Migration of PIP2 lipids on voltage-gated potassium channel surface influences channel deactivation.

Liping Chen,Yang Li,Huaiyu Yang,Hualiang Jiang,Zanyuan Li,Yunguang Qiu,Zhuxi Chen,Qiansen Zhang

doi:10.1038/srep15079

Liping Chen, Yang Li + Show 6 more

Open Access

https://doi.org/10.1038/srep15079

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Abstract

Published studies of lipid-protein interactions have mainly focused on lipid binding to an individual site of the protein. Here, we show that a lipid can migrate between different binding sites in a protein and this migration modulates protein function. Voltage-gated potassium (Kv) channels have several potential binding sites for phosphatidylinositol-4,5-bisphosphate (PIP2). Our molecular dynamics (MD) simulations on the KCNQ2 channel reveal that PIP2 preferentially binds to the S4-S5 linker when the channel is in the open state while maintains a certain probability of migrating to the S2-S3 linker. Guided by the MD results, electrophysiological experiments using KCNQ2, KCNQ1, and hERG channels show that the migration of PIP2 toward the S2-S3 linker controls the deactivation rate of the channel. The data suggest that PIP2 can migrate between different binding sites in Kv channels with significant impacts on channel deactivation, casting new insights into the dynamics and physiological functions of lipid-protein interactions.

Highlights

Mainly focused on lipid binding to an individual site of the channel protein[26,27]
We observed that PIP2 preferentially binds to the S4-S5 linker in the open state, it exhibits a probability to migrate to the S2-S3 linker, where the lipid resides in the closed state
PIP2 migrates between the S2-S3 linker and S4-S5 linker in the open state of KCNQ2

Summary

Introduction

Mainly focused on lipid binding to an individual site of the channel protein[26,27]. Making use of the rich functional and structural results on Kv channels, molecular dynamics (MD) simulations allow visualization of multiple dynamic transitions and large conformational transformation between activated and deactivated states[9], which when combined with functional approaches, will likely give insightful illumination of the integral influence of PIP2 on Kv channels, including how it regulates the slow deactivation process. By combining 200-ns MD simulations, site-directed mutagenesis, and electrophysiological tests, we identified PIP2 interaction sites on both the S4-S5 linker and S2-S3 linker of the KCNQ2 channel, and found that PIP2 affects the activation of KCNQ2 channel differently from that of Shaker and Kv1.2 channels[28]. We performed new and longer (microseconds) MD simulations to examine the dynamics of PIP2 interactions with both the open and closed states of the KCNQ2 channel. We observed that PIP2 preferentially binds to the S4-S5 linker in the open state, it exhibits a probability to migrate to the S2-S3 linker, where the lipid resides in the closed state. The migration was abolished by neutralization of the positive charges in the S2-S3 linker, suggesting that PIP2 can migrate between different binding sites in Kv channels and the positive charges in the S2-S3 linker are critical for this function. Mutant KCNQ2, KCNQ1 and hERG channels and showed that the migration of PIP2 significantly impacts the deactivation kinetics

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