Abstract
In kidney collecting duct cells, vasopressin (AVP) triggers redistribution of aquaporin‐2 (AQP2) water channel protein from intracellular vesicles to the apical plasma membrane to regulate renal water excretion. In our previous proteomic study, we identified Mal2, a lipid‐raft membrane protein known to mediate apical membrane protein trafficking via transcytosis. This study examined roles of Mal2 in AVP‐induced apical AQP2 trafficking via transcytosis. Time course immunofluorescence showed staining of AQP2 in the apical as well as the lateral plasma membrane of the mpkCCD cells after AVP stimulation. The lateral AQP2 staining disappeared gradually with concomitant appearance of apical AQP2 staining, suggesting both direct and indirect mechanisms for apical AQP2 targeting upon AVP stimulation. When the lateral membrane was fixed with tannic acid, a portion of AQP2 accumulated in the lateral space of the cells in response to AVP or forskolin, consistent with an indirect apical AQP2 targeting mechanism via transcytosis upon AVP or forskolin stimulation. The AVP or forskolin‐induced lateral AQP2 staining in the presence of tannic acid was completely absent in the cells lacking Mal2. Our data are compatible with a role of Mal2 in AVP‐induced indirect apical AQP2 targeting via the transcytotic mechanism.Grant Funding Source: Supported by 101‐2320‐B‐002‐038‐MY3, NSC TAIWAN
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