Biology subjects

Haselwandter, C. A.

Publications and source records attributed to Haselwandter, C. A..

3 recordsLinked to original sources

bioRxiv2022

Piezo1 as a force-through-membrane sensor in red blood cells.

Piezo1 is the stretch activated Ca2+ channel in red blood cells that mediates homeostatic volume control. Here we study the organization of Piezo1 in red blood cells using a combination of super resolution microscopy techniques and electron microscopy. Piezo1 adopts a non- uniform distribution on the red blood cell surface, with a bias towards the biconcave "dimple". Trajectories of diffusing Piezo1 molecules, which exhibit confined Brownian diffusion on short timescales and hopping on long timescales, also reflect a bias towards the dimple. This bias can be explained by "curvature coupling" between the intrinsic curvature of the Piezo dome and the curvature of the red blood cell membrane. Piezo1 does not form clusters with itself, nor does it co-localize with F-actin, Spectrin or the Gardos channel. Thus, Piezo1 exhibits the properties of a force-through-membrane sensor of curvature and lateral tension in the red blood cell.

biochemistry↗

bioRxiv2022

Elastic properties and shape of the Piezo dome underlying its mechanosensory function

In a companion paper we show that the free membrane shape of lipid bilayer vesicles containing the mechanosensitive ion channel Piezo can be predicted, with no free parameters, from membrane elasticity theory together with measurements of the protein geometry and vesicle size (accompanying paper). Here we use these results to determine the force that Piezo exerts on the free membrane and, hence, that the free membrane exerts on Piezo, for a range of vesicle sizes. From vesicle shape measurements alone, we thus obtain a force-distortion relationship for Piezo, from which we deduce Piezos intrinsic radius of curvature, 42 {+/-} 12 nm, and bending stiffness, 18 {+/-} 2.1 kB T, in free-standing lipid bilayer membranes mimicking cell membranes. Applying these estimates to a spherical cap model of Piezo embedded in a lipid bilayer, we suggest that Piezos intrinsic curvature, surrounding membrane footprint, small stiffness, and large area are the key properties of Piezo that give rise to low-threshold, high-sensitivity mechanical gating.

biophysics↗

bioRxiv2022

Quantitative prediction and measurement of Piezo's membrane footprint

Piezo proteins are mechanosensitive ion channels that can locally curve the membrane into a dome shape (Y. R. Guo, R. MacKinnon, 2017). The curved shape of the Piezo dome is expected to deform the surrounding lipid bilayer membrane into a membrane footprint, which may serve to amplify Piezos sensitivity to applied forces (C. A. Haselwandter, R. MacKinnon, 2018). If Piezo proteins are embedded in lipid bilayer vesicles, the membrane shape deformations induced by the Piezo dome depend on the vesicle size. We employ here membrane elasticity theory to predict, with no free parameters, the shape of such Piezo vesicles outside the Piezo dome, and show that the predicted vesicle shapes agree quantitatively with the corresponding measured vesicle shapes obtained through cryo-electron tomography, for a range of vesicle sizes (Helfrich W. 1973). On this basis, we explore the coupling between Piezo and membrane shape, and demonstrate that the features of the Piezo dome affecting Piezos membrane footprint follow approximately a spherical cap geometry. Our work puts into place the foundation for deducing key elastic properties of the Piezo dome from membrane shape measurements and provides a general framework for quantifying how proteins deform bilayer membranes. ClassificationBiophysicss

biophysics↗