Multifunctional transporter that transports L-glutamate as well as multiple ions such as chloride, sodium and phosphate. At the synaptic vesicle membrane, mainly functions as an uniporter that mediates the uptake of L-glutamate into synaptic vesicles at presynaptic nerve terminals of excitatory neural cells. The L-glutamate uniporter activity is electrogenic and is driven by the proton electrochemical gradient, mainly by the electrical gradient established by the vacuolar H(+)-ATPase across the synaptic vesicle membrane. In addition, functions as a chloride channel that allows a chloride permeation through the synaptic vesicle membrane that affects the proton electrochemical gradient and promotes synaptic vesicles acidification. At the plasma membrane, following exocytosis, functions as a symporter of Na(+) and phosphate from the extracellular space to the cytoplasm allowing synaptic phosphate homeostasis regulation. The symporter activity is electrogenic. Moreover, operates synergistically with SLC18A3/VACHT under a constant H(+) gradient, thereby allowing striatal vesicular acetylcholine uptake