Browsing by Author "Wu, Jason"
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Item Open Access Mechanisms for Inactivation in Piezo Ion Channels(2017) Wu, JasonAn organism’s ability to sense mechanical forces is critical for the detection of environmental stimuli as well as the regulation of internal processes necessary for survival. In vertebrates, the molecular mechanisms of somatosensation has remained an important and unresolved neurobiological question. In the past decade, Piezo ion channels have emerged as the first vertebrate ion channels identified responsible for transforming somatosensory stimuli into excitatory signals in the nervous system, generating our sense of touch. However, little still is known about the precise mechanisms for how Piezo channels activate and inactivate in the presence of stimuli and how they could potentially be modulated.
By using a combination of engineered and biomolecular methods combined with electrophysiology, I identify distinct structural domains within Piezo ion channels that are necessary for specific aspects of channel inactivation. First, I engineered a method by which magnetic nanoparticles were used to mechanically pull on individual domains of the Piezo channel to screen for mechanically sensitive structures. This experiment revealed a particularly striking effect for one domain, manifested as a profound slowing of channel inactivation kinetics. Next, I generated chimeric constructs to exchange this domain with a homologous structure and demonstrated its sufficiency for mediating the kinetics for inactivation. Finally, I introduced point mutations at key residues within the immediately adjacent pore domain and identified a structural correlate for the modulation of inactivation by voltage. These findings together provide a foundation for understanding the mechanism for inactivation in Piezo channels, and more broadly, for further studying the complexities in transducing mechanical force that create our sense of touch.
Item Open Access Synergy between Piezo1 and Piezo2 channels confers high-strain mechanosensitivity to articular cartilage.(Proc Natl Acad Sci U S A, 2014-11-25) Lee, Whasil; Leddy, Holly A; Chen, Yong; Lee, Suk Hee; Zelenski, Nicole A; McNulty, Amy L; Wu, Jason; Beicker, Kellie N; Coles, Jeffrey; Zauscher, Stefan; Grandl, Jörg; Sachs, Frederick; Guilak, Farshid; Liedtke, Wolfgang BDiarthrodial joints are essential for load bearing and locomotion. Physiologically, articular cartilage sustains millions of cycles of mechanical loading. Chondrocytes, the cells in cartilage, regulate their metabolic activities in response to mechanical loading. Pathological mechanical stress can lead to maladaptive cellular responses and subsequent cartilage degeneration. We sought to deconstruct chondrocyte mechanotransduction by identifying mechanosensitive ion channels functioning at injurious levels of strain. We detected robust expression of the recently identified mechanosensitive channels, PIEZO1 and PIEZO2. Combined directed expression of Piezo1 and -2 sustained potentiated mechanically induced Ca(2+) signals and electrical currents compared with single-Piezo expression. In primary articular chondrocytes, mechanically evoked Ca(2+) transients produced by atomic force microscopy were inhibited by GsMTx4, a PIEZO-blocking peptide, and by Piezo1- or Piezo2-specific siRNA. We complemented the cellular approach with an explant-cartilage injury model. GsMTx4 reduced chondrocyte death after mechanical injury, suggesting a possible therapy for reducing cartilage injury and posttraumatic osteoarthritis by attenuating Piezo-mediated cartilage mechanotransduction of injurious strains.