Divalent cation transport by vesicular nucleotide transporter

Takaaki Miyaji, Keisuke Sawada, Hiroshi Omote, Yoshinori Moriyama

Research output: Contribution to journalArticle

19 Citations (Scopus)

Abstract

The vesicular nucleotide transporter (VNUT) is a secretory vesicle protein that is responsible for the vesicular storage and subsequent exocytosis of ATP (Sawada, K., Echigo, N., Juge, N., Miyaji, T., Otsuka, M., Omote, H., and Moriyama, Y. (2008) Proc. Natl. Acad. Sci. U.S.A. 105, 5683-5686). Because VNUT actively transports ATP in a membrane potential (Δψ)-dependent manner irrespective of divalent cations such as Mg 2+ and Ca 2+, VNUT recognizes free ATP as a transport substrate. However, whether or not VNUT transports chelating complexes with divalent cations remains unknown. Here, we show that proteoliposomes containing purified VNUT actively took up Mg 2+when ATP was present, as detected by atomic absorption spectroscopy. The VNUT-containing proteoliposomes also took up radioactive Ca 2+ upon imposing Δψ (positive-inside) but not ΔpH. The Δψ-driven Ca 2+ uptake required ATP and a millimolar concentration of Cl -, which was inhibited by Evans blue, a specific inhibitor of SLC17-type transporters. VNUT in which Arg-119 was specifically mutated to alanine, the counterpart of the essential amino acid residue of the SLC17 family, lost the ability to take up both ATP and Ca 2+. Ca 2+ uptake was also inhibited in the presence of various divalent cations such as Mg 2+. Kinetic analysis indicated that Ca 2+ or Mg 2+ did not affect the apparent affinity for ATP. RNAi of the VNUT gene in PC12 cells decreased the vesicular Mg 2+ concentration to 67.7%. These results indicate that VNUT transports both nucleotides and divalent cations probably as chelating complexes and suggest that VNUT functions as a divalent cation importer in secretory vesicles under physiological conditions.

Original languageEnglish
Pages (from-to)42881-42887
Number of pages7
JournalJournal of Biological Chemistry
Volume286
Issue number50
DOIs
Publication statusPublished - Dec 16 2011

Fingerprint

Divalent Cations
Nucleotides
Adenosine Triphosphate
Secretory Vesicles
Chelation
Atomic spectroscopy
Evans Blue
Essential Amino Acids
PC12 Cells
Exocytosis
RNA Interference
Absorption spectroscopy
Alanine
Membrane Potentials
Spectrum Analysis
Genes
Membranes

ASJC Scopus subject areas

  • Biochemistry
  • Cell Biology
  • Molecular Biology

Cite this

Divalent cation transport by vesicular nucleotide transporter. / Miyaji, Takaaki; Sawada, Keisuke; Omote, Hiroshi; Moriyama, Yoshinori.

In: Journal of Biological Chemistry, Vol. 286, No. 50, 16.12.2011, p. 42881-42887.

Research output: Contribution to journalArticle

Miyaji, Takaaki ; Sawada, Keisuke ; Omote, Hiroshi ; Moriyama, Yoshinori. / Divalent cation transport by vesicular nucleotide transporter. In: Journal of Biological Chemistry. 2011 ; Vol. 286, No. 50. pp. 42881-42887.
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