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Myofibrillogenesis regulator 1 induces hypertrophy by promoting sarcomere organization in neonatal rat cardiomyocytes.

Wang X, Liu X, Wang S, Luan K - Hypertens. Res. (2012)

Bottom Line: Hypertrophic hallmarks such as cell size and [(3)H]-leucine incorporation were significantly increased when MR-1 was transfected into cardiomyocytes for 48 h.Transfection with small ubiquitin-like modifier-1 (SUMO-1) mimicked the effect of MR-1 inducing translocation of myomesin-1.However, transfection with SUMO-1 in MR-1-silenced cardiomyocytes failed to induce translocation and sarcomere organization, even though SUMO-1 expression was at the same level.

View Article: PubMed Central - PubMed

Affiliation: Department of Pathophysiology, PLA General Hospital, Beijing, China.

ABSTRACT
Human myofibrillogenesis regulator 1, a novel 17-kDa protein, is closely involved in cardiac hypertrophy. We studied the molecular mechanism that links MR-1 to hypertrophic response. Hypertrophic hallmarks such as cell size and [(3)H]-leucine incorporation were significantly increased when MR-1 was transfected into cardiomyocytes for 48 h. However, sarcomere organization was promoted when MR-1 was transfected for 8 h. The finding that cardiac hypertrophy was induced long after increase of sarcomere organization indicates that the promoted sarcomere organization may be one of the crucial factors causing hypertrophy. Furthermore, when MR-1 was transfected into cardiomyocytes, the nuclear localization of myomesin-1 was shifted to the cytoplasm. Transfection with small ubiquitin-like modifier-1 (SUMO-1) mimicked the effect of MR-1 inducing translocation of myomesin-1. However, transfection with SUMO-1 in MR-1-silenced cardiomyocytes failed to induce translocation and sarcomere organization, even though SUMO-1 expression was at the same level. Overexpression of MR-1 may induce cardiomyocyte hypertrophy via myomesin-1-mediated sarcomere organization.

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Transfection with MR-1 causes rapid sarcomere organization in neonatal rat cardiomyocytes. (A) 1-d cultured cardiomyocytes were transfected or normally cultured for another 24 h, fixed and specifically labeled with phalloidin-FITC. The figure shows the ratio of well-organized cardiomyocytes when MR-1 was transfected in cardiomyocytes for 16–24 h. *P<0.01 vs. vector. (B) The ratio of polymerized actin to G-actin in MR-1-transfected cardiomyocytes at 16 h as measured by F/G-actin fractionation and then western blot analysis. *P<0.05 vs. vector. (C) RT-PCR and western blot analysis of mRNA and protein levels of myomesin-1 and MLC-2 normalized to that of glyceraldehyde phosphate dehydrogenase (GAPDH) at 16 h (a) and western blot results (b, c). *P<0.01 vs. vector. A full color version of this figure is available at the Hypertension Research journal online.
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fig3: Transfection with MR-1 causes rapid sarcomere organization in neonatal rat cardiomyocytes. (A) 1-d cultured cardiomyocytes were transfected or normally cultured for another 24 h, fixed and specifically labeled with phalloidin-FITC. The figure shows the ratio of well-organized cardiomyocytes when MR-1 was transfected in cardiomyocytes for 16–24 h. *P<0.01 vs. vector. (B) The ratio of polymerized actin to G-actin in MR-1-transfected cardiomyocytes at 16 h as measured by F/G-actin fractionation and then western blot analysis. *P<0.05 vs. vector. (C) RT-PCR and western blot analysis of mRNA and protein levels of myomesin-1 and MLC-2 normalized to that of glyceraldehyde phosphate dehydrogenase (GAPDH) at 16 h (a) and western blot results (b, c). *P<0.01 vs. vector. A full color version of this figure is available at the Hypertension Research journal online.

Mentions: We previously found that MR-1 is involved in sarcomere organization; therefore, to determine whether MR-1 affects sarcomere organization, 1-day-cultured cardiomyocytes that were cultured or transfected for another 8–24 h were stained for polymerized actin by phalloidin-FITC and the ratios of myocytes containing well-organized sarcomeres were semi-quantified. The normal control displayed a stress fiber-like structure, which is similar to the vector control (Figure 3A). Transfection with MR-1 caused rapid sarcomere organization from 8 h. More than two-thirds of the cell area showed well-organized sarcomeres after MR-1 transfection as compared with the vector control. The ratio was increased by 0.6-fold at 8 h (34.5±5.5 vs. 21.6±7.6% in vector; P>0.05), 1.0-fold at 16 h (58.1±4.3 vs. 29.1±5.3% P<0.01) and 1.3-fold at 24 h (62.1±5.4 vs. 26.4±4.8% P<0.01).


Myofibrillogenesis regulator 1 induces hypertrophy by promoting sarcomere organization in neonatal rat cardiomyocytes.

Wang X, Liu X, Wang S, Luan K - Hypertens. Res. (2012)

Transfection with MR-1 causes rapid sarcomere organization in neonatal rat cardiomyocytes. (A) 1-d cultured cardiomyocytes were transfected or normally cultured for another 24 h, fixed and specifically labeled with phalloidin-FITC. The figure shows the ratio of well-organized cardiomyocytes when MR-1 was transfected in cardiomyocytes for 16–24 h. *P<0.01 vs. vector. (B) The ratio of polymerized actin to G-actin in MR-1-transfected cardiomyocytes at 16 h as measured by F/G-actin fractionation and then western blot analysis. *P<0.05 vs. vector. (C) RT-PCR and western blot analysis of mRNA and protein levels of myomesin-1 and MLC-2 normalized to that of glyceraldehyde phosphate dehydrogenase (GAPDH) at 16 h (a) and western blot results (b, c). *P<0.01 vs. vector. A full color version of this figure is available at the Hypertension Research journal online.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3368235&req=5

fig3: Transfection with MR-1 causes rapid sarcomere organization in neonatal rat cardiomyocytes. (A) 1-d cultured cardiomyocytes were transfected or normally cultured for another 24 h, fixed and specifically labeled with phalloidin-FITC. The figure shows the ratio of well-organized cardiomyocytes when MR-1 was transfected in cardiomyocytes for 16–24 h. *P<0.01 vs. vector. (B) The ratio of polymerized actin to G-actin in MR-1-transfected cardiomyocytes at 16 h as measured by F/G-actin fractionation and then western blot analysis. *P<0.05 vs. vector. (C) RT-PCR and western blot analysis of mRNA and protein levels of myomesin-1 and MLC-2 normalized to that of glyceraldehyde phosphate dehydrogenase (GAPDH) at 16 h (a) and western blot results (b, c). *P<0.01 vs. vector. A full color version of this figure is available at the Hypertension Research journal online.
Mentions: We previously found that MR-1 is involved in sarcomere organization; therefore, to determine whether MR-1 affects sarcomere organization, 1-day-cultured cardiomyocytes that were cultured or transfected for another 8–24 h were stained for polymerized actin by phalloidin-FITC and the ratios of myocytes containing well-organized sarcomeres were semi-quantified. The normal control displayed a stress fiber-like structure, which is similar to the vector control (Figure 3A). Transfection with MR-1 caused rapid sarcomere organization from 8 h. More than two-thirds of the cell area showed well-organized sarcomeres after MR-1 transfection as compared with the vector control. The ratio was increased by 0.6-fold at 8 h (34.5±5.5 vs. 21.6±7.6% in vector; P>0.05), 1.0-fold at 16 h (58.1±4.3 vs. 29.1±5.3% P<0.01) and 1.3-fold at 24 h (62.1±5.4 vs. 26.4±4.8% P<0.01).

Bottom Line: Hypertrophic hallmarks such as cell size and [(3)H]-leucine incorporation were significantly increased when MR-1 was transfected into cardiomyocytes for 48 h.Transfection with small ubiquitin-like modifier-1 (SUMO-1) mimicked the effect of MR-1 inducing translocation of myomesin-1.However, transfection with SUMO-1 in MR-1-silenced cardiomyocytes failed to induce translocation and sarcomere organization, even though SUMO-1 expression was at the same level.

View Article: PubMed Central - PubMed

Affiliation: Department of Pathophysiology, PLA General Hospital, Beijing, China.

ABSTRACT
Human myofibrillogenesis regulator 1, a novel 17-kDa protein, is closely involved in cardiac hypertrophy. We studied the molecular mechanism that links MR-1 to hypertrophic response. Hypertrophic hallmarks such as cell size and [(3)H]-leucine incorporation were significantly increased when MR-1 was transfected into cardiomyocytes for 48 h. However, sarcomere organization was promoted when MR-1 was transfected for 8 h. The finding that cardiac hypertrophy was induced long after increase of sarcomere organization indicates that the promoted sarcomere organization may be one of the crucial factors causing hypertrophy. Furthermore, when MR-1 was transfected into cardiomyocytes, the nuclear localization of myomesin-1 was shifted to the cytoplasm. Transfection with small ubiquitin-like modifier-1 (SUMO-1) mimicked the effect of MR-1 inducing translocation of myomesin-1. However, transfection with SUMO-1 in MR-1-silenced cardiomyocytes failed to induce translocation and sarcomere organization, even though SUMO-1 expression was at the same level. Overexpression of MR-1 may induce cardiomyocyte hypertrophy via myomesin-1-mediated sarcomere organization.

Show MeSH
Related in: MedlinePlus