Structural Characterization of the Mechanosensitive Channel Candidate MCA2 from Arabidopsis thaliana

Abstract

Mechanosensing in plants is thought to be governed by sensory complexes containing a Ca2+-permeable, mechanosensitive channel. The plasma membrane protein MCA1 and its paralog MCA2 from Arabidopsis thaliana are involved in mechanical stress-induced Ca2+ influx and are thus considered as candidates for such channels or their regulators. Both MCA1 and MCA2 were functionally expressed in Sf9 cells using a baculovirus system in order to elucidate their molecular natures. Because of the abundance of protein in these cells, MCA2 was chosen for purification. Purified MCA2 in a detergent-solubilized state formed a tetramer, which was confirmed by chemical cross-linking. Single-particle analysis of cryo-electron microscope images was performed to depict the overall shape of the purified protein. The three-dimensional structure of MCA2 was reconstructed at a resolution of 26 Å from 5,500 particles and appears to comprise a small transmembrane region and large cytoplasmic region.

Plant mechanosensitive ion channels: an ocean of possibilities

“…In fact, MCA proteins have only 1 transmembrane (TM) domain [33], placing them outside the norm for ion channel subunits. Cryo-EM imaging followed by single particle reconstruction of a MCA2 tetramer did not reveal a pore [34]. However, heterologously expressed MCA1 and 2 produce increased current in response to osmotic swelling in whole cells and to membrane stretch in excised patches [35], providing evidence that they directly form a MS ion channel.…”

The plant cell wall integrity maintenance mechanism – A case study of a cell wall plasma membrane signaling network

“…It was originally isolated through its ability to rescue a MID1 deficient yeast strain (Nakagawa et al, 2007). Although it exhibits very limited homology to MID1 the available data from functional studies in Arabidopsis and yeast show that it can function as stretch activated, plasma membrane localized calcium channel (like the other family member MCA2) (Kurusu et al, 2013;Nakagawa et al, 2007;Park et al, 2004;Shigematsu et al, 2014;Yamanaka et al, 2010). Simultaneously it has been shown that MCA1 is involved in both mechano-perception dependent growth processes and short-term responses to isoxaben (Denness et al, 2011;Nakagawa et al, 2007).…”

In silico identification and expression analysis of MscS like gene family in rice

“…In plants, only MscS homologues are present, commonly known as MscS like (MSL) channels (Pivetti et al, 2003). However a group of Ca 2+ -permeable mechanosensitive channels have been reported in the A. thaliana named as MCA1 and MCA2, are known to be involved in mechanical stress-induced Ca 2+ influx (Nakagawa et al, 2007;Yamanaka et al, 2010;Shigematsu et al, 2014). Similarly, rice OsMCA1 is involved in a generation of reactive oxygen species (ROS) and hypoosmotic signaling in the rice (Kurusu et al, 2012a,b).…”