Mitochondrial Iron Overload And Friedreich's Ataxia: The Role Of Frataxin In Iron And Haem Metabolism
Funder
National Health and Medical Research Council
Funding Amount
$285,990.00
Summary
Friedreich's ataxia (FA) is due to the lack of a protein known as frataxin. Recent studies using Baker's yeast have shown that the deletion of frataxin results in the accumulation of toxic iron in the mitochondrion. More recently, a variety of studies have shown that FA patients have iron loading within their cells. The iron build-up may cause severe damage. At present, the role of frataxin in mammalian mitochondrial iron metabolism is unknown. Our preliminary studies demonstrate that frataxin i ....Friedreich's ataxia (FA) is due to the lack of a protein known as frataxin. Recent studies using Baker's yeast have shown that the deletion of frataxin results in the accumulation of toxic iron in the mitochondrion. More recently, a variety of studies have shown that FA patients have iron loading within their cells. The iron build-up may cause severe damage. At present, the role of frataxin in mammalian mitochondrial iron metabolism is unknown. Our preliminary studies demonstrate that frataxin is down-regulated by either erythroid differentiation or the haem precursor protoporphyrin IX (Becker and Richardson, submitted). These data strongly suggest a role for frataxin in iron metabolism. In the present study we will continue to assess if frataxin plays a role in the way cells handle iron. Using a unique model of mitochondrial iron overload developed in my lab (Richardson et al. (1996) BLOOD 87:3477), we will extensively investigate the iron metabolism of the mitochondrion in order to determine the function of frataxin and its role in Friedreich's ataxia. In addition, we have developed a series of new drugs known as iron chelators that can enter the mitochondrion due to their high lipid solubility (Becker and Richardson 1999 J. Lab. Clin. Med. 134:510). These latter drugs are far more effective than the chelator currently used to treat iron overload, desferrioxamine (DFO). Indeed, our chelators have been designed to result in high iron chelation efficacy but low toxicity (see Becker and Richardson, 1999). This exciting research may be crucial in understanding the development of FA and in creating new therapies such as the use of iron chelators.Read moreRead less
Mitochondrial Iron Overload And Friedreich's Ataxia: The Role Of Frataxin In Iron And Haem Metabolism
Funder
National Health and Medical Research Council
Funding Amount
$606,000.00
Summary
Friedreich's ataxia (FA) is due to the lack of a protein known as frataxin. A variety of studies using Baker's yeast and conditional frataxin knockout (KO) mice have shown that deletion of frataxin leads to the accumulation of toxic iron in their mitochondrion. More recently, a variety of studies have shown that FA patients have iron-loading within their mitochondrion. Iron in the highly redox active environment of the mitochondrion could contribute to the generation of cytotoxic radicals that c ....Friedreich's ataxia (FA) is due to the lack of a protein known as frataxin. A variety of studies using Baker's yeast and conditional frataxin knockout (KO) mice have shown that deletion of frataxin leads to the accumulation of toxic iron in their mitochondrion. More recently, a variety of studies have shown that FA patients have iron-loading within their mitochondrion. Iron in the highly redox active environment of the mitochondrion could contribute to the generation of cytotoxic radicals that cause severe damage. Further, cells deficient in frataxin are sensitive to oxidant stress and Fe chelators rescue oxidant-mediated death of cells from FA patients. Indeed, free radical scavengers have shown to be of use in the treatment of this disease. Studies in DR's lab during this NHMRC grant have shown that frataxin is down-regulated by erythroid differentiation or the haem precursor, protoporphyrin IX (BLOOD 2002;99:3813-22). These data indicate a role for frataxin in Fe metabolism and the pathogenesis of FA. In this study we will continue to examine the role of frataxin in the way cells handle Fe using experimental models developed under the current NHMRC grant. These include transfected cell lines with low frataxin expression generated using an expression vector containing anti-sense frataxin cDNA. Further we obtained the frataxin conditional KO mouse and generated a breeding colony. These animals display many of the pathological features of FA and are the best current model of the disease. Indeed, they will be critical for assessing the role of frataxin in Fe metabolism and as a model to test the ability of Fe-binding drugs to prevent the pathology observed. We designed lipid-soluble chelators that can enter the mitochondrion to bind Fe (Biochim Biophys Acta 2001;1536:133-140) and these ligands will be tested to prevent disease progression in the KO mice. This exciting research is crucial for understanding the pathogenesis of FA and in creating new therapies.Read moreRead less
Molecular Mechanisms Of Receptor Activation And Signalling
Funder
National Health and Medical Research Council
Funding Amount
$571,980.00
Summary
Fundamental to our ability to respond to both immediate and long-term environmental changes and stresses is the coordinated regulation of cellular functions by hormonal and neurotransmitter stimuli. The great majority of such stimuli are sensed by G-protein coupled receptors (GPCR), complex glycoprotein molecules on the surface of most cells that selectively bind and are activated by various hormones and neurotransmitters. Although GPCRs are a superfamily of proteins that now compromise several ....Fundamental to our ability to respond to both immediate and long-term environmental changes and stresses is the coordinated regulation of cellular functions by hormonal and neurotransmitter stimuli. The great majority of such stimuli are sensed by G-protein coupled receptors (GPCR), complex glycoprotein molecules on the surface of most cells that selectively bind and are activated by various hormones and neurotransmitters. Although GPCRs are a superfamily of proteins that now compromise several hundred distinct but structurally-related members, the molecular mechanisms involved in their activation and, thus, their regulation of vital cellular functions, remains unclear. Based on insights that we have gained from the development and characterisation of several alpha1-adrenergic receptor mutants, we have developed a model of receptor activation. In this application we are proposing to further test and to extend the hypotheses underlying this model. Importantly, the functions regulated by GPCR include vital responses, such as the maintenance of circulatory homeostasis by augmenting heart pump function and by constricting vascular smooth muscle to maintain blood pressure. In addition, disordered cellular regulation by GPCR has been implicated in a wide variety of diseases, including hypertension, congestive heart failure and cardiac hypertrophy. Thus, the studies detailed here to further understand the molecular mechanisms of receptor activation have broad implications for our knowledge of critical physiological control systems, and may lead to novel therapeutic approaches to treat a variety of diseases.Read moreRead less
A NOVEL MOUSE MODEL TO INVESTIGATE THE MECHANISMS OF VIRUS-INDUCED ARTHRITIS
Funder
National Health and Medical Research Council
Funding Amount
$336,000.00
Summary
We have developed a novel animal model by which to study arthritic disease caused by insect-transmitted viruses known as arboviruses. The existence of this model and novel reagents provides an excellent opportunity to further explore the basic mechanisms of infectious disease in a complete functioning animal, rather than specific cultured cells. The study will use modern approaches in molecular and cellular biology to achieve this goal. The production by our immune systems of soluble mediators ( ....We have developed a novel animal model by which to study arthritic disease caused by insect-transmitted viruses known as arboviruses. The existence of this model and novel reagents provides an excellent opportunity to further explore the basic mechanisms of infectious disease in a complete functioning animal, rather than specific cultured cells. The study will use modern approaches in molecular and cellular biology to achieve this goal. The production by our immune systems of soluble mediators (cytokines-chemokines) and antibodies is an overwhelming positive aspect of our physiological response to infection by microbes. Protection from disease by these immune compounds can happen naturally, or the body's ability to produce these factors can be exploited to our benefit via the administration of vaccines. However, these factors can also be detrimental to the host contributing to severe disease. For instance, work performed almost 40 years ago showed for the first time that under particular conditions, antibodies against viruses can enhance infection, instead of inhibiting infection as normally seen. In the intervening years work by scientists all over the world has associated antibody-dependent enhancement (ADE) of infection to many types of viruses; ADE is even thought to be a risk factor to serious disease with dengue virus, and has been shown in vitro for the AIDS virus and Ebola virus. We have recently discovered a molecular mechanism which explains how antibody enhances viral infection in vitro. In studies on immune cells infected with Ross River Virus (RRV) we found that infection helped by antibody resulted in the specific disruption to the production of cellular chemicals which are toxic to viruses. Are these mechanisms of antibody-enhanced infection also found in animals? Will such mode of infection cause enhanced disease and tissue pathology (arthritis) in animals?Read moreRead less
Development Of Iron Chelators For The Treatment Of Friedreichs Ataxia And The Role Of Frataxin In Iron Metabolism
Funder
National Health and Medical Research Council
Funding Amount
$550,987.00
Summary
Friedreich's ataxia (FA) is a neuro- and cardio-degenerative disease where there is an accumulation of toxic Fe in the mitochondrion. Excitingly, work from our current NHMRC grant showed iron plays a significant role in FA pathology. Importantly, we developed new drugs (Fe chelators) which rescue the cardiac pathology of FA in an animal model. Studies will now assess if our drugs prevent the neurodegeneration of FA in another animal model. This work could lead to novel therapies for FA.
GENETIC PREDICTION OF FRACTURE IN A RISK-STRATIFIED POPULATION
Funder
National Health and Medical Research Council
Funding Amount
$363,000.00
Summary
Osteoporosis is a condition characterised by excessive bone loss and impaired bone quality, which ultimately results in fracture with minimal trauma. Osteoporosis affects 27% of women and 11% of men aged 60 years or above in the community, and costs Australia around $7 billion each year. Individuals with low bone mineral density (BMD) have a significantly higher risk of fracture than those with normal BMD. In the long-term (14-year) Dubbo Osteoporosis Epidemiology Study, more than half of indivi ....Osteoporosis is a condition characterised by excessive bone loss and impaired bone quality, which ultimately results in fracture with minimal trauma. Osteoporosis affects 27% of women and 11% of men aged 60 years or above in the community, and costs Australia around $7 billion each year. Individuals with low bone mineral density (BMD) have a significantly higher risk of fracture than those with normal BMD. In the long-term (14-year) Dubbo Osteoporosis Epidemiology Study, more than half of individuals with osteoporosis (e.g., low BMD) did not sustain a fracture, while approximately 60% of fracture cases had BMD above the high risk levels. Thus, BMD alone is not a good discriminant of fracture versus non-fracture cases. It is widely known that the liability to fracture is determined in part by genes. Previous studies, including from our group, have suggested a number of candidate genes that are associated with fracture risk. The fundamental issue that this study is concerned is that how and whether genetic markers could be used to facilitate case finding. It is proposed that common variations of certain genes are associated with fracture risk independent of BMD. That is, they can identify individuals at relatively high and low fracture risk after stratification for BMD. Hence, some markers may identify those individuals likely (and unlikely) to fracture even with low (osteoporotic) BMD. Similarly, some, possibly the same, markers may identify individuals at high risk of fracture despite relatively good (ie non-osteoporotic) BMD. It is further proposed that no single gene will achieve this outcome, but rather a small set of such gene polymorphisms will provide clinically useful risk information. This effect is entirely analogous to the use of clinical risk indicators (eg, age, weight, sex, family history, etc) to assess the risk of future fracture.Read moreRead less
Targeting PI3K-regulated MicroRNAs To Treat Heart Failure
Funder
National Health and Medical Research Council
Funding Amount
$532,593.00
Summary
Current therapeutics largely delay heart failure progression rather than regressing it. New therapeutic strategies with the capability of improving function of the failing heart are thus greatly needed. The primary goal of this study is to determine whether novel regulatory genes can enhance cardiac function in a setting of heart failure. Ultimately, technologies that target these genes may lead to innovative pharmacotherapies in the clinical management of heart failure.
The Nutritional Geometry Of Ageing In A Rodent Model
Funder
National Health and Medical Research Council
Funding Amount
$979,269.00
Summary
A central belief in ageing research is that eating fewer calories prolongs life, and that the source of calories (carbohydrate, fat or protein) is irrelevant. However, a critical assessment indicates that this conclusion is premature. We will use recent techniques in nutrition to define for the first time in mammals the relationship between diet and ageing in a normal and a prematurely ageing strain of mice. The project will provide a novel nutritional approach for promoting healthy ageing.
Mechanisms Of Proteolysis Of Proteins Containing Oxidised Amino Acids
Funder
National Health and Medical Research Council
Funding Amount
$406,320.00
Summary
There is evidence that during ageing, and age-related diseases, proteins which have been chemically modified by oxidation accumulate in the body, and may have deleterious effects. Oxidation of proteins is a process akin to that by which fats go rancid. It has been demonstrated by the applicants to be an important process in formation of cataracts, and in development of the blood vessel disease, atherosclerosis, which is responsible for most heart attacks and stroke. Other important age-related d ....There is evidence that during ageing, and age-related diseases, proteins which have been chemically modified by oxidation accumulate in the body, and may have deleterious effects. Oxidation of proteins is a process akin to that by which fats go rancid. It has been demonstrated by the applicants to be an important process in formation of cataracts, and in development of the blood vessel disease, atherosclerosis, which is responsible for most heart attacks and stroke. Other important age-related diseases, such as Alzheimer s disease and other neurological disorders, are also claimed to be associated with deranged protein oxidation, and accumulation of oxidised products. There is clear evidence that certain defensive mechanisms, such as those acting to remove invading organisms and clear wounds, are also associated with an enhanced production of oxidised proteins. Perhaps the most important component of defense against oxidised proteins is their removal by complete breakdown to constituent components, and excretion. Normally, the machinery for breakdown of proteins is in vast excess over the required rate of degradation. However, clearly in these conditions of accumulation of oxidised proteins, this is no longer the case, or no longer suffices. Mechanisms by which oxidised proteins are degraded are poorly understood, and quite controversial. Therefore, the present studies bring to bear a new approach to studying this issue, which has been developed by the applicants. The aim is to reveal mechanisms involved in the breakdown of proteins containing oxidised amino acids, both in cellular systems, and in vivo. Such an understanding may allow us to envisage how to remove oxidised proteins by therapeutic means and therefore interfere with the development of age-related diseases such as Alzheimer s disease and cataract formation and the diseases of the blood vessels associated with attack and stroke.Read moreRead less