{'fraction_non_alphanumeric': 0.03355704697986577, 'fraction_numerical': 0.01525320317266626, 'mean_word_length': 6.1615720524017465, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Phorbol Ester and Calcium Regulation of Corticotrophin‐Releasing Factor Receptor 1 Expression in a Neuronal Cell Line

Abstract: We have previously demonstrated that corticotrophin‐releasing factor receptor 1 (CRF‐R1) mRNA levels can be down‐regulated via activation of the cyclic AMP pathway in CATH.a cells, a neuronal cell line. In this study, we show evidence for down‐regulation of CRF‐R1 mRNA levels via activation of the protein kinase C (PKC) and calcium second messenger pathways. Incubation of CATH.a cells with phorbol 12‐myristate 13‐acetate (PMA), an activator of PKC, resulted in a time‐ and concentration‐dependent down‐regulation of CRF‐R1 mRNA levels. Pretreatment with the inactive phorbol ester 4α‐phorbol failed to influence significantly CRF‐R1 mRNA levels. Incubation with carbachol, a cholinergic agonist known to activate PKC and increase intracellular calcium levels via phosphatidylinositol breakdown, also down‐regulated CRF‐R1 mRNA levels. Intracellular calcium levels were directly increased using A23187, a calcium ionophore, and thapsigargin, a calcium‐ATPase inhibitor. Elevation of intracellular calcium content using either A23187 or thapsigargin significantly down‐regulated levels of CRF‐R1 mRNA. Furthermore, chelation of calcium with EGTA or blockade of voltage‐dependent calcium channels with nifedipine inhibited agonist‐mediated down‐regulation of CRF‐R1 mRNA levels. These results indicate that activation of PKC or calcium signal transduction pathways is sufficient to cause down‐regulation of CRF‐R1 mRNA levels and that calcium is required for agonist‐mediated down‐regulation of this receptor.