TCDB is operated by the Saier Lab Bioinformatics Group

1.A.87 The Mechanosensitive Calcium Channel (MCA) Family

Mechano-sensitive channels of plants sense increases in tension induced by mechanical stimuli, such as touch, wind, turgor pressure and gravitation. Plant homologues of MscS bacterial mechano-sensitive channels are known which are gated by membrane tension. Two of them have been shown to be involved in the protection of osmotically stressed plastids in Arabidopsis thaliana (see TC# 1.A.23.4.4).

Iida et al. (2013) identified another group of candidates for mechano-sensitive channels in Arabidopsis, named MCA1 and MCA2, whose homologues are exclusively found in plant genomes. MCA1 and MCA2 are composed of 421 and 416 amino acyl residues, respectively, share 73% identity in their amino acid sequences, and are not homologous to any other known ion channels or transporters. A structural study revealed that the N-terminal region (~173 amino acids) of both proteins is necessary and sufficient for Ca2+ influx activity. This region has one putative transmembrane segment containing an Asp residue whose substitution mutation abolished activity.Their physiological study suggested that MCA1, expressed at the root tip, is required for sensing the hardness of the agar medium or soil. In addition, MCA1 and MCA2 were shown to be responsible for hypo-osmotic shock-induced increases in [Ca2+]cyt . Thus, both proteins appear to be involved in the process of sensing mechanical stresses. Iida et al. (2013) discussed the possible roles of both proteins in sensing mechanical and gravitational stimuli.  Several homologues may serve as receptors and regulatory proteins rather than ion channels, and several of these are included in this family in TCDB.  Their roles as mechanosensitive plasma membrane Ca2+-permeable channels, such as OsMCA1and OsMCA2 in rice seems to allow them to play roles in the generation of reactive oxygen species and in hypo-osmotic signaling (Kurusu et al. 2012; Kurusu et al. 2012; Kurusu et al. 2012).

MCA proteins show various topologies.  Several show a 1 + 3 TMS topology (subfamily 1) while others (subfamily 2) appear to have a 1 + 3 + 3 TMS topology, and still others have just 3 TMSs (subfamily 3).  The 3 TMSs in these last mentioned proteins appear to correspond to the last 3 TMSs in subfamilies 1 and 2. The topologies of subfamilies 4 and 5 are not clear.  There may be additional topological variations.

The generalized reaction reported to be catalyzed by MCA1 and MCA2 is:

Ca2+(out)  →  Ca2+ (in)

This family belongs to the: Leucine-rich Repeat-containing Domain.

References associated with 1.A.87 family:

Choi, J., K. Tanaka, Y. Cao, Y. Qi, J. Qiu, Y. Liang, S.Y. Lee, and G. Stacey. (2014). Identification of a plant receptor for extracellular ATP. Science 343: 290-294. 24436418
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Hamilton, E.S., A.M. Schlegel, and E.S. Haswell. (2015). United in diversity: mechanosensitive ion channels in plants. Annu Rev Plant Biol 66: 113-137. 25494462
Iida H., Furuichi T., Nakano M., Toyota M., Sokabe M. and Tatsumi H. (2014). New candidates for mechano-sensitive channels potentially involved in gravity sensing in Arabidopsis thaliana. Plant Biol (Stuttg). 16 Suppl 1:39-42. 23731064
Kamano S., Kume S., Iida K., Lei KJ., Nakano M., Nakayama Y. and Iida H. (2015). Transmembrane Topologies of Ca2+-permeable Mechanosensitive Channels MCA1 and MCA2 in Arabidopsis thaliana. J Biol Chem. 290(52):30901-9. 26555262
Kurusu, T., D. Nishikawa, Y. Yamazaki, M. Gotoh, M. Nakano, H. Hamada, T. Yamanaka, K. Iida, Y. Nakagawa, H. Saji, K. Shinozaki, H. Iida, and K. Kuchitsu. (2012). Plasma membrane protein OsMCA1 is involved in regulation of hypo-osmotic shock-induced Ca2+ influx and modulates generation of reactive oxygen species in cultured rice cells. BMC Plant Biol 12: 11. 22264357
Kurusu, T., H. Iida, and K. Kuchitsu. (2012). Roles of a putative mechanosensitive plasma membrane Ca2+-permeable channel OsMCA1 in generation of reactive oxygen species and hypo-osmotic signaling in rice. Plant Signal Behav 7: 796-798. 22751305
Kurusu, T., T. Yamanaka, M. Nakano, A. Takiguchi, Y. Ogasawara, T. Hayashi, K. Iida, S. Hanamata, K. Shinozaki, H. Iida, and K. Kuchitsu. (2012). Involvement of the putative Ca²⁺-permeable mechanosensitive channels, NtMCA1 and NtMCA2, in Ca²⁺ uptake, Ca²⁺-dependent cell proliferation and mechanical stress-induced gene expression in tobacco (Nicotiana tabacum) BY-2 cells. J Plant Res 125: 555-568. 22080252
Lei, L. and A.C. Spradling. (2016). Mouse oocytes differentiate through organelle enrichment from sister cyst germ cells. Science 352: 95-99. 26917595
Libault, M. and G. Stacey. (2010). Evolution of FW2.2-like (FWL) and PLAC8 genes in eukaryotes. Plant Signal Behav 5: 1226-1228. 20855956
Oh, M.H., X. Wang, U. Kota, M.B. Goshe, S.D. Clouse, and S.C. Huber. (2009). Tyrosine phosphorylation of the BRI1 receptor kinase emerges as a component of brassinosteroid signaling in Arabidopsis. Proc. Natl. Acad. Sci. USA 106: 658-663. 19124768
Shigematsu, H., K. Iida, M. Nakano, P. Chaudhuri, H. Iida, and K. Nagayama. (2014). Structural Characterization of the Mechanosensitive Channel Candidate MCA2 from Arabidopsis thaliana. PLoS One 9: e87724. 24475319
Song, W.Y., K.S. Choi, d.o.Y. Kim, M. Geisler, J. Park, V. Vincenzetti, M. Schellenberg, S.H. Kim, Y.P. Lim, E.W. Noh, Y. Lee, and E. Martinoia. (2010). Arabidopsis PCR2 is a zinc exporter involved in both zinc extrusion and long-distance zinc transport. Plant Cell 22: 2237-2252. 20647347
Song, W.Y., S. Hörtensteiner, R. Tomioka, Y. Lee, and E. Martinoia. (2011). Common functions or only phylogenetically related? The large family of PLAC8 motif-containing/PCR genes. Mol. Cells 31: 1-7. 21347707
Wang, C., J. Zhang, and J.I. Schroeder. (2017). Two-electrode Voltage-clamp Recordings in Xenopus laevis Oocytes: Reconstitution of Abscisic Acid Activation of SLAC1 Anion Channel via PYL9 ABA Receptor. Bio Protoc 7:. 28516122
Ward, N.L. and D.J. Dumont. (2002). The angiopoietins and Tie2/Tek: adding to the complexity of cardiovascular development. Semin Cell Dev Biol 13: 19-27. 11969368
Xiong, W., P. Wang, T. Yan, B. Cao, J. Xu, D. Liu, and M. Luo. (2018). The rice "fruit-weight 2.2-like" gene family member OsFWL4 is involved in the translocation of cadmium from roots to shoots. Planta. [Epub: Ahead of Print] 29453663