Activation of the cAMP/PKA pathway induces UT-A1 urea transporter monoubiquitination and targets it for lysosomal degradation.
Regulation of urea transporter UT-A1 in the kidney is important for the urinary concentrating mechanism. We previously reported that activation of the cAMP/PKA pathway by forskolin (FSK) leads to UT-A1 ubiquitination, endocytosis, and degradation. In this study, we discovered that FSK-induced UT-A1 ubiquitination is monoubiquitination as judged by immunoblotting with specific ubiquitin antibodies to the different linkages of the ubiquitin chain. UT-A1 monoubiquitination induced by FSK was processed mainly on the cell plasma membrane. Monoubiquitination facilitates UT-A1 endocytosis, and internalized UT-A1 is accumulated in the early endosome. Inhibition of ubiquitination by E1 ubiquitin-activating enzyme inhibitor PYR-41 significantly reduced FSK-induced UT-A1 endocytosis and degradation. Interestingly, FSK-stimulated UT-A1 degradation occurs through a lysosomal protein degradation system. We further found that the PKA phosphorylation sites of UT-A1 at Ser486 and Ser499 are required for FSK-induced UT-A1 monoubiquitination. The physiological significance was confirmed using rat kidney inner medullary collecting duct suspensions, which showed that vasopressin treatment promotes UT-A1 ubiquitination. We conclude that unlike under basal conditions in which UT-A1 is subject to polyubiquitination and proteasome-mediated protein degradation, activation of UT-A1 by FSK induces UT-A1 monoubiquitination and protein lysosomal degradation.
['Su|Hua|H|', 'Chen|Minguang|M|', 'Sands|Jeff M|JM|', 'Chen|Guangping|G|']
D000818:Animals D001565:Benzoates D005576:Colforsin D000242:Cyclic AMP D017868:Cyclic AMP-Dependent Protein Kinases D004285:Dogs D004705:Endocytosis D004791:Enzyme Inhibitors D005663:Furans D057809:HEK293 Cells D006801:Humans D007668:Kidney D008247:Lysosomes D061985:Madin Darby Canine Kidney Cells D026901:Membrane Transport Proteins D023421:Models, Animal D011720:Pyrazoles D012694:Serine D015398:Signal Transduction D054875:Ubiquitination
endocytosis phosphorylation vasopressin membrane protein trafficking