Role Of Nitric Oxide And Reactive Oxygen Species In Excitation-contraction Coupling In Skeletal Muscle.
Funder
National Health and Medical Research Council
Funding Amount
$163,250.00
Summary
Excitation-contraction (E-C) coupling is a term used to broadly describe the sequence of cellular events that starts with an electrical signal at the surface membrane of a muscle cell and which then ultimately leads to muscle contraction. Although the overall sequence is known, there remain many gaps in our understanding of the mechanisms involved not only related to normal muscle function but to how this function may be impaired by excessive exercise and disease. Many cellular metabolites contr ....Excitation-contraction (E-C) coupling is a term used to broadly describe the sequence of cellular events that starts with an electrical signal at the surface membrane of a muscle cell and which then ultimately leads to muscle contraction. Although the overall sequence is known, there remain many gaps in our understanding of the mechanisms involved not only related to normal muscle function but to how this function may be impaired by excessive exercise and disease. Many cellular metabolites contribute towards the normal control of muscle contraction, while others contribute to its impairment. Reactive oxygen species (ROS), which includes nitric oxide (NO) and related molecules, are metabolic factors often referred to as cellular oxidants. They are thought to have an essential role in controlling normal muscle function. Paradoxically, they are also implicated in the impairment of muscle function associated with fatigue, disease and aging. How these molecules both control normal muscle activity and also contribute to impairment of such function remains unclear. Thus, the central aim of this project is to identify the mechanisms by which the cellular oxidants, NO and other ROS, both control normal E-C coupling in skeletal muscle fibres and how they contribute to muscle fatigue. Clearly, understanding how skeletal muscle normally contracts is essential in order to better understand how muscle function can become impaired with exercise, disease and age. The work from this study will provide insight into both normal muscle physiology and how muscles fatigue and ultimately provide new methodologies and drugs that may combat fatigue, disease and age related changes to muscle function.Read moreRead less
Regulation Of Calcium Release Channels (RyR2) In Healthy And Failing Hearts
Funder
National Health and Medical Research Council
Funding Amount
$337,632.00
Summary
In striated muscle, the sarcoplasmic reticulum (SR) is the calcium store from which calcium release through ryanodine receptors (RyR2) is the key determinate of muscle force. We will develop an understanding of the complex functional changes in RyR2 that underlie adaptation of the heart to physiological stress (exercise) and functional changes associated with mal-adaptation in heart failure.
Mechanisms Involved In Reduced Cardiac Contractility As A Consequence Of Growth Restriction During Fetal Development
Funder
National Health and Medical Research Council
Funding Amount
$317,810.00
Summary
Functional development of the heart muscle has been a focus of intense research over the last 40 years. Despite our current understanding of the changes in how excitation of the cardiomyocyte leads to contraction, a process broadly termed excitation-contrcation (E-C) coupling, a major model used to study paralells of human fetal development, the sheep, has not been examined in this context. As such, it remains unclear how E-C coupling evolves from the fetus to the adult. Understanding normal phy ....Functional development of the heart muscle has been a focus of intense research over the last 40 years. Despite our current understanding of the changes in how excitation of the cardiomyocyte leads to contraction, a process broadly termed excitation-contrcation (E-C) coupling, a major model used to study paralells of human fetal development, the sheep, has not been examined in this context. As such, it remains unclear how E-C coupling evolves from the fetus to the adult. Understanding normal physiology is imperative to subsequetly understand pathological states, such as interuterine growth restriction (IUGR). In Australia, the incidence of IUGR leading to low birth weight babies is 7%. IUGR is caused by maternal undernutrition, maternal smoking-drug use and placental insufficiency. It is associated with an increase in perinatal mortality, respiratory problems, SIDS and morbidity. Epidemiological studies show that low birth weight babies are also at an increased risk of cardiovascular disease, including heart failure, in adult life. To date, there is little information on the impact of fetal growth restriction on the normal development and function of the heart muscle. Understanding the impact of IUGR on heart muscle development will allow the elucidation of the underlying physiological mechanisms linking these two temporally distinct events. This mechanistic understanding will allow improved clinical management of those individuals at risk of cardiovascular disease in adult life arising from IUGR. It may also allow for early intervention strategies that can improve cardiovascular function. Therefore, we propose to examine both the normal developmental changes to E-C coupling so that we can understand how placental insufficiency leading to IUGR impairs normal heart muscle development. This will result in impaired function at a cellular level, which will ultimately manifest as an increased susceptibility of the heart to injury in later life.Read moreRead less
Regulatory Mechanisms And Roles Of Calpains In Skeletal Muscle
Funder
National Health and Medical Research Council
Funding Amount
$439,813.00
Summary
The objectives are to understand the regulation and roles of calpains, which are proteases that break proteins in the building and repair of skeletal muscle. We will determine targets that calpains cleave and whether their location changes following activation, as well as the cellular factors regulating their activity. In addition, we will obtain information about the specific type of calpain dysfunction that occurs in particular patients with limb girdle muscular dystrophy 2A.
Clinical trials and experimental investigations have demonstrated that a diet rich in fish oil, containing high levels of omega 3 fatty acids, provides protection against arrhythmias and sudden cardiac death associated with heart failure. Surprisingly little is known about how these dietary omega 3 lipids alter the electrical and mechanical function of cardiac muscle cells when incorporated into the membrane of these cells. The goal of this study is to examine how experimental omega 3 diet treat ....Clinical trials and experimental investigations have demonstrated that a diet rich in fish oil, containing high levels of omega 3 fatty acids, provides protection against arrhythmias and sudden cardiac death associated with heart failure. Surprisingly little is known about how these dietary omega 3 lipids alter the electrical and mechanical function of cardiac muscle cells when incorporated into the membrane of these cells. The goal of this study is to examine how experimental omega 3 diet treatment can modify the heart muscle cell structure and function. In particular we will determine which cellular mechanisms may be important in conferring selective benefit of dietary intervention on pre-failing heart function. For this study we will use mice which exhibit signs of heart failure induced by hormone overproduction (angiotensin II) and by elevation of blood pressure (by surgical constriction). Mice will be fed omega-3 and omega-6 diets and experiments to investigate cardiac muscle cell structure and function will be carried out using a variety of electrical recording, microscopic and molecular biology techniques. Diet-induced changes in the capacity of the heart cells to regulate calcium will be investigated using cells loaded with fluroescent indicators. Single cell electrical recording techniques (patch clamp) will also be used in combination with ECG measurement to evaluate how arrhythmic activity arising from electrically and mechanically unstable cells can be suppressed by omega-3 diet intervention. Finally we will take the first step towards validating the rodent experimental findings in a clinical setting with measurements of calcium transporters and channel expression in human specimens from cardiac surgery patients.Read moreRead less
STRUCTURAL AND FUNCTIONAL INTERACTIONS BETWEEN THE II-III LOOP OF THE SKELETAL DHPR AND THE RYANODINE RECEPTOR
Funder
National Health and Medical Research Council
Funding Amount
$410,250.00
Summary
The project has implications for neuromuscular diseases and for muscle weakness in general and in the elderly, all of which are significant health issues. The results will elucidate molecular mechanisms in muscle contraction and will provide a basis for drug design and treatment of muscle disorders. Respiration and locomotion depend on changes in calcium concentration inside muscle cells. Cardiovascular function, neuronal activity and immune responses also depend on the release of calcium from i ....The project has implications for neuromuscular diseases and for muscle weakness in general and in the elderly, all of which are significant health issues. The results will elucidate molecular mechanisms in muscle contraction and will provide a basis for drug design and treatment of muscle disorders. Respiration and locomotion depend on changes in calcium concentration inside muscle cells. Cardiovascular function, neuronal activity and immune responses also depend on the release of calcium from internal stores. Ryanodine receptor (RyR) calcium channels, either alone or in combination with a different internal calcium channel, regulate calcium release in each of these diverse functions. The essential nature of RyRs is underlined by death at or before birth when RyR expression is defective. Genetic defects in the RyR cause cardiac arrhythmias, malignant hyperthermia and central core disease. RyR function is compromised in heart failure and fatigue. The key role of RyRs makes them a potential therapeutic target, but they are not used as such because of the limited knowledge of the nature and structure of their regulatory sites. Electrical signals from the brain are able to release calcium from internal stores in muscle and initiate muscle contraction by virtue of a physical interaction between two calcium channel proteins, a surface membrane channel and the RyR. The molecular basis of this protein-protein interaction is is not understood and is a subject of this proposal. We will (a) solve the structure of one part of the surface channel that is known to contribute to the protein-protein interaction with the RyR, (b) determine the amino acid residues that interact with each other and (c) evaluate the functional consequences of the the binding of proteins. Understanding more about RyR regulation will pave the way for rational drug design and the eventual use of the RyR as a therapeutic target.Read moreRead less
Characteristics Of Splice Variants Of The Skeletal Muscle Ryanodine Receptor: Implications For Myotonic Dystrophy
Funder
National Health and Medical Research Council
Funding Amount
$258,000.00
Summary
The project is to address some of the basic molecular changes that occur in skeletal muscle during development and in myotonic dystrophy. Myotonic dystrophy is a significant health issue since it is the most common adult muscular dystrophy, with an occurrence of ~1 in 7000. The results will provide much needed information about the membrane-associated molecular mechanisms that regulate muscle contraction and may provide a basis for drug design and treatment of myotonic dystrophy. Respiration and ....The project is to address some of the basic molecular changes that occur in skeletal muscle during development and in myotonic dystrophy. Myotonic dystrophy is a significant health issue since it is the most common adult muscular dystrophy, with an occurrence of ~1 in 7000. The results will provide much needed information about the membrane-associated molecular mechanisms that regulate muscle contraction and may provide a basis for drug design and treatment of myotonic dystrophy. Respiration and locomotion depend on the release of calcium ions from stores inside muscle cells. Ryanodine receptor calcium channels regulate calcium release from the stores. The essential nature of ryanodine receptors is underlined by death at or before birth when ryanodine receptor expression is defective. In addition genetic defects in the ryanodine receptor cause cardiac arrhythmias, malignant hyperthermia and central core disease. Ryanodine receptor function is compromised in heart failure and fatigue. The essential role of ryanodine receptors makes them a potential therapeutic target, but they are not used in this way because of our limited knowledge of the protein. Myotonic dystrophy is an autosomal dominant multi-system disorder, in which an expansion of non-coding DNA leads to changes in expression of several different proteins. Although the genetic basis of myotonic dystrophy is now reasonably well understood, the contribution of molecular changes in the affected proteins to the myopathy has not been investigated. Our group has recently discovered that the juvenile form of the ryanodine receptor protein is highly expressed in adults suffering from myotonic dystrophy. By discovering more about the properties of the juvenile isoform, we will understand more about the basic mechanisms of ryanodine receptor function in developing muscle and in myotonic dystrophy and be able to design drugs to specifically modify ryanodine receptor activity.Read moreRead less
Communication Between Calcium Ion Channels In Skeletal Muscle Excitation-contraction Coupling
Funder
National Health and Medical Research Council
Funding Amount
$603,100.00
Summary
Ageing, injury, drugs or genetic defects cause muscle weakness, prevent exercise, compromise life style and contribute to poor health and osteoporosis. In order to move signals travel from our brain to muscles, where one calcium ion channel detects the signal and tells a second calcium channel to open and release calcium ions to initiate contraction. The project will pave the way for developing drugs to help with muscle disorders by trageting the site of interaction between the channels.
A Single Fibre Study Of The Relationship Between Glucose Transport And Skeletal Muscle Contractility
Funder
National Health and Medical Research Council
Funding Amount
$284,625.00
Summary
Type 2 diabetes (a progressive disorder often accompanied by obesity) is claimed to be the most common metabolic disease in the world and is predicted to affect 1.15 million Australians by the year 2010. Muscle contraction (in the form of physical exercise or exercise training) is now an essential component in the management of type 2 diabetes and-or obesity.This project has been planned from a perspective that combines theoretical and experimental expertise in the field of muscle cell contracti ....Type 2 diabetes (a progressive disorder often accompanied by obesity) is claimed to be the most common metabolic disease in the world and is predicted to affect 1.15 million Australians by the year 2010. Muscle contraction (in the form of physical exercise or exercise training) is now an essential component in the management of type 2 diabetes and-or obesity.This project has been planned from a perspective that combines theoretical and experimental expertise in the field of muscle cell contractility with a keen interest in the role of skeletal muscle in glucose homeostasis. Work carried out within the scope of this project will contribute new insights into the pathogenesis of type 2 diabetes-obesity and new information on the cellular mechanisms involved in contraction-stimulated glucose transport by skeletal muscle. As part of this project we will develop single muscle cell-fibre preparations and appropriate protocols for monitoring cellular aspects of glucose transport in skeletal muscle. These preparations-protocols will have the potential to be used for testing anti-diabetic drugs directed towards intracellular targets. From an educational benefit point of view, the project will create the opportunity for 4-6 honours and 2-3 PhD students to acquire a rare and useful combination of skills and expertise in muscle cell biochemistry and physiology, while working on an issue of medical concern.Read moreRead less