Structure and physiological function of the human KCNQ1 channel voltage sensor intermediate state
- Vanderbilt University, United States
- Washington University in St Louis, United States
- Northwestern University, United States
- University of Alabama in Huntsville, United States
Abstract
Voltage-gated ion channels feature voltage sensor domains (VSDs) that exist in three distinct conformations during activation: resting, intermediate, and activated. Experimental determination of the structure of a potassium channel VSD in the intermediate state has previously proven elusive. Here, we report and validate the experimental three-dimensional structure of the human KCNQ1 voltage-gated potassium channel VSD in the intermediate state. We also used mutagenesis and electrophysiology in Xenopus laevis oocytes to functionally map the determinants of S4 helix motion during voltage-dependent transition from the intermediate to the activated state. Finally, the physiological relevance of the intermediate state KCNQ1 conductance is demonstrated using voltage-clamp fluorometry. This work illuminates the structure of the VSD intermediate state and demonstrates that intermediate state conductivity contributes to the unusual versatility of KCNQ1, which can function either as the slow delayed rectifier current (IKs) of the cardiac action potential or as a constitutively active epithelial leak current.
Data availability
The structures determined in this work have been deposited into the Protein Databank (PDB ID 6MIE).NMR data assignments and structural restraints have been deposited in the BioMagResBank (BMRB ID 30517).All electrophysiology and voltage-clamp fluorometry data generated or analysed during this study are included in the manuscript, supporting files, and source data file.
-
NMR structure of the KCNQ1 voltage-sensing domainProtein Data Base, 6MIE.
Article and author information
Author details
Funding
National Institutes of Health (R01 HL122010)
- Alfred L George
- Jens Meiler
- Charles R Sanders
National Institutes of Health (R01 NS092570)
- Jianmin Cui
National Institutes of Health (R01 HL126774)
- Jianmin Cui
National Institutes of Health (F32 GM117770)
- Keenan C Taylor
American Heart Association (18POST34030203)
- Panpan Hou
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
Ethics
Animal experimentation: Oocytes from Xenopus laevis (frogs) were employed in this work (at Washington University) and the frogs were cared for in accordance with the protocol approved by the Washington University Animal Studies Committee (Protocol # 20190030).
Reviewing Editor
- Merritt Maduke, Stanford University School of Medicine, United States
Version history
- Received: November 23, 2019
- Accepted: February 24, 2020
- Accepted Manuscript published: February 25, 2020 (version 1)
- Version of Record published: March 13, 2020 (version 2)
Copyright
© 2020, Taylor et al.
This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.
Metrics
-
- 3,462
- Page views
-
- 451
- Downloads
-
- 20
- Citations
Article citation count generated by polling the highest count across the following sources: Crossref, PubMed Central, Scopus.
Download links
A two-part list of links to download the article, or parts of the article, in various formats.
Downloads (link to download the article as PDF)
Open citations (links to open the citations from this article in various online reference manager services)
Cite this article (links to download the citations from this article in formats compatible with various reference manager tools)
Structure and physiological function of the human KCNQ1 channel voltage sensor intermediate state
eLife 9:e53901.
https://doi.org/10.7554/eLife.53901
Further reading
-
- Microbiology and Infectious Disease
- Structural Biology and Molecular Biophysics
The transcriptional regulator SsrB acts as a switch between virulent and biofilm lifestyles of non-typhoidal Salmonella enterica serovar Typhimurium. During infection, phosphorylated SsrB activates genes on Salmonella Pathogenicity Island-2 (SPI-2) essential for survival and replication within the macrophage. Low pH inside the vacuole is a key inducer of expression and SsrB activation. Previous studies demonstrated an increase in SsrB protein levels and DNA-binding affinity at low pH; the molecular basis was unknown (Liew et al., 2019). This study elucidates its underlying mechanism and in vivo significance. Employing single-molecule and transcriptional assays, we report that the SsrB DNA binding domain alone (SsrBc) is insufficient to induce acid pH-sensitivity. Instead, His12, a conserved residue in the receiver domain, confers pH sensitivity to SsrB allosterically. Acid-dependent DNA binding was highly cooperative, suggesting a new configuration of SsrB oligomers at SPI-2-dependent promoters. His12 also plays a role in SsrB phosphorylation; substituting His12 reduced phosphorylation at neutral pH and abolished pH-dependent differences. Failure to flip the switch in SsrB renders Salmonella avirulent and represents a potential means of controlling virulence.
-
- Neuroscience
- Structural Biology and Molecular Biophysics
Ca2+/calmodulin-dependent protein kinase II (CaMKII) is essential for long-term potentiation (LTP) of excitatory synapses that is linked to learning and memory. In this study, we focused on understanding how interactions between CaMKIIα and the actin-crosslinking protein α-actinin-2 underlie long-lasting changes in dendritic spine architecture. We found that association of the two proteins was unexpectedly elevated within 2 minutes of NMDA receptor stimulation that triggers structural LTP in primary hippocampal neurons. Furthermore, disruption of interactions between the two proteins prevented the accumulation of enlarged mushroom-type dendritic spines following NMDA receptor activation. α-Actinin-2 binds to the regulatory segment of CaMKII. Calorimetry experiments, and a crystal structure of α-actinin-2 EF hands 3 and 4 in complex with the CaMKII regulatory segment, indicate that the regulatory segment of autoinhibited CaMKII is not fully accessible to α-actinin-2. Pull-down experiments show that occupation of the CaMKII substrate-binding groove by GluN2B markedly increases α-actinin-2 access to the CaMKII regulatory segment. Furthermore, in situ labelling experiments are consistent with the notion that recruitment of CaMKII to NMDA receptors contributes to elevated interactions between the kinase and α-actinin-2 during structural LTP. Overall, our study provides new mechanistic insight into the molecular basis of structural LTP and reveals an added layer of sophistication to the function of CaMKII.
