How Does The Mitochondria Regulate Cardiac L-type Ca2+ Channel Function?
Funder
National Health and Medical Research Council
Funding Amount
$328,267.00
Summary
Oxygen is vital to cellular metabolism and function. Oxygen delivery to cells is critical and a lack of oxygen such as occurs during a heart attack can be lethal. The L-type Ca2+ channel is a protein in the membrane of heart muscle cells responsible for regulating the entry of calcium into heart muscle cells. It plays a role in maintaining the heart beat and contraction. We have found that a lack of oxygen (hypoxia) alters the function of the L-type Ca2+ channel and its response to adrenergic st ....Oxygen is vital to cellular metabolism and function. Oxygen delivery to cells is critical and a lack of oxygen such as occurs during a heart attack can be lethal. The L-type Ca2+ channel is a protein in the membrane of heart muscle cells responsible for regulating the entry of calcium into heart muscle cells. It plays a role in maintaining the heart beat and contraction. We have found that a lack of oxygen (hypoxia) alters the function of the L-type Ca2+ channel and its response to adrenergic stimulation (adrenaline).This may be one of the ways that rhythm disturbances or sudden cardiac death occurs with a heart attack. The activity of the L-type Ca2+ channel is sensitive to changes in reactive oxygen species caused by changes in oxygen concentration. The reactive oxygen species are generated from a part of the cell responsible for maintaining the cell's energy requirements (the mitochondria). Oxidative stress is a feature of various cardiovascular pathologies and we are now interested in determining the effect of oxidative stress on function of the L-type Ca2+ channel and the role of the mitochondria in generating reactive oxygen species. Oxidative stress can damage mitochondria leading to an increase in production of reactive oxygen species. We will determine how oxidative stress damages the mitochondria and how this then alters the channel function, directly or indirectly. The information gained will provide insight into how reactive oxygen species influence L-type Ca2+ channel function and the mechanisms that contribute to pathology involving reactive oxygen species such as heart failure and arrhythmia.Read moreRead less
L-amino Acid Sensing By The Extracellular Calcium-sensing Receptor: Molecular, Cellular And In Vivo Studies
Funder
National Health and Medical Research Council
Funding Amount
$362,545.00
Summary
Recent work by Dr Conigrave and colleagues demonstrates for the first time that protein and calcium metabolism are linked at the molecular level by the widely distributed calcium-sensing receptor. The project will aim to demonstrate the physiological significance of this finding by testing whether L-amino acids, the building blocks of body protein, exert receptor-dependent control over the secretion and blood levels of hormones that regulate body calcium levels. It will further test the hypothes ....Recent work by Dr Conigrave and colleagues demonstrates for the first time that protein and calcium metabolism are linked at the molecular level by the widely distributed calcium-sensing receptor. The project will aim to demonstrate the physiological significance of this finding by testing whether L-amino acids, the building blocks of body protein, exert receptor-dependent control over the secretion and blood levels of hormones that regulate body calcium levels. It will further test the hypothesis by determining whether amino acids exert receptor-dependent control over the proliferation of bone forming cells and urinary excretion of calcium.Read moreRead less
The Effect Of Ischaemia And Reperfusion On Sarcoplasmic Reticulum Calcium Handling In The Heart
Funder
National Health and Medical Research Council
Funding Amount
$236,208.00
Summary
Ischaemic heart disease is one of the most common causes of premature death in our society. Ischaemia occurs when the blood flow to the heart is obstructed so that oxygen cannot get to the muscle cells and metabolic waste products cannot be washed away. During ischaemia the concentration of free calcium within a cardiac muscle cell increases, and when blood flow is returned to the muscle this calcium concentration can increase further to very high levels. It is this change in calcium that is res ....Ischaemic heart disease is one of the most common causes of premature death in our society. Ischaemia occurs when the blood flow to the heart is obstructed so that oxygen cannot get to the muscle cells and metabolic waste products cannot be washed away. During ischaemia the concentration of free calcium within a cardiac muscle cell increases, and when blood flow is returned to the muscle this calcium concentration can increase further to very high levels. It is this change in calcium that is responsible for the reduced muscle force and abnormal cardiac rhythm that are the main cause of death. Cardiac muscle cells contain an intracellular compartment called the sarcoplasmic reticulum (SR). Under normal conditions the SR stores large amounts of calcium in order to maintain a low concentration of calcium free within the cell. However, even in a resting cell, calcium can escape from the SR through channels in SR membrane. We are using a state-of-the-art microscope to visualize these tiny packets of calcium, termed calcium sparks, as they travel through the SR membrane. If the number of calcium sparks increases, the amount of calcium being released from the SR also increases. We are studying what happens to calcium sparks, and therefore SR calcium release, during ischaemic heart disease. We are also examining the effect of ischaemic heart disease on the concentration of calcium within the SR and the activity of the transporters that pump calcium back into the SR. We hope to show that a change in the way the SR regulates calcium contributes to ischaemic damage. Understanding how changes in SR function alter muscle force and cardiac rhythm will help in the development of drugs to protect against ischaemic damage.Read moreRead less