Ca2+/H+ exchange by acidic organelles regulates cell migration in vivo - PubMed (original) (raw)

CAXs are widespread in the animal kingdom. (a) Proposed consensus topology of animal CAXs depicting a cytosolic N terminus, 13 transmembrane regions (cylinders), and a luminal C terminus. An N-terminal domain of unknown function (DUF 307) and a Ca2+/H+ antiporter (ChaA) domain comprising 11 transmembrane regions numbered 0–10 are highlighted. (b) CAX phylogeny in major metazoan phyla. Organisms depicted from left to right are Aplysia californica, Capitella teleta, Strongylocentrotus purpuratus, Branchiostoma floridae, Takifugu rubripes, Latimeria chalumna, Xenopus tropicalis, Anolis carolinensis, Gallus gallus, Ornithorhynchus anatinus, and Sarcophilus harrisii. See

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for accession numbers. (c) Expression of animal CAXs. Agarose gel analysis of PCR reactions using primers specific for S. purpuratus (left) or Xenopus (right) CAX and templates prepared from RNA isolated from eggs and stage 16–18 embryos, respectively. Reactions were performed either with (+) or without (−) reverse transcription (RT). (d) Sequence comparison of animal, plant, and yeast CAXs. ClustalW2 multiple sequence alignment of TM2 and TM7 of the α1 and α2 repeats of CAX, respectively, from the sea urchin (SpuCAX), frog (XlaCAX), yeast (SceVCX1), and plant (AthCAX). *, glutamate residues conserved in both repeats. (e) Structural model of animal CAX. Magnified view of TM2 and 7 of Xenopus CAX highlighting E420 and E648, likely important for ion coordination. (f and g) Effect of CAX on Ca2+ homeostasis in yeast. (f) Inductively coupled plasma emission spectroscopy of total Ca2+ content. Data (n = 9) are from wild-type (WT) or Δvcx1Δpmc1 yeast grown in 10 mM Ca2+ and transformed with empty vector (Vec.) or vectors expressing CAX, CAXΔN, and CAXE420A. (g) Ca2+/H+ exchange measurements using endomembrane-enriched membrane vesicles and acridine orange fluorescence recovery in response to 50 µM Ca2+. Data (n = 4 preparations) are from wild-type or Δvcx1Δvnx1 yeast transformed with the indicated vector. Error bars represent SEM. **, P < 0.01.