Hyman, A. J. | Search bioRxiv

bioRxiv2019

Sphingomyelinase disables Piezo1 channel inactivation to enable sustained response to mechanical force

Piezo1 channels are determinants of vascular responses to fluid flow. They importantly provide sustained response to flow, but this property contrasts with the rapid inactivation that has become a hallmark of the channels in heterologous overexpression studies. Here we reveal a mechanism by which blood vessels disable inactivation to enable sustained physiological response. Creation of a molecular model of Piezo1 channel in defined lipid membranes suggested potential modulation by sphingomyelin and its product ceramide. Biological relevance was indicated by the observation that exogenous sphingomyelinase enhanced Piezo1-mediated Ca2+ entry in cultured endothelial cells. We therefore hypothesised that endogenous sphingomyelinase suppresses channel inactivation. Remarkably, in endothelium freshly-isolated from murine artery, neutral sphingomyelinase inhibitors or genetic disruption of sphingomyelin phosphodiesterase 3 (SMPD3) caused flow- and pressure-activated Piezo1 channels to become inactivating. SMPD3 retained its ability to disable inactivation in cell-free membrane patches, providing evidence for a membrane localised effect. The data suggest that inherent inactivation of Piezo1 channels is disabled by enzymatic control of lipid environment to enable physiological response to mechanical force.

physiology↗

bioRxiv2019

Computational reconstruction of the complete Piezo1 structure reveals a unique footprint and specific lipid interactions

Piezo1 is a critical mechanical sensor in many cells. It is activated by mechanical force thus allowing cells to sense the physical environment and respond to stress. Structural data have suggested that Piezo1 has a curved shape. Here, we use computational approaches to model, for the first time, the 3D structure of the full-length Piezo1 in an asymmetric membrane. A number of novel insights emerge: (i) Piezo1 creates a dome in the membrane with a trilobed topology that extends beyond the radius of the protein, (ii) Piezo1 changes the lipid environment in its vicinity via specific interactions with cholesterol and PIP2 molecules, (iii) changes in cholesterol concentration that change the membrane stiffness result in changes in the depth of the dome created by Piezo1, and iv) modelling of the N-terminal region that is missing from current structures modifies Piezo1 membrane footprint, suggesting the importance of this region in Piezo1 function.

biophysics↗