The body tightly controls when and where proteins are made. Likewise once a protein has performed its function, it must be removed. Targeted proteolysis serves to reset the cell so that it can respond anew to stimuli that trigger growth and cell development. The Siah proteins are a family of proteins that control the turnover of other proteins. Siah proteins are remarkably highly conserved in evolution, and counterparts of the human proteins can be found in fruitflies, worms and plants. There ar ....The body tightly controls when and where proteins are made. Likewise once a protein has performed its function, it must be removed. Targeted proteolysis serves to reset the cell so that it can respond anew to stimuli that trigger growth and cell development. The Siah proteins are a family of proteins that control the turnover of other proteins. Siah proteins are remarkably highly conserved in evolution, and counterparts of the human proteins can be found in fruitflies, worms and plants. There are three different types of Siah protein in mice and this study investigates the function of the each protein by creating mice that lack one or more of these proteins. Our work to date has revealed that the Siah genes are involved in growth and fertility of mammals. The genes are also important for cell division, which implicates them in proliferative diseases such as cancer.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
Understanding how the brain grows and is organised is one of the great challenges of science. This project seeks to identify key regulators of neural progenitors as these are the building blocks from which all brains cells are derived. This knowledge may also identify new avenues through which to manipulate neural progenitor function. This has implications not only for normal brain development but also potential therapies for neural disorders and disease.
The Role Of Cbl Proteins In Mast Cell Signalling And Function.
Funder
National Health and Medical Research Council
Funding Amount
$239,250.00
Summary
Allergies such as asthma are caused by cells known as mast cells and basophils. These cells cause allergies because they possess pre-formed granules that contain mediators of allergic reactions, such as histamine, which are released when the cells are activated by allergens. Understanding how this activation occurs, and the biochemical mechanisms that allow the release of allergic mediators, are important steps towards identifying ways to intervene and control allergic responses. The key event t ....Allergies such as asthma are caused by cells known as mast cells and basophils. These cells cause allergies because they possess pre-formed granules that contain mediators of allergic reactions, such as histamine, which are released when the cells are activated by allergens. Understanding how this activation occurs, and the biochemical mechanisms that allow the release of allergic mediators, are important steps towards identifying ways to intervene and control allergic responses. The key event that activates the release of allergic mediators is the binding of environmental allergens to a particular type of antibody called IgE that can bind to a specific receptor on the surface of mast cells and basophils. These IgE-bound receptors transmit strong biochemical signals into the cell which causes a cascade of events resulting in many proteins being biochemically modified and recruited to sites of functional activity. One group of proteins, known as tyrosine kinases, are at the front line of this cascade and they function by targeting and modifying a wide range of other proteins so they become functionally active. Indeed if it were not for tyrosine kinases there would be no signal leading to degranulation of mast cells and basophils and therefore no allergic reactions. Therefore if it were possible to regulate the activity of tyrosine kinases we would be able to control the severity of allergic reactions. For many years we have been studying a protein called Cbl that functions in cells to negatively regulate many tyrosine kinases, including those present in mast cells and basophils. In this grant we aim to investigate whether by deregulating Cbl function in mast cells, derived from mice with mutated forms of Cbl, we can change the activity of tyrosine kinases and thus alter the magnitude of allergic responses. This will determine whether Cbl is candidate target protein for controlling allergies.Read moreRead less
Developing Novel Molecules To Down-Regulate Src Family Tyrosine Kinases
Funder
National Health and Medical Research Council
Funding Amount
$201,261.00
Summary
Leukaemia and cancer cells have altered biochemical properties resulting in their high rate of growth compared to normal cells. One of the common biochemical characteristics of cancer-leukaemia cells is augmented activity levels of enzymes called tyrosine kinases. A major group of tyrosine kinase involved in several cancer-leukaemia types is called the Src family of tyrosine kinases. One member of this family called Lyn has been our focus of study for several years, investigating the signalling ....Leukaemia and cancer cells have altered biochemical properties resulting in their high rate of growth compared to normal cells. One of the common biochemical characteristics of cancer-leukaemia cells is augmented activity levels of enzymes called tyrosine kinases. A major group of tyrosine kinase involved in several cancer-leukaemia types is called the Src family of tyrosine kinases. One member of this family called Lyn has been our focus of study for several years, investigating the signalling pathways that it is involved in. This molecule has also been implicated in several specific leukaemia (Chronic Myeloid Leukaemia and Acute Myeloid Leukaemia) as well as cancer (Prostate, Colon, Breast) in recent years. We have identified a novel mechanism of down-regulation of this enzyme mediated by an adapter molecule called Cbp, which recruits the Lyn inactivating molecules Csk-Ctk as well as SOCS-1; together they inhibit the activity of Lyn and degrade the enzyme. Using our knowledge of the essential interaction elements of Cbp we will design and test various mini-Cbp molecules for their ability to inactivate and degrade Lyn in leukemic and cancer cells. These molecules may allow us to develop novel therapeutics capable of inactivating-degrading specific tyrosine kinases in cancer and leukaemia.Read moreRead less
Structural Determinants Of Siah Ubiquitin Ligase Complexes
Funder
National Health and Medical Research Council
Funding Amount
$267,750.00
Summary
Controlled degradation of cellular proteins is an important process. The turnover of proteins is a fine balance between protein expression and degradation and alterations can control many cellular processes such as mitosis and intracellular signaling. Whilst a lot of research has been directed at understanding protein expression in response to stimuli such as hormones, stress etc. little has been known about the mechanisms for targeting protein degradation. In recent years it has been shown that ....Controlled degradation of cellular proteins is an important process. The turnover of proteins is a fine balance between protein expression and degradation and alterations can control many cellular processes such as mitosis and intracellular signaling. Whilst a lot of research has been directed at understanding protein expression in response to stimuli such as hormones, stress etc. little has been known about the mechanisms for targeting protein degradation. In recent years it has been shown that proteins can be modified by the addition of a signaling protein called ubiquitin, and it is this modified form that is recognised for degradation. The degradation of these proteins occurs within a large protein complex called the proteasome, which recognizes the ubiquitinated protein substrates. The ubiquitination of proteins is a multistep process, the final step of which is catalyzed by a ubiquitin ligase, or E3 enzyme. It is the E3 which is able to recognize the protein to be degraded, and catalyze the transfer of ubiquitin onto that protein. The E3 proteins (or sometimes complexes) are a diverse group which have to recognize many different proteins, in order that they be degraded at appropriate times. We have been working on the protein Siah (seven in absentia homologue), a member of an E3 complex and important in controlled cell death, cell division and inflammatory responses. One part of the Siah protein is involved in binding proteins and targeting them for ubiquitination, though it is not known how Siah recognizes its targets. Using protein crystallography we have solved the 3D structure of this part of Siah and now propose to co-crystallize Siah with target proteins and binding partners so as to understand how Siah recognizes these proteins. Understanding the basis of these interactions will allow us to determine other potential targets for the Siah protein and also how we may be able to interfere with these interactions with therapeutic drugs.Read moreRead less
Characterisation Of Putative Targets Of The Ubiquitin-protein Ligase, Nedd4
Funder
National Health and Medical Research Council
Funding Amount
$258,055.00
Summary
Cellular proteins are synthesised and degraded depending on the metabolic state of the cell. The normal turnover of a number of cellular proteins is mediated by a complex pathway involving a highly conserved polypeptide called ubiquitin. Ubiquitin-dependent proteolysis of a number of proteins is essential for the maintenance of the health of a cell. Many cell cycle proteins, membrane channels, receptors and products of some oncogenes are known targets of the ubiquitin-dependent turnover. Clearly ....Cellular proteins are synthesised and degraded depending on the metabolic state of the cell. The normal turnover of a number of cellular proteins is mediated by a complex pathway involving a highly conserved polypeptide called ubiquitin. Ubiquitin-dependent proteolysis of a number of proteins is essential for the maintenance of the health of a cell. Many cell cycle proteins, membrane channels, receptors and products of some oncogenes are known targets of the ubiquitin-dependent turnover. Clearly, a defect in this tightly regulated mechanism for the downregulation of proteins can result in a pathological condition and therefore it is important to understand how this pathway is regulated at molecular level. In the multistep ubiquitin pathway, some component enzymes called E3 are required for specifying the targets to be degraded. We discovered one such enzyme Nedd4. One of the proteins regulated by Nedd4 is epithelial sodium channel (ENaC). Loss of Nedd4-mediated regulation of ENaC results in Liddle's Syndrome, a genetic form of hypertension. Since Nedd4 is expressed in many tissues and during development, we predicted that Nedd4 may regulate other important proteins in addition to ENaC. We have recently identified several proteins which interact with Nedd4. Some of these proteins are likely to play important roles in cellular regulation and during development. The proposed project is designed to characterise these proteins. We believe that by studying these proteins we will learn a great deal about the cellular regulatory pathways. In summary, Nedd4 is an important protein involved in cellular regulation and has a proven role in human disease. A study of characterising targets of Nedd4 will be vital in understanding the molecular basis of cell regulation and its implication in disease.Read moreRead less
The Role Of C-Cbl In The Regulation Of T Cell Signalling And Development
Funder
National Health and Medical Research Council
Funding Amount
$527,250.00
Summary
c-Cbl is a member of a multi-adaptor protein family that can interact with many signalling proteins via its different domains. Cbl proteins have been implicated as negative regulators of signalling pathways involving protein tyrosine kinases (PTKs). PTKs are enzymes which add phosphate groups to tyrosine residues on other protein substrates, and the process of tyrosine phosphorylation acts as a potent biochemical switch to turn signalling cascades on and off. Studies of Cbl-deficient (knockout) ....c-Cbl is a member of a multi-adaptor protein family that can interact with many signalling proteins via its different domains. Cbl proteins have been implicated as negative regulators of signalling pathways involving protein tyrosine kinases (PTKs). PTKs are enzymes which add phosphate groups to tyrosine residues on other protein substrates, and the process of tyrosine phosphorylation acts as a potent biochemical switch to turn signalling cascades on and off. Studies of Cbl-deficient (knockout) mice show that Cbl proteins are important in regulating the development of, and signalling by, cells of the immune system called T cells. c-Cbl knockout mice show greatly enhanced PTK-signalling responses and deregulated activity of a PTK called ZAP-70. The mechanism of this is not known, but analysis of a c-Cbl mutant mouse shows that this is not dependent on the tyrosine kinase binding (TKB) domain of c-Cbl. Therefore other functional domains of Cbl must be responsible for the increased signalling response in the c-Cbl knockout mouse. One candidate is the highly conserved RING finger domain which can modify Cbl-associated PTKs by addition of ubiquitin molecules. Ubiquitination of a protein often, but not always, leads to its degradation, and this could be how Cbl controls the strength and duration of signalling in T cells. However there may be other functions of the conserved RING finger yet to be identified. c-Cbl itself is prominently and very rapidly modified by tyrosine phosphorylation on tyrosine 737 by the Fyn PTK following T cell activation, but the role of this modification is not known and could also be essential for c-Cbl s function in T cells. We plan to investigate the roles of the RING finger domain and Fyn-mediated tyrosine phosphorylation in c-Cbl regulation of T cell signalling by analyzing knock-in mice that carry specific mutations disrupting the RING finger or tyrosine 737 in the c-Cbl gene.Read moreRead less
Regulation Of The Nedd4 Family Of Ubiquitin Ligases By Adaptor And Accessory Proteins In Normal Physiology And In Disease
Funder
National Health and Medical Research Council
Funding Amount
$609,424.00
Summary
In part this proposal is to understand how the body controls iron uptake through iron transporters DMT1 and Nramp1. We will study the regulation of these transporters by proteins called Ndfip1, Ndfip2 and arrestins. We will also study the functions of these proteins in controlling ubiquitination, a fundamental process required for cellular homeostasis. The results from this study may ultimately contribute to the development of novel therapies for certain human diseases.