Identification And Characterization Of Novel PI3-kinase Signal Transducing Elements In Platelets
Funder
National Health and Medical Research Council
Funding Amount
$457,500.00
Summary
Platelets play an important role in blood clotting and blood vessel repair. Upon vessel injury, platelets rapidly adhere to the site of damage where they undergo dramatic shape change to spread over the site of injury. Activation and regulation of these processes relies on a complex network of signal transduction processes, involving the integration of multiple receptors and pathways. One pathway demonstrated to play a role in regulating platelet responses is the enzyme phosphatidylinositol 3-ki ....Platelets play an important role in blood clotting and blood vessel repair. Upon vessel injury, platelets rapidly adhere to the site of damage where they undergo dramatic shape change to spread over the site of injury. Activation and regulation of these processes relies on a complex network of signal transduction processes, involving the integration of multiple receptors and pathways. One pathway demonstrated to play a role in regulating platelet responses is the enzyme phosphatidylinositol 3-kinase (PI3-kinase) and its lipid products PtdIns(3,4,5)P3 and PtdIns(3,4)P2. However, very little is known about exactly how PI3-kinase and its products regulate the platelet responses. Our research studies aim to gain a deeper understanding into the molecular mechanisms of PI3-kinase signal transduction in platelets, through the identification and characterization of novel platelet proteins that bind to PI3-kinase lipid products, and to define what role these proteins play in platelet PI3-kinase dependent responses.Read moreRead less
Molecular Determinants Of Subcellular Localisation And Function Of The Transmembrane 4 Superfamily Protein, PETA-3
Funder
National Health and Medical Research Council
Funding Amount
$322,911.00
Summary
Several years ago we identified the cell membrane protein PETA-3-CD151 based on its ability to cause activation of blood platelets, suggesting a role in thrombosis. More recently we found that the protein is present in a variety of tissues, although its distribution in those tissues is often restricted. It is abundant in a variety of cancer cells, and is present on tissue mast cells that mediate allergic reactions. PETA-3-CD151 forms complexes with molecules (integrins) that are associated with ....Several years ago we identified the cell membrane protein PETA-3-CD151 based on its ability to cause activation of blood platelets, suggesting a role in thrombosis. More recently we found that the protein is present in a variety of tissues, although its distribution in those tissues is often restricted. It is abundant in a variety of cancer cells, and is present on tissue mast cells that mediate allergic reactions. PETA-3-CD151 forms complexes with molecules (integrins) that are associated with cell adhesion and migration, and antibodies to this protein inhibit cell movement. Thus PETA-3-CD151 appears to be involved in cellular interactions that are critical for normal tissue development and function, and may be involved in several disease processes including cancer invasion and metastasis. The molecular basis of PETA-3-CD151 function is not understood and is the focus of this application.Read moreRead less
The Role Of Plasma Membrane Microdomains In Regulating Ras-dependent Raf Activation
Funder
National Health and Medical Research Council
Funding Amount
$216,100.00
Summary
In human cancers one or more of the signaling pathways leading from growth factor receptors at the cell surface to the nucleus where cell division is initiated are subverted. For example, a protein called Ras, that regulates a series of major signaling pathways, is mutated in 25% of all human tumours. This leaves Ras and the signaling pathways permanently switched on causing uncontrolled cell proliferation. Our previous work has demonstrated that Ras must be attached to the inner surface of the ....In human cancers one or more of the signaling pathways leading from growth factor receptors at the cell surface to the nucleus where cell division is initiated are subverted. For example, a protein called Ras, that regulates a series of major signaling pathways, is mutated in 25% of all human tumours. This leaves Ras and the signaling pathways permanently switched on causing uncontrolled cell proliferation. Our previous work has demonstrated that Ras must be attached to the inner surface of the cell membrane in order to function properly. This project now seeks to understand exactly how Ras attaches to and interacts with specific sites in the plasma membrane. Its is becoming clear that different isoforms of Ras, called H-, N- and K-ras have different functions in the cell which may in turn result from their different sites of attachment to the cell membrane. This is important because by understanding the precise micro-environment in which the different Ras proteins operate and how they activate subsequent proteins in their signaling networks we will be in a good position to design drugs that selectively compromise the function of each specific Ras isoform. A highly relevant example is provided by K-ras which is mutated in 90% of all pancreatic cancers and 50% of all colon cancers. Clearly the clinical impact of a drug that could selectively neutralise K-Ras function in these tumours is potentially enormous.Read moreRead less
LPS-regulated SNAREs And Control Of Cytokine Secretion In Macrophages.
Funder
National Health and Medical Research Council
Funding Amount
$470,750.00
Summary
TNF(tumour necrosis factor alpha) is a potent proinflammatory cytokine secreted by immune activated macrophages. TNF has essential roles in host defense, tumour killing and energy metabolism. Excessive secretion of TNF in acute and chronic inflammatory conditions, such as septic shock, Crohn s disease, rheumatoid arthritis and in cancer has many severe, even fatal, consequences. Improved anti-TNF therapeutics are needed for clinical management in all of these conditions. Our studies are focused ....TNF(tumour necrosis factor alpha) is a potent proinflammatory cytokine secreted by immune activated macrophages. TNF has essential roles in host defense, tumour killing and energy metabolism. Excessive secretion of TNF in acute and chronic inflammatory conditions, such as septic shock, Crohn s disease, rheumatoid arthritis and in cancer has many severe, even fatal, consequences. Improved anti-TNF therapeutics are needed for clinical management in all of these conditions. Our studies are focused on investigating how macrophages synthesize and secrete TNF, with the ultimate goal of characterizing the molecules and vesicles in the TNF secretory pathway. Our recent findings show the expression of SNARE proteins, part of the vesicle docking and fusion machinery, is regulated in concert with cytokine secretion and other trafficking changes in activated macrophages. We identified the proteins Syntaxin4, Munc-18c and SNAP-23 as the specific t-SNARE complex that regulates TNF delivery to the cell surface. In the proposed studies we will investigate how SNAREs are regulated during macrophage activation by studying their gene expression and protein modifications. We have developed a single-cell assay to measure TNF trafficking in macrophages; this allows the identification of molecules with roles in TNF secretion and it will be used in a series of experiments to identify the specific v-SNARE proteins that partner the t-SNARE for TNF delivery. Finally we will use live cell imaging to investigate how and where TNF is delivered to the macrophage cell surface and membrane fractionation to examine a role for membrane microdomains in organizing SNARE-mediated TNF secretion. Manipulation of SNAREs, using data generated by these studies, holds potential for the development of new anti-TNF therapies.Read moreRead less