Loop G of the GABAA receptor orthosteric binding site is involved in the final stages of channel gating

• Autorzy: Brodzki M. , Michalowski M.A. , Gos M. , Mozrzymas J.W.
• Języki publikacji: EN

Abstrakty

EN

INTRODUCTION: Inhibition of neuronal activity is shaped primarily by GABAA receptors. Agonist binding site (BS) at the β+/α‑ intersubunit interface is composed of 7 loops (A‑C from β and D‑G from α subunit), and the Loop G has been reported to play a major role in receptor activation, however the exact mechanism is not clear. α1F45 residue at Loop G has been shown to be engaged in receptor activation despite not directly contacting the agonist, and is well positioned for interactions with other crucial BS residues. Since this loop spans from the BS to the extracellular-transmembrane domain interface, it might have an important role in transferring energy of BS conformational transitions to the pore region. AIM(S): This study aims to reveal the role of loop G in distinct steps of receptor activation. METHOD(S): We used rapid agonist application to elicit macroscopic responses and single-channel recordings of GABA-evoked currents for wild-type (WT) and mutated (α1F45C/L/K/G) receptors. Model simulations of macroscopic and single-channel activity and in silico structural analysis have been performed. RESULTS: Mutated receptors showed a different kinetic profile of macroscopic currents (except α1F45L) with faster deactivation (α1F45C/K/G) and impaired desensitization (α1F45C/G). Single‑channel currents showed profound differences in all mutants; that is, closures were prolonged, openings were shortened, and Popen within bursts was reduced. Model simulations revealed changes primarily in opening/closing transitions. The homology model of WT showed loop G energy minimum at the α1F45 position, underlining its role in loop stability. In α1F45G/K mutants, this minimum declined. In α1F45G mutant, it can be attributed to the BS aromatic box disruption and α1F45K substitution could impair the GABA – α1R66 interaction. CONCLUSIONS: Mutations of the α1F45 residue in loop G of the BS affects final gating stages. This indicates the role of loop G in linking binding and gating processes. FINANCIAL SUPPORT: Supported by NCN grant UMO‑2015/18/A/NZ1/00395.

• Wydawca: -
• Czasopismo: Acta Neurobiologiae Experimentalis
• Rocznik: 2019
• Tom: 79
• Numer: Suppl.1
• Opis fizyczny: p.LXII-LXIII

Twórcy

autor

Brodzki M.

• Department of Molecular Physiology and Neurobiology, University of Wroclaw, Wroclaw, Poland
• Laboratory of Neuroscience, Department of Biophysics, Wroclaw Medical University, Wroclaw, Poland

autor

Michalowski M.A.

• Department of Molecular Physiology and Neurobiology, University of Wroclaw, Wroclaw, Poland
• Laboratory of Neuroscience, Department of Biophysics, Wroclaw Medical University, Wroclaw, Poland

autor

Gos M.

• Department of Molecular Physiology and Neurobiology, University of Wroclaw, Wroclaw, Poland,

autor

Mozrzymas J.W.

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