Mechanisms Controlling The Excitability Of Corneal Nociceptor Nerve Terminals
Funder
National Health and Medical Research Council
Funding Amount
$364,759.00
Summary
The project uses a new approach that allows, for the first time, electrical activity to be recorded and analysed from the very fine nerve endings of nerves whose activation results in painful sensations. Using this technique the mechanisms by which substances released in damaged and inflamed tissues lead to discharge of action potentials and the sensation of pain will be investigated. In particular the project investigates the role of a population of sodium ion selective pores (channels) that ar ....The project uses a new approach that allows, for the first time, electrical activity to be recorded and analysed from the very fine nerve endings of nerves whose activation results in painful sensations. Using this technique the mechanisms by which substances released in damaged and inflamed tissues lead to discharge of action potentials and the sensation of pain will be investigated. In particular the project investigates the role of a population of sodium ion selective pores (channels) that are uniquely expressed in pain sensing nerves. These channels have been hypothesised to play an important role in determining the behaviour of these nerves. In addition, the project investigates how some substances released in inflamed tissues sensitize pain sensing nerves, causing them to more readily discharge action potentials. This change is the major cause of pain associated with inflammatory diseases such as arthritis. In summary, the proposed project will provide new insight into how pain sensing nerves function. This knowledge is essential for the development of more effective strategies for treating pain resulting from inflamed and damaged tissue.Read moreRead less
Differential Regulation Of Two Modes Of Exocytosis By Protein Phosphatases
Funder
National Health and Medical Research Council
Funding Amount
$399,750.00
Summary
The release of signals from nerve endings (exocytosis) is of fundamental importance to nervous system function. The recent recognition that nerve cells can release transmitter by at least two distinct modes of exocytosis has led to the need for a deeper understanding of the mechanisms that regulate exocytosis. Our identification of the key role played by two enzymes, PP2A and PP2B, represents a major insight into the molecular mechansisms regulating this process. The experiments will lead to the ....The release of signals from nerve endings (exocytosis) is of fundamental importance to nervous system function. The recent recognition that nerve cells can release transmitter by at least two distinct modes of exocytosis has led to the need for a deeper understanding of the mechanisms that regulate exocytosis. Our identification of the key role played by two enzymes, PP2A and PP2B, represents a major insight into the molecular mechansisms regulating this process. The experiments will lead to the identification of how PP2A and PP2B are regulated at the molecular level and the targets that are important in the control of exocytosis. The project will also develop new tools to specifically manipulate the two modes of exocytosis in order to understand their contribution to normal and pathological neurotransmission. Strong stimulation of exocytosis is associated with learning and memory in normal brain and neuronal damage under certain pathological conditions. Since switching from 1 mode of exocytosis to another is also induced by strong stimulation, an understanding of the molecular mechanisms that control the different modes of exocytosis may eventually lead to clinical applications.Read moreRead less
Mechanisms Of Synaptic Vesicle Endocytosis Revealed By Its Regulatory Phosphoproteome
Funder
National Health and Medical Research Council
Funding Amount
$545,216.00
Summary
The nerve cells in our brains are in constant communication to sustain life. Communication involves electrical stimulation of one nerve cell which then responds by releasing chemical messengers, from vesicles, onto the next cell. Our research focuses on the mechanism of recycling of vesicles. Targeting this mechanism is a way to gain fundamental knowledge of how to intervene medically when communication fails, or when communication needs to be dampened, such as in some neurological diseases.
Dynamin Inhibitors As Tools For Dissecting The Endocytic Pathway In Neurons
Funder
National Health and Medical Research Council
Funding Amount
$470,250.00
Summary
Nerve cells communicate by the release of neurotransmitters which are packaged in synaptic vesicles inside nerve endings. There is a finite number of vesicles, so they are recycled (endocytosis) for reuse. Some human neural diseases hijack the endocytic pathway for entry of pathological peptides, proteins or viruses to paralyse, kill or infect neurons. Our overall aim is to control nerve communication to ultimately allow us to treat disorders of nerve communication like epilepsy. At its most ext ....Nerve cells communicate by the release of neurotransmitters which are packaged in synaptic vesicles inside nerve endings. There is a finite number of vesicles, so they are recycled (endocytosis) for reuse. Some human neural diseases hijack the endocytic pathway for entry of pathological peptides, proteins or viruses to paralyse, kill or infect neurons. Our overall aim is to control nerve communication to ultimately allow us to treat disorders of nerve communication like epilepsy. At its most extreme, completely blocking endocytosis quickly results in a complete block in nerve communication. Therefore slowing it down (rather than blocking) might be a means to control some neural diseases. For example, a seizure is the uncontrolled firing of neurons. The main mechanisms controlling endocytosis converge on the protein dynamin. Dynamin can assemble into a tiny, tightly wound helix or spring. When energy (GTP hydrolysis) is applied to the nanospring it rapidly releases to cleave off empty recycling synaptic vesicles from the cell wall back into the neuron. Our premise is that blocking the nanospring may lead to a new generation of antiepileptic drugs. To achieve this we have already discovered the first chemical inhibitors of dynamin. In this project we will determine how they work, by showing that they target distinct sites in dynamin. We have embarked on an ambitious chemical synthesis program to greatly improve the potency and specificity of the inhibitors. We will expand this with an iterative approach using combinatorial chemistry. When applied to neurons, the drugs appear to be the first endocytosis inhibitors. Will test our proposal that they will reveal multiple points of action of dynamin in various stages of endocytosis. This project will prove the principle that the development of anti-dynamin drugs could lead to the first anti-endocytic drugs. This has the potential to lead to future development of targeted antiepileptic and anticancer drugs.Read moreRead less
Synaptic Transmission In The Mammalian Central Nervous System
Funder
National Health and Medical Research Council
Funding Amount
$460,500.00
Summary
In order to properly understand the complex functions of the brain and the abnormalities underlying neurological disorders, we must understand how individual neurons communicate with each other. Communication occurs at specialized contacts, or synapses. An individual neuron may receive tens of thousands of synaptic contacts from hundreds or thousands of other neurons. Despite intensive investigation, the processes which regulate synaptic strength between central neurons are poorly understood. Th ....In order to properly understand the complex functions of the brain and the abnormalities underlying neurological disorders, we must understand how individual neurons communicate with each other. Communication occurs at specialized contacts, or synapses. An individual neuron may receive tens of thousands of synaptic contacts from hundreds or thousands of other neurons. Despite intensive investigation, the processes which regulate synaptic strength between central neurons are poorly understood. The overall aim of this proposal is to understand the basic mechanisms underlying synaptic transmission at excitatory and inhibitory synaptic connections in the mammalian brain. We will investigate specific synaptic connections in the central pathways of the auditory system, because our previous studies have demonstrated a number of key technical advantages in studying these synapses. We will use electrophysiological recording from synaptic terminals and neurons in isolated living slices of the brainstem of mice. We will use imaging techniques and electron-microscopy to examine the structural details of synaptic connections, as structure is thought to play a major role in determining the strength of synaptic transmission. We will also study the structural and functional properties of auditory synaptic connections in congenitally deaf animals. Our recent study comparing normal and congenitally deaf mice has already revealed significant differences. Our results will provide important insights in the regulation of synaptic strength in the central nervous system, and into the regulation of synaptic transmission at central synapses which have developed under conditions of abnormal sensory activation.Read moreRead less
Sulfonadyn-based Dynamin I-specific Inhibitors And Epilepsy
Funder
National Health and Medical Research Council
Funding Amount
$835,291.00
Summary
Epilepsy affects 1% of people, yet 30% do not respond to anti-epileptic drugs (AEDs). Traditional drug discovery fails to improve this situation. Our team discovered dynamin as a new target for better AED design and our lead sulphonadyns reduces seizures in animals. We will design better sulfonadyns that can ultimately be used for clinical trials by designing the drugs away from its actions outside of neurons. If successful, this will accelerate new AED development with less side-effects.
Nerve cells have unique properties like their ability to put out axons that reach long distances from the cell body (differentiation), their ability to make contacts with other cells and initiate communication by the release of neurotransmitters from synaptic vesicles inside nerve endings (exocytosis) and the recycling of those synaptic vesicles (endocytosis). These events are mainly controlled by a large number of synapse-specific proteins, and partly regulated by a signalling molecule, cGMP, w ....Nerve cells have unique properties like their ability to put out axons that reach long distances from the cell body (differentiation), their ability to make contacts with other cells and initiate communication by the release of neurotransmitters from synaptic vesicles inside nerve endings (exocytosis) and the recycling of those synaptic vesicles (endocytosis). These events are mainly controlled by a large number of synapse-specific proteins, and partly regulated by a signalling molecule, cGMP, which mainly stimulates the enzyme PKG. In previous studies supported by the NHMRC we identified many proteins that are phosphorylated and activated by PKG. One of them, septin 3, is the focus of this proposal. We initially cloned septin 3 as a new member of a family of 10 genes that are essential for cell division. Some septins assemble as filaments that allow the two new daughter cells to finally separate. When the filament formation is perturbed certain septins end up in microscopic clumps that are found in the post-mortem brains of people affected by Alzheimer's disease, suggesting they might contribute to the disease. However, septin 3 is unlike most septins because it is a brain-specific septin, which we found in neurons and found to be highly concentrated in nerve terminals, locations not normally associated with cell division. The only other known brain-specific septin, CDCrel-1, regulates the protein machinery of exocytosis. We will examine the hypothesis that G-septin is also a regulator of synaptic vesicle endocytosis. We will determine whether septin represents a convergence point for cGMP signalling to control endocytosis. A better understanding of septin 3 and endocytosis is crucial to understanding brain disorders and ultimately developing better therapies.Read moreRead less
The Function Of Dynamin Phosphorylation Sites In Synaptic Vesicle Endocytosis
Funder
National Health and Medical Research Council
Funding Amount
$794,565.00
Summary
Neurons communicate with each other via the release of neurotransmitters which are packaged in synaptic vesicles inside nerve endings. There are a finite number of vesicles, so they are recycled (endocytosis) for reuse. Synaptic vesicle exocytosis is very fast and normally endocytosis is a little slower, mopping up the used vesicles. Recently we showed that endocytosis can control synaptic transmission, hence it's an integral part of an overall cycle of synaptic transmission. We found that when ....Neurons communicate with each other via the release of neurotransmitters which are packaged in synaptic vesicles inside nerve endings. There are a finite number of vesicles, so they are recycled (endocytosis) for reuse. Synaptic vesicle exocytosis is very fast and normally endocytosis is a little slower, mopping up the used vesicles. Recently we showed that endocytosis can control synaptic transmission, hence it's an integral part of an overall cycle of synaptic transmission. We found that when endocytosis cannot keep up then exocytosis slows, greatly reducing the function of neurons. A complete block would result in paralysis of brain and muscles. Our team has been revealing the underlying molecular mechanisms of endocytosis in order to better understand diseases of the synapse like schizophrenia, epilepsy and Alzheimer's disease. We discovered that endocytosis is a regulated process at the heart of which is a pair of phosphorylation sites (points of phosphate attachment) in the key protein dynamin I. Our hypothesis is that endocytosis occurs in two forms, fast and slow. We propose to test the idea that proteins that associate with dynamin via the phosphorylation sites determine whether the fast or slow mode is used. Additionally, we propose that the first phosphorylation site is the trigger for endocytosis, while the second serves to recruit reserve supplies of dynamin to support the slow mode when it's required. A better understanding of Dyn and endocytosis is crucial to understanding brain disorders of synaptic transmission and ultimately for developing therapies. For example, a seizure is the uncontrolled firing of neurons. Our overall aim is to understand the control mechanisms of nerve communication to ultimately allow us to treat disorders of nerve communication like epilepsy.Read moreRead less
Role Of Dynamin In Modes Of Synaptic Vesicle Endocytosis
Funder
National Health and Medical Research Council
Funding Amount
$905,985.00
Summary
Neurons communicate by neurotransmitter release from synaptic vesicles stored in nerve endings. There is a finite vesicle number, so they are recycled (endocytosis) by dynamin. Our aim is to reveal the molecular mechanisms underlying endocytosis to better understand diseases of the synapse like epilepsy. We propose that two forms of the dynamin gene mediate two forms of endocytosis, one of which is activated only under conditions of high neuronal firing, such as occurs during a seizure.
Postsynaptic Signalling Systems That Sustain The Nerve-muscle Synapse
Funder
National Health and Medical Research Council
Funding Amount
$598,041.00
Summary
Neuromuscular junctions (NMJ) are the synapses through which motor nerves control our voluntary muscle cells. This project will investigate the molecular signalling system between nerve and muscle that helps maintain healthy NMJs. Normal ageing involves a progressive decline in muscle strength, often leading to loss of independence in the elderly. We will use a mouse model to test whether a breakdown of the NMJ signalling system contributes to the loss of strength in old age.