Selective disruption of high sensitivity heat activation but not capsaicin activation of TRPV1 channels by pore turret mutations

Department of Physiology and Membrane Biology, School of Medicine, University of California, Davis, Davis, CA 95616, USA.
The Journal of General Physiology (Impact Factor: 4.79). 03/2012; 139(4):273-83. DOI: 10.1085/jgp.201110724
Source: PubMed


The capsaicin receptor transient receptor potential vanilloid (TRPV)1 is a highly heat-sensitive ion channel. Although chemical activation and heat activation of TRPV1 elicit similar pungent, painful sensation, the molecular mechanism underlying synergistic activation remains mysterious. In particular, where the temperature sensor is located and whether heat and capsaicin share a common activation pathway are debated. To address these fundamental issues, we searched for channel mutations that selectively affected one form of activation. We found that deletion of the first 10 amino acids of the pore turret significantly reduced the heat response amplitude and shifted the heat activation threshold, whereas capsaicin activation remained unchanged. Removing larger portions of the turret disrupted channel function. Introducing an artificial sequence to replace the deleted region restored sensitive capsaicin activation in these nonfunctional channels. The heat activation, however, remained significantly impaired, with the current exhibiting diminishing heat sensitivity to a level indistinguishable from that of a voltage-gated potassium channel, Kv7.4. Our results demonstrate that heat and capsaicin activation of TRPV1 are structurally and mechanistically distinct processes, and the pore turret is an indispensible channel structure involved in the heat activation process but is not part of the capsaicin activation pathway. Synergistic effect of heat and capsaicin on TRPV1 activation may originate from convergence of the two pathways on a common activation gate.

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Available from: Yuanyuan Cui, Mar 26, 2014
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    • "But they are not. For example, it was repeatedly observed that mutations to the pore turret exhibited strong disruptive effects on heat activation but spared capsaicin activation (Cui et al., 2012; Yang et al., 2010, 2014). This type of observations , taken as evidence in support of the structural separation of different gating pathways, is in fact fully expected from an allosteric coupling point of view: a perturbation to the structure underlying one gating modal is " sensed " by another allosterically coupled modal ONLY when measurement is made under conditions requiring the participation of the perturbed structure. "
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    ABSTRACT: Temperature-sensitive transient receptor potential (TRP) channels are structurally similar to other tetrameric cation channels, but can be potently activated by heat. Recent studies suggest that the pore-forming region directly participates in activation gating. In this chapter, we summarize major findings from both structural and functional studies concerning the gating role of the pore region, focusing in particular on TRPV1. The emerging picture is that the peripheral S1-S4 region of TRPV1 is rigid and plays a supporting role for the pore to undergo conformational rearrangements. This places the pore region in the center of activation gating.
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    • "Besides by capsaicin, TRPV1 receptor is activated by heat, low pH, and other ligands, leading to a burning pain sensation. Recent findings suggest that heat and capsaicin activate TRPV1 at different sites and they may act synergistically to stimulate channel gating (Cui et al. 2012). The expression of TRPV1 has been demonstrated in most of the tumor cells analyzed. "
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    • "In addition, they further support the notion that heat and capsaicin activate TRPV1 through different pathways (Jordt et al., 2000; Matta and Ahern, 2007; Yang et al., 2010; Cui et al., 2012). Our findings demonstrate that divalent cations can be a useful tool in the search for the heat activation mechanism. "
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    ABSTRACT: Transient receptor potential vanilloid type 1 (TRPV1) channel responds to a wide spectrum of physical and chemical stimuli. In doing so, it serves as a polymodal cellular sensor for temperature change and pain. Many chemicals are known to strongly potentiate TRPV1 activation, though how this is achieved remains unclear. In this study we investigated the molecular mechanism underlying the gating effects of divalent cations Mg(2+) and Ba(2+). Using a combination of fluorescence imaging and patch-clamp analysis, we found that these cations potentiate TRPV1 gating by most likely promoting the heat activation process. Mg(2+) substantially lowers the activation threshold temperature; as a result, a significant fraction of channels are heat-activated at room temperature. Although Mg(2+) also potentiates capsaicin- and voltage-dependent activation, these processes were found either to be not required (in the case of capsaicin) or insufficient (in the case of voltage) to mediate the activating effect. In support of a selective effect on heat activation, Mg(2+) and Ba(2+) cause a Ca(2+)-independent desensitization that specifically prevents heat-induced channel activation but does not prevent capsaicin-induced activation. These results can be satisfactorily explained within an allosteric gating framework in which divalent cations strongly promote the heat-dependent conformational change or its coupling to channel activation, which is further coupled to the voltage- and capsaicin-dependent processes.
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