Determining The Cellular Mechanisms Involved In The Airway Response To Topical Citrate
Funder
National Health and Medical Research Council
Funding Amount
$444,491.00
Summary
The air passages of the lungs are lined by mucous membranes. These membranes are covered by a thin layer of fluid to protect the airways from drying. This fluid allows the cilia, the hair like projections on top of the airway cells to beat more effectively to remove mucous and inhaled particles from the lungs. The volume and composition of this fluid is determined by the salt and water movement across the mucous membranes of the airways. These processes are abnormal in cystic fibrosis (CF), the ....The air passages of the lungs are lined by mucous membranes. These membranes are covered by a thin layer of fluid to protect the airways from drying. This fluid allows the cilia, the hair like projections on top of the airway cells to beat more effectively to remove mucous and inhaled particles from the lungs. The volume and composition of this fluid is determined by the salt and water movement across the mucous membranes of the airways. These processes are abnormal in cystic fibrosis (CF), the most common lethal inherited disease affecting Australians. In CF, an abnormal gene disrupts one of the major mechanisms for salt and water movement in the air passages. This abnormal salt transport causes drying of the airway surface which impairs the working of the cilia. This leads to retention of mucous in the airways with repeated bacterial infections damaging the lungs. Over the last 10 years, we have developed a series of simple tests to measure the abnormalities in the CF airway of human subjects. We have isolated an exciting new clinical application for sodium citrate, a substance used in blood transfusions. Citrate appears to alter both the salt transport abnormalities found in CF. This research proposal seeks to better understand the dual effects of citrate and to test similar compounds that may have stronger effects. The ultimate aim of our research is to have sufficient knowledge to work out the best way to develop a new treatment for CF.Read moreRead less
Characterisation And Regulation Of Chloride Channels In Cardiac And Skeletal Sarcoplasmic Reticulum In Mammals
Funder
National Health and Medical Research Council
Funding Amount
$381,856.00
Summary
An understanding of the operation of ion channels in cell membranes is fundamental to our knowledge of the function of muscles under normal conditions and in pathological states that modify cell function, e.g. myotonia and cardiac failure. Ion channels control the flow of currents and the transport of substances which ultimately determine whether cells live or die, and hence whether cell pathologies are expressed as muscle failure, as when hypoxia causes tissue damage to the heart, or as severe ....An understanding of the operation of ion channels in cell membranes is fundamental to our knowledge of the function of muscles under normal conditions and in pathological states that modify cell function, e.g. myotonia and cardiac failure. Ion channels control the flow of currents and the transport of substances which ultimately determine whether cells live or die, and hence whether cell pathologies are expressed as muscle failure, as when hypoxia causes tissue damage to the heart, or as severe arrythmia or cardiac arrest. The objective is to understand channel involvement in the mechanisms underlying the function of cardiac and skeletal muscle. We believe that by mimicking the factors that occur in pathological conditions we can understand how ion channels are altered and controlled, and find ways of reversing harmful alterations, thereby reversing cell damage and failure of vital muscle function.Drugs will be used to modify the 'gating' of the channels. By comparing the effects of different drugs, we hope to determine the important features of the mechanisms that control the gating of the channels, making them more or less sensitive to different influences, especially those that occur in pathological states. The study has great application to the study of other pathologies, e.g. cystic fibrosis, severe diarrhoea, paralysis and chronic fatigue. The pharmacological emphasis offers the fundamental science needed to design novel and specific drugs to combat the many serious pathologies related to ion channel effects. Aside from its importance to basic science and to immediate issues of health, the study offers considerable economic gains, both through improved public health and through development of pharmaceuticals.Read moreRead less
The ClC-5 Cl- Channel, A Key Regulatory Role In Albumin Uptake By The Proximal Tubule
Funder
National Health and Medical Research Council
Funding Amount
$510,500.00
Summary
The clinical association between protein loss in the urine and retention of salt, resulting in high blood pressure and progressive decline in kidney function, is well known. Under normal conditions, the kidneys filter 180 litres of water and reabsorb 1.7 kg of salt per day, a function which is principally performed by the kidney tubules in the kidney. Similarly the kidney tubule cells reabsorb and break down up to 3 grams of albumin per day. In the past, it has been considered that excessive pro ....The clinical association between protein loss in the urine and retention of salt, resulting in high blood pressure and progressive decline in kidney function, is well known. Under normal conditions, the kidneys filter 180 litres of water and reabsorb 1.7 kg of salt per day, a function which is principally performed by the kidney tubules in the kidney. Similarly the kidney tubule cells reabsorb and break down up to 3 grams of albumin per day. In the past, it has been considered that excessive protein loss in the urine is primarily due to problems in the filtering units of the kidneys, rather than due to abnormalities in the reabsorption of protein in the kidney tubules. However, we consider that common abnormalities in the processes within the kidney tubules that regulate both the reabsorption of salt and the excretion of acid may result in concomitant high blood pressure and increased protein loss in the kidney. Thus the overall aim of the project is to investigate the mechanisms by which the complex responsible for protein uptake determines the interrelationship between protein reabsorption and catabolism and the ion transporting proteins in the membrane of the proximal tubule. This project will comprehensively characterise the mechanisms of protein uptake in kidney tubule cells. The exact nature of the interaction of the proteins involved in performing the salt reabsorption and ensuring correct catabolism of protein uptake with the actual protein uptake mechanism will be determined. As persistent proteinuria is the most important predictor of tubulointerstitial pathology and progressive decline in renal function in almost all renal disease, the understanding of the precise mechanism by which this occurs is essential in the design of renoprotective therapies.Read moreRead less
CBS Domain Modulation Of Muscle Chloride Channels; Molecular Mechanism And Physiological Role.
Funder
National Health and Medical Research Council
Funding Amount
$523,455.00
Summary
Muscle chloride channels regulate how readily muscles are activated, particularly during muscle fatigue. Recently we have identified a feed-back mechanism linking chloride channel function to muscle acidosis and energy depletion, key factors in fatigue. Here we will investigate the molecular details of this mechanism and its role in muscle physiology and fatigue. This mechanism may present a future target for the treatment of myotonia, a condition where muscles are too readily activated.
Probing The Control And Action Of CLIC1/NCC27, An Unusual Chloride Ion Channel, By X-ray Crystallography
Funder
National Health and Medical Research Council
Funding Amount
$271,320.00
Summary
Cells must regulate the flow of ions and water across their membranes in order to survive and function normally. The balance of ions and water is controlled by ion channels - proteins that control the permeability of the cell membrane. Of the ion channels, chloride channels are the most abundant in cells. They are central to the functioning of normal cells as well as playing a key role in many disease states. Our group was the first to identify and characterise a new class of chloride channel wh ....Cells must regulate the flow of ions and water across their membranes in order to survive and function normally. The balance of ions and water is controlled by ion channels - proteins that control the permeability of the cell membrane. Of the ion channels, chloride channels are the most abundant in cells. They are central to the functioning of normal cells as well as playing a key role in many disease states. Our group was the first to identify and characterise a new class of chloride channel which plays a key roles in the regulation of the immune system. These channels are unusual in that they can move between two states: a soluble state and a state that resides in the cell membrane. We have determined the first structure of this class of channel in the soluble state. In this project, we will determine: how the protein makes the transition into the membrane state; which factors control this transition; and the structure of the protein in the membrane state. We will also determine how several drugs control the activity of this channel. The results of our work will have specific implications for our channel and will serve as a paradigm for other members of this new class of chloride channel. Understanding how this channel functions and how the current drugs control it will lead to the development of a new class of therapeutic agents that will control these channels by preventing the transition from the soluble to the membrane state.Read moreRead less
Cells must regulate the flow of ions and water across their membranes in order to survive and function normally. The balance of ions and water is controlled by ion channels - proteins that control the permeability of the cell membrane. Of the ion channels, chloride channels are the most abundant in cells. They are central to the functioning of normal cells as well as playing a key role in many disease states. Our group was the first to identify and characterise a new class of chloride channel wh ....Cells must regulate the flow of ions and water across their membranes in order to survive and function normally. The balance of ions and water is controlled by ion channels - proteins that control the permeability of the cell membrane. Of the ion channels, chloride channels are the most abundant in cells. They are central to the functioning of normal cells as well as playing a key role in many disease states. Our group was the first to identify and characterise a new class of chloride channel which plays a key roles in the regulation of the immune system. These channels are unusual in that they can move between two states: a soluble state and a state that resides in the cell membrane. We have determined the first structures of this class of channel in both the soluble state and what is believed to be the membrane docking state. This has given us the first atomic picture of how this channel protein can alter its structure so as to carry out its function. In this project, we will determine: how the protein completes the transition into the membrane state; the structures of other key members of this class of channel protein; complexes between channel proteins and other cellular proteins; and the structure of the protein in the membrane state. We will also determine how several drugs control the activity of this channel. The results of our work will have specific implications for our channel and will serve as a paradigm other members of this new class of chloride channel. Understanding how this channel functions and how the current drugs control it will lead to the development of a new class of therapeutic agents that will control these channels by preventing the transition from the soluble to the membrane state.Read moreRead less
A Novel Ionic Current Contributing To Spasm Of Small Blood Vessels
Funder
National Health and Medical Research Council
Funding Amount
$287,500.00
Summary
Vascular smooth muscle can produce strong constrictions or spasms that can severely limit blood flow. Disorders arising from such spasms include sudden death, neurological deficits, visual and hearing loss or impairment, Raynaud's phenomenon (painful episodic contraction of the fingers and toes) and intestinal necrosis. Common mechanisms are likely to underlie the spasms associated with these disparate disorders. In a recent electrophysiological study of vascular smooth muscle, we discovered a n ....Vascular smooth muscle can produce strong constrictions or spasms that can severely limit blood flow. Disorders arising from such spasms include sudden death, neurological deficits, visual and hearing loss or impairment, Raynaud's phenomenon (painful episodic contraction of the fingers and toes) and intestinal necrosis. Common mechanisms are likely to underlie the spasms associated with these disparate disorders. In a recent electrophysiological study of vascular smooth muscle, we discovered a novel membrane current which we refer to as the plateau current. This current has a strong depolarizing influence that is likely to make a major contribution to the spasms, particularly in arterioles and small arteries which are more dependent on depolarization for contraction. Block of this current is expected to minimize the depolarization and therefore prevent or ameliorate spasm of the vessels. Thus the plateau current represents a new field of therapeutic potential for addressing vascular problems that have significant health implications. However, therapeutic manipulation of the current requires knowledge of its properties. In this project we will determine the biophysical and pharmacological properties of this current using voltage-clamp techniques. We will then use this information to assess its functional significance by recording membrane potential with intracellular microelectrodes simultaneously with contractile activity. We will also compare small vessels obtained from volunteers with or without the vasospastic disorder of Raynaud's phenomenon. Our previous work using these techniques was described in J Physiol as a microelectrode, patch clamp and myograph study of the highest quality and of supreme technical difficulty and scored a Top-Ten hit rate. Since we are the only ones to record the plateau current, we are in a unique position to make significant progress to our understanding of contraction, including spasm, in small blood vessels.Read moreRead less
Glutamate is one of the major neurotransmitters in the brain. It plays a very important role in most brain functions such as the ability to learn and the development of memory, but the lack of control of glutamate concentrations in the brain also underlies many pathological changes that cause neurological disorders such Alzheimer's disease, disability following a stroke, motor neurone disease and Parkinson's disease. These diseases place an enormous social and economic burden on society and in o ....Glutamate is one of the major neurotransmitters in the brain. It plays a very important role in most brain functions such as the ability to learn and the development of memory, but the lack of control of glutamate concentrations in the brain also underlies many pathological changes that cause neurological disorders such Alzheimer's disease, disability following a stroke, motor neurone disease and Parkinson's disease. These diseases place an enormous social and economic burden on society and in order to better understand and treat these diseases it is important to understand some of the fundamental biochemical processes that underlie both normal and pathogical functions of the key neurotransmitter glutamate. This project will investigate how the concentrations of glutamate are tightly regulated to maintain normal brain function and also to avoid the potentially pathological consequences when these control mechanisms fail.Read moreRead less