Endothelin-Converting Enzyme-1 Actions Determine Differential Trafficking and Signaling of Corticotropin-Releasing Factor Receptor 1 at High Agonist Concentrations

摘要

CRF receptor 1 (CRF1), a key neuroendocrine mediator of the stress response, has two known agonists corticotropin-releasing factor (CRF) and urocortin 1 (Ucn1). Here we report that endothelin-converting enzyme-1 (ECE-1) differentially degrades CRF and Ucn1; ECE-1 cleaves Ucn1, but not CRF, at critical residue Arginine-34/35′, which is essential for ligand-receptor binding. At near KD agonist concentration (30 nm), both Ucn1- and CRF-mediated Ca²⁺ mobilization are ECE-1 dependent. Interestingly, at high agonist concentration (100 nm), Ucn1-mediated Ca²⁺ mobilization remains ECE-1 dependent, whereas CRF-mediated mobilization becomes independent of ECE-1 activity. At high agonist concentration, ECE-1 inhibition disrupted Ucn1-, but not CRF-induced CRF1 recycling and resensitization, but did not prolong the association of CRF1 with β-arrestins. RNA interference-mediated knockdown of Rab suggests that both Ucn1- and CRF-induced CRF1 resensitization is dependent on activity of Rab11, but not of Rab4. CRF1 behaves like a class A G protein-coupled receptor with respect to transient β-arrestins interaction. We propose that differential degradation by ECE-1 is a novel mechanism by which CRF1 receptor is protected from overactivation by physiologically relevant high concentrations of higher affinity ligand to mediate distinct resensitization and downstream signaling.