A scaffold protein that connects plasma membrane proteins and regulatory components, regulating their surface expression in epithelial cells apical domains. May be involved in the coordination of a diverse range of regulatory processes for ion transport and second messenger cascades. In complex with SLC9A3R1, may cluster proteins that are functionally dependent in a mutual fashion and modulate the trafficking and the activity of the associated membrane proteins. May play a role in the cellular mechanisms associated with multidrug resistance through its interaction with ABCC2 and PDZK1IP1. May potentiate the CFTR chloride channel activity. Required for normal cell-surface expression of SCARB1. Plays a role in maintaining normal plasma cholesterol levels via its effects on SCARB1. Plays a role in the normal localization and function of the chloride-anion exchanger SLC26A6 to the plasma membrane in the brush border of the proximal tubule of the kidney. May be involved in the regulation of proximal tubular Na(+)-dependent inorganic phosphate cotransport therefore playing an important role in tubule function (By similarity). Interacts with PDZK1IP1 and ABCC2. Binds to the C-terminal region of SLC26A3. Interacts (via PDZ domains 1 and 3) with SCARB1 (C-terminal domain). Forms a heterodimeric complex with SLC9A3R1. Interacts with AKAP2, BCR, CFTR, SLCO1A1, SLC22A12, SLC22A4, SLC22A5, SLC9A3R2 and SLC17A1. Component of a complex, composed of PDZK1, SYNGAP1, KLHL17 and NMDA receptors. Interacts (via PDZ1 domain) directly with KLHL17; the interaction is important for integrity of actin cytoskeleton structures in neurons. Interacts (via C-terminal PDZ domain) with SLC26A6 (via C-terminal domain). Interacts (via C-terminal PDZ domain) with SLC9A3 (via C-terminal domain). Interacts (via the first PDZ domain) with PTGIR (via non-isoprenylated C-terminus) (By similarity). Associated with peripheral membranes. Localizes to the apical compartment of proximal tubular cells and to sinusoidal liver membranes. The PDZ 2 and 3 domains seem to be involved in the interaction with SLC26A3. Interaction with the C-terminus of CFTR could be mediated through independent binding of PDZ 1, 3 and 4 domains. The PDZ 1 and 3 domains seem to be involved in the interaction with SLCO1A1. The PDZ 1 domain interacts with BCR. The PDZ 2 and 4 domains do not interact with the C-terminal region of SCARB1. Belongs to the NHER family.