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Osteopontin traffic in hypoxic renal epithelial cells
Dierk J Hampel1, Christine Sansome, Victor I Romanov
1Department of Medicine, Division of Nephrology and Hypertension, State University of New York at Stony Brook, Stony Brook, NY, USA. dierk.hampel@charite.de
Nephron. Experimental Nephrology
|July 8, 2003
Summary
Stress inhibits osteopontin (OPN) secretion in kidney cells via the Golgi apparatus and actin cytoskeleton. Recovery from stress restores OPN secretion, though its cellular location may change.
Area of Science:
- Nephrology
- Cell Biology
- Molecular Biology
Background:
- Osteopontin (OPN) is a phosphoprotein involved in acute kidney injury.
- Understanding OPN secretion mechanisms under stress is crucial for renal protection.
Purpose of the Study:
- To investigate the secretion pathway of osteopontin (OPN) in human renal proximal tubular epithelial cells (RPTEC) under stress conditions.
- To elucidate the roles of the Golgi apparatus and actin cytoskeleton in OPN secretion during hypoxia and reoxygenation.
Main Methods:
- Western blot and fluorescence microscopy to assess intracellular OPN levels.
- Immunoelectron microscopy to determine OPN localization.
- ELISA to quantify secreted OPN in apical and basolateral media.
- Treatment with brefeldin A, monensin, and cytochalasin B to disrupt cellular processes.
Main Results:
- Hypoxia increased intracellular OPN and apical plasma membrane localization.
- Reoxygenation augmented both apical and basolateral OPN labeling.
- Secreted OPN decreased during hypoxia but recovered upon reoxygenation.
- OPN secretion in normoxic cells required functional Golgi and actin cytoskeleton; recovery from hypoxia required only a functional Golgi.
Conclusions:
- Stress inhibits OPN secretion through a process involving the Golgi apparatus and actin cytoskeleton.
- Recovery from stress restores OPN secretion, but may alter its apical-basolateral polarity.