The Journal of Cell Biology, Vol 90, 40-54, Copyright © 1981 by The Rockefeller University Press

ARTICLES

Beginning of exocytosis captured by rapid-freezing of Limulus amebocytes

RL Ornberg and TS Reese

Structural changes underlying exocytosis evoked by the application of endotoxin to Limulus amebocytes were studied at the level of detail afforded by freeze-fracture and freeze-substitution techniques combined with the time resolution of direct rapid-freezing. The results with amebocytes prepared in this manner differed from those with other secretory cells prepared by conventional means. Exocytosis begins within seconds of endotoxin treatment when the plasmalemma invaginates to form pedestallike appositions with peripheral secretory granules. The juxtaposed membranes at these pedestal appositions form several punctate pentalaminar contacts, but examination of freeze-fractured pedestals failed to reveal any corresponding changes in the intramembrane particle distribution. Small secretory granule openings or pores, which are very infrequent, appear within the first 5 s after endotoxin treatment. These pores rapidly widen and this widening is immediately followed by the sequential dissolution of the granule contents, which then move into the surrounding extracellular space. Cytoplasmic filaments connecting the plasmalemma with the granule membrane are suitably deployed to be responsible for the plasmalemma invaginations. How pores begin is not certain, but the appearance of clear spaces between the granule core and the granule membrane at this point in exocytosis supports the possibility of a role of osmotic forces.
CiteULike    Complore    Connotea    Del.icio.us    Digg    Facebook    Reddit    Technorati    Twitter    What's this?

This article has been cited by other articles:

• Neco, P., Fernandez-Peruchena, C., Navas, S., Gutierrez, L. M., de Toledo, G. A., Ales, E. (2008). Myosin II Contributes to Fusion Pore Expansion during Exocytosis. J. Biol. Chem. 283: 10949-10957 [Abstract] [Full Text]  
• Conrad, M., DeNobile, J., Chaikhoutdinov, I., Escribano, D., Lee, K.-G., Cohen, W. D. (2004). Cytoskeletal Organization of Limulus Amebocytes Pre- and Post-Activation: Comparative Aspects. Biol. Bull. 207: 56-66 [Abstract] [Full Text]  
• Kuzmin, P. I., Zimmerberg, J., Chizmadzhev, Y. A., Cohen, F. S. (2001). A quantitative model for membrane fusion based on low-energy intermediates. Proc. Natl. Acad. Sci. USA 10.1073/pnas.121191898v1 [Abstract] [Full Text]  
• Roberts, R., Barbieri, M., Pryse, K., Chua, M, Morisaki, J., Stahl, P. (1999). Endosome fusion in living cells overexpressing GFP-rab5. J. Cell Sci. 112: 3667-3675 [Abstract]  
• Nass, R., Rao, R. (1998). Novel Localization of a Na+/H+ Exchanger in a Late Endosomal Compartment of Yeast. IMPLICATIONS FOR VACUOLE BIOGENESIS. J. Biol. Chem. 273: 21054-21060 [Abstract] [Full Text]  
• Fernandez, J. M. (1997). Cellular and molecular mechanics by atomic force microscopy: Capturing the exocytotic fusion pore in vivo?. Proc. Natl. Acad. Sci. USA 94: 9-10 [Full Text]  
• Miura, Y., Kawabata, S.-i., Wakamiya, Y., Nakamura, T., Iwanaga, S. (1995). A Limulus Intracellular Coagulation Inhibitor Type 2. J. Biol. Chem. 270: 558-565 [Abstract] [Full Text]  
• Zimmerberg, J., Vogel, S.S., Whalley, T., Plonsky, I., Sokoloff, A., Chanturia, A., Chernomordik, L.V. (1995). Intermediates in Membrane Fusion. Cold Spring Harb Symp Quant Biol 60: 589-599 [Abstract]  
• White, J. (1992). Membrane fusion. Science 258: 917-924 [Abstract]  
• Cohen, F., Akabas, M., Finkelstein, A (1982). Osmotic swelling of phospholipid vesicles causes them to fuse with a planar phospholipid bilayer membrane. Science 217: 458-460 [Abstract]  
• Kuzmin, P. I., Zimmerberg, J., Chizmadzhev, Y. A., Cohen, F. S. (2001). A quantitative model for membrane fusion based on low-energy intermediates. Proc. Natl. Acad. Sci. USA 98: 7235-7240 [Abstract] [Full Text]  

Home | Help | Feedback | Subscriptions | Archive | Search | Table of Contents