A novel inwardly rectifying K+ channel, Kir7.1, with unique pore properties, was cloned recently. Working in the field of osmoregulation, we have also identified the same human and rat channel and found that the channel is unique not only in its pore sequence but also in its dense localization in the follicular cells of the thyroid gland. Northern blot analysis revealed that the channel message was abundantly expressed in the thyroid gland and small intestine, and moderately in the kidney, stomach, spinal cord and brain. Immunohistochemistry of the rat thyroid, intestine and choroid plexus demonstrated the expression of the channel protein in the follicular cells and epithelial cells, suggesting a role in the regulation of the ion-transporting functions of these specialized cells. The unique pore properties of Kir7.1 make it a strong candidate for the hypothetical low-conductance K+ channel that is functionally coupled with Na+,K+-ATPase by recycling K+. We therefore further examined the co-localization of Kir7.1 and Na+,K+-ATPase and found that both are localized in the basolateral membrane of the thyroid follicular cell; in the choroid plexus, which is known to be unique in having Na+,K+-ATPase in the apical side of the epithelial cells, Kir7.1 was found in the apical membrane, implying a close functional coupling between the channel and Na+,K+-ATPase.
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September 1999
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Research Article|
August 24 1999
Inwardly rectifying K+ channel Kir7.1 is highly expressed in thyroid follicular cells, intestinal epithelial cells and choroid plexus epithelial cells: implication for a functional coupling with Na+,K+-ATPase
Nobuhiro NAKAMURA;
Nobuhiro NAKAMURA
*Department of Biological Sciences, Tokyo Institute of Technology, Yokohama 226-8501, Japan
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Yoshiro SUZUKI;
Yoshiro SUZUKI
*Department of Biological Sciences, Tokyo Institute of Technology, Yokohama 226-8501, Japan
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Hidenari SAKUTA;
Hidenari SAKUTA
*Department of Biological Sciences, Tokyo Institute of Technology, Yokohama 226-8501, Japan
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Kayoko OOKATA;
Kayoko OOKATA
*Department of Biological Sciences, Tokyo Institute of Technology, Yokohama 226-8501, Japan
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Katsumasa KAWAHARA;
Katsumasa KAWAHARA
†Department of Physiology, Kitasato University School of Medicine, Sagamihara 228, Japan
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Shigehisa HIROSE
Shigehisa HIROSE
1
*Department of Biological Sciences, Tokyo Institute of Technology, Yokohama 226-8501, Japan
1To whom correspondence should be addressed (shirose@bio.titech.ac.jp).
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Publisher: Portland Press Ltd
Received:
May 06 1999
Accepted:
June 28 1999
Online ISSN: 1470-8728
Print ISSN: 0264-6021
The Biochemical Society, London © 1999
1999
Biochem J (1999) 342 (2): 329–336.
Article history
Received:
May 06 1999
Accepted:
June 28 1999
Citation
Nobuhiro NAKAMURA, Yoshiro SUZUKI, Hidenari SAKUTA, Kayoko OOKATA, Katsumasa KAWAHARA, Shigehisa HIROSE; Inwardly rectifying K+ channel Kir7.1 is highly expressed in thyroid follicular cells, intestinal epithelial cells and choroid plexus epithelial cells: implication for a functional coupling with Na+,K+-ATPase. Biochem J 1 September 1999; 342 (2): 329–336. doi: https://doi.org/10.1042/bj3420329
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