Selective regulation of apical endocytosis in polarized Madin-Darby canine kidney cells by mastoparan and cAMP

• Published in: The Journal of biological chemistry 1994-07, Vol.269 (28), p.18607-18615
• Main Authors: EKER, P, HOLM, P. K, VAN DEURS, B, SANDVIG, K
• Format: Article
• Language: English
• Subjects: 8-Bromo Cyclic Adenosine Monophosphate - pharmacology; Adenylyl Cyclases - metabolism; Animals; Biological and medical sciences; Cell Line; Cell Membrane - drug effects; Cell Membrane - metabolism; Cell Membrane - ultrastructure; Cell physiology; Cholera Toxin - pharmacology; Colforsin - pharmacology; Cyclic AMP - metabolism; Cytosol - metabolism; Dogs; Endocytosis; Endocytosis - drug effects; Fundamental and applied biological sciences. Psychology; Hydrogen-Ion Concentration; Intercellular Signaling Peptides and Proteins; Kidney; Kinetics; Microscopy, Electron; Molecular and cellular biology; Peptides; Ricin - metabolism; Sodium Fluoride - pharmacology; Transferrin - metabolism; Wasp Venoms - pharmacology
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1016/S0021-9258(17)32353-0

We here demonstrate that mastoparan, fluoride, forskolin, cholera toxin, and 8-bromoadenosine-3'-5'-cyclic monophosphate all selectively stimulate apical endocytosis of the protein toxin ricin without increasing the uptake at the basolateral side of polarized Madin-Darby canine kidney cells. Activation of adenylyl cyclase and an increased level of cAMP seem to increase ricin endocytosis by a clathrin-independent mechanism since stimulation of endocytosis by cholera toxin and 8-bromoadenosine-3'-5'-cyclic monophosphate occurred even when the clathrin-dependent pathway was blocked by low cytosolic pH. The data suggest that mastoparan stimulates apical endocytosis by interacting with heterotrimeric G proteins, and also this stimulation of endocytosis appears to be clathrin independent since the uptake of transferrin at the apical side was strongly inhibited by mastoparan after brefeldin A-induced missorting of the transferrin receptor to this pole of the cell. In addition, mastoparan stimulated apical endocytosis when clathrin-mediated endocytosis was blocked by acidification of the cytosol. Furthermore, we provide evidence for the existence of clathrin-independent endocytosis on both the apical and the basolateral surface of control Madin-Darby canine kidney cells. Our results suggest that endocytosis at the apical pole of epithelial cells can be regulated selectively by a physiological signal.