| First Author | Ruiz-Ederra J | Year | 2007 |
| Journal | J Biol Chem | Volume | 282 |
| Issue | 30 | Pages | 21866-72 |
| PubMed ID | 17525153 | Mgi Jnum | J:124606 |
| Mgi Id | MGI:3722024 | Doi | 10.1074/jbc.M703236200 |
| Citation | Ruiz-Ederra J, et al. (2007) Evidence against functional interaction between aquaporin-4 water channels and Kir4.1 potassium channels in retinal Muller cells. J Biol Chem 282(30):21866-72 |
| abstractText | Indirect evidence suggests that the Muller/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 Muller cells from retinas of wild-type (+/+) and AQP4 knock-out (-/-) mice. Immunocytochemistry showed a comparable Kir4.1 protein expression pattern in Muller cells from +/+ and -/- retinas, with greatest expression at their end feet. Osmotic water permeability was >4-fold reduced in -/- than in +/+ Muller cells. Resting membrane potential did not differ significantly in +/+ versus -/- Muller 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 Ba(2+)-sensitive and showed no significant differences in magnitude in +/+ versus -/- Muller 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 Muller cell bodies were also comparable in +/+ versus -/- Muller cells. Single-channel cell-attached patch clamp showed comparable unitary conductance, current-voltage data, and open probability in +/+ versus -/- Muller cells. Thus, contrary to the generally accepted view, our results provide direct evidence against functionally significant AQP4 modulation of Muller cell Kir4.1 K(+) channel function. |
