Protein kinase A regulates chloride conductance in endocytic vesicles from proximal tubule. |
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Authors: | H R Bae A S Verkman |
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Institution: | Department of Medicine, University of California, San Francisco 94143-0532. |
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Abstract: | 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. |
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