Trafficking of gap junction channels at a vertebrate electrical synapse in vivo.
Trafficking and turnover of transmitter receptors required to maintain and modify the strength of chemical synapses have been characterized extensively. In contrast, little is known regarding trafficking of gap junction components at electrical synapses. By combining ultrastructural and in vivo physiological analysis at identified mixed (electrical and chemical) synapses on the goldfish Mauthner cell, we show here that gap junction hemichannels are added at the edges of GJ plaques where they dock with hemichannels in the apposed membrane to form cell-cell channels and, simultaneously, that intact junctional regions are removed from centers of these plaques into either presynaptic axon or postsynaptic dendrite. Moreover, electrical coupling is readily modified by intradendritic application of peptides that interfere with endocytosis or exocytosis, suggesting that the strength of electrical synapses at these terminals is sustained, at least in part, by fast (in minutes) turnover of gap junction channels. A peptide corresponding to a region of the carboxy terminus that is conserved in Cx36 and its two teleost homologs appears to interfere with formation of new gap junction channels, presumably by reducing insertion of hemichannels on the dendritic side. Thus, our data indicate that electrical synapses are dynamic structures and that their channels are turned over actively, suggesting that regulated trafficking of connexons may contribute to the modification of gap junctional conductance.
Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, NY 10461, USA.
Carmen E
CE
Flores
Srikant
S
Nannapaneni
Kimberly G V
KG
Davidson
Thomas
T
Yasumura
Michael V L
MV
Bennett
John E
JE
Rash
Alberto E
AE
Pereda
D000818:Animals; D001692:Biological Transport; D002450:Cell Communication; D017630:Connexins / Q000737:chemistry / Q000502:physiology; D054351:Electrical Synapses / Q000187:drug effects / Q000502:physiology* / Q000648:ultrastructure; D004705:Endocytosis / Q000187:drug effects; D005089:Exocytosis / Q000187:drug effects; D005614:Freeze Fracturing; D006054:Goldfish; D007150:Immunohistochemistry; D007473:Ion Channels / Q000187:drug effects / Q000502:physiology* / Q000648:ultrastructure; D008561:Membrane Fusion; D009473:Neuronal Plasticity; D010446:Peptide Fragments / Q000494:pharmacology; D021381:Protein Transport; D050600:SNARE Proteins / Q000378:metabolism; D009435:Synaptic Transmission / Q000502:physiology*; D050825:Synaptosomal-Associated Protein 25 / Q000737:chemistry; D000097004:Gap Junction delta-2 Protein
D017630:Connexins; D007473:Ion Channels; D010446:Peptide Fragments; D050600:SNARE Proteins; D050825:Synaptosomal-Associated Protein 25; D000097004:Gap Junction delta-2 Protein