May 2005
Volume 46, Issue 13
Free
ARVO Annual Meeting Abstract  |   May 2005
Odorant–Binding Protein–1a Regulates Aquaporin–5 Gating in Mouse
Author Affiliations & Notes
  • Y. Ohashi
    Ophthalmology, Tokyo Dental College, Ichikawa, Japan
  • Y. Sasaki
    Ophthalmology, Tokyo Dental College, Ichikawa, Japan
  • N. Ishida
    Research & Development Center, Santen Pharmaceutical Co. Ltd., Ikoma, Japan
  • S.–I. Hirai
    Research & Development Center, Santen Pharmaceutical Co. Ltd., Ikoma, Japan
  • K. Watanabe
    Research & Development Center, Santen Pharmaceutical Co. Ltd., Ikoma, Japan
  • M. Yasui
    Department of Biological chemistry, Johns Hopkins University School of Medicine, Baltimore, MD
  • K. Tsubota
    Department of Ophthalmology, School of Medicine, Keio University, Shinjuku, Japan
  • Footnotes
    Commercial Relationships  Y. Ohashi, None; Y. Sasaki, None; N. Ishida, None; S. Hirai, None; K. Watanabe, None; M. Yasui, None; K. Tsubota, None.
  • Footnotes
    Support  Grant–in–Aid for Scientific Research from the Japanese Ministry of Science and Technology
Investigative Ophthalmology & Visual Science May 2005, Vol.46, 4412. doi:
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      Y. Ohashi, Y. Sasaki, N. Ishida, S.–I. Hirai, K. Watanabe, M. Yasui, K. Tsubota; Odorant–Binding Protein–1a Regulates Aquaporin–5 Gating in Mouse . Invest. Ophthalmol. Vis. Sci. 2005;46(13):4412.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

Abstract: : Purpose: Aquaporin5 (AQP5) is a water–selective channel protein and located at apical membranes of the acinar cells of the lacrimal glands. AOP5 plays an important role in tear secretion. The tear secretion is regulated exactly by on/off mechanism, suggesting that AQP5 is regulated by gating. However, the gating mechanisms are still unknown. Our purpose is, therefore, to clarify the gating mechanisms of AQP5 in the lacrimal glands. Methods: Poly(A) RNAs from the lacrimal glands were prepared from 5–6 week–old BALB/c mouse. The poly(A) RNAs and AQP5 cRNA were microinjected into Xenopus laevis oocytes to examine if AQP5 inhibitory factor exists in the lacrimal glands. Antisense DNA or dibutyryl cAMP was added to the extra–oocytes solution to test the water permeability of AQP5 is regulated. For cross–linking analysis, the oocytes microinjected with the poly(A)RNAs and AQP5 cRNA were homogenized and incubated with imidoester–type crosslinker. Immunoblot analysis was performed with anti–mouse AQP5 antibodies. The inhibitory factors were purified from the mouse lacrimal glands by affinity chromatography coupled to the C–terminal peptides of mouse AQP5. Results: The osmotic water permeability of AQP5 was inhibited by the co–injection of poly(A)RNAs from the lacrimal glands into oocytes, and dibutyryl–cAMP restored the suppressed water permeability of AQP5 oocytes. The inhibitory factors that bind to AQP5 were shown by the administration of imidoester–type cross–linker. Using affinity chromatography, odorant–binding protein–1a (OBP–1a) is isolated from mouse lacrimal glands as one of the inhibitory factors for AQP5. Antisense DNA to OBP–1a also restored the suppressed water permeability of AQP5 oocytes. Conclusions: AQP5 is gated by binding of OBP–1a to the C–terminus of the molecule, which may be regulated by phosphorylation.

Keywords: cornea: tears/tear film/dry eye • lacrimal gland • phosphorylation 
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