Insulin potentiates AVP-induced AQP2 expression in cultured renal collecting duct principal cells.
In the renal collecting duct (CD), water reabsorption depends on the presence of aquaporin-2 (AQP2) in the apical membrane of principal cells. AQP2 expression and subcellular repartition are under the control of AVP. Some pieces of experimental evidence indicate that additional hormonal factors, including insulin, may also control AQP2 expression and thereby CD water permeability. We have previously shown that AVP induces endogenous AQP2 expression in cultured mouse mpkCCD(cl4) CD principal cells (23). In the present study, we investigated the effect of insulin on AQP2 expression in mpkCCD(cl4) cells. Addition of insulin to the basal medium of cells grown on filters slightly increased AQP2 mRNA and protein expression, whereas insulin potentiated the effect of AVP. The potentiation of AVP-induced AQP2 expression by insulin was abolished by actinomycin D, a transcriptional inhibitor. Analysis of AQP2 protein expression under conditions of AVP washout and/or in the presence of chloroquine, a lysosomal degradation inhibitor, revealed that insulin did not significantly alter AQP2 protein degradation. Inhibition of ERK, p38 kinase, and phosphatidylinositol 3'-kinase (PI 3-kinase) activities prevented the insulin-induced stimulation of AQP2 expression, whereas inhibition of PKC has no effect. Taken together, our results indicate that insulin increased AQP2 protein expression mostly through increased AQP2 mRNA levels in cultured mpkCCD(cl4) cells. This effect most likely relies on increased AQP2 gene transcription in response to MAPK and PI 3-kinase activation.
Bustamante
Mauro
M
Fondation pour Recherches Médicales, Service of Nephrology, 64 Ave. de la Roseraie, CH-1211 Geneva 4, Switzerland.
Hasler
Udo
U
Kotova
Olga
O
Chibalin
Alexander V
AV
Mordasini
David
D
Rousselot
Martine
M
Vandewalle
Alain
A
Martin
Pierre-Yves
PY
Féraille
Eric
E
D051399:Aquaporin 2; D020346:Aquaporins / Q000096:biosynthesis*; D001834:Body Water / Q000378:metabolism; D018929:Cell Culture Techniques; D006801:Humans; D007004:Hypoglycemic Agents / Q000494:pharmacology*; D007328:Insulin / Q000494:pharmacology*; D007685:Kidney Tubules, Collecting / Q000502:physiology*; D020929:Mitogen-Activated Protein Kinase Kinases / Q000494:pharmacology*; D009481:Neurophysins / Q000494:pharmacology*; D011498:Protein Precursors / Q000494:pharmacology*; D012333:RNA, Messenger / Q000096:biosynthesis; D014158:Transcription, Genetic; D014667:Vasopressins / Q000494:pharmacology*; D014882:Water-Electrolyte Balance
C496023:AQP2 protein, human; C438657:AVP protein, human; D051399:Aquaporin 2; D020346:Aquaporins; D007004:Hypoglycemic Agents; D007328:Insulin; D009481:Neurophysins; D011498:Protein Precursors; D012333:RNA, Messenger; D014667:Vasopressins; D020929:Mitogen-Activated Protein Kinase Kinases