Synaptic vesicles: Key organelles involved in neurotransmission

This article summarizes some of the recent advances in the understanding of structural and functional properties of isolated small synaptic vesicles (SSV) from mammalian brain. SSV contain a set of integral membrnae proteins which are highly specific for this organelle and which occur on all SSV of the central and peripheral nervous system irrespective of their transmitter content. In contrast, these proteins are absent from the membrane of peptide-containing large dense-core vesicles indicating that the two type of organelle have a different membrane composition. The availability of antibodies for these proteins has allowed the evaluation of the purity of vesicle preparations which is instrumental for functional studies. Recent advances in the study of neurotransmitter uptake have revealed that SSV contain specific carrier systems for glutamate and GABA. They are different from the transporters of the plasma membrane, and are dependent on the energy of a proton electrochemical gradient. The uptake of glutamate has been characterized in some detail and the mechanistic and physiological implications of these findings are discussed.