{'fraction_non_alphanumeric': 0.01971830985915493, 'fraction_numerical': 0.005633802816901409, 'mean_word_length': 5.501144164759725, '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}}
Identification and Functional Characterization of the Novel Mineralocorticoid Receptor Target Gene Cnksr

The mineralocorticoid receptor (MR) is a ligand-dependent transcription factor mainly expressed in epithelial cells at the distal nephron and distal colon where it regulates salt and water homeostasis. MR expression and function is also found in several non-epithelial tissues particularly in the cardiovascular system. Dysregulation of aldosterone-MR signaling is frequently involved in hypertension and cardiac failure. While therapeutic benefits of MR antagonists in the above noted diseases are undisputed, the molecular mechanisms of action remain to be fully elucidated. Activated by aldosterone the MR elicits most of its physiological actions by altering gene expression of target genes including genes that modulate the activity of the epithelial sodium channel (ENaC) in the kidney. In the recent years a number of gene expression studies have been carried out to identify primary MR target genes. The search for MR target genes is yet hampered by the ubiquitously expressed glucocorticoid receptor (GR). Both MR and GR can be activated by aldosterone and cortisol, albeit at different concentrations. Hence, the current knowledge of MR target genes is likely to be mixed with actual GR target genes. In order to identify MR target genes involved in aldosterone signaling cell culture models were established that allow a clear separation of MR-versus GR-mediated effects on gene regulation and transepithelial sodium transport as physiological readout. Microarray gene expression profiling in human embryonic kidney cells (HEK293) stably expressing MR led to the identification of 36 aldosterone regulated genes. Chromatin Immunoprecipitation (ChIP) in combination with reporter gene assays confirmed that at least 12 out of these 36 candidate genes were directly regulated by MR. This approach led to the identification of the novel MR target gene cnksr3. Expression analysis in different nephron segments, microdissected from mice kidneys, confirmed that cnksr3 was highly expressed in the renal cortical collecting duct (CCD), the prime target segment of aldosterone-regulated sodium retention in the kidney. Mouse CCD-derived cells (M1) that either stably overexpressing or silencing CNKSR3 were electrophysiologically analyzed and showed that CNKSR3 expression correlated with, and was required for, ENaC-mediated transepithelial sodium transport. Moreover, CNKSR3 expression inhibited the RAS-RAF-MEK-ERK signaling cascade, a pathway involved in the modulation of ENaC cell surface expression. In conclusion, CNKSR3 a member of a family of scaffold proteins involved in RAS-RAF-MEK-ERK pathway regulation is a direct MR target gene and is crucial for the maintenance of transepithelial sodium transport in the kidney.