Patterns of synaptic activity in neural networks recorded by light emission from synaptolucins.
The emission of light, coupled to exocytosis, can in principle be utilized to monitor the activity of a large number of individual synapses simultaneously. To illustrate this concept, fusion proteins of Cypridina luciferase and synaptotagmin-I or VAMP-2/synaptobrevin (which we term "synaptolucins") were expressed in cultured hippocampal neurons with the help of viral vectors. Synaptolucins were targeted to synaptic vesicles and, upon exocytosis, formed light-emitting complexes with their cognate luciferin, which was added to the extracellular medium. Photon emissions required a depolarizing stimulus, occurred from regions with high synaptic density as ascertained by vital staining of recycling synaptic vesicles, and were sensitive to Ca2+ depletion and clostridial neurotoxins. The method can currently detect exocytosis of the readily releasable pool of synaptic vesicles at a hippocampal synapse, corresponding to about two dozen quanta, but has the potential for greater sensitivity.
Miesenböck
G
G
Cellular Biochemistry and Biophysics Program, Memorial Sloan-Kettering Cancer Center, New York, NY 10021, USA.
Rothman
J E
JE
D000818:Animals; D002135:Calcium-Binding Proteins; D003530:Cyprinidae; D008027:Light; D008156:Luciferases / Q000235:genetics; D008562:Membrane Glycoproteins / Q000378:metabolism*; D008565:Membrane Proteins / Q000378:metabolism*; D008969:Molecular Sequence Data; D009415:Nerve Net; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D016716:PC12 Cells; D050683:R-SNARE Proteins; D051381:Rats; D017207:Rats, Sprague-Dawley; D013569:Synapses / Q000502:physiology*; D050863:Synaptotagmin I; D050857:Synaptotagmins
D002135:Calcium-Binding Proteins; D008562:Membrane Glycoproteins; D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; D050683:R-SNARE Proteins; D050863:Synaptotagmin I; C494312:Syt1 protein, rat; D050857:Synaptotagmins; D008156:Luciferases