Acts as a regulatory protein that associates with GUCY2C and negatively modulates its heat-stable enterotoxin-mediated activation (PubMed:11950846). Stimulates SLC9A3 activity in the presence of elevated calcium ions (PubMed:19088451). Interacts with the C-terminal region of GUCY2C (PubMed:11950846). Interacts with the C-terminal region SLC9A3 and the interactions decrease in response to elevated calcium ion levels (PubMed:19088451). Interacts with the C-terminal region of SLC34A1 (By similarity). Interacts with USP2 isoform 4 (PubMed:26756164). Preferentially accumulates at the apical surface and ileal brush border of intestinal epithelial cells (PubMed:11950846, PubMed:19088451). Expressed in kidney and the gastrointestinal tract. Not detected in brain, heart, skeletal muscle or cells of hematopoietic origin.