We have developed simple light scattering assays and fluorescent dye transfer assays to follow membrane fusion reactions. Using these assays we have studied the localization of the molecular machinery that mediates calcium-triggered exocytosis in sea urchin eggs. We find that isolated exocytic vesicles are capable of fusing with each other in response to micromolar concentrations of calcium. This reaction is specific for calcium, 10 mM magnesium does not support fusion. Vesicle-vesicle fusion does not require any added cytoplasmic proteins or organic factors. In addition we find that calcium-triggered fusion can be inhibited by pre-treatment of the vesicles with either trypsin or NEM. Thus we believe that at least part of the fusion mechanism is comprised of proteins, and that these proteins must reside on the vesicles themselves. We have also begun to measure the speed of the fusion reaction of sea urchin cortical granules with the egg plasma membrane and find that we can observe fusion within 10 msec of presenting a calcium trigger. In addition we find that the granule-plasma membrane fusion reaction can be inhibited by either polyoxyethylene sorbitan monooleate or polyoxyethylene sorbitan monolaurate but not by sorbitan monooleate suggesting that polyoxyethylene can interact with a hydrophilic site, near the surface of the exocytic vesicle to inhibit fusion. Finally we find that lysophosphatidylcholine but not phosphatidylcholine or oleic acid can inhibit calcium triggered fusion in isolated planar cortices. This inhibition, like that of tween detergents, is reversible.
| Lizunov, Vladimir A; Lisinski, Ivonne; Stenkula, Karin et al. (2009) Insulin regulates fusion of GLUT4 vesicles independent of Exo70-mediated tethering. J Biol Chem 284:7914-9 |
| Biswas, Subrata; Yin, Shu-Rong; Blank, Paul S et al. (2008) Cholesterol promotes hemifusion and pore widening in membrane fusion induced by influenza hemagglutinin. J Gen Physiol 131:503-13 |
| Shnyrova, Anna; Frolov, Vadim A; Zimmerberg, Joshua (2008) ER biogenesis: self-assembly of tubular topology by protein hairpins. Curr Biol 18:R474-6 |
| Plonsky, Ilya; Kingsley, David H; Rashtian, Afshin et al. (2008) Initial size and dynamics of viral fusion pores are a function of the fusion protein mediating membrane fusion. Biol Cell 100:377-86 |
| Akimov, Sergey A; Frolov, Vladimir A J; Kuzmin, Peter I et al. (2008) Domain formation in membranes caused by lipid wetting of protein. Phys Rev E Stat Nonlin Soft Matter Phys 77:051901 |
| Shnyrova, Anna V; Ayllon, Juan; Mikhalyov, Ilya I et al. (2007) Vesicle formation by self-assembly of membrane-bound matrix proteins into a fluidlike budding domain. J Cell Biol 179:627-33 |
| Hess, Samuel T; Gould, Travis J; Gudheti, Manasa V et al. (2007) Dynamic clustered distribution of hemagglutinin resolved at 40 nm in living cell membranes discriminates between raft theories. Proc Natl Acad Sci U S A 104:17370-5 |
| Akimov, Sergey A; Kuzmin, Peter I; Zimmerberg, Joshua et al. (2007) Lateral tension increases the line tension between two domains in a lipid bilayer membrane. Phys Rev E Stat Nonlin Soft Matter Phys 75:011919 |
| Chernomordik, Leonid V; Zimmerberg, Joshua; Kozlov, Michael M (2006) Membranes of the world unite! J Cell Biol 175:201-7 |
| Chen, Xiaocheng; Arac, Demet; Wang, Tzu-Ming et al. (2006) SNARE-mediated lipid mixing depends on the physical state of the vesicles. Biophys J 90:2062-74 |
Showing the most recent 10 out of 32 publications
