Structures and gating mechanisms of TRP ion channels

University Of California, San Francisco, San Francisco CA

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Abstract

? DESCRIPTION (provided by applicant): TRP channels represent a group of non-selective cation channels that respond to a wide range of chemical and physical stimuli. It is a large and diverse superfamily, second only to potassium channels. TRP Vanilloid (TRPV) is a subfamily of thermosensitive TRP channels that enable somatosensory neurons to detect changes in ambient temperature. They are expressed in sensory nerves and/or other cell types, where they play important roles in sensing environmental noxious stimuli such as high temperature, acidic pH and natural or synthetic irritants. However, despite their intriguing roles in a number of physiological and pathophysiological processes, structural studies of TRP ion channels have been very challenging. A major bottleneck has been the difficulties in obtaining well-ordered three-dimensional (3D) crystals for any member of the TRP channel superfamily, which is a prerequisite for structure determination by X-ray crystallography as the most successful and well-established method for protein structure determination. Recent technological breakthroughs in single particle electron cryomicroscopy (cryoEM) have enabled near atomic resolution structure determination of macromolecules of various sizes and symmetry, no longer limited to highly symmetrical large object. It also enabled atomic structure determination of integral membrane proteins without requiring formation of 3D crystals. We determined the atomic structure of TRPV1 ion channel, which is the first atomic structure of the entire TRP channel family and the first atomic structure of an integral membrane protein determined by single particle cryoEM. We will use near atomic resolution single particle cryoEM as our main structural analysis tool, together with other methods in molecular biology, biochemistry and biophysics, to elucidate the mechanism that governs the functions of a subfamily of TRP channels, TRPV. We will address following specific questions: (1) what is the mechanism of polymodal activation of TRPV1 ion channel, a receptor for capsaicin; (2) what is the mechanism of thermosensitivity of TRPV channels; and (3) to improve the resolution of single particle cryoEM further to visualize ligands and ions binding. Substantial completion of these aims will advance our knowledge about the TRP channel function as well as advancing the technology of single particle cryoEM.