Activation of TRPV1 channels inhibits mechanosensitive Piezo channel activity by depleting membrane phosphoinositides

Abstract

Capsaicin is an activator of the heat-sensitive TRPV1 (transient receptor potential vanilloid 1) ion channels and has been used as a local analgesic. We found that activation of TRPV1 channels with capsaicin either in dorsal root ganglion neurons or in a heterologous expression system inhibited the mechanosensitive Piezo1 and Piezo2 channels by depleting phosphatidylinositol 4,5-bisphosphate [PI(4,5)P2] and its precursor PI(4)P from the plasma membrane through Ca2+-induced phospholipase Cδ (PLCδ) activation. Experiments with chemically inducible phosphoinositide phosphatases and receptor-induced activation of PLCβ indicated that inhibition of Piezo channels required depletion of both PI(4)P and PI(4,5)P2. The mechanically activated current amplitudes decreased substantially in the excised inside-out configuration, where the membrane patch containing Piezo1 channels is removed from the cell. PI(4,5)P2 and PI(4)P applied to these excised patches inhibited this decrease. Thus, we concluded that Piezo channel activity requires the presence of phosphoinositides, and the combined depletion of PI(4,5)P2 or PI(4)P reduces channel activity. In addition to revealing a role for distinct membrane lipids in mechanosensitive ion channel regulation, these data suggest that inhibition of Piezo2 channels may contribute to the analgesic effect of capsaicin.

Cell Type Specific Splicing of Piezo2 Regulates Mechanotransduction

“…However, our analysis has not been exhaustive as we did not examine all splice variants of Piezo2 and we did not investigate the potential interaction of Piezo2 with other membrane proteins. Other intracellular signaling pathways (Borbiro et al, 2015;Dubin et al, 2012) and protein interactions (Narayanan et al, 2016;Poole et al, 2014) have been shown to modulate Piezo2 function. More importantly, to fully appreciate the contribution of receptor diversification, it will be important to determine the in vivo consequences of Piezo2 splicing.…”

Piezo1 Channels are Inherently Mechanosensitive

“…However, our data does not argue that other factors are not involved in modulating Piezo mechanosensitivity. For example, cytoskeleton and associated proteins such as STOML3 regulate the mechanosensitivity of Piezo1 (Borbiro et al, 2015;Gottlieb et al, 2012;Poole et al, 2014). Regardless, our studies establish that like the bacterial MS channels, the mechanosensitivity of Piezo1 is inherent, and no other proteins or second messenger signals are required for the baseline mechanosensitivity of Piezo1.…”

Spicing up the sensation of stretch: TRPV1 controls mechanosensitive Piezo channels

“…The fi ndings from Borbiro et al (7) uncover part of the underlying mechanisms of capsaicin-induced attenuation in mechanical pain, which employs a TRPV1-mediated calcium infl ux that triggers depletion of phosphoinositides. Given the fi ndings from Patapoutian's group indicating that Piezo2 does not account for painful mechanosensation (8), further study is required to confi rm this inhibitory effect in vivo and ascertain which Piezo channel subtype is regulated in hyperalgesic states.…”

“…In this issue of Science Signaling, Borbiro et al (7) demonstrate that activation of TRPV1 inhibits rapidly adapting, mechanically activated (MA) cation channels. They report that the majority (>70%) of TRPV1-positive neurons exhibit rapidly adapting, intermediate, or slowly adapting MA current.…”

“…Borbiro et al (7) ascertained how the inhibitory response was tied to dynamic changes of phosphoinositides, which differed between capsaicin stimulation of TRPV1 and carbachol stimulation of the M1 receptor. Using fl uorescence resonance energy transfer (FRET)-based phosphoinositide sensors, they found a correlation between Piezo channel inhibition and phosphoinositide depletion.…”