Related Experiment Video

Updated: Jun 18, 2026

Assessment of Myofilament Ca2+ Sensitivity Underlying Cardiac Excitation-contraction Coupling
08:29

Assessment of Myofilament Ca2+ Sensitivity Underlying Cardiac Excitation-contraction Coupling

Published on: August 1, 2016

Overexpression of myosin phosphatase reduces Ca(2+) sensitivity of contraction and impairs cardiac function

Hideo Mizutani1, Ryuji Okamoto, Nobuyuki Moriki

  • 1Department of Cardiology and Nephrology, Mie University Graduate School of Medicine, Japan.

Circulation Journal : Official Journal of the Japanese Circulation Society
|December 8, 2009
PubMed
Abstract

Insights

Myosin phosphatase target subunit 2 (MYPT2) acts as a cardiac myosin phosphatase (MP) regulatory subunit in vivo. MYPT2 overexpression reduces myosin light chain (MLC) phosphorylation, impairing cardiac function and causing heart enlargement.

Area of Science:

  • Cardiovascular Biology
  • Molecular Cardiology
  • Enzyme Regulation

Background:

  • Myosin light chain (MLC) phosphorylation is crucial for cardiac function.
  • Myosin phosphatase target subunit 2 (MYPT2) is a suspected regulatory subunit of cardiac myosin phosphatase (MP) in vitro.
  • In vivo evidence for MYPT2 function in the heart was lacking.

Purpose of the Study:

  • To investigate the in vivo function of MYPT2 in the heart.
  • To determine the role of MYPT2 in regulating cardiac myosin phosphatase (MP) activity.
  • To elucidate the impact of MYPT2 on cardiac contractility and function.

Main Methods:

  • Generation of transgenic (Tg) mice overexpressing MYPT2 using the alpha-MHC promoter.
  • Measurement of MYPT2 and PP1cdelta expression in Tg hearts.
  • Assessment of MLC phosphorylation levels.
  • Analysis of pCa-tension relationship in permeabilized cardiac fibers.
  • Evaluation of left ventricular (LV) function and structure.

Main Results:

  • Tg hearts exhibited increased MYPT2 and PP1cdelta expression, enhancing MP holoenzyme formation.
  • Ventricular MLC phosphorylation was significantly reduced in Tg hearts.
  • Decreased Ca(2+) sensitization of contraction and impaired LV contractility were observed.
  • LV enlargement and cardiomyocyte degeneration were evident in Tg hearts.

Conclusions:

  • MYPT2 functions as the regulatory subunit of cardiac MP in vivo.
  • Increased MYPT2 leads to decreased MLC phosphorylation, causing impaired cardiac contractility.
  • MYPT2 plays a critical role in modulating cardiac function and maintaining cardiac health.

More Related Videos

Assessment of Sarcoplasmic Reticulum Calcium Reserve and Intracellular Diastolic Calcium Removal in Isolated Ventricular Cardiomyocytes11:00

Assessment of Sarcoplasmic Reticulum Calcium Reserve and Intracellular Diastolic Calcium Removal in Isolated Ventricular Cardiomyocytes

Published on: September 18, 2017

Analysis of Cardiac Contractile Dysfunction and Ca2+ Transients in Rodent Myocytes07:32

Analysis of Cardiac Contractile Dysfunction and Ca2+ Transients in Rodent Myocytes

Published on: May 25, 2022

Related Concept Videos

Pathophysiology of Cardiac Performance01:29

Pathophysiology of Cardiac Performance

Typical heart performance is influenced by heart rate, rhythm, myocardial contraction, and metabolism or blood flow. The cardiac muscle exhibits distinct electrophysiological features, including pacemaker activity and calcium channel control, which play a vital role in the heart's response to various drugs. The autonomic nervous system, comprising the sympathetic and parasympathetic branches, regulates heart rate. Sympathetic activation increases heart rate, while parasympathetic activation...
Smooth Muscle Contraction01:25

Smooth Muscle Contraction

Smooth muscle contraction is a complex process vital for various bodily functions, from maintaining blood vessel tension to facilitating the movement of food through the digestive tract. Unlike striated muscles, smooth muscle contraction begins more slowly and lasts longer.
The onset of contraction is triggered by an increase in calcium ions within the sarcoplasm, similar to the process in striated muscle. However, smooth muscles have a relatively smaller reservoir of the sarcoplasmic...
Cross-bridge Cycle01:26

Cross-bridge Cycle

As muscle contracts, the overlap between the thin and thick filaments increases, decreasing the length of the sarcomere—the contractile unit of the muscle—using energy in the form of ATP. At the molecular level, this is a cyclic, multistep process that involves binding and hydrolysis of ATP, and movement of actin by myosin.
Imbalances in Cardiac Output01:26

Imbalances in Cardiac Output

The heart's primary function is to pump blood throughout the body, maintaining a balance between blood sent out (cardiac output) and blood returning (venous return). If this balance is disrupted, it can result in congestive heart failure (CHF), a severe condition where the heart becomes an inefficient pump, leading to inadequate blood circulation.
CHF can occur due to the failure of either side of the heart. Left-side failure leads to pulmonary congestion—the right side continues to send blood...
Specialized Characteristics of Cardiac Muscles01:27

Specialized Characteristics of Cardiac Muscles

The primary role of cardiac muscles is to propel blood throughout the cardiovascular system. The cardiac muscle cells, or cardiomyocytes, exhibit specialized characteristics that allow them to perform this function.
Cardiac muscle cells are smaller than skeletal muscles, averaging 10–20 mm in diameter and 50–100 mm in length. However, they have large energy demands for continuous contraction and relaxation. This energy is almost exclusively derived from aerobic metabolism of energy reserves in...
Heart Failure Drugs: Inotropic Agents01:26

Heart Failure Drugs: Inotropic Agents

Positive inotropic agents are commonly used as the first line of treatment for heart failure. One such agent is digoxin, derived from the genus Digitalis, which has been known for centuries but effectively utilized since 1785. However, these cardiac glycosides can have potentially toxic effects due to their mechanism of action, which involves inhibiting Na+/K+-ATPase and increasing contractility. Digoxin is absorbed orally and distributed in various tissues, including the CNS. It has a long...