INVESTIGADORES
PLAZAS Paola Viviana
congresos y reuniones científicas
Título:
MUTATION OF CONSERVED RESIDUES IN THE M2 DOMAIN ALTER CHANNEL GATING OF THE 910 NICOTINIC RECEPTOR
Autor/es:
PLAZAS PV; DE ROSA MJ; KATZ E; BOUZAT C; ELGOYHEN AB
Reunión:
Conferencia; Society for Neuroscience 34th Annual Meeting; 2004
Resumen:
Nicotinic acetylcholine receptors (nAChRs) form
part of a gene superfamily, which includes GABAA, GABAc,
serotonin type 3 and glycine receptors. The putative channel-forming M2 domains
of these receptors contain two highly conserved residues: a leucine (L9´) and a
valine (V13´), which are postulated to form a constricting hydrophobic girdle
in the middle of the ion pathway. The aim of the present work was to study the
role of these residues in the a9a10 nAChR function. cDNAs from
rat a9 and a10 subunits, in which the
amino acids L9´ or V13´ were mutated to threonine (T), were expressed in Xenopus
laevis oocytes and agonist-evoked currents were measured under
two-electrode voltage-clamp. When compared to wild type receptors, ACh-evoked
currents through a9a10(L9´T) and a9a10(V13´T) nAChRs exhibited
much lower desensitization kinetics and an increase in their apparent affinity
for this agonist. Choline, a weak partial agonist of the wild type receptor,
behaved as a full agonist of the mutant receptors. Furthermore, nicotine,
muscarine and ICS-205 930, antagonists of the wild type receptor, elicited
ionic currents in oocytes expressing these mutants. A constitutive activation
of mutant receptors was observed, even in the absence of the agonist. Single
channel recordings in the cell-attached mode in oocytes, revealed an increase
in the ton of the mutants, being more pronounced in the
case of V13 and indicating a stabilization of the open state. Our results
suggest that sites centrally located at the TM2 region of the pore are involved
in channel gating of the a9a10 nAChR. Supported by
ANPCyT, NOHR and HHMI.