- Peptide CRQTGNT(S)KELRD, corresponding to amino acid residues 178-190 of rat synaptophysin (Accession P07825). 2nd intravesicular loop.
- Rat and mouse brain membranes and rat PC12 pheochromocytoma cell lysate (1:400-1:800).
- Western blot analysis of rat brain membranes (lanes 1 and 4), mouse brain membranes (lanes 2 and 5) and rat PC12 pheochromocytoma cell line lysate (lanes 3 and 6):1-3. Anti-Synaptophysin Antibody (#ANR-013), (1:400).
4-6. Anti-Synaptophysin Antibody, preincubated with Synaptophysin Blocking Peptide (#BLP-NR013).
- Rat dorsal root ganglia (1:100).
Synaptophysin is the major integral membrane protein of small synaptic vesicles1-3. It belongs to a family of proteins which includes synaptogyrin and synaptoporin. The protein contains 4 transmembrane domains and cytoplasmic N- and C-termini4. There are two intravesicular loops that contain disulfide bonds. The protein is N-glycosylated on the first intravesicular loop, a modification important for the synaptic vesicle targeting of synaptophysin. Indeed, a mutant form of the protein, unable to undergo glycolysation, leads to the accumulation of the protein in the cell body of neurons indicating that N-glycosylation is required for the synaptic localization of synaptophysin5. The C-terminal tail is extensively phosphorylated on Tyr residues. However, the biological significance of the post-translational modification is not yet determined6.
Although exact and specific role of synaptophysin remains a mystery, a study suggests that the protein is required for efficient endocytosis of synaptic vesicles in cultured hippocampal neurons6.
Since synaptophysin is exclusively detected in synaptic vesicles, it is widely used as a marker for presynaptic vesicles.
Genetic screening in humans and behavioral studies in rodents show that loss of synaptophysin expression or expression of a truncated form of the protein may be attributed to mental retardation and/or learning deficits7,8. Interestingly though, synaptic transmission in synaptophysin knockout mice remains normal6.