Excitatory amino acid transporters (EAATs) present on the plasma membrane regulate and modulate glutamate neurotransmission by removing synaptically released glutamate back into cells, thereby having a profound impact on the level of receptor activation. EAATs also release glutamate into the extracellular space in a calcium-independent manner during ischemia.
The main goals of my research are to investigate the role of EAAT2, the main CNS astrocytic carrier, in neurodegenerative disorders including ischemia, stroke and Traumatic Brain Injury (TBI).
Molecules that limit glutamate release, antagonists of ionotropic glutamate receptors and compounds that target calcium influx have been demonstrated to reduce secondary effects of TBI, such as tissue edema and cell death. In addition, compounds that enhance EAAT2 activity in pathological conditions, as has been shown for ß-lactam antibiotics attenuate damage in both acute and chronic neurodegenerative disorders.
Through the characterization of Brazilian spider venoms, a valuable source of compounds bioactive on synaptic transmission we have discovered unique natural compounds that modulate glutamate transport. For instance, Parawixin1, a compound purified from Parawixia bistriata spider venom, stimulates glutamate uptake through EAAT2 and has neuroprotective effect on retinal tissue from ischemic damage.
Our lab will examine the effects of Parawixin1 on several aspects of TBI, by analyzing glutamate transport with radioactive assays in synaptosome preparations of the brains of rats injected with the compound prior and after the injury; and by cellular analyses that includes estimation of edema, tissue loss, activation of calpain and caspase-3 activation and loss of neuronal MAP-2 (markers of neurodegeneration and apoptosis).
We also aim to identify structural components that interact with these compounds by using chimeras of EAAT2 and other subtypes of glutamate transporters.
Finally, we are also interested in the pharmacological characterization of monoamine transporters of the human parasite Schistosoma mansoni to generate information on interaction of mammalian transporters with psychostimulants.
"A catecholamine transporter from the human parasite Schistosoma mansoni with low affinity for psychostimulants"
Larsen MB, Fontana AC, Magallhães LG, Rodrigues V, Mortensen OV.
Mol Biochem Parasitol. 2011 Jan 18.
"Two allelic isoforms of the serotonin transporter from Schistosoma mansoni display electrogenic transport and high selectivity for serotonin"
Fontana AC, Sonders MS, Pereira-Junior OS, Knight M, Javitch JA, Rodrigues V, Amara SG, Mortensen OV.
Eur J Pharmacol. 2009 Aug 15;616(1-3):48-57.
"Enhancing glutamate transport: mechanism of action of Parawixin1, a neuroprotective compound from Parawixia bistriata spider venom"
Fontana AC, de Oliveira Beleboni R, Wojewodzic MW, Ferreira Dos Santos W, Coutinho-Netto J, Grutle NJ, Watts SD, Danbolt NC, Amara SG.
Mol Pharmacol. 2007 Nov;72(5):1228-37. Epub 2007 Jul 23.
"Spider and wasp neurotoxins: pharmacological and biochemical aspects"
de O Beleboni R, Pizzo AB, Fontana AC, de O G Carolino R, Coutinho-Netto J, Dos Santos WF.
Eur J Pharmacol. 2004 Jun 16;493(1-3):1-17.
"Purification of a neuroprotective component of Parawixia bistriata spider venom that enhances glutamate uptake"
Fontana AC, Guizzo R, de Oliveira Beleboni R, Meirelles E Silva AR, Coimbra NC, Amara SG, dos Santos WF, Coutinho-Netto.
J. Br J Pharmacol. 2003 Aug;139(7):1297-309.
"Excitatory amino acid transporters: keeping up with glutamate"
Amara SG, Fontana AC.
Neurochem Int. 2002 Nov;41(5):313-8. Review.
"Paralizing activity of the Parawixia bistriata crude venom in termites: a new bioassay"
Fontana AC, Cairrão MA, Colusso AJ, Santos WF, Coutinho-Netto J.
Toxicon. 2000 Jan;38(1):133-8.