The Molecular Basis Of Cytochrome P450 And UDP-glucuronosyltransferase Isoform Substrate Selectivity
Funder
National Health and Medical Research Council
Funding Amount
$448,500.00
Summary
Drugs and chemicals (e.g. dietary constituents, environmental pollutants and industrial chemicals) are broken down in the body by specific enzymes, a process referred to as metabolism. Drug and chemical metabolism serves as a detoxification mechanism (since the end products of metabolism generally lack biological activity) and as a means of eliminating these substances from the body. Enzymes are highly specialised proteins made up from amino acids as the building blocks. There are two enzymes in ....Drugs and chemicals (e.g. dietary constituents, environmental pollutants and industrial chemicals) are broken down in the body by specific enzymes, a process referred to as metabolism. Drug and chemical metabolism serves as a detoxification mechanism (since the end products of metabolism generally lack biological activity) and as a means of eliminating these substances from the body. Enzymes are highly specialised proteins made up from amino acids as the building blocks. There are two enzymes in humans primarily responsible for the metabolism of drugs and other chemicals; cytochrome P450 (CYP) and UDP-glucuronosyltransferase (UGT). Indeed, CYP and UGT are together responsible for the elimination of over 90% of metabolised drugs in humans. Both UGT and CYP exist as superfamilies of structurally related enzymes (called 'isoforms'). Approximately fifteen CYP isoforms are known to metabolise drugs, and a similar number of UGT isoforms also appear to have the capacity to metabolise drugs in humans. The separate CYP and UGT isoforms preferentially metabolise different types of drugs and chemicals, due to the fact each isoform comprises a different sequence of amino acids. However, which of the approximately 500 amino acids present in each UGT and CYP isoform that bind and metabolise specific drugs and chemicals is unknown. This project will identify the individual amino acids of several important CYP and UGT isoforms responsible for binding and metabolising drugs and other chemicals. A variety of techniques will be used, including modification of the amino acid sequence of the isoforms and computer modelling of their 'internal' structure. Elucidating the structural basis of how drugs and chemicals interact with CYP and UGT isoforms is fundamental to our understanding of these important enzymes and their function, and can be used to design drugs with better metabolic stability and decreased propensity for troublesome interactions with other drugs.Read moreRead less
Molecular Mechanisms Of Feed-forward Regulation Of Bile Acid Detoxification And Elimination In Cholestasis
Funder
National Health and Medical Research Council
Funding Amount
$334,500.00
Summary
Liver diseases in which there is obstruction to bile flow (cholestatic liver diseases) can lead to liver failure, liver cirrhosis as well as a diminished quality of life. Patients suffer from severe itching which may prove difficult to control. It is thought that may of these adverse effects of obstructed bile flow are due to the retention of a component or bile, called bile acids, within the body. Bile acids are detergent-like compounds formed from cholesterol. Some bile acids are highly toxic ....Liver diseases in which there is obstruction to bile flow (cholestatic liver diseases) can lead to liver failure, liver cirrhosis as well as a diminished quality of life. Patients suffer from severe itching which may prove difficult to control. It is thought that may of these adverse effects of obstructed bile flow are due to the retention of a component or bile, called bile acids, within the body. Bile acids are detergent-like compounds formed from cholesterol. Some bile acids are highly toxic and cause the death of cells within the liver if their concentration becomes too high. Evidence has emerged that the body has control mechanisms to try and combat rising levels of bile acids in cholestatic liver diseases. These control mechanisms are complex and include enzymes from the cytochrome P450 family as well as several specialized transport molecules. In cholestasis these mechanisms promote the removal of bile acids through the urine as well as converting very toxic bile acids to less toxic forms. The present projects builds on discoveries concerning the regulation of cytochrome P450 enzymes made by our group over the last few years, including an in-depth understanding of the way the production of CYP3As is increased by some drugs. We intend to determine in detail how defense mechanisms against toxic bile acids are engaged. In particular, we wish to identify the receptor molecules that 'sense' the rising levels of bile acids that occur in cholestatic liver diseases. An understanding of these issues will allow us to better manage patents with these diseases and develop new strategies for treating cholestatic disorders, for example, development of novel drugs that can influence bile acid detoxification in the liver and other organs.Read moreRead less
Phenotypic Characterization Of Chloroquine Resistance In Plasmodia
Funder
National Health and Medical Research Council
Funding Amount
$585,473.00
Summary
In the Asia-Pacific region, vivax malaria is becoming the dominant species of infection. The emergence and spread of chloroquine resistant strains of P. vivax threatens malaria control and elimination efforts. This project aims to elucidate fundamental aspects of chloroquine resistance in non-falciparum malaria and identify novel therapeutic options. We will develop novel tests that will help national malaria control programs to monitor declining activity of standard anti-malarial drugs.
Interaction Of New Kinase Inhibitor Drugs With Multi-drug Resistance (MDR) Transporter Proteins.
Funder
National Health and Medical Research Council
Funding Amount
$411,000.00
Summary
Multidrug transporter proteins are remarkable molecular pumps that expel a wide variety of drugs and toxins from cells. They are located at strategic sites where they eliminate harmful substances from the body or prevent them being absorbed from our diet in the first place. Multidrug transporters are also found at natural barriers within the body where they protect vulnerable tissue compartments, including the brain, cerebrospinal fluid, testes and, in preganant women, the foetus. Nevertheless, ....Multidrug transporter proteins are remarkable molecular pumps that expel a wide variety of drugs and toxins from cells. They are located at strategic sites where they eliminate harmful substances from the body or prevent them being absorbed from our diet in the first place. Multidrug transporters are also found at natural barriers within the body where they protect vulnerable tissue compartments, including the brain, cerebrospinal fluid, testes and, in preganant women, the foetus. Nevertheless, multidrug transporters sometimes interfere with drug therapy. They can prevent efficient absorption of drugs, increase the rate of drug elimination from the body, or prevent drug access to some tissues . Moreover, the activity of the transporters is quite variable, both between patients and within the same patient over time. This makes it difficult to provide optimal drug doses, particularly when treating cancer, where the drugs must be given at the maximum tolerated dose. The presence of drug transporter proteins in tumour cells can prevent entry of anticancer drugs, rendering them resistant to treatment. This is the main cause of failure in chemotherapy. This project will investigate a class of very promising new anticancer drugs, kinase inhibitors, to determine whether they are pumped by multidrug transporters, whether they alter the amounts of drug transporters in cells, and whether they alter transporter activity. We will also determine the consequences that follow from this for drug therapy. This information will help clinicians to rationally optimise therapy with the new drugs, to identify in advance both favourable (synergistic) and unfavourable (harmful) drug interactions in combination chemotherapy, to optimise drug doses and to minimise toxic side effects. The information will also add to our general understanding of drug absorption and elimination, and to the basic science of the remarkable multidrug transporter proteins.Read moreRead less