Posted on March 14, 2017 by MaryO
Context: Cushing disease (CD) is due to pituitary corticotrope adenomas that produce unrestrained ACTH secretion and have lost the negative feedback exerted by glucocorticoids (GCs). GCs also restrain corticotrope proliferation, and the mechanisms of this inhibition are poorly understood.
Objective: The aim of the study was to identify cell cycle regulatory genes that are regulated by GCs and the glucocorticoid receptor and to assess regulatory genes that have a rate-limiting action on corticotrope proliferation and may be disregulated in CD.
Design: The mouse corticotrope tumor cells AtT-20 were used to identify GC-regulated genes that contribute to control of cell cycle progression. Surgery sections from patients with CD were used to assess expression of CABLES1 in corticotrope adenomas.
Methods: Gene expression profiling, small interfering RNA knockdowns, cell cycle analyses, and genetic manipulations were performed in AtT-20 cells. Sequencing of chromatin immunoprecipitation for pituitary-restricted transcription factors and RNA polymerase II were used to identify regulatory elements and genes that bind GR and are direct transcriptional targets. A panel of previously well-characterized corticotrope adenomas was used to correlate expression of CABLES1 with that of other markers. Results: GCs altered expression of 3 positive and 3 negative regulators of cell cycle progression. Two Myc genes (L-Myc and N-Myc) and E2F2 are repressed by GCs, whereas genes for the negative regulators of the cell cycle, Gadd45, Gadd45, and Cables1 are activated by GCs. Cables1 small interfering RNA knockdown strongly stimulates AtT-20 cell proliferation and antagonizes the growth inhibition produced by GCs. The Gadd45 and Cables1 genes have the hallmarks of direct GC targets. CABLES1 is expressed in normal human pituitary cells, but expression is lost in 55% of corticotrope adenomas, and this is strongly correlated with the loss of p27 Kip1 expression.
Conclusions: CABLES1 is a critical regulator of corticotrope proliferation that defines a pathway often inactivated in CD and links proliferation to GC resistance. (J Clin Endocrinol Metab
Filed under: Clinical trials, Cushing's, pituitary | Tagged: abstract, ACTH, Adrenocorticotropic hormone, Cushing's Disease, glucocortoids, pituitary | Leave a comment »
Posted on February 8, 2017 by MaryO
Filed under: Cushing's, pituitary, Rare Diseases, symptoms, Treatments | Tagged: abstract, amenorrhea, erectile disfunction, galactorrhea, headache, hyperthryoidism, infertility, ketoconazole, libido, mifepristone, panhypopituitarism, pasireotide, Pituitary adenoma, transsphenoidal, treatment | Leave a comment »
Posted on December 21, 2016 by MaryO
Posted on December 15, 2016 by MaryO
Joshua M Lubner, Kimberly L Dodge-Kafka, Cathrine R Carlson, George M Church, Michael F Chou, Daniel Schwartz
This article is a preprint and has not been peer-reviewed.
The PKAL205R hotspot mutation has been implicated in Cushing’s Syndrome through hyperactive gain-of-function PKA signaling, however its influence on substrate specificity has not been investigated.
Here, we employ the Proteomic Peptide Library (ProPeL) approach to create high-resolution models for PKAWT and PKAL205R substrate specificity. We reveal that the L205R mutation reduces canonical hydrophobic preference at the substrate P+1 position, and increases acidic preference in downstream positions. Using these models, we designed peptide substrates that exhibit altered selectivity for specific PKA variants, and demonstrate the feasibility of selective PKAL205R loss-of-function signaling.
Through these results, we suggest that substrate rewiring may contribute to Cushing’s Syndrome disease etiology, and introduce a powerful new paradigm for investigating mutation-induced kinase substrate rewiring in human disease.
Full PDF at http://biorxiv.org/content/early/2016/12/05/091231.full.pdf+html
Filed under: Cushing's | Tagged: abstract, Cushing's Syndrome, PKAL205R | Leave a comment »