Abstract
Current views on quantal release of neurotransmitters hold that after the vesicle migrates towards release sites (active zones), multiple protein interactions mediate the docking of the vesicle to the presynaptic membrane and the formation of a multimolecular protein complex (the 'fusion machine') which ultimately makes the vesicle competent to release a quantum in response to the action potential. Classical biophysical studies of quantal release have modelled the process by a binomial system where n vesicles (sites) competent for exocytosis release a quantum, with probability p, in response to the action potential. This is likely to be an oversimplified model. Furthermore, statistical and kinetic studies have given results which are difficult to reconcile within this framework. Here, data are presented and discussed which suggest a revision of the biophysical model. Transient silencing of release is shown to occur following the pulse of synchronous transmitter release, which is evoked by the presynaptic action potential. This points to a schema where the vesicle fusion complex assembly is a reversible, stochastic process. Asynchronous exocytosis may occur at several intermediate stages in the process, along paths which may be differentially regulated by divalent cations or other factors. The fusion complex becomes competent for synchronous release (armed vesicles) only at appropriately organized sites. The action potential then triggers (deterministically rather than stochastically) the synchronous discharge of all armed vesicles. The existence of a specific conformation for the fusion complex to be competent for synchronous evoked fusion reconciles statistical and kinetic results during repetitive stimulation and helps explain the specific effects of toxins and genetic manipulation on the synchronization of release in response to an action potential.
Full Text
The Full Text of this article is available as a PDF (246.3 KB).
Selected References
These references are in PubMed. This may not be the complete list of references from this article.
- Betz W. J. Depression of transmitter release at the neuromuscular junction of the frog. J Physiol. 1970 Mar;206(3):629–644. doi: 10.1113/jphysiol.1970.sp009034. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Broadie K., Prokop A., Bellen H. J., O'Kane C. J., Schulze K. L., Sweeney S. T. Syntaxin and synaptobrevin function downstream of vesicle docking in Drosophila. Neuron. 1995 Sep;15(3):663–673. doi: 10.1016/0896-6273(95)90154-x. [DOI] [PubMed] [Google Scholar]
- Brown T. H., Perkel D. H., Feldman M. W. Evoked neurotransmitter release: statistical effects of nonuniformity and nonstationarity. Proc Natl Acad Sci U S A. 1976 Aug;73(8):2913–2917. doi: 10.1073/pnas.73.8.2913. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Calakos N., Scheller R. H. Synaptic vesicle biogenesis, docking, and fusion: a molecular description. Physiol Rev. 1996 Jan;76(1):1–29. doi: 10.1152/physrev.1996.76.1.1. [DOI] [PubMed] [Google Scholar]
- Ceccarelli B., Hurlbut W. P., Mauro A. Turnover of transmitter and synaptic vesicles at the frog neuromuscular junction. J Cell Biol. 1973 May;57(2):499–524. doi: 10.1083/jcb.57.2.499. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Ceccarelli B., Hurlbut W. P. Vesicle hypothesis of the release of quanta of acetylcholine. Physiol Rev. 1980 Apr;60(2):396–441. doi: 10.1152/physrev.1980.60.2.396. [DOI] [PubMed] [Google Scholar]
- Christensen B. N., Martin A. R. Estimates of probability of transmitter release at the mammalian neuromuscular junction. J Physiol. 1970 Nov;210(4):933–945. doi: 10.1113/jphysiol.1970.sp009250. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Courtney K. R. Extended moment analysis for binomial parameters of transmitter release. J Theor Biol. 1978 Jul 20;73(2):285–292. doi: 10.1016/0022-5193(78)90191-1. [DOI] [PubMed] [Google Scholar]
- Cremona O., De Camilli P. Synaptic vesicle endocytosis. Curr Opin Neurobiol. 1997 Jun;7(3):323–330. doi: 10.1016/s0959-4388(97)80059-1. [DOI] [PubMed] [Google Scholar]
- DeBello W. M., O'Connor V., Dresbach T., Whiteheart S. W., Wang S. S., Schweizer F. E., Betz H., Rothman J. E., Augustine G. J. SNAP-mediated protein-protein interactions essential for neurotransmitter release. Nature. 1995 Feb 16;373(6515):626–630. doi: 10.1038/373626a0. [DOI] [PubMed] [Google Scholar]
- Elmqvist D., Quastel D. M. A quantitative study of end-plate potentials in isolated human muscle. J Physiol. 1965 Jun;178(3):505–529. doi: 10.1113/jphysiol.1965.sp007639. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Fesce R., Grohovaz F., Valtorta F., Meldolesi J. Neurotransmitter release: fusion or 'kiss-and-run'? Trends Cell Biol. 1994 Jan;4(1):1–4. doi: 10.1016/0962-8924(94)90025-6. [DOI] [PubMed] [Google Scholar]
- Fesce R. Stochastic approaches to the study of synaptic function. Prog Neurobiol. 1990;35(2):85–133. doi: 10.1016/0301-0082(90)90019-d. [DOI] [PubMed] [Google Scholar]
- Gansel M., Penner R., Dreyer F. Distinct sites of action of clostridial neurotoxins revealed by double-poisoning of mouse motor nerve terminals. Pflugers Arch. 1987 Aug;409(4-5):533–539. doi: 10.1007/BF00583812. [DOI] [PubMed] [Google Scholar]
- Geppert M., Goda Y., Hammer R. E., Li C., Rosahl T. W., Stevens C. F., Südhof T. C. Synaptotagmin I: a major Ca2+ sensor for transmitter release at a central synapse. Cell. 1994 Nov 18;79(4):717–727. doi: 10.1016/0092-8674(94)90556-8. [DOI] [PubMed] [Google Scholar]
- Hanson P. I., Heuser J. E., Jahn R. Neurotransmitter release - four years of SNARE complexes. Curr Opin Neurobiol. 1997 Jun;7(3):310–315. doi: 10.1016/s0959-4388(97)80057-8. [DOI] [PubMed] [Google Scholar]
- Heuser J. E., Reese T. S. Evidence for recycling of synaptic vesicle membrane during transmitter release at the frog neuromuscular junction. J Cell Biol. 1973 May;57(2):315–344. doi: 10.1083/jcb.57.2.315. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Hurlbut W. P., Longenecker H. B., Jr, Mauro A. Effects of calcium and magnesium on the frequency of miniature end-plate potentials during prolonged tetanization. J Physiol. 1971 Dec;219(1):17–38. doi: 10.1113/jphysiol.1971.sp009647. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Katz B., Miledi R. Ionic requirements of synaptic transmitter release. Nature. 1967 Aug 5;215(5101):651–651. doi: 10.1038/215651a0. [DOI] [PubMed] [Google Scholar]
- LILEY A. W., NORTH K. A. An electrical investigation of effects of repetitive stimulation on mammalian neuromuscular junction. J Neurophysiol. 1953 Sep;16(5):509–527. doi: 10.1152/jn.1953.16.5.509. [DOI] [PubMed] [Google Scholar]
- Llinás R., Sugimori M., Silver R. B. Microdomains of high calcium concentration in a presynaptic terminal. Science. 1992 May 1;256(5057):677–679. doi: 10.1126/science.1350109. [DOI] [PubMed] [Google Scholar]
- Mallart A., Martin A. R. An analysis of facilitation of transmitter release at the neuromuscular junction of the frog. J Physiol. 1967 Dec;193(3):679–694. doi: 10.1113/jphysiol.1967.sp008388. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Meiri H., Rahamimoff R. Clumping and oscillations in evoked transmitter release at the frog neuromuscular junction. J Physiol. 1978 May;278:513–523. doi: 10.1113/jphysiol.1978.sp012321. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Miyamoto M. D. Probability of quantal transmitter release from nerve terminals: theoretical considerations in the determination of spatial variation. J Theor Biol. 1986 Dec 7;123(3):289–304. doi: 10.1016/s0022-5193(86)80244-2. [DOI] [PubMed] [Google Scholar]
- Molgó J., Siegel L. S., Tabti N., Thesleff S. A study of synchronization of quantal transmitter release from mammalian motor endings by the use of botulinal toxins type A and D. J Physiol. 1989 Apr;411:195–205. doi: 10.1113/jphysiol.1989.sp017568. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Montecucco C., Schiavo G. Structure and function of tetanus and botulinum neurotoxins. Q Rev Biophys. 1995 Nov;28(4):423–472. doi: 10.1017/s0033583500003292. [DOI] [PubMed] [Google Scholar]
- Palfrey H. C., Artalejo C. R. Vesicle recycling revisited: rapid endocytosis may be the first step. Neuroscience. 1998 Apr;83(4):969–989. doi: 10.1016/s0306-4522(97)00453-3. [DOI] [PubMed] [Google Scholar]
- Sacchi O., Rossi M. L., Canella R., Fesce R. Synaptic current at the rat ganglionic synapse and its interactions with the neuronal voltage-dependent currents. J Neurophysiol. 1998 Feb;79(2):727–742. doi: 10.1152/jn.1998.79.2.727. [DOI] [PubMed] [Google Scholar]
- Stevens C. F., Wang Y. Facilitation and depression at single central synapses. Neuron. 1995 Apr;14(4):795–802. doi: 10.1016/0896-6273(95)90223-6. [DOI] [PubMed] [Google Scholar]
- THIES R. E. NEUROMUSCULAR DEPRESSION AND THE APPARENT DEPLETION OF TRANSMITTER IN MAMMALIAN MUSCLE. J Neurophysiol. 1965 May;28:428–442. doi: 10.1152/jn.1965.28.3.427. [DOI] [PubMed] [Google Scholar]
- Wu M. N., Bellen H. J. Genetic dissection of synaptic transmission in Drosophila. Curr Opin Neurobiol. 1997 Oct;7(5):624–630. doi: 10.1016/s0959-4388(97)80081-5. [DOI] [PubMed] [Google Scholar]