Protein kinase A regulates chloride conductance in endocytic vesicles from proximal tubule.
Regulation of ion transport by phosphorylation and G proteins occurs in several epithelial and non-epithelial cell plasma membranes1-5. It is not known whether transporters on intracellular membranes are target sites for second messengers. Here we present direct evidence that a chloride conductance in endocytic vesicles from rabbit proximal tubule is activated by phosphorylation through a cyclic AMP-dependent protein kinase. To measure chloride transport, endocytic vesicles were labelled in vivo with a Cl(-)-sensitive fluorescent indicator6-8. It was found that labelled endosomes contained an inward proton pump and a chloride conductance, but no ion-coupled chloride transport, and that the chloride conductance was regulated by protein kinase A. These results, taken together with measurements of chloride effects on ATP-dependent acidification, suggest that endosomal pH can be controlled by phosphorylation of a stilbene-sensitive conductive chloride transporter.
Department of Medicine, University of California, San Francisco 94143-0532.
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Bae
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Verkman
D000818:Animals; D018118:Chloride Channels; D002712:Chlorides / Q000378:metabolism*; D004705:Endocytosis / Q000187:drug effects; D005033:Ethylmaleimide / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D007473:Ion Channels / Q000502:physiology*; D007687:Kidney Tubules, Proximal / Q000502:physiology*; D007700:Kinetics; D008565:Membrane Proteins / Q000502:physiology*; D008861:Microsomes / Q000502:physiology; D011494:Protein Kinases / Q000378:metabolism*; D011817:Rabbits; D014634:Valinomycin / Q000494:pharmacology
D018118:Chloride Channels; D002712:Chlorides; D007473:Ion Channels; D008565:Membrane Proteins; D014634:Valinomycin; D011494:Protein Kinases; D005033:Ethylmaleimide