Hou C et al. (2014), DUF221 proteins are a family of osmosensitive c...

XB-ART-50497

Cell Res 2014 May 01;245:632-5. doi: 10.1038/cr.2014.14.

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DUF221 proteins are a family of osmosensitive calcium-permeable cation channels conserved across eukaryotes.

Hou C , Tian W , Kleist T , He K , Garcia V , Bai F , Hao Y , Luan S , Li L .

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Figure 1. (A) Representative images taken from CHO cells transfected with empty pCDNA3 vector or the same vector harboring AtCSC1. These images show that AtCSC1-expressing CHO cells respond to hyperosmotic stress by cytosolic [Ca2+]i elevation not seen in control cells. [Ca2+]i changes are indicated by Fura-2 emission ratios (F340 nm/F380 nm) scaled by a pseudo-color bar in relative units. Hyperosmotic stress was applied by including 300 mM mannitol in isoosmotic saline solution. (B) Time course of intracellular calcium [Ca2+]i changes in AtCSC1-expressing CHO cells. Open and filled bars show the isoosmotic and hyperosmotic conditions, respectively. The average response of 10-20 cells from a representative experiment is presented. (C) (left) Typical whole-cell current traces recorded from AtCSC1-expressing Xenopus laevis oocytes (AtCSC1) and the water-injected control oocyte (water) with periodic perfusion of saline solution containing 500 mM D-mannitol. (right) Current amplitudes evoked by the first application of hypersosmotic stress (n = 5). (D) Typical whole-cell current traces recorded from the AtCSC1-expressing oocytes perfused with bath solution containing 185 mM D-mannitol or 96 mM Na-gluconate (Na-glu) plus 500 mM D-mannitol. (E) Current amplitudes produced by 96 mM Na+ or K+ or 80 mM Ca2+. (F) AtCSC1-produced inward current was activated by equal osmolality of NaCl or mannitol. (G) AtCSC1 failed to inactivate under calcium-free extracellular conditions, implicating calcium-dependent channel closure. (H) (left) Typical whole-cell current traces recorded from the water-injected control and AtCSC1-expressing oocytes perfused with calcium-free isoosmotic buffer (Iso), calcium-free hyperosmotic buffer (Hyper) or isoosmotic buffer with 1.8 mM Ca2+ (Iso + Ca2+). (right) Current/voltage (I/V) relationship of the same recordings. The current values were extracted at the end of 2 s voltage pulses (n = 5). The bars represent means ± SD. The membrane potential was held at 0 mV and stepped in 20 mV increments from −80 to +40 mV. (I) Predicted transmembrane topology of AtCSC1 and CSC homologs; the first predicted transmembrane helix is hypothetically a cleavable signal peptide. (J) ML phylogenetic tree of DUF221-containing proteins created using PhyML v.2.2.0. Yellow stars mark the positions of AtCSC1, ScCSC1, and HsCSC1. Land plants contain four clades of CSCs, including one clade that clusters with metazoan homologs. One fungal clade contains an additional DUF3779, which is located at the C-terminus of these homologs. Support values (aLRT) are labeled for select clades. (K) Representative images taken from Fura-2-loaded CHO cells expressing ScCSC1 or HsCSC1 after they were treated with isoosmotic saline solution or hyperosmotic solution containing 300 mM mannitol. These data indicate that yeast and human CSC proteins are also osmosensitive, calcium-permeable cation channels. (L) (left) Typical whole-cell current traces recorded from water-injected or ScCSC1- or HsCSC1-expressing oocytes with periodic application of 500 mM D-mannitol. (right) The current amplitudes evoked by the first application of 500 mM D-mannitol (n = 5). The bars represent means ± SD. The holding potential was −60 mV.

References [+] :

Chatzigeorgiou, tmc-1 encodes a sodium-sensitive channel required for salt chemosensation in C. elegans. 2013, Pubmed