Glutamate concentration increases significantly in the extracellular compartment during brain ischaemia and anoxia. This increase has an important Ca2+-independent component, which is due in part to the reversal of glutamate transporters of the plasma membrane of neurons and glia. The toxin phoneutriatoxin 3-4 (Tx3-4) from the spider Phoneutria nigriventer has been reported to decrease the evoked glutamate release from synaptosomes by inhibiting Ca2+ entry via voltage-dependent Ca2+ channels. However, we report here that Tx3-4 is also able to inhibit the uptake of glutamate by synaptosomes in a time-dependent manner and that this inhibition in turn leads to a decrease in the Ca2+-independent release of glutamate. No other polypeptide toxin so far described has this effect. Our results suggest that Tx3-4 can be a valuable tool in the investigation of function and dysfunction of glutamatergic neurotransmission in diseases such as ischaemia.
Inhibition of glutamate uptake by a polypeptide toxin (phoneutriatoxin 3-4) from the spider Phoneutria nigriventer
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Helton J. REIS, Marco A. M. PRADO, Evanguedes KALAPOTHAKIS, Marta N. CORDEIRO, Carlos R. DINIZ, Luiz A. DE MARCO, Marcus V. GOMEZ, Marco A. ROMANO-SILVA; Inhibition of glutamate uptake by a polypeptide toxin (phoneutriatoxin 3-4) from the spider Phoneutria nigriventer. Biochem J 15 October 1999; 343 (2): 413–418. doi: https://doi.org/10.1042/bj3430413
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