Trafficking and Membrane Targeting of NBCn1 in MCF-7 Breast Cancer Cells

We previously showed that the Na+,HCO3- cotransporter NBCn1 (SLC4A7) is upregulated in breast cancer, and that cisplatin treatment of breast cancer cells causes pronounced loss of NBCn1 plasma membrane localization. However, essentially nothing is known regarding the mechanisms of NBCn1 trafficking and turnover. NBCn1 localized predominantly to the basolateral membrane in polarized breast cancer cells, with a highly cell-density dependent expression profile. Removal of the cytosolic NBCn1 C-terminal tail (NBCn1-Ct) strongly reduced NBCn1 membrane localization in HEK293 cells. GST pull-down in MCF-7 cells followed by LTQ Orbitrap Mass spectrometry identified Receptor C kinase-1 (RACK1), retromer complex components vacuolar protein sorting-associated protein 35 (VPS35) and Sorting Nexin 27 (SNX27), and AP1 and -2 adaptor proteins, as NBCn1-Ct interaction partners. Co-immunoprecipitation and immunofluorescence analysis confirmed interaction between RACK1 and NBCn1 in MCF-7 cells. Furthermore, siRNA-mediated ...