KCNQ1 channels voltage dependence through a voltage-dependent binding of the S4-S5 linker to the pore domain.

Frank S Choveau (1, 2) , Nicolas Rodriguez (1, 2) , Fayal Abderemane Ali (2, 1) , Alain J Labro (3) , Thierry Rose , Shehrazade Dahimène , Hélène Boudin (4) , Carole Le Hénaff (5) , Denis Escande (1, 2) , Dirk J Snyders (6) , Flavien Charpentier (2, 1) , Jean Mérot (2, 1) , Isabelle Baró (1, 2) , Gildas Loussouarn (1, 2)

1 Institut du thorax
2 Cardiopathies et mort subite [ERL 3147]
3 UA - University of Antwerp
4 Immunointervention dans les allo et xénotransplantations
5 Interface biomatériaux/Tissus hôtes
6 IP - Institut Pasteur [Paris]

Voltage-dependent potassium (Kv) channels are tetramers of six transmembrane domain (S1-S6) proteins. Crystallographic data demonstrate that the tetrameric pore (S5-S6) is surrounded by four voltage sensor domains (S1-S4). One key question remains: how do voltage sensors (S4) regulate pore gating? Previous mutagenesis data obtained on the Kv channel KCNQ1 highlighted the critical role of specific residues in both the S4-S5 linker (S4S5$_L$) and S6 C terminus (S6($_T$)). From these data, we hypothesized that S4S5$_L$ behaves like a ligand specifically interacting with S6$_T$ and stabilizing the closed state. To test this hypothesis, we designed plasmid-encoded peptides corresponding to portions of S4S5$_L$ and S6$_T$ of the voltage-gated potassium channel KCNQ1 and evaluated their effects on the channel activity in the presence and absence of the ancillary subunit KCNE1. We showed that S4S5$_L$ peptides inhibit KCNQ1, in a reversible and state-dependent manner. S4S5$_L$ peptides also inhibited a voltage-independent KCNQ1 mutant. This inhibition was competitively prevented by a peptide mimicking S6$_T$, consistent with S4S5$_L$ binding to S6$_T$. Val$^{254}$ in S4S5$_L$ is known to contact Leu$^{353}$ in S6$_T$ when the channel is closed, and mutations of these residues alter the coupling between the two regions. The same mutations introduced in peptides altered their effects, further confirming S4S5$_L$ binding to S6$_T$. Our results suggest a mechanistic model in which S4S5$_L$ acts as a voltage-dependent ligand bound to its receptor on S6 at rest. This interaction locks the channel in a closed state. Upon plasma membrane depolarization, S4 pulls S4S5$_L$ away from S6$_T$, allowing channel opening.

Domaines: Biochimie, Biologie Moléculaire

Frank S Choveau, Nicolas Rodriguez, Fayal Abderemane Ali, Alain J Labro, Thierry Rose, et al.. KCNQ1 channels voltage dependence through a voltage-dependent binding of the S4-S5 linker to the pore domain.. Journal of Biological Chemistry, 2011, 286 (1), pp.707-716. ⟨10.1074/jbc.M110.146324⟩. ⟨hal-00642776⟩