CHIP28 water channels are localized in constitutively water-permeable segments of the nephron

Søren Nielsen, Barbara L. Smith, Erik Ilsø Christensen, Mark A. Knepper, Peter C Agre

Research output: Contribution to journalArticle

Abstract

The sites of water transport along the nephron are well characterized, but the molecular basis of renal water transport remains poorly understood. CHIP28 is a 28-kD integral protein which was proposed to mediate transmembrane water movement in red cells and kidney (Preston, G. M., T. P. Carroll, W. B. Guggino, and P. Agre. 1992. Science [Wash. DC]. 256:385-387). To determine whether CHIP28 could account for renal epithelial water transport, we used specific polyclonal antibodies to quantitate and localize CHIP28 at cellular and subcellular levels in rat kidney using light and electron microscopy. CHIP28 comprised 3.8% of isolated proximal tubule brush border protein. Except for the first few cells of the Sl segment, CHIP28 was immunolocalized throughout the convoluted and straight proximal tubules where it was observed in the microvilli of the apical brush border and in basolateral membranes. Very little CHIP28 was detected in endocytic vesicles or other intracellular structures in proximal tubules. Uninterrupted, heavy immunostaining of CHIP28 was also observed over both apical and basolateral membranes of descending thin limbs, including both short and long loops of Henle. These nephron sites have constitutively high osmotic water permeabilities. CHIP28 was not detected in ascending thin limbs, thick ascending limbs, or distal tubules, which are highly impermeable to water. Moreover, CHIP28 was not detected in collecting duct epithelia, where water permeability is regulated by antidiuretic hormone. These determinations of abundance and structural organization provide evidence that the CHIP28 water channel is the predominant pathway for constitutive transepithelial water transport in the proximal tubule and descending limb of Henle's loop.

Original languageEnglish (US)
Pages (from-to)371-383
Number of pages13
JournalJournal of Cell Biology
Volume120
Issue number2
StatePublished - Jan 1993
Externally publishedYes

Fingerprint

Aquaporins
Nephrons
Water
Microvilli
Loop of Henle
Kidney
Extremities
Permeability
Water Movements
Transport Vesicles
Membranes
Vasopressins
Electron Microscopy
Proteins
Epithelium
Light
Antibodies

ASJC Scopus subject areas

  • Cell Biology

Cite this

Nielsen, S., Smith, B. L., Christensen, E. I., Knepper, M. A., & Agre, P. C. (1993). CHIP28 water channels are localized in constitutively water-permeable segments of the nephron. Journal of Cell Biology, 120(2), 371-383.

CHIP28 water channels are localized in constitutively water-permeable segments of the nephron. / Nielsen, Søren; Smith, Barbara L.; Christensen, Erik Ilsø; Knepper, Mark A.; Agre, Peter C.

In: Journal of Cell Biology, Vol. 120, No. 2, 01.1993, p. 371-383.

Research output: Contribution to journalArticle

Nielsen, S, Smith, BL, Christensen, EI, Knepper, MA & Agre, PC 1993, 'CHIP28 water channels are localized in constitutively water-permeable segments of the nephron', Journal of Cell Biology, vol. 120, no. 2, pp. 371-383.
Nielsen, Søren ; Smith, Barbara L. ; Christensen, Erik Ilsø ; Knepper, Mark A. ; Agre, Peter C. / CHIP28 water channels are localized in constitutively water-permeable segments of the nephron. In: Journal of Cell Biology. 1993 ; Vol. 120, No. 2. pp. 371-383.
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