Abstract
Mechanically activated (MA) ion channels convert physical forces into electrical signals, and are essential for eukaryotic physiology. Despite their importance, few bona-fide MA channels have been described in plants and animals. Here, we show that various members of the OSCA and TMEM63 family of proteins from plants, flies, and mammals confer mechanosensitivity to naïve cells. We conclusively demonstrate that OSCA1.2, one of the Arabidopsis thaliana OSCA proteins, is an inherently mechanosensitive, pore-forming ion channel. Our results suggest that OSCA/TMEM63 proteins are the largest family of MA ion channels identified, and are conserved across eukaryotes. Our findings will enable studies to gain deep insight into molecular mechanisms of MA channel gating, and will facilitate a better understanding of mechanosensory processes in vivo across plants and animals.
Highlights
Mechanotransduction, the conversion of mechanical cues into biochemical signals, is crucial for many biological processes in plants and animals (Arnadottir and Chalfie, 2010; Ranade et al, 2015)
We explored the possibility that OSCA1.1 and OSCA1.2 are mechanosensitive, and that the modest hyperosmolarity-induced currents might be due to osmotic shock causing cell shrinking, and affecting membrane tension (Sachs, 2010)
mechanically activated (MA) whole-cell currents recorded from cells transfected with OSCA1.1 or OSCA1.2 were 10- and 100-fold larger than their hyperosmolarity-activated currents, respectively (Figure 1A,B vs. Figure 1—figure supplement 1), and were comparable to those recorded from cells transfected with mouse PIEZO1, a well-characterized mechanosensitive ion channel (Figure 1B)
Summary
Mechanotransduction, the conversion of mechanical cues into biochemical signals, is crucial for many biological processes in plants and animals (Arnadottir and Chalfie, 2010; Ranade et al, 2015). Some mechanosensory processes such as touch sensation and vascular development are mediated by the PIEZO family of mechanically activated (MA) ion channels (Coste et al, 2010; Coste et al, 2012; Murthy et al, 2017). The mechanotransduction complex in hair cells includes TMC1 as the pore-forming ion channel, and comprises of TMHS and TMIE (Ballesteros et al, 2018; Pan et al, 2018; Qiu and Muller, 2018). Beyond MSLs, hyperosmolarity-evoked intracellular calcium increase is shown to be dependent on the genes OSCA1.1 and OSCA1.2 in Arabidopsis thaliana (Hou et al, 2014; Yuan et al, 2014); the activation mechanism for these proteins and whether they encode a pore-forming ion channel remains unknown
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