Banca de DEFESA: Luis Felipe Santos Menezes

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
STUDENT : Luis Felipe Santos Menezes
DATE: 22/03/2023
TIME: 14:00
LOCAL: Meio virtual
TITLE:

Effect on voltage-gated sodium channel kinetics of mutations in the SCN2A gene associated with epilepsy and of Tst2 peptide isolated from the scorpion Tityus stigmurus.

KEY WORDS:

Epilepsy, voltage-gated sodium channel, patch-clamp, channelopathies, Tityus stigmurus, Tst2, scorpion, electrophysiology and scorpion toxin.

PAGES: 106
BIG AREA: Ciências Biológicas
AREA: Biologia Geral
SUMMARY:

Voltage-gated sodium channels (Nav) are responsible for the initiation and propagation of the action potential. These channels are distributed throughout the body and have nine different subtypes (Nav1.1-Nav1.9). Structurally, they have four transmembrane domains, with each domain having six α-helices (S1-S6) and two or three β subunits. Changes in the kinetics of these channels can occur due to mutations in the genes that encode ion channels, resulting in channelopathies (eg epilepsy and arrhythmia) and the effect of animal toxins. Epilepsy is a disease caused by abnormal electrical activity in the brain. It can be focal, generalized, focal and generalized combined, or unknown. Infections (viral or bacterial in the brain), autoimmune diseases, acquired causes and genetic mutations are the main etiologies. Among the mutations, we can mention those caused in the genes that express voltage-dependent ion channels (Na+ , K+ , Ca2+ and Cl- ), such as those in the SCN2A gene that encodes the Nav1.2 channel. The I1596S variant has been associated with epilepsy by causing benign neonatal infantile seizure (BFNIS); the V1627M variant is associated with childhood epilepsy with focal migratory seizures (EIMFS) and the L1650P variant has been described to be related to early infantile epileptic encephalopathy (EIEE). Furthermore, the scorpions of the Buthidae family are of greater medical importance due to the number and severity of accidents caused by their species in humans. The venom of these animals has also been shown to be important for its biotechnological potential due to the presence of ion channel modulators. Tst2 is a peptide obtained from the venom of the scorpion Tityus stigmurus that has a high percentage of identity with peptides that act on voltage-gated sodium channels (NaScTxs). The objectives of this work were to evaluate the effect of the pathogenic variants I1596S, V1627M and L1650P, associated with epilepsy, on the kinetics of mutated human Nav1.2 channels and to carry out the electrophysiological characterization of the Tst2 peptide in Navs channels. As a result, it was found that the channel kinetics with the I1596S variant had the probability of opening upon activation altered for more hyperpolarized potentials and the probability of opening upon inactivation altered for less hyperpolarized potentials, and the V1627M mutation caused the Nav1. 2 had a slower recovery from inactivation that was faster than the control. The electrophysiological characterization (Nav1.1-Nav1.7) of the peptide Tst2 (100 nM) was performed. For the probability of opening on activation, the most affected channel was Nav1.1 (with pre-pulse) and Nav1.7 (without pre-pulse). Nav1.3 was most affected in the probability of opening on inactivation and Nav1.4 in the recovery of slow channel inactivation. No changes were observed in the rapid inactivation of any subtype tested. The Nav1.2 channel is expressed in the central nervous system (predominance in glutamatergic neurons). That said, mutations in the SCN2A gene that generate gain of function can lead to abnormal brain electrical activity. Finally, the Tst2 peptide has a high percentage of identity with both alpha and beta peptides. After the electrophysiological characterization, only the beta toxin activity could be observed, with the observed effect of shifting the probability of channel opening due to the entrapment of the domain II voltage sensor in a pre-activated state. In addition, a reduction in the macrocurrent was observed due to the passage of some channels from the closed state directly to the inactivated state. The electrophysiological characterization of the kinetics of the L1650P variant has not yet been carried out and the partial sequencing of the Tst2 peptide is being carried out in collaboration with Prof. Lourival Possani's group from the Institute of Biotechnology at UNAM, Mexico.

BANKING MEMBERS:
Presidente - 405268 - ELISABETH NOGUEIRA FERRONI
Interno - 233.125.178-93 - AISEL VALLE GARAY - UnB
Interno - 1666182 - WERNER LEOPOLDO TREPTOW
Externa à Instituição - LILIAN DOS ANJOS CARNEIRO - UNIEURO
Externa à Instituição - LUCIANA MIDORI INUZUKA NAKAHARADA - SÍRIO