Regulation of Synaptic Vesicle Docking by Different Classes of Macromolecules in Active Zone Material
Figure 9
Classes of AZM macromolecules connected to undocked vesicles at various distances from vacated docking sites in activated terminals.
A) Based on 3-D measurements in surface models from activated active zones, undocked synaptic vesicles (SV) >∼30 nm from vacated docking sites on the presynaptic membrane (PM) have relatively few connections to main body AZM macromolecules. The number of connection sites gradually increases with decreasing distance of the undocked vesicles from the presynaptic membrane to <∼15 nm, where it is similar to that for docked vesicles at resting active zones (indicated by the open symbol on the Y-axis ± SD). B) Viewed from the median plane of the active zone, undocked synaptic vesicles 42–29 nm from the presynaptic membrane have connection sites formed mostly by booms (purple), vesicles 24–17 nm from the presynaptic membrane have connection sites formed mostly by booms and spars (red), while vesicles 16–4 nm from the presynaptic membrane have connection sites formed by similar numbers of booms, spars and ribs (yellow gold) as on docked vesicles (compare with Figure 6A). C) Viewed in the horizontal plane, undocked vesicles 15–4 nm from the presynaptic membrane have connection sites formed by pins (copper) as well as ribs.