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Group Leader: Professor Michael Berndt Overview: In thrombosis, platelet adhesion and aggregation are initiated by engagement of specific membrane receptors that lead to platelet activation and GPIIb-IIIa integrin-dependent aggregation. At high shear stress, platelet adhesion is mediated primarily by binding of the platelet membrane glycoprotein (GP) Ib-IX-V complex to its ligand, von Willebrand Factor (vWF). At low shear, collagen receptors such as the integrin GPIa-IIa and/or GPVI initiate platelet activation without the requirement of vWF. Thrombosis precipitating heart disease and stroke is the leading cause of death in the Western world. The binding of vWF to GPIb-IX-V is a critical event in initiating thrombosis. We have identified distinct sites in the vWF A1 domain for binding GPIb-IX-V, have demonstrated that leucine-rich repeats two through four of GPIb are involved in the binding of vWF, have confirmed the importance of 14-3-3 signalling protein in mediating signalling through GPIb-IX-V and in linking the alpha chain of GPIb with the p85 subunit of PI 3-kinase, have identified P-selectin as a novel ligand for GPIb-IX-V, and have identified the leukocyte integrin, Mac-1, as an additional novel ligand for GPIb-IX-V. Adhesion of platelets to a damaged blood vessel via vWF binding to GPIb-IX-V or collagen binding GPVI triggers a series of intracellular events that lead to platelet aggregation, spreading, and degranulation. We have shown that 14-3-3 protein is a key mediator of signalling in platelets. We have also recently shown that the cytosolic regulatory protein, calmodulin, interacts directly with the cytoplasmic domains of both GPIb-IX-V and GPVI, associations postulated to regulate the adhesive function and/or signal transduction mediated by these receptors. Projects: To dissect the molecular interactions involved in 14-3-3 binding to PI 3-kinase and to determine how 14-3-3 regulates the assemblage of GPIb-IX-V signalling complexes.
To characterize the functional significance of the receptor/14-3-3/PI 3-kinase complex in transfected cells and animal models.
To identify the molecular determinants of vWF involved in recognition of platelet GPIb-IX-V, and regulation of this interaction under shear stress in flowing blood.
To analyze the functional significance of calmodulin association with both GPIb-IX-V and GPVI, in terms of ligand recognition, surface expression, cytoskeletal regualation, and/or signalling.
To explore the adhesive interactions and signalling of platelet and leukocyte adhesion receptors involved in platelet-leukocyte-endothelial cell cross-talk.Group Members: Key Publications: Shen, Y., Romo, G.M., Dong, J.-F., Schade, A., McIntire, L.V., Kenny, D., Whisstock, J.C., Berndt, M.C., López, J.A., Andrews, R.K. (2000)
Requirement of leucine-rich repeats of GP Iba for shear-dependent and static binding of von Willebrand factor to the platelet membrane GP Ib-IX-V complex. Blood 95:903-910. Berndt, M.C., Shen, Y., Dopheide, S.M., Gardiner, E.E., Andrews, R.K. (2001)
The vascular biology of the glycoprotein Ib-IX-V complex. Thromb. Haemostas. 86:178-178. Andrews, R.K., Munday, A.D., Mitchell, C.A., Berndt, M.C. (2001)
Interaction of calmodulin with the cytoplasmic domain of the glycoprotein Ib-IX-V complex. Blood. 98:681-687. Gardiner, E.E., De Luca, M., McNally, T., Michelson, A.D., Andrews, R.K., Berndt, M.C. (2001)
Regulation of ligand binding to the neutrophil P-selectin receptor PSGL-1, by neutrophil elastase and cathepsin G.Blood. 98:1440-1447. Andrews, R.K., Gardiner, E.E., Asazuma, N., Berlanga, O., Tulasne, D., Nieswandt, B., Smith, A.I., Berndt, M.C., Watson, S.P. (2001)
A novel viper venom metalloproteinase, alborhagin, is an agonist at the platelet collagen receptor GPVI. J. Biol. Chem. 276:28092-28097. Shen, Y., Dong, J.-F., Romo, G.M., Arceneaux, W., Aprico, A., Gardiner, E.E., López, J.A., Berndt, M.C., Andrews, R.K. (2002)
Functional analysis of the C-terminal flanking sequence of platelet GPIba using canine-human chimeras. Blood. 99:145-150. Andrews, R.K., Suzuki-Inoue, K., Shen, Y., Tulasne, D., Watson, S.P., Berndt, M.C. (2002)
Interaction of calmodulin with the cytoplasmic domain of platelet glycoprotein VI. Blood. 99:4219-4221. Funding Sources: Research is supported in part by grants and/or fellowships from the National Health & Medical Research Council of Australia and the National Heart Foundation of Australia.Collaborators: J. Whisstock, Melbourne. Structural modeling of von Willebrand factor and the leucine-rich repeats of GPIba. J. López, Houston, USA. Structure/function of the GPIb-IX-V complex in thrombosis, haemostasis and vascular biology. S. Watson, Oxford, U.K. GPVI dependent signalling. Patents: Berndt, M.C., Dunlop, L.C., De Luca, M., Andrews, R.K. "Mocarhagin, a novel cobra venom protease, and therapeutic uses thereof." Filed U.S.A, 1995, Awarded, 1997. Berndt, M.C., Andrews, R.K., Lopez, J.A. Dong, J.-F., Favaloro, E.J. "Antibodies". Provisional patent filed, PQ4846, December 1999. Links: Monash University
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