Kanazawa University NanoLSI Podcast:Experiments reveal chilli-sensitive molecular structure fluctuation changes in TRPV1

Kanazawa University NanoLSI Podcast:Experiments reveal chilli-sensitive molecular structure fluctuation changes in TRPV1

Transcript of this podcast

 Hello and welcome to the NanoLSI podcast. Thank you for joining us today. In this episode we feature the latest research by Ayumi Sumino at the Kanazawa University NanoLSI alongside Motoyuki Hattori at Fudan University in China, and their colleagues.

 The research described in this podcast was published in the journal Proceedings of the National Academy of Science in May 2023

 Kanazawa University NanoLSI website

https://nanolsi.kanazawa-u.ac.jp/en/

Experiments reveal chilli-sensitive molecular structure fluctuation changes in TRPV1

Researchers at Kanazawa University report high-speed atomic force microscopy experiments that show how ligands associated with stimulating and suppressing activation of the TRPV1 protein increase and decrease the molecule’s structural variations. The observations provide insights into how these heat- and chilli-sensing proteins function.

The skin senses heat – both from increased temperature and molecules like capsaicin in chillies – through the activation of protein receptors called Transient receptor potential vanilloid member 1 or TRPV1. However, the mechanisms behind the function of TRPV1 have not been clear. Now Ayumi Sumino at Kanazawa University in Japan and Motoyuki Hattori at the Fudan University in China and their colleagues provide important insights into this mechanism. Using high-speed atomic force microscopy to compare the protein with and without stimulating or suppressing molecules – ligands – bound to it, they obtain what they describe as “the first experimental evidence showing the correlation between molecular fluctuation and the gating state (ligand binding)”.

So what was already known about this mechanism?

Well once activated, the TRPV1 channel opens, allowing ions to permeate and signalling to the nervous system that a noxious stimulant is present. And in 2011 researchers at the Howard Hughes Medical Institute in the US put forward a theoretical basis for the activation of the receptor derived from thermodynamics, a theoretical framework that has since been corroborated by experiment. The idea was that the molecule would respond to heat with a change in heat capacity, which is related to the fluctuations in the molecule’s conformation. Structures for the TRPV1 protein were known from previous cryo electron microscopy studies but these did not clarify how the fluctuations in protein conformation might change with stimulating or suppressing molecules, or even whether temperature and chilli sensing shared the same molecular mechanism.

Here's where the high-speed atomic force microscopy comes in

Atomic force microscopy (AFM) senses the topology of surfaces through the effect of distance on the forces on a nanosized tip positioned directly above the surface. The microscope was first invented in 1986 but gained a new lease of life through work at Kanazawa University that enabled it to capture topologies at high speed thereby providing a window into the dynamics of structures.

Sumino, Hattori and colleagues used high-speed AFM to image the TRPV1 receptor both in its unbound state and when bound to ligand molecules that either stimulate, that is agonist molecules, or suppress - antagonist molecules - the protein’s activity. They used the molecule resiniferatoxin, which is 1000 times hotter than capsaicin, as the agonist and for the antagonist they used capsazepine, which blocks the pain of capsaicin.

From the structures captured the researchers were able to observe fluctuations in the conformation of both the bound and unbound states of TRPV1. They found that resinifera

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