Imaging+the+TRPV1+Protein+Channel

Definition of Cryo-electron imaging:
"Over the past decade, the phrase “cryo-electron microscopy”, often abbreviated as “cryo-EM”, has evolved to encompass a broad range of experimental methods. At the core, each of these is based upon the principle of imaging radiation-sensitive specimens in a transmission electron microscope under cryogenic conditions. In biology, applications of cryo-EM now span a wide spectrum, ranging from imaging intact tissue sections and plunge-frozen cells to individual bacteria, viruses and protein molecules. Cryo-electron tomography, single-particle cryo-electron microscopy, and electron crystallography are all sub-disciplines of cryo-EM that have been used successfully to analyze biological structures in different contexts. These methods have been used singly as well as in hybrid approaches, where the information from electron microscopy is combined with complementary information obtained using X-ray crystallographic and NMR spectroscopic approaches."  (From "Cryo-electron microsopy: a primer for the non-microscopist," available at https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3537914/)

==**In 2013, Liao et al published images of a mammalian TRPV1 channel realized through electron cryo-microscopy at a 3.4A resolution (Figure 2). The images reveal a wide-mouthed, four-fold symmetrical design around a central ion pathway. The pathway itself arose from transmembrane helices and an interior pore loop with voltage sensor elements on the side. Liao et al explain the significance of their work:**==

"Here, we exploit advances in electron cryo-microscopy to determine the structure of a mammalian TRP channel, TRPV1, at 3.4Å resolution, breaking the side-chain resolution barrier for membrane proteins without crystallization. Like voltage-gated channels, TRPV1 exhibits four-fold symmetry around a central ion pathway formed by transmembrane helices S5–S6 and the intervening pore loop, which is flanked by S1–S4 voltage sensor-like domains. TRPV1 has a wide extracellular ‘mouth’ with short selectivity filter. The conserved ‘TRP domain’ interacts with the S4–S5 linker, consistent with its contribution to allosteric modulation. Subunit organization is facilitated by interactions among cytoplasmic domains, including N-terminal ankyrin repeats. These observations provide a structural blueprint for understanding unique aspects of TRP channel function."

The image below shows the results of the cryo-electron imaging (left) and its reconstruction into color-coded, 3D images:



The structural details of a single TRPV1 subunit are shown below. The structural domains are color coded in ribbons.



Finally, the unique structural features of the TRPV1 channel are shown



**Another view of the TRPV1 channel comes from the work of Moiseenkova-Bell at al (2008).**
We see first the location of the channel in its full roundness and then as cut vertically:



Next, we see a comparison between the TRPV channel and that of a potassium channel. We may note the greater density of the TRPV channel:



Z**heng (2013) captures the way the TRPV1 Protein Channel works in the experience of pain:**


(Left panel) At the cellular level, heat and capsaicin share the same target (TRPV1) for activating sensory neurons, which elicits the sensation of heat or pain. (Right panel) At the molecular level, heat and capsaicin work through distinct activation pathways.

Materials and Methods Prevalence of Fibromyalgia TRPV Genes Family Portrait Broader Impact - Pharmacogenetics and Fibromyalgia Criticism of the Proove Genetic Test Discussion - The Genetic Approach to Fibromyalgia Works Cited