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New Isoform of Cardiac Myosin Light Chain Kinase and the Role of Cardiac Myosin Phosphorylation in α1-Adrenoceptor Mediated Inotropic Response.

Taniguchi M, Okamoto R, Ito M, Goto I, Fujita S, Konishi K, Mizutani H, Dohi K, Hartshorne DJ, Itoh T - PLoS ONE (2015)

Bottom Line: The levels of MLC2v phosphorylation was significantly lower in C57BL/6N than in C57BL/6J.Phenylephrine had no effect on MLC2v phosphorylation in either strains but increased the twitch tension more potently in C57BL/6J than in C57BL/6N.There was a significant positive correlation between the phenylephrine-induced inotropic response and the levels of MLC2v phosphorylation within ranges of 15-30%.

View Article: PubMed Central - PubMed

Affiliation: Department of Cardiology and Nephrology, Mie University Graduate School of Medicine, Edobashi, Tsu 514-8507, Mie, Japan.

ABSTRACT

Background & aims: Cardiac myosin light chain kinase (cMLCK) plays an obligatory role in maintaining the phosphorylation levels of regulatory myosin light chain (MLC2), which is thought to be crucial for regulation of cardiac function. To test this hypothesis, the role played by ventricular MLC2 (MLC2v) phosphorylation was investigated in the phenylephrine-induced increase in twitch tension using the naturally-occurring mouse strain, C57BL/6N, in which cMLCK is down regulated.

Methods and results: By Western blot and nanoLC-MS/MS analysis, cMLCKs with molecular mass of 61-kDa (cMLCK-2) and/or 86-kDa were identified in mice heart. Among various mouse strains, C57BL/6N expressed cMLCK-2 alone and the closest relative strain C57BL/6J expressed both cMLCKs. The levels of MLC2v phosphorylation was significantly lower in C57BL/6N than in C57BL/6J. The papillary muscle twitch tension induced by electrical field stimulation was smaller in C57BL/6N than C57BL/6J. Phenylephrine had no effect on MLC2v phosphorylation in either strains but increased the twitch tension more potently in C57BL/6J than in C57BL/6N. Calyculin A increased papillary muscle MLC2v phosphorylation to a similar extent in both strains but increased the phenylephrine-induced inotropic response only in C57BL/6N. There was a significant positive correlation between the phenylephrine-induced inotropic response and the levels of MLC2v phosphorylation within ranges of 15-30%.

Conclusions: We identified a new isoform of cMLCK with a molecular mass of 61kDa(cMLCK-2) in mouse heart. In the C57BL/6N strain, only cMLCK-2 was expressed and the basal MLC2v phosphorylation levels and the phenylephrine-induced inotropic response were both smaller. We suggest that a lower phenylephrine-induced inotropic response may be caused by the lower basal MLC2v phosphorylation levels in this strain.

No MeSH data available.


Related in: MedlinePlus

Baseline indexes for isometric tension in papillary muscles from C57BL/6J and C57BL/6N.Tension parameters were measured after 60-minute equilibration period. (A) Representative tension recordings are shown. Electrical field stimulation was made to induce twitch tension in isolated papillary muscles. The tension (B) and the time to the peak (C) or the half relaxation (D) in C57BL/6J and C57BL/6N. *P<0.05, n = 9.
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pone.0141130.g004: Baseline indexes for isometric tension in papillary muscles from C57BL/6J and C57BL/6N.Tension parameters were measured after 60-minute equilibration period. (A) Representative tension recordings are shown. Electrical field stimulation was made to induce twitch tension in isolated papillary muscles. The tension (B) and the time to the peak (C) or the half relaxation (D) in C57BL/6J and C57BL/6N. *P<0.05, n = 9.

Mentions: Twitch tension was induced by electrical field stimulation in papillary muscle and the absolute tension was compared between C57BL/6J and C57BL/6N (Fig 4A). The twitch tension was significantly greater in C57BL/6J (1.29±0.06 mN/mm2) compared to C57BL/6N (1.00±0.11 mN/mm2, Fig 4B). The time required to peak tension was longer in C57BL/6N (118±2 msec) than in C57BL/6J (109±3 msec)(Fig 4C). Furthermore, the time required for the half relaxation was longer in C57BL/6N (83.2±1.5 msec) than in C57BL/6J (77.1±1.8 msec) (Fig 4D).


New Isoform of Cardiac Myosin Light Chain Kinase and the Role of Cardiac Myosin Phosphorylation in α1-Adrenoceptor Mediated Inotropic Response.

Taniguchi M, Okamoto R, Ito M, Goto I, Fujita S, Konishi K, Mizutani H, Dohi K, Hartshorne DJ, Itoh T - PLoS ONE (2015)

Baseline indexes for isometric tension in papillary muscles from C57BL/6J and C57BL/6N.Tension parameters were measured after 60-minute equilibration period. (A) Representative tension recordings are shown. Electrical field stimulation was made to induce twitch tension in isolated papillary muscles. The tension (B) and the time to the peak (C) or the half relaxation (D) in C57BL/6J and C57BL/6N. *P<0.05, n = 9.
© Copyright Policy
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4626101&req=5

pone.0141130.g004: Baseline indexes for isometric tension in papillary muscles from C57BL/6J and C57BL/6N.Tension parameters were measured after 60-minute equilibration period. (A) Representative tension recordings are shown. Electrical field stimulation was made to induce twitch tension in isolated papillary muscles. The tension (B) and the time to the peak (C) or the half relaxation (D) in C57BL/6J and C57BL/6N. *P<0.05, n = 9.
Mentions: Twitch tension was induced by electrical field stimulation in papillary muscle and the absolute tension was compared between C57BL/6J and C57BL/6N (Fig 4A). The twitch tension was significantly greater in C57BL/6J (1.29±0.06 mN/mm2) compared to C57BL/6N (1.00±0.11 mN/mm2, Fig 4B). The time required to peak tension was longer in C57BL/6N (118±2 msec) than in C57BL/6J (109±3 msec)(Fig 4C). Furthermore, the time required for the half relaxation was longer in C57BL/6N (83.2±1.5 msec) than in C57BL/6J (77.1±1.8 msec) (Fig 4D).

Bottom Line: The levels of MLC2v phosphorylation was significantly lower in C57BL/6N than in C57BL/6J.Phenylephrine had no effect on MLC2v phosphorylation in either strains but increased the twitch tension more potently in C57BL/6J than in C57BL/6N.There was a significant positive correlation between the phenylephrine-induced inotropic response and the levels of MLC2v phosphorylation within ranges of 15-30%.

View Article: PubMed Central - PubMed

Affiliation: Department of Cardiology and Nephrology, Mie University Graduate School of Medicine, Edobashi, Tsu 514-8507, Mie, Japan.

ABSTRACT

Background & aims: Cardiac myosin light chain kinase (cMLCK) plays an obligatory role in maintaining the phosphorylation levels of regulatory myosin light chain (MLC2), which is thought to be crucial for regulation of cardiac function. To test this hypothesis, the role played by ventricular MLC2 (MLC2v) phosphorylation was investigated in the phenylephrine-induced increase in twitch tension using the naturally-occurring mouse strain, C57BL/6N, in which cMLCK is down regulated.

Methods and results: By Western blot and nanoLC-MS/MS analysis, cMLCKs with molecular mass of 61-kDa (cMLCK-2) and/or 86-kDa were identified in mice heart. Among various mouse strains, C57BL/6N expressed cMLCK-2 alone and the closest relative strain C57BL/6J expressed both cMLCKs. The levels of MLC2v phosphorylation was significantly lower in C57BL/6N than in C57BL/6J. The papillary muscle twitch tension induced by electrical field stimulation was smaller in C57BL/6N than C57BL/6J. Phenylephrine had no effect on MLC2v phosphorylation in either strains but increased the twitch tension more potently in C57BL/6J than in C57BL/6N. Calyculin A increased papillary muscle MLC2v phosphorylation to a similar extent in both strains but increased the phenylephrine-induced inotropic response only in C57BL/6N. There was a significant positive correlation between the phenylephrine-induced inotropic response and the levels of MLC2v phosphorylation within ranges of 15-30%.

Conclusions: We identified a new isoform of cMLCK with a molecular mass of 61kDa(cMLCK-2) in mouse heart. In the C57BL/6N strain, only cMLCK-2 was expressed and the basal MLC2v phosphorylation levels and the phenylephrine-induced inotropic response were both smaller. We suggest that a lower phenylephrine-induced inotropic response may be caused by the lower basal MLC2v phosphorylation levels in this strain.

No MeSH data available.


Related in: MedlinePlus