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Muscle ring finger protein-1 inhibits PKC{epsilon} activation and prevents cardiomyocyte hypertrophy.

Arya R, Kedar V, Hwang JR, McDonough H, Li HH, Taylor J, Patterson C - J. Cell Biol. (2004)

Bottom Line: Much effort has focused on characterizing the signal transduction cascades that are associated with cardiac hypertrophy.MURF1 inhibits focal adhesion formation, and the activity of downstream effector ERK1/2 is also inhibited in the presence of MURF1.MURF1 inhibits phenylephrine-induced (but not IGF-1-induced) increases in cell size.

View Article: PubMed Central - PubMed

Affiliation: Carolina Cardiovascular Biology Center, University of North Carolina, Chapel Hill, NC 27599, USA.

ABSTRACT
Much effort has focused on characterizing the signal transduction cascades that are associated with cardiac hypertrophy. In spite of this, we still know little about the mechanisms that inhibit hypertrophic growth. We define a novel anti-hypertrophic signaling pathway regulated by muscle ring finger protein-1 (MURF1) that inhibits the agonist-stimulated PKC-mediated signaling response in neonatal rat ventricular myocytes. MURF1 interacts with receptor for activated protein kinase C (RACK1) and colocalizes with RACK1 after activation with phenylephrine or PMA. Coincident with this agonist-stimulated interaction, MURF1 blocks PKCepsilon translocation to focal adhesions, which is a critical event in the hypertrophic signaling cascade. MURF1 inhibits focal adhesion formation, and the activity of downstream effector ERK1/2 is also inhibited in the presence of MURF1. MURF1 inhibits phenylephrine-induced (but not IGF-1-induced) increases in cell size. These findings establish that MURF1 is a key regulator of the PKC-dependent hypertrophic response and can blunt cardiomyocyte hypertrophy, which may have important implications in the pathophysiology of clinical cardiac hypertrophy.

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MURF1 inhibits focal adhesion formation in NRVM. NRVM were infected with Ad.GFP (A, B, and E) or Ad.MURF1 (C, D, and F) for 24 h in serum-free medium followed by induction with PE for 48 h (B and D). The cells were fixed in 3.7% formaldehyde followed by incubation with anti-paxillin (A–D) or anti-vinculin (E and F) antibodies. Arrows indicate focal adhesions. (G) Quantitative determination of paxillin-positive focal adhesions per cell under the indicated conditions.
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fig6: MURF1 inhibits focal adhesion formation in NRVM. NRVM were infected with Ad.GFP (A, B, and E) or Ad.MURF1 (C, D, and F) for 24 h in serum-free medium followed by induction with PE for 48 h (B and D). The cells were fixed in 3.7% formaldehyde followed by incubation with anti-paxillin (A–D) or anti-vinculin (E and F) antibodies. Arrows indicate focal adhesions. (G) Quantitative determination of paxillin-positive focal adhesions per cell under the indicated conditions.

Mentions: Previous reports indicate that PE-induced hypertrophy in isolated neonatal cardiomyocytes requires signaling through FAK (Taylor et al., 2000), and activation of FAK, in turn, depends on PKCε (Eble et al., 2000; Heidkamp et al., 2003). To determine whether the effects of MURF1 on PKCε translocation and activation influence focal adhesion assembly, we first examined the localization of paxillin, a resident focal adhesion protein, by immunostaining with anti-paxillin antibody after PE treatment in NRVM. Paxillin staining was dispersed in untreated cells (Fig. 6 A), but after PE treatment staining appeared in distinct focal complexes in the Ad.GFP-infected cells (Fig. 6 B). In contrast, the subcellular redistribution of paxillin in response to PE was markedly inhibited in the presence of Ad.MURF1 (Fig. 6, C and D). Similarly, vinculin staining revealed characteristic staining of Z-disc structures and peripheral focal adhesions after PE treatment, whereas cells infected with Ad.MURF1 lost the focal adhesion pattern but retained Z-disc–tethered vinculin expression. A quantitative analysis of paxillin-positive focal adhesions per cell is shown in Fig. 6 G. These data suggest that MURF1 inhibits PE-induced focal adhesion formation in NRVM.


Muscle ring finger protein-1 inhibits PKC{epsilon} activation and prevents cardiomyocyte hypertrophy.

Arya R, Kedar V, Hwang JR, McDonough H, Li HH, Taylor J, Patterson C - J. Cell Biol. (2004)

MURF1 inhibits focal adhesion formation in NRVM. NRVM were infected with Ad.GFP (A, B, and E) or Ad.MURF1 (C, D, and F) for 24 h in serum-free medium followed by induction with PE for 48 h (B and D). The cells were fixed in 3.7% formaldehyde followed by incubation with anti-paxillin (A–D) or anti-vinculin (E and F) antibodies. Arrows indicate focal adhesions. (G) Quantitative determination of paxillin-positive focal adhesions per cell under the indicated conditions.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2172633&req=5

fig6: MURF1 inhibits focal adhesion formation in NRVM. NRVM were infected with Ad.GFP (A, B, and E) or Ad.MURF1 (C, D, and F) for 24 h in serum-free medium followed by induction with PE for 48 h (B and D). The cells were fixed in 3.7% formaldehyde followed by incubation with anti-paxillin (A–D) or anti-vinculin (E and F) antibodies. Arrows indicate focal adhesions. (G) Quantitative determination of paxillin-positive focal adhesions per cell under the indicated conditions.
Mentions: Previous reports indicate that PE-induced hypertrophy in isolated neonatal cardiomyocytes requires signaling through FAK (Taylor et al., 2000), and activation of FAK, in turn, depends on PKCε (Eble et al., 2000; Heidkamp et al., 2003). To determine whether the effects of MURF1 on PKCε translocation and activation influence focal adhesion assembly, we first examined the localization of paxillin, a resident focal adhesion protein, by immunostaining with anti-paxillin antibody after PE treatment in NRVM. Paxillin staining was dispersed in untreated cells (Fig. 6 A), but after PE treatment staining appeared in distinct focal complexes in the Ad.GFP-infected cells (Fig. 6 B). In contrast, the subcellular redistribution of paxillin in response to PE was markedly inhibited in the presence of Ad.MURF1 (Fig. 6, C and D). Similarly, vinculin staining revealed characteristic staining of Z-disc structures and peripheral focal adhesions after PE treatment, whereas cells infected with Ad.MURF1 lost the focal adhesion pattern but retained Z-disc–tethered vinculin expression. A quantitative analysis of paxillin-positive focal adhesions per cell is shown in Fig. 6 G. These data suggest that MURF1 inhibits PE-induced focal adhesion formation in NRVM.

Bottom Line: Much effort has focused on characterizing the signal transduction cascades that are associated with cardiac hypertrophy.MURF1 inhibits focal adhesion formation, and the activity of downstream effector ERK1/2 is also inhibited in the presence of MURF1.MURF1 inhibits phenylephrine-induced (but not IGF-1-induced) increases in cell size.

View Article: PubMed Central - PubMed

Affiliation: Carolina Cardiovascular Biology Center, University of North Carolina, Chapel Hill, NC 27599, USA.

ABSTRACT
Much effort has focused on characterizing the signal transduction cascades that are associated with cardiac hypertrophy. In spite of this, we still know little about the mechanisms that inhibit hypertrophic growth. We define a novel anti-hypertrophic signaling pathway regulated by muscle ring finger protein-1 (MURF1) that inhibits the agonist-stimulated PKC-mediated signaling response in neonatal rat ventricular myocytes. MURF1 interacts with receptor for activated protein kinase C (RACK1) and colocalizes with RACK1 after activation with phenylephrine or PMA. Coincident with this agonist-stimulated interaction, MURF1 blocks PKCepsilon translocation to focal adhesions, which is a critical event in the hypertrophic signaling cascade. MURF1 inhibits focal adhesion formation, and the activity of downstream effector ERK1/2 is also inhibited in the presence of MURF1. MURF1 inhibits phenylephrine-induced (but not IGF-1-induced) increases in cell size. These findings establish that MURF1 is a key regulator of the PKC-dependent hypertrophic response and can blunt cardiomyocyte hypertrophy, which may have important implications in the pathophysiology of clinical cardiac hypertrophy.

Show MeSH
Related in: MedlinePlus