Evidence against involvement of aquaporin-4 in cell-cell adhesion.
Aquaporin-4 (AQP4) water channels are expressed strongly in glial cells, where they play a role in brain water balance, neuroexcitation, and glial cell migration. Here, we investigated a proposed new role of AQP4 in facilitating cell-cell adhesion. Measurements were made in differentiated primary glial cell cultures from wild-type versus AQP4 knockout mice as well as in null versus AQP4-transfected L-cells, a cell type lacking endogenous adhesion molecules, and in null versus AQP4-transfected Chinese hamster ovary (CHO)-K1 cells and Fisher rat thyroid cells. Using established assays of cell-cell adhesion, we found no significant effect of AQP4 expression on adhesion in each of the cell types. As a positive control, transfection with E-cadherin greatly increased cell-cell adhesion. High-level AQP4 expression also did not affect aggregation of plasma membrane vesicles in a sensitive quasi-elastic light-scattering assay. Further, we found no specific AQP4 binding of a fluorescently labeled oligopeptide containing the putative adhesion sequence in the second extracellular loop of AQP4. These data provide evidence against involvement of AQP4 in cell-cell adhesion.
Zhang
Hua
H
Department of Medicine, University of California, 1246 Health Sciences East Tower, San Francisco, CA 94143-0521, USA.
Verkman
A S
AS
D000818:Animals; D051401:Aquaporin 4 / Q000737:chemistry / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D016466:CHO Cells; D002448:Cell Adhesion / Q000502:physiology*; D002449:Cell Aggregation / Q000502:physiology; D002478:Cells, Cultured; D006224:Cricetinae; D003412:Cricetulus; D007739:L Cells; D051379:Mice; D018345:Mice, Knockout; D008958:Models, Molecular; D009457:Neuroglia / Q000166:cytology / Q000502:physiology; D009842:Oligopeptides / Q000737:chemistry / Q000235:genetics / Q000502:physiology; D051381:Rats; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D014162:Transfection
C496031:Aqp4 protein, mouse; D051401:Aquaporin 4; D009842:Oligopeptides; D011994:Recombinant Proteins