Evidence against Functional Interaction between Aquaporin-4 Water Channels and Kir4.1 Potassium Channels in Retinal Müller Cells*

Indirect evidence suggests that the Müller/glial cell water channel aquaporin-4 (AQP4) modulates K+ channel function of the closely associated Kir4.1 protein. We used patch clamp to compare Kir4.1 K+ channel function in freshly isolated Müller cells from retinas of wild-type (+/+) and AQP4 knock-out (-/-) mice. Immunocytochemistry showed a comparable Kir4.1 protein expression pattern in Müller cells from +/+ and -/- retinas, with greatest expression at their end feet. Osmotic water permeability was >4-fold reduced in -/- than in +/+ Müller cells. Resting membrane potential did not differ significantly in +/+ versus -/- Müller cells (-64 ± 1 versus -64 ± 1 mV, S.E., n = 24). Whole-cell K+ currents recorded with a micropipette inserted into the cell soma were Ba2+-sensitive and showed no significant differences in magnitude in +/+ versus -/- Müller cells (1.3 ± 0.1 versus 1.2 ± 0.1 nA at -160 mV) or in inwardly rectifying current-voltage relationships. Spatially resolved K+ currents generated by pulsed K+ injections along Müller cell bodies were also comparable in +/+ versus -/- Müller cells. Single-channel cell-attached patch clamp showed comparable unitary conductance, current-voltage data, and open probability in +/+ versus -/- Müller cells. Thus, contrary to the generally accepted view, our results provide direct evidence against functionally significant AQP4 modulation of Müller cell Kir4.1 K+ channel function.

• Publication year

  2007

• Venue

  Journal of Biological Chemistry

• Publication date

  2007-07-27

• Fields of study

  Biology, Medicine

• Identifiers
  DOI 10.1074/jbc.M703236200PMID 17525153
• External record

  Open on Semantic Scholar

• Source metadata

  Semantic Scholar, PubMed

• No claims are published for this paper.

• No concepts are published for this paper.

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