The plasma membrane protein SNAP-25, but not syntaxin, is present at photoreceptor and bipolar cell synapses in the rat retina.
The two neuronal plasma membrane proteins synaptosomal associated protein 25 kDa (SNAP-25) and syntaxin form, in current models of synaptic vesicle exocytosis, a docking complex on the presynaptic plasma membrane. This docking complex interacts with the integral synaptic vesicle protein, synaptobrevin. We have examined, in the rat retina, the distribution of SNAP-25 and syntaxin using light and electron microscopic immunocytochemistry. SNAP-25 immunoreactivity was present in the outer and inner nuclear layers at the membranes of photoreceptor and amacrine cell somata, in the outer plexiform layer in the terminals of photoreceptor cells and throughout the inner plexiform layer in the terminals of bipolar and amacrine cells. In contrast, syntaxin immunoreactivity was not found in the terminals of photoreceptor and bipolar cells, but only in the terminals of amacrine cells. Because of the absence of detectable syntaxin from the terminals of photoreceptor and bipolar cells, we propose that either a novel syntaxin isoform or a syntaxin-like protein exists at the ribbon synapses formed by these neurons.
Brandstätter
J H
JH
Abteilung für Neuroanatomie, Max-Planck-Institut für Hirnforschung, Frankfurt am Main, Germany.
Wässle
H
H
Betz
H
H
Morgans
C W
CW
D000818:Animals; D007150:Immunohistochemistry; D008565:Membrane Proteins / Q000378:metabolism*; D008854:Microscopy, Electron; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D010786:Photoreceptor Cells / Q000378:metabolism* / Q000648:ultrastructure; D050765:Qa-SNARE Proteins; D051381:Rats; D012160:Retina / Q000166:cytology / Q000378:metabolism* / Q000648:ultrastructure; D013569:Synapses / Q000378:metabolism* / Q000648:ultrastructure; D050825:Synaptosomal-Associated Protein 25
D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; D050765:Qa-SNARE Proteins; C494210:Snap25 protein, rat; D050825:Synaptosomal-Associated Protein 25