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Prostaglandin F2(alpha) stimulates growth of skeletal muscle cells via an NFATC2-dependent pathway.

Horsley V, Pavlath GK - J. Cell Biol. (2003)

Bottom Line: We demonstrate that prostaglandin F2alpha (PGF2alpha) as well as two analogues augment muscle cell size in vitro.We show that NFAT is activated by PGF2alpha, and the isoform NFATC2 is required for PGF2alpha-induced muscle cell growth and nuclear accretion, demonstrating the first intersection between prostaglandin receptor activation and NFAT signaling.Given this novel role for PGF2alpha in skeletal muscle cell growth, these studies raise caution that extended use of drugs that inhibit PG production, such as nonsteroidal antiinflammatory drugs, may be deleterious for muscle growth.

View Article: PubMed Central - PubMed

Affiliation: Cell and Developmental Biology, Emory University School of Medicine, Atlanta, GA 30322, USA.

ABSTRACT
Skeletal muscle growth requires multiple steps to form large multinucleated muscle cells. Molecules that stimulate muscle growth may be therapeutic for muscle loss associated with aging, injury, or disease. However, few factors are known to increase muscle cell size. We demonstrate that prostaglandin F2alpha (PGF2alpha) as well as two analogues augment muscle cell size in vitro. This increased myotube size is not due to PGF2alpha-enhancing cell fusion that initially forms myotubes, but rather to PGF2alpha recruiting the fusion of cells with preexisting multinucleated cells. This growth is mediated through the PGF2alpha receptor (FP receptor). As the FP receptor can increase levels of intracellular calcium, the involvement of the calcium-regulated transcription factor nuclear factor of activated T cells (NFAT) in mediating PGF2alpha-enhanced cell growth was examined. We show that NFAT is activated by PGF2alpha, and the isoform NFATC2 is required for PGF2alpha-induced muscle cell growth and nuclear accretion, demonstrating the first intersection between prostaglandin receptor activation and NFAT signaling. Given this novel role for PGF2alpha in skeletal muscle cell growth, these studies raise caution that extended use of drugs that inhibit PG production, such as nonsteroidal antiinflammatory drugs, may be deleterious for muscle growth.

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PGF2α increases myotube size through an NFAT-dependent pathway. (A) Primary myoblasts were infected either with control retrovirus (Cntl RV) or with a retrovirus expressing VIVIT, a peptide inhibitor of NFAT (VIVIT RV). Cells were induced to differentiate in the presence of vehicle or 10−6 M PGF2α for 48 h, and then immunostained for EMyHC. Bar, 60 μm. (B) Nuclear number assays were performed on the retrovirally infected cultures as in Fig. 1 E. Data are mean ± SEM of three independent experiments. *Significantly different from vehicle, P < 0.05.
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fig3: PGF2α increases myotube size through an NFAT-dependent pathway. (A) Primary myoblasts were infected either with control retrovirus (Cntl RV) or with a retrovirus expressing VIVIT, a peptide inhibitor of NFAT (VIVIT RV). Cells were induced to differentiate in the presence of vehicle or 10−6 M PGF2α for 48 h, and then immunostained for EMyHC. Bar, 60 μm. (B) Nuclear number assays were performed on the retrovirally infected cultures as in Fig. 1 E. Data are mean ± SEM of three independent experiments. *Significantly different from vehicle, P < 0.05.

Mentions: PGF2α signaling is known to increase levels of intracellular calcium in a variety of cell types including smooth muscle and cardiac muscle (Yew et al., 1998; Yousufzai and Abdel-Latif, 1998). NFAT is a family of calcium-regulated transcription factors that has been implicated in skeletal muscle growth (Musaro et al., 1999; Horsley et al., 2001; Kegley et al., 2001). To investigate whether NFAT is involved in PGF2α-induced skeletal muscle growth, cells were infected with a retrovirus encoding VIVIT, a specific peptide inhibitor of NFAT activation. VIVIT acts by preventing the interaction between NFAT and calcineurin but not between calcineurin and other substrates (Aramburu et al., 1999; Friday et al., 2000; Friday and Pavlath, 2001). Primary muscle cells infected with control retrovirus exhibit an increase in cell size when treated with 10−6 M PGF2α (Fig. 3 A), similar to uninfected cells (Fig. 1 A). In contrast, cells infected with VIVIT retrovirus do not increase cell size when treated with PGF2α. To quantify these observations, we analyzed the cultures with the nuclear number assay used in Fig. 1. Cells infected with control retrovirus and treated with PGF2α show a significant increase in the percentage of myotubes with five or more nuclei. However, cells infected with the VIVIT retrovirus and treated with PGF2α are similar in nuclear number to nontreated cells. These data implicate that a calcineurin- and NFAT-dependent signaling pathway is involved in skeletal muscle growth induced by PGF2α.


Prostaglandin F2(alpha) stimulates growth of skeletal muscle cells via an NFATC2-dependent pathway.

Horsley V, Pavlath GK - J. Cell Biol. (2003)

PGF2α increases myotube size through an NFAT-dependent pathway. (A) Primary myoblasts were infected either with control retrovirus (Cntl RV) or with a retrovirus expressing VIVIT, a peptide inhibitor of NFAT (VIVIT RV). Cells were induced to differentiate in the presence of vehicle or 10−6 M PGF2α for 48 h, and then immunostained for EMyHC. Bar, 60 μm. (B) Nuclear number assays were performed on the retrovirally infected cultures as in Fig. 1 E. Data are mean ± SEM of three independent experiments. *Significantly different from vehicle, P < 0.05.
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fig3: PGF2α increases myotube size through an NFAT-dependent pathway. (A) Primary myoblasts were infected either with control retrovirus (Cntl RV) or with a retrovirus expressing VIVIT, a peptide inhibitor of NFAT (VIVIT RV). Cells were induced to differentiate in the presence of vehicle or 10−6 M PGF2α for 48 h, and then immunostained for EMyHC. Bar, 60 μm. (B) Nuclear number assays were performed on the retrovirally infected cultures as in Fig. 1 E. Data are mean ± SEM of three independent experiments. *Significantly different from vehicle, P < 0.05.
Mentions: PGF2α signaling is known to increase levels of intracellular calcium in a variety of cell types including smooth muscle and cardiac muscle (Yew et al., 1998; Yousufzai and Abdel-Latif, 1998). NFAT is a family of calcium-regulated transcription factors that has been implicated in skeletal muscle growth (Musaro et al., 1999; Horsley et al., 2001; Kegley et al., 2001). To investigate whether NFAT is involved in PGF2α-induced skeletal muscle growth, cells were infected with a retrovirus encoding VIVIT, a specific peptide inhibitor of NFAT activation. VIVIT acts by preventing the interaction between NFAT and calcineurin but not between calcineurin and other substrates (Aramburu et al., 1999; Friday et al., 2000; Friday and Pavlath, 2001). Primary muscle cells infected with control retrovirus exhibit an increase in cell size when treated with 10−6 M PGF2α (Fig. 3 A), similar to uninfected cells (Fig. 1 A). In contrast, cells infected with VIVIT retrovirus do not increase cell size when treated with PGF2α. To quantify these observations, we analyzed the cultures with the nuclear number assay used in Fig. 1. Cells infected with control retrovirus and treated with PGF2α show a significant increase in the percentage of myotubes with five or more nuclei. However, cells infected with the VIVIT retrovirus and treated with PGF2α are similar in nuclear number to nontreated cells. These data implicate that a calcineurin- and NFAT-dependent signaling pathway is involved in skeletal muscle growth induced by PGF2α.

Bottom Line: We demonstrate that prostaglandin F2alpha (PGF2alpha) as well as two analogues augment muscle cell size in vitro.We show that NFAT is activated by PGF2alpha, and the isoform NFATC2 is required for PGF2alpha-induced muscle cell growth and nuclear accretion, demonstrating the first intersection between prostaglandin receptor activation and NFAT signaling.Given this novel role for PGF2alpha in skeletal muscle cell growth, these studies raise caution that extended use of drugs that inhibit PG production, such as nonsteroidal antiinflammatory drugs, may be deleterious for muscle growth.

View Article: PubMed Central - PubMed

Affiliation: Cell and Developmental Biology, Emory University School of Medicine, Atlanta, GA 30322, USA.

ABSTRACT
Skeletal muscle growth requires multiple steps to form large multinucleated muscle cells. Molecules that stimulate muscle growth may be therapeutic for muscle loss associated with aging, injury, or disease. However, few factors are known to increase muscle cell size. We demonstrate that prostaglandin F2alpha (PGF2alpha) as well as two analogues augment muscle cell size in vitro. This increased myotube size is not due to PGF2alpha-enhancing cell fusion that initially forms myotubes, but rather to PGF2alpha recruiting the fusion of cells with preexisting multinucleated cells. This growth is mediated through the PGF2alpha receptor (FP receptor). As the FP receptor can increase levels of intracellular calcium, the involvement of the calcium-regulated transcription factor nuclear factor of activated T cells (NFAT) in mediating PGF2alpha-enhanced cell growth was examined. We show that NFAT is activated by PGF2alpha, and the isoform NFATC2 is required for PGF2alpha-induced muscle cell growth and nuclear accretion, demonstrating the first intersection between prostaglandin receptor activation and NFAT signaling. Given this novel role for PGF2alpha in skeletal muscle cell growth, these studies raise caution that extended use of drugs that inhibit PG production, such as nonsteroidal antiinflammatory drugs, may be deleterious for muscle growth.

Show MeSH
Related in: MedlinePlus