MCAs in Arabidopsis are Ca2+-permeable mechanosensitive channels inherently sensitive to membrane tension

Mechanosensitive ion channels convert mechanical stimuli into intracellular electric and ionic signals. Here the authors show that Arabidopsis MCA2 is a Ca2+-permeable mechanosensitive channel that is directly activated by membrane tension. Mechanosensitive (MS) ion channels respond to mechanical stress and convert it into intracellular electric and ionic signals. Five MS channel families have been identified in plants, including the Mid1-Complementing Activity (MCA) channel; however, its activation mechanisms have not been elucidated in detail. We herein demonstrate that the MCA2 channel is a Ca2+-permeable MS channel that is directly activated by membrane tension. The N-terminal 173 residues of MCA1 and MCA2 were synthesized in vitro, purified, and reconstituted into artificial liposomal membranes. Liposomes reconstituted with MCA1(1-173) or MCA2(1-173) mediate Ca2+ influx and the application of pressure to the membrane reconstituted with MCA2(1-173) elicits channel currents. This channel is also activated by voltage. Blockers for MS channels inhibit activation by stretch, but not by voltage. Since MCA proteins are found exclusively in plants, these results suggest that MCA represent plant-specific MS channels that open directly with membrane tension.

Automated summary

The authors demonstrate that Arabidopsis MCA2 is a Ca2+-permeable mechanosensitive channel directly activated by membrane tension. This plant-specific channel can open with membrane tension and is also activated by voltage, involving Ca2+ influx and channel currents.