Biology subjects

Ozkan, A. D.

Publications and source records attributed to Ozkan, A. D..

3 recordsLinked to original sources

bioRxiv2022

Rearrangements of Piezo1 blade domains correlate with pore opening

PIEZO1 channels open in response to numerous mechanical stimuli, such as physical membrane deformations, which modulate the curvature of flexible domains called blades. Yet, whether different stimuli cause similar blade motions and whether these rearrangements correlate with pore opening remain unclear. Here, we scan local conformational changes along the PIEZO1 blade using fluorescent probes. We identify two distant probes, one intracellular proximal and the other extracellular distal, which independently and robustly respond to flow stimuli. Flow-induced signals from both probes exquisitely correlate with PIEZO1-dependent calcium influx and specifically increase in presence of fast-inactivating pore mutations. In contrast, both probes remain fluorimetrically silent to hypotonic shocks and indentations, two stimuli that otherwise evoke normal electrochemical responses in both engineered channels. This study reveals that flow-induced blade motions are functionally coupled to the pore and that at least two distant blade regions discriminate flow from two other stimuli, suggesting that PIEZO1 mobilizes distinct mechanisms to sense a broad range of mechanical cues. TeaserFluorimetric evidence suggests that different mechanical stimuli impart distinct rearrangements in PIEZO1s mechanosensory domains.

biophysics↗

bioRxiv2021

An inter-channel cooperative mechanism mediates PIEZO1's exquisite mechanosensitivity

The bowl-shaped structure of PIEZO channels is predicted to flatten in response to mechanical stimuli, gating their pore open. However, how this unique structure allows them to detect exquisitely small changes in membrane tension remains unclear. Here, using pressure clamp electrophysiology, modeling, and molecular dynamics simulations, we show that the single channel open probability of PIEZO1 increases weakly with respect to pressure-induced tension. In contrast, when multiple channels are present in a membrane patch, channel open probability increases steeply as a function of the number of open channels. These cooperative effects are consistent with an inter-channel energetic repulsion due to the local membrane deformation created by the non-planar PIEZO structure. When channels open, this deformation shrinks, allowing open channels to diffuse closer to each other, thus delaying closure. This study reveals how PIEZO1 channels acquire their exceptional mechanosensitivity and suggests a possible mechanism by which cells could rapidly tune mechanosensitivity.

biophysics↗

bioRxiv2020

Multimodal activation of GPR68 (OGR1) probed with a genetically-encoded fluorescent reporter

G-protein coupled receptor (GPCR) 68 (GPR68, or OGR1) couples extracellular acidifications and mechanical stimuli to G protein signaling and plays important roles in vascular physiology, neuroplasticity and cancer progression. Here, we designed a genetically-encoded fluorescent reporter of GPR68 activation called "iGlow". iGlow responds to known GPR68 activators including fluid shear stress, extracellular pH and the synthetic agonist ogerin. Remarkably, iGlow activation occurred from both primary cilia-like structures and from intracellular vesicles, showing iGlow senses extracellular flow from within the cell. Flow-induced iGlow activation is not eliminated by pharmacological modulation of G protein signaling, disruption of actin filaments, or the presence of GsMTx4, a non-specific inhibitor of mechanosensitive ion channels. Genetic deletion of the conserved Helix 8, proposed to mediate GPCR mechanosensitivity, did not eliminate flow-induced iGlow activation, suggesting GPR68 uses a hitherto unkonwn, Helix8-independent mechanism to sense mechanical stimuli. iGlow will be useful to investigate the contribution of GPR68-mediated mechanotransduction in health and diseases.

biophysics↗