor receptors are permanently lost during skeletal muscle terminal differentiation in culture.

The Journal of Cell Biology ◽

10.1083/jcb.107.2.761 ◽

1988 ◽

Vol 107 (2) ◽

pp. 761-769 ◽

Cited By ~ 131

Author(s):

B B Olwin ◽

S D Hauschka

Keyword(s):

Skeletal Muscle ◽

Growth Factor ◽

Epidermal Growth Factor ◽

Cell Surface ◽

Fibroblast Growth Factor ◽

Growth Factor Receptor ◽

Growth Factor Receptors ◽

Skeletal Muscle Differentiation ◽

Fibroblast Growth ◽

Epidermal Growth

One characteristic of skeletal muscle differentiation is the conversion of proliferating cells to a population that is irreversibly postmitotic. This developmental change can be induced in vitro by depriving the cultures of specific mitogens such as fibroblast growth factor (FGF). Analysis of cell surface FGF receptor (FGFR) in several adult mouse muscle cell lines and epidermal growth factor receptor (EGFR) in mouse MM14 cells reveals a correlation between receptor loss and the acquisition of a postmitotic phenotype. Quiescent MM14 cells, mitogen-depleted, differentiation-defective MM14 cells, and differentiated BC3H1 muscle cells (a line that fails to become postmitotic upon differentiation) retained their cell surface FGFR. These results indicate that FGFR loss is not associated with either reversible cessation of muscle cell proliferation or biochemical differentiation and thus, further support a correlation between receptor loss and acquisition of a postmitotic phenotype. Comparison of the kinetics for growth factor receptor loss and for commitment of MM14 cells to a postmitotic phenotype reveals that FGFR rises transiently from approximately 700 receptors/cell to a maximum of approximately 2,000 receptors/cell 12 h after FGF removal, when at the same time, greater than 95% of the cells are postmitotic. FGFR levels then decline to undetectable levels by 24 h after FGF removal. During the interval in which FGFR increases and then disappears there is no change in its affinity for FGF. The transient increase in growth factor receptors appears to be due to a decrease in ligand-mediated internalization because EGFR, which undergoes an immediate decline when cultures are deprived of FGF (Lim, R. W., and S. D. Hauschka. 1984. J. Cell Biol. 98:739-747), exhibits a similar transient rise when cultures are grown in media containing both EGF and FGF before switching the cells to media without these added factors. These results indicate that the loss of certain growth factor receptors is a specific phenotype acquired during skeletal muscle differentiation, but they do not resolve whether regulation of FGFR number is causal for initiation of the postmitotic phenotype. A general model is presented in the discussion.

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