We study the mechanisms of biological membrane fusion, a ubiquitous process in cell biology. To elucidate the key intermediates of lipid bilayer rearrangements in the fusion reaction, we investigated the effects of membrane lipid composition on the rates of diverse fusion processes including Ca + + -triggered cortical exocytosis and low pH-triggered syncytia formation of baculovirus infected insect cells. Lysolipids, naturally-occurring lipids, whether added exogenously or produced in situ by phospholipase A2 treatment, were found to arrest fusion reversibly at an """"""""activated state"""""""" between fusion-triggering and membrane merging. In both experimental systems the specific fusion trigger (H + or Ca + +) was applied in the presence of inhibiting concentrations of short- chain lysophosphatidylcholine. Next the cells and granules were washed with buffers containing lysolipid but without a trigger. No fusion or lysis was observed at this stage. Removal of the lysolipid 5-10 min later by washing with buffers lacking the fusion-trigger resulted in the initiation of fusion. The extent of fusion was comparable with samples which were not treated with lysolipids. The """"""""trigger-independent"""""""" stage of biological fusion, arrested by lysolipids, required trigger application to contacting membranes for its development. Our results suggest that i) while different fusion processes utilize different triggers, the pivotal step involving membrane merger is trigger independent and lipid sensitive, ii) fast exocytotic processes share a common mechanism for membrane merger with slow viral fusion, and, finally, iii) diverse biological fusion reactions proceed through highly bent membrane intermediates, """"""""stalks"""""""", which cannot form when inverted- cone-shaped lysolipids are present in the contacting leaflets. It is also intriguing to speculate that membrane phospholipids, controlled by phospholipase activity, might regulate calcium- triggered exocytosis by integrating multiple calcium pulses into a coordinated exocytotic event.
| Zaitseva, E; Chernomordik, L (2012) Fusion stage of dengue virus entry: mechanisms and assays. Microsc Microanal 18 Suppl 2:52-3 |
| Rafikova, Elvira R; Melikov, Kamran; Ramos, Corinne et al. (2009) Transmembrane protein-free membranes fuse into xenopus nuclear envelope and promote assembly of functional pores. J Biol Chem 284:29847-59 |
| Chernomordik, Leonid V; Kozlov, Michael M (2008) Mechanics of membrane fusion. Nat Struct Mol Biol 15:675-83 |
| Sapir, Amir; Avinoam, Ori; Podbilewicz, Benjamin et al. (2008) Viral and developmental cell fusion mechanisms: conservation and divergence. Dev Cell 14:11-21 |
| Sapir, Amir; Choi, Jaebok; Leikina, Evgenia et al. (2007) AFF-1, a FOS-1-regulated fusogen, mediates fusion of the anchor cell in C. elegans. Dev Cell 12:683-98 |
| Zhukovsky, Mikhail A; Markovic, Ingrid; Bailey, Austin L (2007) Influence of calcium on lipid mixing mediated by influenza hemagglutinin. Arch Biochem Biophys 465:101-8 |
| Efrat, Avishay; Chernomordik, Leonid V; Kozlov, Michael M (2007) Point-like protrusion as a prestalk intermediate in membrane fusion pathway. Biophys J 92:L61-3 |
| Gattegno, Tamar; Mittal, Aditya; Valansi, Clari et al. (2007) Genetic control of fusion pore expansion in the epidermis of Caenorhabditis elegans. Mol Biol Cell 18:1153-66 |
| Ramos, Corinne; Rafikova, Elvira R; Melikov, Kamran et al. (2006) Transmembrane proteins are not required for early stages of nuclear envelope assembly. Biochem J 400:393-400 |
| Chernomordik, Leonid V; Melikov, Kamran (2006) Are there too many or too few SNAREs in proteoliposomes? Biophys J 90:2657-8 |
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