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Aquaporin-1: an osmoinducible water channel in cultured mIMCD-3 cells
W Jenq1, I M Mathieson, W Ihara
1Department of Internal Medicine, James A. Haley V. A. Medical Center, Tampa, Florida 33612, USA. wjenq@com1.med.usf.edu
Abstract:
The expressions of aquaporin-1 (AQP-1) in cultured mIMCD-3 cells were studied. There was no detectable AQP-1 in cells grown in serum-containing growth medium (SM, 297 +/- 2 mOsm/kg. H2O). When SM was supplemented with NaCl (406 +/- 2 mOsm/kg. H2O), cellular AQP-1 was induced. A further increase in medium osmolarity with NaCl (493 +/- 3 mOsm/kg. H2O) had conferred cells an 2.5 to 3-fold increase of AQP-1 expression over those grown in the 406 +/- 2 mOsm/kg. H2O medium. Moreover, AQP-1 was found to be translocated from cytosol to membrane. In addition, exposing the mIMCD-3 cells to vasopressin (AVP, 10(-8) M) and/or NaCl-supplemented serum-free media (496 +/- 3 mOsm/kg. H2O) for 6h did not render them to produce AQP-1. However, AQP-1 was induced after 24h of incubation, with an 1.5-fold additive effect by AVP. Our RT-PCR data had confirmed the NaCl inducibility and AVP synergism in AQP-1 expression at both mRNA and protein levels. This suggests a new role for cellular AQP-1 and AVP in overcoming osmotic stress in an in vitro system.
Insights
High salt concentrations induce aquaporin-1 (AQP-1) expression and membrane translocation in kidney cells. Vasopressin (AVP) further enhances AQP-1 levels, suggesting a role in overcoming osmotic stress.
Area of Science:
- Cell Biology
- Renal Physiology
- Molecular Biology
Background:
- Aquaporin-1 (AQP-1) is a water channel protein crucial for kidney function.
- Osmotic stress is a significant challenge for cellular homeostasis in the kidney.
- The regulation of AQP-1 expression under varying osmotic conditions is not fully understood.
Purpose of the Study:
- To investigate the effect of hyperosmolarity and vasopressin (AVP) on aquaporin-1 (AQP-1) expression in cultured mIMCD-3 cells.
- To determine the localization of AQP-1 under different osmotic conditions.
- To explore the potential role of AQP-1 and AVP in cellular adaptation to osmotic stress.
Main Methods:
- Cell culture of mIMCD-3 cells under varying NaCl concentrations and osmolarities.
- Quantitative analysis of AQP-1 expression using RT-PCR and Western blotting.
- Assessment of AQP-1 translocation using immunofluorescence microscopy.
- Treatment with vasopressin (AVP) to evaluate its synergistic effects.
Main Results:
- AQP-1 expression was undetectable in basal growth medium but induced by NaCl supplementation.
- Increased medium osmolarity (up to 493 mOsm/kg H2O) led to a 2.5-3 fold increase in AQP-1 expression.
- AQP-1 translocated from the cytosol to the cell membrane.
- AVP treatment for 24 hours, combined with hyperosmolar media, resulted in a 1.5-fold additive increase in AQP-1 expression.
Conclusions:
- Hyperosmolarity induced by NaCl is a potent stimulus for AQP-1 expression and membrane localization in mIMCD-3 cells.
- Vasopressin (AVP) synergistically enhances AQP-1 expression under hyperosmotic conditions.
- Cellular AQP-1 and AVP play a significant role in mitigating osmotic stress in vitro.