Persistent corticotropin-releasing factor, receptor desensitization and downregulation in the human neuroblastoma cell line IMR-32

Brain corticotropin-releasing factor (CRF) systems integrate various respon ses to stress. Pathological responses to stress may result from errors in C RF receptor regulation in response to changes in synaptic CRF levels. To es tablish an in vitro model to study brain CRF receptors, we characterized th e CRF-induced modulation of CRF1 receptors in the human neuroblastoma cell line, IMR-32. Treatment with CRF decreased CRF1 receptor binding and desens itized CRF-induced increases in cAMP. The decrease in binding had an EC50 o f similar to 10 nM, was maximal by 30 min, and was blocked by the CRF recep tor antagonist [D-Phe(12), Nle(21,38), C-alpha-MeLeu(37)]CRF12-41. The dese nsitization was homologous as vasoactive intestinal polypeptide-induced inc reases in cAMP were unchanged, and elevation of cAMP did not alter CRF1 rec eptor binding. Treatment with CRF for up to 24 h did not alter CRF1 recepto r mRNA levels, suggesting that a posttranscriptional mechanism maintains th e decrease in receptor binding. Interestingly, recovery of CRF receptor bin ding and CRF-stimulated cAMP production was only partial following exposure to 100 nM CRF. In contrast, receptor binding recovered to control levels f ollowing exposure to 10 nM CRF. These data suggest that exposure to high do ses of CRF result in permanent changes characterized by only partial recove ry. Identifying the mechanisms underlying this partial recovery may provide insights into mechanisms underlying the acute and chronic effects of stres s on CRF receptor regulation. (C) 2001 Elsevier Science BY. All rights rese rved.