Water permeability of aquaporin-4 is decreased by protein kinase C and dopamine.
Aquaporin-4 (AQP4) plays an important role in the basolateral movement of water in the collecting duct. Here we show that this water channel can be dynamically regulated. Water permeability (P(f)) was measured in individual LLC-PK1 cells that were transiently transfected with AQP4. To identify which cells were transfected, AQP4 was tagged at the NH2 terminus with green fluorescent protein. Transfected cells showed a strong fluorescent signal in basolateral membrane and a low-to-negligible signal in the cytosol and apical membrane. Activation of protein kinase C (PKC) with phorbol 12,13-dibutyrate (PDBu) significantly decreased P(f) of cells expressing AQP4 but had no effect on neighboring untransfected cells. No redistribution of AQP4 in response to PDBu was detected. Dopamine also decreased the P(f) in transfected cells. The effect was abolished by the PKC inhibitor Ro 31-8220. Reduction of AQP4 water permeability by PDBu and dopamine was abolished by point mutation of Ser(180), a consensus site for PKC phosphorylation. We conclude that PKC and dopamine decrease AQP4 water permeability via phosphorylation at Ser180 and that the effect is likely mediated by gating of the channel.
Zelenina
Marina
M
Department of Woman and Child Health, Karolinska Institute, Astrid Lindgren Children's Hospital, S-171 76 Stockholm, Sweden.
Zelenin
Sergey
S
Bondar
Alexander A
AA
Brismar
Hjalmar
H
Aperia
Anita
A
D000818:Animals; D051401:Aquaporin 4; D020346:Aquaporins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D001692:Biological Transport / Q000187:drug effects / Q000502:physiology; D002273:Carcinogens / Q000494:pharmacology; D004298:Dopamine / Q000494:pharmacology*; D049452:Green Fluorescent Proteins; D007202:Indicators and Reagents / Q000378:metabolism; D018374:LLC-PK1 Cells; D008164:Luminescent Proteins / Q000235:genetics; D016297:Mutagenesis, Site-Directed / Q000502:physiology; D015240:Phorbol 12,13-Dibutyrate / Q000494:pharmacology; D010766:Phosphorylation; D011493:Protein Kinase C / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D012694:Serine / Q000235:genetics; D013552:Swine; D014162:Transfection; D014867:Water / Q000378:metabolism*
D051401:Aquaporin 4; D020346:Aquaporins; D002273:Carcinogens; D007202:Indicators and Reagents; D008164:Luminescent Proteins; D014867:Water; D049452:Green Fluorescent Proteins; D015240:Phorbol 12,13-Dibutyrate; D012694:Serine; D011493:Protein Kinase C; D004298:Dopamine