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Qiu-Xing Jiang

Qiu-Xing Jiang

University of Florida, USA

Title: Structural basis for the lipid-dependent gating of a Kv channel

Biography

Biography: Qiu-Xing Jiang

Abstract

Human cell membranes are made of both phospholipids and nonphospholipids. The nonphospholipids, such as cholesterol (CHOL), have no phosphate groups in their headgroup regions and are quite abundant in cell membranes. Mainly due to technical difficulties, quantitative study of possible effects of nonphospholipids on voltage-gated ion channels has been very challenging. Our prior studies have achieved three major developments: 1) a working hypothesis of lipid-dependent gating based on nonphospholipids stabilizing the voltage sensor domain (VSD) of the KvAP channel in the resting (“down”) conformation; 2) a novel bead-supported unilamellar membrane (bSUM) system and a new method to stabilize the KvAP channel in the resting state; and 3) chemically functionalized carbon (ChemiC) films for cryoEM imaging of low abundance complexes by high-affinity selection or of small macromolecular complexes (100-200 kDa) by keeping vitrified ice thinner than usual. The general idea for lipid dependent gating is that the annular lipids around a Kv channel change their arrangements in accompany with the conformational changes of the voltage-sensor domains. Our technical development made it feasible to study the CHOL-dependent gating effects on Kv channels. We studied the CHOL-dependent gating effects on Kv channels in bSUMs. Because almost all known lipid metabolic defects result from dysregulated homeostasis of nonphospholipids, our studies in animal models carrying CHOL metabolic defects will provide the first test of lipid-dependent gating in an in vivo physiological setting. Secondly, we apply our ChemiC method to cryoEM study of the 120 kDa KvAP in both an inactivated and a peptide-stabilized “down” state. The peptides selected from the nonphospholipid-stabilized down state have been showed to recognize the voltage sensors in the right conformation and keep the channels in the right conformation. Our results will reveal the structural basis for the nonphospholipid-induced conformational changes in Kv channels, and unveil connections to the lipid-metabolic defects in humans.

References:

  1. Hui Zheng, Weiran Liu, Lingyan Anderson, and Qiu-Xing Jiang. Lipid-dependent gating of a voltage-gated ion channel. Nature Comm., 2:250 doi:10.1038/ncomms1254, 2011.
  2. Marc Llaguno, Hui Xu, Liang Shi, Nian Huang, Hong Zhang, Qinghua Liu, and Qiu-Xing Jiang. (2014) Chemically functionalized nanometer-thick carbon films for single molecule imaging. J. Struct. Biol. 185(3):405-17.
  3. Hui Zheng, Sungsoo Lee, Marc Llaguno, and Qiu-Xing Jiang. (2016). bSUM: A bead-supported unilamellar membrane system facilitating unidirectional insertion of membrane proteins into giant vesicles. J Gen Physiol. 147(1):77-93.
  4. Hui Xu, Xiaojing He, Hui Zheng, Lily J. Huang, Fajian Hou, Zhiheng Yu, M. Jason de la Cruz, Brian Borkowski, Xuewu Zhang*, Zhijian J. Chen* and Qiu-Xing Jiang*. (2014) Structural basis for the prion-like MAVS filaments in antiviral innate immunity. eLife. 3:e01489. doi: 10.7554/eLife.01489.
  5. Sohini Mukherjee, Hui Zheng, Mehabaw Derebe, Keith Callenberg, Carrie L. Partch, Darcy Rollins, Daniel C. Propheter, Josep Rizo, Michael Grabe, Qiu-Xing Jiang*, and Lora V. Hooper*. (2014) Antibacterial membrane attach by a pore-forming C-type lectin. Nature, 505(7481): 103-7. (*co-senior authors).