Functional differences between two CRF-related diuretic hormone receptors in Drosophila

In Drosophila, two related G-protein-coupled receptors are members of the corticotropin releasing factor (CRF) receptor subfamily. We have previously reported that one of these receptors, encoded by CG8422 is a functional receptor for a diuretic hormone, DH44. Here, we report that the other CRF receptor subfamily member, encoded by CG12370, is also a receptor for the DH44 neuropeptide. The lines of evidence to support this identification include increases in cAMP levels due to CG12370 receptor activation and the recruitment of beta-arrestin-GFP to the plasma membrane in response to DH44 application. We compared these features of the receptors DH44-R2 (encoded by CG12370) and DH44-R1 (encoded by CG8422) and found fundamental differences in signaling, association with the arrestins, and peptide sensitivity. We found that the sensitivity of DH44-R2 to the DH44 peptide is lower than that of DH44-R1, specifically an estimated EC50 of 7.98E-07 mol l(-1) for DH44 by DH44-R2 to an EC50 of 5.12E-09 mol l(-1) by DH44-R1 and found that previous reports on the sensitivity of the tubule to DH44 is in agreement with our measurements of DH44-R2 sensitivity. We employed a specific RNAi construct to selectively knock-down DH44-R2 expression and this led to heightened sensitivity to osmotic challenges. The functional characterization of this diuretic hormone receptor in Drosophila demonstrates a high degree of conservation of CRF-like signaling.