Activity dependent internalization of the glutamate transporter GLT-1 requires calcium entry through the NCX sodium/calcium exchanger

Publication date: Available online 21 March 2018 Source:Neurochemistry International Author(s): Ignacio Ibáñez, David Bartolomé-Martín, Dolores Piniella, Cecilio Giménez, Francisco Zafra GLT-1 is the main glutamate transporter in the brain and its trafficking controls its availability at the cell surface, thereby shaping glutamatergic neurotransmission under physiological and pathological conditions. Extracellular glutamate is known to trigger ubiquitin-dependent GLT-1 internalization from the surface of the cell to the intracellular compartment, yet here we show that internalization also requires the participation of calcium ions. Consistent with previous studies, the addition of glutamate (1 mM) to mixed primary cultures (containing neurons and astrocytes) promotes GLT-1 internalization, an effect that was suppressed in the absence of extracellular Ca2+. The pathways of Ca2+ mobilization by astrocytes were analyzed in these mixed cultures using the genetically encoded calcium sensor GCaMP6f. A complex pattern of calcium entry was activated by glutamate, with a dramatic and rapid rise in the intracellular Ca2+ concentration partially driven by glutamate transporters, especially in the initial stages after exposure to glutamate. The Na+/Ca2+ exchanger (NCX) plays a dominant role in this Ca2+ mobilization and its blockade suppresses the glutamate induced internalization of GLT-1, both in astrocytes and in a more straightforward experimental system like HEK293 c...
Source: Neurochemistry International - Category: Neuroscience Source Type: research