INVESTIGADORES
SPITZMAUL Guillermo Federico
artículos
Título:
Single-channel Kinetic Analysis of Quimeric alpha7-5HT3A Receptors
Autor/es:
DIEGO RAYES; GUILLERMO SPITZMAUL; STEVEN M. SINE; CECILIA BOUZAT
Revista:
MOLECULAR PHARMACOLOGY
Editorial:
AMER SOC PHARMACOLOGY EXPERIMENTAL THERAPEUTICS
Referencias:
Lugar: Rockville Pike; Año: 2005 vol. 68 p. 1475 - 1483
ISSN:
0026-895X
Resumen:
The receptor chimera alpha7-5HT3A
has served as a prototype for understanding the pharmacology of alpha7
neuronal nicotinic receptors, yet its low single channel conductance has
prevented studies of the activation kinetics of single receptor
channels. In this study, we show that introducing mutations in the M3-M4 cytoplasmic linker of the chimera alters neither the apparent affinity for the agonist nor the EC50,
but increases the amplitude of agonist-evoked single channel currents
to enable kinetic analysis. Channel events appear as single brief
openings or as bursts of several openings in quick succession. Both
the open and closed time distributions are described as the sum of
multiple exponential components, but these do not change over a wide
range of acetylcholine (ACh), nicotine or choline concentrations. Bursts
elicited by a saturating concentration of ACh contain brief and long
openings and closings, and a cyclic scheme containing two open and two
closed states is found to adequately describe the data. The analysis
indicates that once fully occupied, the receptor opens rapidly and
efficiently, and closes and reopens several times before it
desensitizes. Channel closing and desensitization occur at similar rates
and account for the invariant open and closed time distributions.