Caveolins bind to (Na(+), K(+))/H(+) exchanger NHE7 by a novel binding module.
NHE7 was identified as the first mammalian organelle-membrane type (Na(+), K(+))/H(+) exchanger that may contribute to the ion homeostasis in the trans-Golgi network (TGN) and endosomes. Here we show that caveolins directly bind to the C-terminal extension of NHE7 by an unconventional binding-module. NHE7 is partly associated with caveolae/lipid raft fractions, and heterologous expression of caveolin dominant-negative mutants as well as cholesterol depriving drugs diminished such associations. In contrast to the wild type NHE7, a deletion mutant lacking the C-terminal extension was predominantly detected in non-caveolae/lipid rafts. We further show that a small fraction of NHE7 is targeted to the cell surface and subsequently internalized. Endocytosis of NHE7 was efficiently inhibited by pharmacological maneuvers that block clathrin-dependent endocytosis, whereas dominant-negative caveolin mutants or methyl beta-cyclodextrin did not affect NHE7-internalization. Thus, NHE7 associates with both caveolae/lipid rafts and non-caveolae/lipid raft, and the two pools likely exhibit separate dynamics.[1]References
- Caveolins bind to (Na(+), K(+))/H(+) exchanger NHE7 by a novel binding module. Lin, P.J., Williams, W.P., Kobiljski, J., Numata, M. Cell. Signal. (2007) [Pubmed]
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