Reticulon 4A/Nogo-A influences the distribution of Kir4.1 but is not essential for potassium conductance in retinal Müller glia.
In the adult retina, we have previously shown that Nogo-A was highly expressed in Müller glia. However, the role of Nogo-A in the glial cell physiology is not clear. In this study, we investigated the possible influence that Nogo-A may exert on other polarized molecules in Müller cells, in particular inwardly rectifying potassium channel 4.1 (Kir4.1) and aquaporin 4 (AQP4) that respectively control potassium and water exchange in glial cells. Our results showed that adenovirus-mediated Nogo-A overexpression with AdNogo-A increased the immunofluorescent signal of Kir4.1 in rat Müller cell line 1 (rMC-1) cells but did not change its expression level by Western blotting. In vivo, AdNogo-A induced ectopic Kir4.1 immunoreactivity throughout the radial processes of Müller cells compared with AdLacZ control virus. Surprisingly, AdNogo-A did not modify the distribution of Dp71 and AQP4 that are common binding partners for Kir4.1 in the dystrophin-associated protein (DAP) complex anchored at the plasma membrane of Müller glia. Immunoprecipitation experiments revealed molecular interactions between Nogo-A and Kir4.1. In Nogo-A KO mouse retinae, the distribution of Kir4.1 was not different from that observed in Wild-Type (WT) animals. In addition, potassium conductance did not change in freshly dissociated Nogo-A KO Müller glia compared with WT cells. In summary, the increase of Nogo-A expression can selectively influence the distribution of Kir4.1 in glia but is not essential for Kir4.1-mediated potassium conductance at the plasma membrane in physiological conditions. Nogo-A-Kir4.1 interactions may, however, contribute to pathological processes taking place in the retina, for instance, after ischemia.
CUO-Recherche, Médecine Régénératrice-Centre de recherche FRQS du CHU de Québec-Université Laval, Université Laval, Québec, Canada; Centre de Recherche en Organogénèse expérimentale de l'Université Laval/LOEX, Québec, QC, Canada; Département d'Ophtalmologie, Faculté de médecine, Université Laval, Québec, QC, Canada.
Sandrine
S
Joly
University of Texas Southwestern Medical Center, Department of Microbiology, Dallas, TX, USA.
Dana A
DA
Dodd
Institute of Neuroinformatics, ETH Zurich, Zurich, Switzerland.
Benjamin F
BF
Grewe
CUO-Recherche, Médecine Régénératrice-Centre de recherche FRQS du CHU de Québec-Université Laval, Université Laval, Québec, Canada; Centre de Recherche en Organogénèse expérimentale de l'Université Laval/LOEX, Québec, QC, Canada; Département d'Ophtalmologie, Faculté de médecine, Université Laval, Québec, QC, Canada. Electronic address: vincent.pernet.1@ulaval.ca.
Vincent
V
Pernet
D000256:Adenoviridae / Q000502:physiology; D000818:Animals; D051401:Aquaporin 4 / Q000378:metabolism*; D002478:Cells, Cultured; D016189:Dystrophin / Q000378:metabolism; D063928:Ependymoglial Cells / Q000378:metabolism*; D005822:Genetic Vectors; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D000070798:Nogo Proteins / Q000378:metabolism*; D011188:Potassium / Q000378:metabolism; D024661:Potassium Channels, Inwardly Rectifying / Q000378:metabolism*; D051381:Rats; D015854:Up-Regulation; D000098854:Kcnj10 Channel
C496031:Aqp4 protein, mouse; D051401:Aquaporin 4; D016189:Dystrophin; D000098854:Kcnj10 Channel; D000070798:Nogo Proteins; D024661:Potassium Channels, Inwardly Rectifying; C085339:apo-dystrophin 1; D011188:Potassium
Glia; Kir4.1; Müller cells; Nogo-A; Retina