The Role Of The Gastric H/K ATPase In Parietal Cell Function
Funder
National Health and Medical Research Council
Funding Amount
$166,885.00
Summary
The cells of the body contain many specialised membrane structures. At present it is not clear how the synthesis of these stuctures is directed. To study this problem we are examining the acid secretory parietal cells of the stomach. These cells have a very elaborate membrane system that contains a major proton pump protein. By manipulating the levels and form of the proton pump we will gain novel insights into the mechanism of membrane structure and function.
The Role Of The Glutamine Transporter SNAT3 In Ion Transport, Cell Signaling And Ammonia Detoxification
Funder
National Health and Medical Research Council
Funding Amount
$393,249.00
Summary
Hepatic encephalopathy is a syndrome observed in patients with liver cirrhosis and is caused by increased amounts of ammonia in the blood. The proposed project investigates a transporter that is involved in ammonia and glutamine metabolism in liver and brain. The two organs are critical to the pathology of liver failure and ammonia toxicity resulting from reduced liver function. The transporter thus could become a drug target for a variety of liver diseases.
Regulation Of Voltage-Gated Potassium Channels: X-ray Structures Of Cytosolic Components Of The BK Nd Kv Families
Funder
National Health and Medical Research Council
Funding Amount
$235,500.00
Summary
This research will investigate aspects of ion channel gating (opening). Ion channels are specialised pores perforating cell membranes that facilitate transport of ions, or charged atoms, across its breadth. The flow of ions from one side to another is measurable as an electrical current. The pore, or channel, through which ions pass narrows in regions, creating an impasse, or gate , prohibiting passage. The gate is controlled by external factors, such as the binding of certain molecules (ligands ....This research will investigate aspects of ion channel gating (opening). Ion channels are specialised pores perforating cell membranes that facilitate transport of ions, or charged atoms, across its breadth. The flow of ions from one side to another is measurable as an electrical current. The pore, or channel, through which ions pass narrows in regions, creating an impasse, or gate , prohibiting passage. The gate is controlled by external factors, such as the binding of certain molecules (ligands), or, in the case of voltage-dependent ion channels, the application of a voltage to the membrane. Such perturbations widen the pore sufficiently to permit conduction. Voltage-gated potassium channels specifically transport potassium ions. They fall into multiple categories, and generally form large complexes with intracellular, as well as membrane-bound, portions. For some types, cues from intracellular chemical processes are known to regulate electrical excitability, using the intracellular domains to transfer information to the membrane. In others it is not clear if and how this might happen. Our efforts will focus on exploring this theme in two contrasting systems, Kv and BK channels. Kv channels open in response to voltage, whereas activation of BK channels requires both voltage and moderate levels of intracellular calcium. X-ray crystallography will be used to generate accurate three-dimensional images of selected potassium channel components, allowing us to visualise discrete steps in the regulation processes. Potassium channels are essential for life. They effect transmission of our nerve impulses, and are thus fundamental to central nervous system activity. This research will help us to understand the factors that control them.Read moreRead less
Molecular Reorganization During K+ Channel Gating: Determination Of Alternate Pore Configurations By X-ray Diffraction.
Funder
National Health and Medical Research Council
Funding Amount
$489,000.00
Summary
Ion channels are specialised pores that control the flow of charge across cell membranes. They have electrical activity, measurable as current. Potassium channels allow only potassium ions to transit the cell membrane to the exclusion of all others. Without potassium channels our nerves, heart, and other organs, would not function. The channels regulate ion flow by an innate ability to open and close at the behest of specific biological signals, and switch easily between physiological states. In ....Ion channels are specialised pores that control the flow of charge across cell membranes. They have electrical activity, measurable as current. Potassium channels allow only potassium ions to transit the cell membrane to the exclusion of all others. Without potassium channels our nerves, heart, and other organs, would not function. The channels regulate ion flow by an innate ability to open and close at the behest of specific biological signals, and switch easily between physiological states. Influencing factors include depolarising pulses and small molecules that bind to their surface, causing the pore to unblock. Hundreds of types of potassium channel, receptive to a variety of cues, exist in man. The architecture of the pore has recently been confirmed, in the form of three-dimensional models of four quite different channels. This has been invaluable in elucidating aspects of ion permeation. It has not, however, satisfactorily explained what causes the pore to open and close, how it does so, and if this mechanism is general to all potassium channels. Complementary models of the same potassium channel would permit a direct comparison of structural features. Only then can one verify the molecular rearrangements accompanying opening. The experimental aim of this project is to acquire such information using X-ray crystallographic methods. An expedient approach is to tackle one of the four channels already crystallised, capturing its alternate configuration. Although this is an ambitious plan, it has the potential to be highly rewarding. It is also of unparalleled scientific interest, if the current level of debate in biophysics circles is anything to go by. A high proportion of the world s pharmaceuticals are directed at ion channels, as numerous diseases have been ascribed to compromised potassium channel activity. Our research outcomes will provide a fresh basis for the rational design of new drug therapies.Read moreRead less
Molecular Characterization Of Unique Recognition Sites On The Surface Of Human Spermatozoa
Funder
National Health and Medical Research Council
Funding Amount
$212,036.00
Summary
Developing an understanding of the molecular mechanisms that regulate human sperm function is central to the clinical management of male infertility, attempts to develop novel forms of male contraception and strategies for the introduction of transgenes into the male germ line. Defective sperm function is the largest single defined cause of human infertility. Despite the prevalence of this condition we have no idea how most cases of male infertility arise nor, in a vast majority of patients, do ....Developing an understanding of the molecular mechanisms that regulate human sperm function is central to the clinical management of male infertility, attempts to develop novel forms of male contraception and strategies for the introduction of transgenes into the male germ line. Defective sperm function is the largest single defined cause of human infertility. Despite the prevalence of this condition we have no idea how most cases of male infertility arise nor, in a vast majority of patients, do we understand which particular aspect of sperm biochemistry is defective. As a consequence we have not been able to develop sensitive biochemical diagnostic tests for the infertile male nor do we have any rational methods of treatment that address the cause of this condition. Similarly no new methods of male fertility regulation have been introduced since vasectomy despite the major advances that have been made in the field of female contraception over the same period of time. Clearly if we are to develop sensitive methods for the diagnosis of defective sperm function, introduce protocols for the treatment and prevention of male infertility and discover novel approaches to male contraception, we must first understand the cellular mechanisms that enable these highly specialized cells to perform their unique function. In this study we shall focus on one of the most important attributes of sperm function the capacity of these cells to recognize the egg. Once the biochemical basis of this fundamental recognition process is understood, it should pave the way for the development of clinical applications that target this signaling system with implications for a range of disciplines including reproductive toxicology, occupational medicine, family planning, infertility and biotechnology.Read moreRead less
The Structure - Function Relationship Of NCC27, A Novel Nuclear Chloride Ion Channel Protein
Funder
National Health and Medical Research Council
Funding Amount
$241,527.00
Summary
Ion channels (IC) are complex proteins that regulate the transport of salts, an essential cell function. We have recently cloned a new IC, NCC27, unique in its location on the nuclear membrane, a site where they were previously thought to be unnecessary. The function of nuclear membrane ICs is unknown but our studies suggest that NCC27 is involved in regulating cell division. Because NCC27 has unique functional and structural characteristics, it will be particularly useful for answering fundamen ....Ion channels (IC) are complex proteins that regulate the transport of salts, an essential cell function. We have recently cloned a new IC, NCC27, unique in its location on the nuclear membrane, a site where they were previously thought to be unnecessary. The function of nuclear membrane ICs is unknown but our studies suggest that NCC27 is involved in regulating cell division. Because NCC27 has unique functional and structural characteristics, it will be particularly useful for answering fundamental questions relevant to the biology of animal cells: the role of nuclear membrane ICs in cell division; the way the structure of NCC27 allows it to carry out its function.Read moreRead less
E-cadherin is one of the major proteins responsible for mediating cell-to-cell adhesion in the body. During development, E-cadherin is essential for establishing the cellular architecture of epithelial organs and for maintaining epithelial function in the adult. In this context, E-cadherin acts to establish and maintain the polarity of epithelial cells. E-cadherin is also a powerful tumour suppressor and the loss of E-cadherin expression or function is a primary event in metastasis and cancer in ....E-cadherin is one of the major proteins responsible for mediating cell-to-cell adhesion in the body. During development, E-cadherin is essential for establishing the cellular architecture of epithelial organs and for maintaining epithelial function in the adult. In this context, E-cadherin acts to establish and maintain the polarity of epithelial cells. E-cadherin is also a powerful tumour suppressor and the loss of E-cadherin expression or function is a primary event in metastasis and cancer invasion. Proteins at the surface of epithelial cells must be sorted and trafficked, or transported, to different membrane domains. E-cadherin, for instance, must be trafficked to the lateral domain of cells in order to function in cell-cell adhesion. We recently discovered that cell surface E-cadherin is re-internalized and recycled back to the surface via a pathway that is poised to contribute to the regulation of cell adhesion. Our proposed studies aim to reveal how newly-synthesized E-cadherin and recycling E-cadherin are trafficked, which molecules and which vesicle carriers accomplish this transport. E-cadherin has specific amino acids that act as targeting signals for its sorting and trafficking; we have recently identified one such signal and will now seek the signal responsible for its endocytosis. Using specifically engineered mutants of E-cadherin we will also study other proteins that interact with E-cadherin during its trafficking for sorting and regulation. One of these is polycystin, a protein that is mutated in a common inherited kidney disease. Insights into this disease and normal kidney epithelial function will emerge from this work. A growing understanding of E-cadherin function and regulation is essential for the health of epithelial organs and for controlling and preventing cancer.Read moreRead less