Abstract
Nephrogenic diabetes insipidus (NDI) is caused by impairment of vasopressin (VP) receptor type 2 signaling. Because potential therapies for NDI that target the canonical VP/cAMP/protein kinase A pathway have so far proven ineffective, alternative strategies for modulating aquaporin 2 (AQP2) trafficking have been sought. Successful identification of compounds by our high-throughput chemical screening assay prompted us to determine whether EGF receptor (EGFR) inhibitors stimulate AQP2 trafficking and reduce urine output. Erlotinib, a selective EGFR inhibitor, enhanced AQP2 apical membrane expression in collecting duct principal cells and reduced urine volume by 45% after 5 days of treatment in mice with lithium-induced NDI. Similar to VP, erlotinib increased exocytosis and decreased endocytosis in LLC-PK1 cells, resulting in a significant increase in AQP2 membrane accumulation. Erlotinib increased phosphorylation of AQP2 at Ser-256 and Ser-269 and decreased phosphorylation at Ser-261 in a dose-dependent manner. However, unlike VP, the effect of erlotinib was independent of cAMP, cGMP, and protein kinase A. Conversely, EGF reduced VP-induced AQP2 Ser-256 phosphorylation, suggesting crosstalk between VP and EGF in AQP2 trafficking and a role of EGF in water homeostasis. These results reveal a novel pathway that contributes to the regulation of AQP2-mediated water reabsorption and suggest new potential therapeutic strategies for NDI treatment.