Limits...
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.

Show MeSH

Related in: MedlinePlus

MURF1 inhibits adrenergic agonist-induced PKCε activity (but not PKCβII activity) in the particulate fraction of NRVM. (A–C) After infection with Ad.GFP or Ad.MURF1 for 24 h in serum-free medium, NRVM were induced with PE or PMA for 15 min and subjected to subcellular fractionation. The detergent-soluble (S) and particulate (P) fractions were immunoprecipitated with anti-PKCβII (A) or anti-PKCε antibody (B and C) and were subjected to in vitro kinase assays using histone H1 and γ[32P]ATP. (D and E) The results from densitometric scanning of kinase assays from three independent experiments are presented as means ± SEM of PKCε (D) or PKCβII (E) activity in the particulate fraction compared with soluble fraction. *, P < 0.05 compared with control.
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC2172633&req=5

fig5: MURF1 inhibits adrenergic agonist-induced PKCε activity (but not PKCβII activity) in the particulate fraction of NRVM. (A–C) After infection with Ad.GFP or Ad.MURF1 for 24 h in serum-free medium, NRVM were induced with PE or PMA for 15 min and subjected to subcellular fractionation. The detergent-soluble (S) and particulate (P) fractions were immunoprecipitated with anti-PKCβII (A) or anti-PKCε antibody (B and C) and were subjected to in vitro kinase assays using histone H1 and γ[32P]ATP. (D and E) The results from densitometric scanning of kinase assays from three independent experiments are presented as means ± SEM of PKCε (D) or PKCβII (E) activity in the particulate fraction compared with soluble fraction. *, P < 0.05 compared with control.

Mentions: To further define the function of MURF1 in NRVM, PKC activity was measured with an in vitro kinase assay. NRVM were treated with PE or PMA in the presence or absence of ectopic MURF1 expression. The lysates were subsequently fractionated into soluble and particulate components. After immunoprecipitation with either anti-PKCε or anti-PKCβII antibody, the immunocomplexes were mixed with histone H1 as an exogenous substrate. Consistent with our immunofluorescence data, MURF1 did not inhibit PKCβII activity in response to PE or PMA treatment. The majority of PKCβII phosphotransferase activity (72.5% ± 5) was observed in the particulate fraction of Ad.GFP- and Ad.MURF1-infected cells after PE or PMA treatment (Fig. 5 A), and there was no significant effect of MURF1 on PKCβII activity (Fig. 5 E). However, PKCε activity was observed in the soluble fraction even after PE (62.5% ± 5) or PMA (68.5% ± 2) treatment in Ad.MURF1-infected cells, and translocation to the particulate fraction was inhibited (Fig. 5, B–D). We cannot determine whether these effects are totally dependent on the ability of MURF1 to interact with RACK1; nevertheless, these data indicate that MURF1 specifically inhibits the translocation and activity of PKCε in the particulate fractions of 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 adrenergic agonist-induced PKCε activity (but not PKCβII activity) in the particulate fraction of NRVM. (A–C) After infection with Ad.GFP or Ad.MURF1 for 24 h in serum-free medium, NRVM were induced with PE or PMA for 15 min and subjected to subcellular fractionation. The detergent-soluble (S) and particulate (P) fractions were immunoprecipitated with anti-PKCβII (A) or anti-PKCε antibody (B and C) and were subjected to in vitro kinase assays using histone H1 and γ[32P]ATP. (D and E) The results from densitometric scanning of kinase assays from three independent experiments are presented as means ± SEM of PKCε (D) or PKCβII (E) activity in the particulate fraction compared with soluble fraction. *, P < 0.05 compared with control.
© Copyright Policy
Related In: Results  -  Collection

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

fig5: MURF1 inhibits adrenergic agonist-induced PKCε activity (but not PKCβII activity) in the particulate fraction of NRVM. (A–C) After infection with Ad.GFP or Ad.MURF1 for 24 h in serum-free medium, NRVM were induced with PE or PMA for 15 min and subjected to subcellular fractionation. The detergent-soluble (S) and particulate (P) fractions were immunoprecipitated with anti-PKCβII (A) or anti-PKCε antibody (B and C) and were subjected to in vitro kinase assays using histone H1 and γ[32P]ATP. (D and E) The results from densitometric scanning of kinase assays from three independent experiments are presented as means ± SEM of PKCε (D) or PKCβII (E) activity in the particulate fraction compared with soluble fraction. *, P < 0.05 compared with control.
Mentions: To further define the function of MURF1 in NRVM, PKC activity was measured with an in vitro kinase assay. NRVM were treated with PE or PMA in the presence or absence of ectopic MURF1 expression. The lysates were subsequently fractionated into soluble and particulate components. After immunoprecipitation with either anti-PKCε or anti-PKCβII antibody, the immunocomplexes were mixed with histone H1 as an exogenous substrate. Consistent with our immunofluorescence data, MURF1 did not inhibit PKCβII activity in response to PE or PMA treatment. The majority of PKCβII phosphotransferase activity (72.5% ± 5) was observed in the particulate fraction of Ad.GFP- and Ad.MURF1-infected cells after PE or PMA treatment (Fig. 5 A), and there was no significant effect of MURF1 on PKCβII activity (Fig. 5 E). However, PKCε activity was observed in the soluble fraction even after PE (62.5% ± 5) or PMA (68.5% ± 2) treatment in Ad.MURF1-infected cells, and translocation to the particulate fraction was inhibited (Fig. 5, B–D). We cannot determine whether these effects are totally dependent on the ability of MURF1 to interact with RACK1; nevertheless, these data indicate that MURF1 specifically inhibits the translocation and activity of PKCε in the particulate fractions of 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