Selective regulation of apical endocytosis in polarized Madin-Darby canine kidney cells by mastoparan and cAMP.
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.
Institute for Cancer Research, Norwegian Radium Hospital, Montebello, Oslo.
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Eker
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Holm
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van Deurs
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Sandvig
D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology*; D000262:Adenylyl Cyclases / Q000378:metabolism; D000818:Animals; D002460:Cell Line; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D002772:Cholera Toxin / Q000494:pharmacology; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism*; D003600:Cytosol / Q000378:metabolism; D004285:Dogs; D004705:Endocytosis / Q000187:drug effects*; D006863:Hydrogen-Ion Concentration; D036341:Intercellular Signaling Peptides and Proteins; D007668:Kidney; D007700:Kinetics; D008854:Microscopy, Electron; D010455:Peptides; D012276:Ricin / Q000378:metabolism*; D012969:Sodium Fluoride / Q000494:pharmacology; D014168:Transferrin / Q000378:metabolism; D014862:Wasp Venoms / Q000494:pharmacology*
D036341:Intercellular Signaling Peptides and Proteins; D010455:Peptides; D014168:Transferrin; D014862:Wasp Venoms; D005576:Colforsin; D015124:8-Bromo Cyclic Adenosine Monophosphate; C037500:mastoparan; D012969:Sodium Fluoride; D012276:Ricin; D002772:Cholera Toxin; D000242:Cyclic AMP; D000262:Adenylyl Cyclases