Contribution of the KCa3.1 channel–calmodulin interactions to the regulation of the KCa3.1 gating process
| Autor: | Marie-France Lavoie, Line Garneau, Patricia Morales, Lucie Parent, Hélène Klein, Rémy Sauvé |
|---|---|
| Rok vydání: | 2013 |
| Předmět: |
Calmodulin
Physiology Stereochemistry Protein subunit Molecular Sequence Data Static Electricity Gating Plasma protein binding Molecular Dynamics Simulation Hydrophobic effect 03 medical and health sciences 0302 clinical medicine Protein structure Animals Amino Acid Sequence Research Articles 030304 developmental biology 0303 health sciences biology Chemistry C-terminus Intermediate-Conductance Calcium-Activated Potassium Channels Potassium channel Protein Structure Tertiary Rats Protein Subunits Mutation biology.protein Calcium Ion Channel Gating 030217 neurology & neurosurgery Protein Binding |
| Zdroj: | The Journal of General Physiology |
| ISSN: | 1540-7748 0022-1295 |
| DOI: | 10.1085/jgp.201210933 |
| Popis: | The Ca2+-activated potassium channel of intermediate conductance, KCa3.1, is now emerging as a therapeutic target for a large variety of health disorders. The Ca2+ sensitivity of KCa3.1 is conferred by the Ca2+-binding protein calmodulin (CaM), with the CaM C-lobe constitutively bound to an intracellular domain of the channel C terminus. It was proposed on the basis of the crystal structure obtained for the C-terminal region of the rat KCa2.2 channel (rSK2) with CaM that the binding of Ca2+ to the CaM N-lobe results in CaM interlocking the C-terminal regions of two adjacent KCa3.1 subunits, leading to the formation of a dimeric structure. A study was thus undertaken to identify residues of the CaM N-lobe–KCa3.1 complex that either contribute to the channel activation process or control the channel open probability at saturating Ca2+ (Pomax). A structural homology model of the KCa3.1–CaM complex was first generated using as template the crystal structure of the C-terminal region of the rat KCa2.2 channel with CaM. This model was confirmed by cross-bridging residues R362 of KCa3.1 and K75 of CaM. Patch-clamp experiments were next performed, demonstrating that the solvation energy of the residue at position 367 in KCa3.1 is a key determinant to the channel Pomax and deactivation time toff. Mutations of residues M368 and Q364 predicted to form anchoring points for CaM binding to KCa3.1 had little impact on either toff or Pomax. Finally, our results show that channel activation depends on electrostatic interactions involving the charged residues R362 and E363, added to a nonpolar energy contribution coming from M368. We conclude that electrostatic interactions involving residues R362 and E363 and hydrophobic effects at M368 play a prominent role in KCa3.1 activation, whereas hydrophobic interactions at S367 are determinant to the stability of the CaM–KCa3.1 complex throughout gating. |
| Databáze: | OpenAIRE |
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