Immunogold evidence suggests that coupling of K+ siphoning and water transport in rat retinal M�ller cells is mediated by a coenrichment of Kir4.1 and AQP4 in specific membrane domains

Potassium channel Kir4.1 macromolecular complex in retinal glial cells

“…The staining for AQP4 also shows this highly polarized distribution; however, notable staining can also be seen in the outer plexiform layer (OPL) and throughout the inner plexiform layer (IPL). These results are in agreement with previous findings (Dalloz et al, 2003;Nagelhus et al, 1999), confirming that Kir4.1 and AQP4 are specifically localized to particular subcellular regions within M€ uller cells. Similar results were also observed in rat retinas (results not shown).…”

“…proteins in the endfeet and perivascular processes of M€ uller cells shown in Figure 1 and in prior studies (Nagelhus et al, 1999). Furthermore, AQP4 was shown to interact with the DGC in M€ uller cells (Dalloz et al, 2003) and brain astrocytes (Amiry-Moghaddam et al, 2003aNeely et al, 2001).…”

“…A unique property of Kir4.1 within these cells is its subcellular localization, being highly concentrated in M€ uller cell endfeet and in perivascular processes (Nagelhus et al, 1999;Kofuji et al, 2000). This localization pattern is thought to facilitate the potassium siphoning mechanism by enrichment of Kir4.1 in cellular regions where K 1 can be released from M€ uller cells without altering the stability of neuronal physiology (Odette and Newman, 1988;Newman and Reichenbach, 1996).…”

“…Interestingly, the water channel aquaporin-4 (AQP4) maintains a very similar distribution pattern to that of Kir4.1 in M€ uller cells (Nagelhus et al, 1999). Recent findings suggest that AQP4 may also be necessary for effective [K 1 ] o buffering in brain (Amiry-Moghaddam et al, 2003a;Nagelhus et al, 2004).…”

Morphological plasticity of astroglia: Understanding synaptic microenvironment

“…( C ) Double‐immunogold labeling of Kir4.1 (small particles, arrows) and aquaporin 4 (large particles) in vitreal perisynaptic Müller cell membranes (denoted M) surrounding photoreceptor terminals (Pt). Adapted from (Nagelhus et al, 1999). ( D ) Double labeling of astrocytic processes demonstrating co‐localization of GLT‐1 (small particles) and GLAST (large particles) (*) in rat hippocampus.…”