Chloride Channel in Vanadocytes of a Vanadium-Rich Ascidian Ascidia sydneiensis samea

Ueki Tatsuya

Yamaguchi Nobuo

Michibata Hitoshi

Comparative biochemistry and physiology. B, Biochemistry

Ascidians, so-called sea squirts, can accumulate high levels of vanadium in the vacuoles of signet ring cells, which are one type of ascidian blood cell and are also called vanadocytes. In addition to containing high concentrations of vanadium in the +3 oxidation state, the proton concentrations in vanadocyte vacuoles are extremely high. In order to elucidate the entire mechanism of the accumulation and reduction of vanadium by ascidian vanadocytes, it is necessary to clarify the participation of anions, which might be involved as counter ions in the active accumulation of both vanadium and protons. We examined the chloride channel, since chloride ions are necessary for the acidification of intracellular vesicles and coexist with H+ ATPase. We cloned cDNA encoding a chloride channel from blood cells of a vanadium-rich ascidian, Ascidia sydneiensis samea. It encoded a 787-amino-acid protein, which showed striking similarity to mammalian ClC3/4/5-type chloride channels. Using a whole-mount in situ hybridization method that we developed for ascidian blood cells, the chloride channel was revealed to be transcribed in vanadocytes, suggesting its participation in the process of vanadium accumulation.

Ascidian

Blood Cells

Chloride Channel

CLC-type

Gene Expression

H+-ATPase

Metal Accumulation

Vanadium

Chemistry [ 430 ]

eng

Elsevier Science Inc

Copyright (c) 2003 Elsevier Science Inc

[ISSN] 1096-4959

[DOI] 10.1016/S1096-4959(03)00175-1

[DOI] http://dx.doi.org/10.1016/S1096-4959(03)00175-1 isVersionOf