Dear Vladimir Khayenko

Early studies showed that synaptophysin (SY) is restricted to vesicles and Golgi tubular membranes:

https://journals.sagepub.com/doi/abs/10.1177/39.11.1918927

Evidence using the confocal microscope showed that most SY is identified as axon terminal vesicles

https://www.sciencedirect.com/science/article/abs/pii/S0165027099001636

Since it is a vesicle protein, you would expect to find it wherever there are vesicles. You may look through studies that stain SY in neurons like the following paper:

https://content.iospress.com/articles/journal-of-alzheimers-disease/jad160297

As for extrasynaptic locations, the following paper is very interesting to read as it involves vesicular tracking through monitoring SY.

https://www.sciencedirect.com/science/article/pii/S258900421930197X