WWP2 regulates DMT1 transport activity and ubiquitinates DMT1 in an Ndfip-dependent manner. (A) The relative transport activity of DMT1 in the presence of Nedd4 family members. *P < .05. □ indicates CHO wild-type cells; ■, CHO-DMT1-II-expressing cells. Data are mean plus or minus SEM. (B) Interaction of DMT1 with WWP2, Ndfip1, and Ndfip2. CHO-DMT1-II cells transfected as indicated were subjected to immunoprecipitation with α-myc followed by immunoblotting (IB) as indicated. (C) Ubiquitination of DMT1 by WWP2. CHO-DMT1-II cells were transfected with vector (−), WWP2 (wild-type and a catalytically inactive mutant, cm), Ndfip1, Ndfip2, and HA-tagged ubiquitin. DMT1-II was immunoprecipitated with α-myc followed by IB as indicated.