Presence of aquaporin and V-ATPase on the contractile vacuole of Amoeba proteus

Eri Nishihara, Etsuo Yokota, Akira Tazaki, Hidefumi Orii, Maki Katsuhara, Kensuke Kataoka, Hisako Igarashi, Yoshinori Moriyama, Teruo Shimmen, Seiji Sonobe

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Abstract

Background information: The results of water permeability measurements suggest the presence of an AQP (aquaporin) in the membrane of the CV i contractile vacuole) in Amoeba proteus [Nishihara, Shimmen and Sonobe (2004) Cell Struct. Funct. 29, 85-90]. Results: In the present study, we cloned an AQP gene from A. proteus [ApAQP (A. proteus AQP)] that encodes a 295-amino-acid protein. The protein has six putative TMs (transmembrane domains) and two NPA (Asn-Pro-Ala) motifs, which are conserved among various AQPs and are thought to be involved in the formation of water channels that span the lipid bilayer. Using Xenopus oocytes, we have demonstrated that the ApAQP protein product can function as a water channel. Immunofluorescence microscopy with anti-ApAQP antibody revealed that ApAQP is detected on the CV membrane and on the vesicles around the CV. The presence of V-ATPase (vacuolar H+-ATPase) on the vesicle membrane around the CV was also detected. Conclusions: Our data on ApAQP allow us to provide the first informed explanation of the high water permeability of the CV membrane in amoeba. Moreover, the results suggest that vesicles possessing V-ATPase are involved in generating an osmotic gradient. Based on our findings, we propose a new hypothesis for the mechanism of CV function.

Original languageEnglish
Pages (from-to)179-188
Number of pages10
JournalBiology of the Cell
Volume100
Issue number3
DOIs
Publication statusPublished - Mar 1 2008

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Keywords

  • Amoeba proteus
  • Aquaporin
  • Contractile vacuole
  • Osmoregulation
  • Vacuolar H+-ATPase (V-ATPase)

ASJC Scopus subject areas

  • Cell Biology

Cite this

Nishihara, E., Yokota, E., Tazaki, A., Orii, H., Katsuhara, M., Kataoka, K., Igarashi, H., Moriyama, Y., Shimmen, T., & Sonobe, S. (2008). Presence of aquaporin and V-ATPase on the contractile vacuole of Amoeba proteus. Biology of the Cell, 100(3), 179-188. https://doi.org/10.1042/BC20070091