时间：2023年10月18日（周三）15:00~17:00

Time：3:00-5:00 PM, Wednesday, October 18, 2023

地点：西湖大学云栖校区 5号楼学术报告厅

Venue: Lecture Hall, Building 5, Yunqi Campus

主持人：西湖大学生命科学学院特聘研究员 卢培龙&吴建平

Host: Dr. Peilong Lu & Dr. Jianping Wu, PIs of School of Life Sciences

主讲人/Speaker：

Simon Scheuring

Professor of Weill Cornell Medicine College (WCM)

Crina Nimigean

Professor of Weill Cornell Medicine College (WCM)

报告题目及摘要/Title & Abstract:

1. Simon Scheuring: A Pentameric TRPV3 Channel with A Dilated Pore

Transient receptor potential (TRP) channels are a large, eukaryotic ion channel superfamily that control diverse physiological functions, and therefore are attractive drug targets. To date, more than 210 structures from over 20 different TRP channels have been determined, all are tetramers. Despite this wealth of structural information, many aspects concerning TRP-channels, and more specifically regarding TRPV-channels, remain poorly understood, including the pore-dilation phenomenon, whereby prolonged activation leads to an increase in conductance, permeability to large ions, and loss of rectification. Here, using high-speed atomic force microscopy (HS-AFM), we analyzed membrane-embedded TRPV3 at the single-molecule level, and discovered a hitherto unobserved pentameric state. Utilizing the ability of HS-AFM to visualize dynamic processes in real-time, we revealed the transience and reversibility of the pentamer that is in a dynamic equilibrium with the canonical tetramer through membrane diffusive protomer exchange. The prevalence of pentamers is increased upon addition of diphenylboronic anhydride (DPBA), an agonist that has been shown to induce pore-dilation in TRPV3. Based on these findings, we designed a protein production and single particle cryo-EM data analysis pipeline that allowed us to determine a 4.4Å cryo-EM structure of the TRPV3 pentamer, displaying a ~2.4 times enlarged pore as compared to the open state tetramer. The slow kinetics to enter and exit the pentameric state through protomer membrane diffusion, the increased pentamer formation following DPBA addition, and the enlarged pentamer pore, all indicate that the pentameric state represents the structural correlate of pore-dilation. Overall, we provide first structural evidence for a non-canonical pentameric TRP-channel assembly, laying the foundation for new directions in TRP-channel research. Furthermore, we discover 2D membrane diffusive protomer exchange as a novel mechanism for structural and functional plasticity of membrane proteins.

2. Crina Nimigean: Calcium Gating and Ball-and-chain Inactivation in Potassium Channels

Inactivation is the process by which ion channels terminate ion flux through pores while opening stimulus is still present. Inactivation of both Na and K channels is crucial for action potential generation and regulation of firing frequency in neurons.  Using cryo-EM we obtained structures of a Ca2+-gated and inactivating K (MthK) channel in lipid nanodiscs, which revealed a wide-open gate and a ball-and-chain inactivation mechanism in the presence of Ca2+. In the absence of Ca2+ we obtained a structure in closed state, where the bundle-crossing is sterically shut but where fenestrations are now visible between subunits, connecting the channel pore with the lipid bilayers. 

We showed that these fenestrations are the pathways that quaternary amine channel blockers use to access the channel pore in the closed state, highlighting a novel state-dependent access for potential drugs in this channel family. In addition, we showed that a reassessment may be needed about inferring gate location from channel block experiments when multiple access pathways into the pore are available.  

Finally, we found that ball-and-chain inactivation in MthK channels is highly lipid bilayer thickness dependent. We determined that this is not due to a change of the channel pore dimensions (the receptor site for the inactivation peptide) in the different thickness bilayers, but rather that the linkage to the channel is important. These results highlight the ease of modulating channel activity by simply changing bilayer thickness.

讲座联系人/Contact:

科技合作部Sci-tech02@westlake.edu.cn