Dystroglycan and Kir4.1 coclustering in retinal Müller glia is regulated by laminin-1 and requires the PDZ-ligand domain of Kir4.1.
Inwardly rectifying potassium (Kir) channels in Müller glia play a critical role in the spatial buffering of potassium ions that accumulate during retinal activity. To this end, Kir channels show a polarized subcellular distribution with the predominant channel subunit in Müller glia, Kir4.1, clustered in the endfeet of these cells at the inner limiting membrane. However, the molecular mechanisms underlying their distribution have yet to be identified. Here, we show that laminin, agrin and alpha-dystroglycan (DG) codistribute with Kir4.1 at the inner limiting membrane in the retina and that laminin-1 induces the clustering of alpha-DG, syntrophin and Kir4.1 in Müller cell cultures. In addition, we found that alpha-DG clusters were enriched for agrin and sought to investigate the role of agrin in their formation using recombinant C-agrins. Both C-agrin 4,8 and C-agrin 0,0 failed to induce alpha-DG clustering and neither of them potentiated the alpha-DG clustering induced by laminin-1. Finally, our data reveal that deletion of the PDZ-ligand domain of Kir4.1 prevents their laminin-induced clustering. These findings indicate that both laminin-1 and alpha-DG are involved in the distribution of Kir4.1 to specific Müller cell membrane domains and that this process occurs via a PDZ-domain-mediated interaction. Thus, in the basal lamina laminin is an essential regulator involved in clearing excess potassium released during neuronal activity, thereby contributing to the maintenance of normal synaptic transmission in the retina.
Noël
Geoffrey
G
Département de Sciences Biologiques, Université de Montréal, Montréal, Québec, Canada.
Belda
Marina
M
Guadagno
Eric
E
Micoud
Julien
J
Klöcker
Nikolaj
N
Moukhles
Hakima
H
D018171:Agrin / Q000378:metabolism / Q000494:pharmacology; D000818:Animals; D015153:Blotting, Western / Q000379:methods; D002460:Cell Line; D003952:Diagnostic Imaging / Q000379:methods; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D049030:Dystroglycans / Q000378:metabolism*; D049029:Dystrophin-Associated Proteins / Q000378:metabolism; D005455:Fluorescent Antibody Technique / Q000379:methods; D005786:Gene Expression Regulation / Q000187:drug effects / Q000502:physiology; D049452:Green Fluorescent Proteins / Q000378:metabolism; D007797:Laminin / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology; D009457:Neuroglia / Q000378:metabolism*; D024661:Potassium Channels, Inwardly Rectifying / Q000378:metabolism*; D021381:Protein Transport / Q000187:drug effects; D051381:Rats; D012160:Retina / Q000166:cytology*; D014162:Transfection / Q000379:methods; D000098854:Kcnj10 Channel
D018171:Agrin; D049029:Dystrophin-Associated Proteins; D000098854:Kcnj10 Channel; D007797:Laminin; D024661:Potassium Channels, Inwardly Rectifying; C121346:laminin 1; C091824:syntrophin; D049030:Dystroglycans; D049452:Green Fluorescent Proteins