Fig. 6.

Mutation of PKA sites at serine 486 and 499 reduces FSK-induced UT-A1 ubiquitination. A: wild-type UT-A1 or S486A/S499A-UT-A1 MDCK cells were treated with 10 μM FSK for 3 h or 10 μM MG132 for 6 h. The cells were lysed in RIPA buffer and equal amounts of cell lysates were immunoprecipitated with UT-A1 antibody, then blotted with ubiquitin or UT-A1 antibodies. B: densitometry analysis. Ubiquitinated UT-A1 was quantified and normalized to the total immunoprecipitated UT-A1 (n = 4). The relative intensity of the wild-type cells without treatment was set as 1 (NS, not significant; **P < 0.01).