Ectopic GABAA receptor ß3 subunit determines Cl- / HCO 3 -
FEBS J
; 288(2): 699-712, 2021 01.
Article
en En
| MEDLINE
| ID: mdl-32383536
Neuronal intracellular chloride concentration ([Cl- ]i ) is a crucial determinant of transmission mediated by the γ-aminobutyric acid type A receptor (GABAA R), which subserves synaptic and extrasynaptic inhibition as well as excitation. The Cl- ion is the main carrier of charge through the GABAA R; however, bicarbonate ions ( HCO3- ) flowing in the opposite direction can also contribute to the net current. The direction of Cl- and HCO3- fluxes is determined by the underlying electrochemical gradient, which is controlled by Cl- transporters and channels. Accumulating evidence suggests that active mechanisms of chloride transport across the GABAA R pore can underlie the regulation of [Cl- ]i . Measurement of Cl- / HCO3- -ATPase activity and Cl- transport in HEK 293FT cells expressing homomeric or heteromeric GABAA R ensembles (α2, ß3, or γ2) with fluorescent dye for chloride demonstrated that receptor subtypes containing the ß3 subunit show enzymatic activity and participate in GABA-mediated or ATP-dependent Cl- transport. GABA-mediated flow of Cl- ions into and out of the cells occurred for a short time period but then rapidly declined. However, Cl- ion flux was stabilized for a long time period in the presence of HCO3- ions. The reconstituted ß3 subunit isoform, purified as a fusion protein, confirmed that ß3 is critical for ATPase; however, only the triplet variant showed the full receptor function. The high sensitivity of the enzyme to γ-phosphate inhibitors led us to postulate that the ß3 subunit is catalytic. Our discovery of a GABAA R type that requires ATP consumption for chloride movement provides new insight into the molecular mechanisms of inhibitory signaling.
Palabras clave
Texto completo:
1
Colección:
01-internacional
Base de datos:
MEDLINE
Asunto principal:
Bicarbonatos
/
Cloruros
/
Adenosina Trifosfatasas
/
Receptores de GABA-A
Límite:
Animals
/
Humans
Idioma:
En
Revista:
FEBS J
Asunto de la revista:
BIOQUIMICA
Año:
2021
Tipo del documento:
Article
País de afiliación:
Rusia
Pais de publicación:
Reino Unido