A SNARE complex containing syntaxin 3 is present in ribbon synapses of the retina.
In contrast to conventional synapses, which release neurotransmitter transiently, ribbon synapses formed by photoreceptors and bipolar cells of the retina release neurotransmitter continuously and modulate the rate in response to light. Both modes of release are mediated by synaptic vesicles but probably differ in the regulation of docking and fusion of synaptic vesicles with the plasma membrane. We have found that syntaxin 1, an essential component of the core fusion complex in conventional synapses, is absent from ribbon synapses of the retina, raising the possibility that these synapses contain a different type of syntaxin or syntaxin-like protein. By immunoprecipitating syntaxin 1-depleted retina and brain extracts with a SNAP-25 antibody and microsequencing the precipitated proteins, syntaxin 3 was detected in retina complexed with SNAP-25, synaptobrevin, and complexin. Using an anti-syntaxin 3 antiserum, syntaxin 3 was demonstrated to be present at high levels in retina compared to brain. Immunofluorescent staining of rat retina sections confirmed that syntaxin 3 is expressed by photoreceptor and bipolar cells in the retina. Thus, in the retina, expression of syntaxin 3 is correlated with ribbon synapses and may play a role in the tonic release of neurotransmitter.
Morgans
C W
CW
Department of Neuroanatomy, Max Planck Institute for Brain Research, 60528 Frankfurt, Germany.
Brandstätter
J H
JH
Kellerman
J
J
Betz
H
H
Wässle
H
H
D033942:Adaptor Proteins, Vesicular Transport; D000595:Amino Acid Sequence; D000818:Animals; D000954:Antigens, Surface / Q000032:analysis; D002417:Cattle; D008565:Membrane Proteins / Q000032:analysis*; D016253:Microscopy, Immunoelectron; D008969:Molecular Sequence Data; D009419:Nerve Tissue Proteins / Q000032:analysis / Q000378:metabolism; D009474:Neurons / Q000737:chemistry*; D011485:Protein Binding / Q000502:physiology; D050765:Qa-SNARE Proteins; D050683:R-SNARE Proteins; D051381:Rats; D012160:Retina / Q000737:chemistry / Q000166:cytology*; D050600:SNARE Proteins; D013569:Synapses / Q000737:chemistry* / Q000648:ultrastructure; D050825:Synaptosomal-Associated Protein 25; D050827:Syntaxin 1; D033921:Vesicular Transport Proteins
D033942:Adaptor Proteins, Vesicular Transport; D000954:Antigens, Surface; D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; D050765:Qa-SNARE Proteins; D050683:R-SNARE Proteins; D050600:SNARE Proteins; C494210:Snap25 protein, rat; C494213:Stx1a protein, rat; D050825:Synaptosomal-Associated Protein 25; D050827:Syntaxin 1; D033921:Vesicular Transport Proteins; C095992:complexin I