Corticotropin‐releasing factor receptor crosstalk pivotal to ligand‐specific signaling and trafficking (795.3)

Corticotropin‐releasing factor receptors 1 and 2 (CRF 1 and CRF 2 ) are GPCRs for the ligands CRF and urocortins (Ucn1‐3). CRF 1 and CRF 2 activation by their ligands evokes distinct cellular responses, but the signaling and trafficking mechanisms are unclear. In neuronal SK‐N‐MH cells, we show that both CRF receptors are expressed, but only Ucn1 mediates intracellular Ca 2+ [Ca2+] i responses, suggesting CRF receptor crosstalk is important in mediating signaling in a context‐dependent manner. Cultured HEK cells expressing CRF 1 had a robust [Ca2+] i response to challenge with 100 nM CRF and/or Ucn1, but not Ucn2 or Ucn3. HEK cells expressing CRF 2 had a [Ca2+] i response at 10‐100nM doses of Ucn3, but only at high 100nM doses of Ucn1 or Ucn2. Coexpression of CRF 1 with CRF 2 significantly attenuated CRF and Ucn3‐mediated [Ca2+] i signaling. Cell‐surface labeling of epitope‐tagged receptor showed trafficking to different endosomal compartments after stimulation with a single ligand vs. two simultaneously. By co‐immunoprecipitation and mass spectrometry analysis, we show for the first time that CRF 1 and CRF 2 physically interact to form functional heterodimers. Tubulin interacts with the CRF receptor complex differently differentially only after stimulation with CRF+Ucn2. Thus, we propose a novel mechanism by which the two CRF receptors physically interact and recruit ancillary proteins in a ligand‐specific manner to regulate signaling. Grant Funding Source : Supported by NIH NIDDK080787