Three Unrelated Perturbations Similarly Uncouple Fluid, Bulk-Membrane, and Receptor Endosomal Flow in Rat Fetal Fibroblasts

• Published in: Biochemical and biophysical research communications 1997-07, Vol.236 (3), p.661-664
• Main Authors: Cupers, Philippe, Veithen, Alex, Hoekstra, Dick, Baudhuin, Pierre, Courtoy, Pierre J.
• Format: Article
• Language: English
• Subjects: Animals; Cell Fractionation; Cell Membrane - physiology; Cells, Cultured; Centrifugation, Density Gradient; Embryo, Mammalian; Endocytosis; Endosomes - physiology; Fibroblasts - drug effects; Fibroblasts - physiology; Fibroblasts - ultrastructure; Half-Life; Horseradish Peroxidase - metabolism; Intracellular Fluid - physiology; Monensin - pharmacology; Potassium - administration & dosage; Rats; Receptors, Transferrin - metabolism; Saline Solution, Hypertonic; Sodium Chloride - administration & dosage; Sodium Chloride - pharmacology; Transferrin - metabolism
• ISSN: 0006-291X; 1090-2104
• DOI: 10.1006/bbrc.1997.7033

We have compared the effects of three perturbations (treatment with 2 μM monensin, potassium depletion, and incubation in 0.35 M NaCl) on recycling of internalized fluid-phase, bulk-membrane, and receptor-mediated tracers in rat fetal fibroblasts. Monensin accelerated 2-fold the regurgitation of the fluid-phase tracer horseradish peroxidase (HRP), as previously described in these cells after potassium depletion or upon incubation in hypertonic medium (1), and all treatments severely inhibited transfer of HRP from endosomes to lysosomes. In comparison, recycling of (6[N-(7-nitro-2,1,3-benzoxadiazol-4-yl)amino]hexanoyl glucosylsphingosine (C6-NBD-GlcCer), a fluorescent lipid used as a bulk-membrane probe, was not significantly affected while transferrin recycling was slowed down 2-fold. The striking similarities of these unrelated perturbations in their distinct effects on fluid, bulk-membrane, and receptor addressing point to common targets regulating these mechanisms.