Potassium depletion and hypertonic medium reduce "non-coated" and clathrin-coated pit formation, as well as endocytosis through these two gates.
Intracellular potassium depletion inhibits receptor-mediated endocytotic processes occurring through clathrin-coated pits. Besides the clathrin-coated pit route, flask-shaped invaginations that do not bear a typical clathrin coat have been recently implicated in receptor-mediated endocytosis of cholera toxin. These invaginations are called "non-coated" to distinguish them from the typical clathrin-coated pits. In the present study, we have investigated whether "non-coated" invaginations are sensitive, as are clathrin-coated pits, to potassium depletion and whether hypertonic medium, which inhibits receptor-mediated endocytosis, also affects "non-coated" invaginations. We found that 1) both potassium depletion and hypertonic medium reduce "non-coated" invaginations on the cell surface; 2) similar to potassium depletion, hypertonic medium markedly decreases the number of clathrin-coated pits; 3) these changes are accompanied by an inhibition of the internalization (measured morphologically) of cholera toxin-gold through "non-coated" invaginations, as well as of alpha 2-macroglobulin-gold taken up by clathrin-coated pits; and 4) in addition, both the hypertonic medium and potassium depletion inhibit the uptake of horseradish peroxidase, a marker of fluid-phase endocytosis.
Carpentier
J L
JL
Institute of Histology and Embryology, University of Geneva Medical Center, Switzerland.
Sawano
F
F
Geiger
D
D
Gorden
P
P
Perrelet
A
A
Orci
L
L
D000818:Animals; D002462:Cell Membrane / Q000648:ultrastructure; D002772:Cholera Toxin / Q000378:metabolism; D002966:Clathrin / Q000502:physiology*; D003034:Coated Pits, Cell-Membrane / Q000502:physiology*; D004705:Endocytosis; D011992:Endosomes / Q000502:physiology*; D006735:Horseradish Peroxidase / Q000378:metabolism; D066298:In Vitro Techniques; D007700:Kinetics; D051379:Mice; D008854:Microscopy, Electron; D009994:Osmolar Concentration; D011188:Potassium / Q000502:physiology*; D000511:alpha-Macroglobulins / Q000378:metabolism
D002966:Clathrin; D000511:alpha-Macroglobulins; D002772:Cholera Toxin; D006735:Horseradish Peroxidase; D011188:Potassium