Phosphoinositide Regulation of the Mechanosensitive Piezo Channels

Abstract

Phosphoinositides are fundamental membrane lipids, e.g. phosphatidylinositol 4,5-bisphosphate (PIP2) is the long known precursor for second messengers such as inositol 1,4,5-trisphosphate (IP3) and diacylglycerol (DAG). They are also involved in the regulation of ion channels, serve as membrane anchor for the cytoskeleton and required for hair cell function. The novel mechanically gated ion channel Piezo1 is a key player in erythrocyte volume regulation and Piezo2 is responsible for the rapidly adapting mechanically activated currents in sensory neurons. Mechanosensitive ion channels are proposed to be regulated by the cytoskeleton and membrane lipids in general. Piezo1 channel activity is inhibited by the disruption of the actin cytoskeleton, and its sensitivity to mechanical stimuli is increased by hypotonic swelling, however, the lipid regulation of these channels remains unexplored.Piezo channels are activated by mechanical stimuli when expressed in heterologous systems unlike most mechanosensitive ion channel candidates. Taking advantage of this we used electrophysiological techniques on HEK293 cells expressing Piezo channels to investigate the effects of Phospholipase C (PLC) activating pathways and specifically phosphoinositide depletion. PLC activation, which converts PIP2 into IP3 and DAG, inhibited mechanically activated currents in Piezo expressing cells. Phosphoinositide depletion using rapidly inducible lipid phosphatases also inhibited Piezo channel activity, but without generating IP3 or DAG. Our data provides evidence that phosphoinositides are involved in the regulation of Piezo channels, thus our study contributes to the understanding of lipid regulation of mechanically gated channels.