Calcium Influx through TRPV1 Inhibits Piezo Channels via Phosphoinositide Depletion

Abstract

Capsaicin, the activator of the noxious heat sensor TPRV1 is clinically used to relieve chronic pain. Desensitization of TRPV1 involves downstream PLCδ activation, but the mechanism how capsaicin treatment can also alleviate mechanical allodynia is unknown. Piezo2 encodes rapidly adapting mechanically activated currents in sensory neurons. Expression of these novel mechanosensitive ion channels in a subset of TPRV1 positive neurons suggests their role in pain related sensory mechanotransduction.Our study shows that capsaicin application inhibited rapidly adapting mechanically activated currents in TRPV1 expressing sensory neurons. We also show that TRPV1 activation inhibited heterologously expressed Piezo1 and Piezo2 ion channels in whole-cell patch clamp experiments. Inclusion of either phosphatidylinositol 4,5-bisphosphate [PI(4,5)P2] or its precursor PI(4)P in the patch pipette alleviated this inhibitory effect. Activation of PLCβ by stimulating muscarinic receptors only marginally inhibited mechanically activated Piezo1 currents. Experiments using phosphoinositide sensors revealed that activation of PLCδ by a robust calcium influx through TRPV1 severely depleted PI(4,5)P2 and PI(4)P. On the other hand, muscarinic stimulation of PLCβ significantly decreased PI(4,5)P2 levels, but only induced a small decrease of PI(4)P. This differential activation of PLC isoforms may explain the difference between the inhibitory effects of these PLC pathways. Targeted depletion of PI(4,5)P2 and PI(4)P using a chemically inducible lipid phosphatase replicated the inhibition of Piezo1 currents. Additionally, PI(4,5)P2 and PI(4)P applied to excised inside-out patches inhibited the rundown of Piezo1 activity further emphasizing the significance of these phosphoinositides in Piezo channel regulation.Here we demonstrate that the activity of Piezo channels require the presence of either PI(4,5)P2 or PI(4)P and severe depletion of both phosphoinositides by TRPV1 activation limits channel activity. In conclusion our data may explain how capsaicin alleviates mechanically induced pain.