GABAA receptor binding site residue Beta2 glutamate 155:possible role in channel preactivation

• Autorzy: Kisiel M. , Jatczak M. , Czyzewska M.M. , Brodzki M. , Cajkowski C. , Mozrzymas J.W.
• Języki publikacji: EN

Abstrakty

EN

BACKGROUND AND AIMS: The GABAA receptor is the main mediator responsible for inhibitory transmission in the brain. In our previous work (Szczot et al. 2014), we demonstrated for α1β2γ2 receptors that “classical” channel gating (opening/closing and desensitization) is preceded by a preactivation step, which is most likely initiated at the agonist-binding site. Here, we investigated the role of β2E155 residue in channel gating focusing on preactivation. Residue β2E155 is located in the GABA-binding site and may directly interact with agonist. Moreover, agonist induced local motions near this residue suggests it is an initial trigger that couples agonist binding to channel gating. METHODS: In this study, we combined ultrafast solution exchange with patch-clamp electrophysiology to record macroscopic currents mediated by wild-type and mutant (β2E155C) α1β2γ2 and α1β2 receptors. RESULTS: Cysteine substitution of β2E155 caused a large right-shift of the dose–response curves for GABA-elicited currents, which was independent of the presence of γ2 subunit. Furthermore, especially for α1β2γ2 receptors, β2E155C slowed down macroscopic desensitization kinetics. The mutant receptors also exhibited spontaneous channel activity. Taken together, the data suggest this mutation alters not only GABA binding but also GABA-mediated gating transitions. Nonstationary noise analysis of variance showed that for α1β2γ2 receptors, the β2E155C mutation significantly decreased maximal open probability without affecting single channel conductance. CONCLUSIONS: Model kinetic simulations of our data indicate that β2E155 is likely involved in preactivation transitions that precede channel opening supporting its role as an initial trigger for coupling binding to gating. This research has been financially supported by grant National Centre of Science grant: DEC-2013/11/B/NZ3/00983 and by ministry grant Pbmn135.

• Wydawca: -
• Czasopismo: Acta Neurobiologiae Experimentalis
• Rocznik: 2015
• Tom: 75
• Numer: Supl.
• Opis fizyczny: p.S51

Twórcy

autor

Kisiel M.

• Laboratory of Neuroscience, Department of Biophysics, Wroclaw Medical University, Wroclaw, Poland

autor

Jatczak M.

• Laboratory of Neuroscience, Department of Biophysics, Wroclaw Medical University, Wrocłlaw, Poland
• Laboratory of Cellular Neurobiology, Department of Animal Molecular Physiology, Wroclaw University, Wroclaw, Poland

autor

Czyzewska M.M.

• Laboratory of Neuroscience, Department of Biophysics, Wroclaw Medical University, Wrocłlaw, Poland

autor

Brodzki M.

• Laboratory of Neuroscience, Department of Biophysics, Wroclaw Medical University, Wrocłlaw, Poland
• Laboratory of Cellular Neurobiology, Department of Animal Molecular Physiology, Wroclaw University, Wroclaw, Poland

autor

Cajkowski C.

• Department of Neuroscience, School of Medicine and Public Health, University of Wisconsin-Madison, Madison, USA

autor

Mozrzymas J.W.

• Laboratory of Neuroscience, Department of Biophysics, Wroclaw Medical University, Wrocłlaw, Poland
• Laboratory of Cellular Neurobiology, Department of Animal Molecular Physiology, Wroclaw University, Wroclaw, Poland