AIP mutations impair AhR signaling in pituitary adenoma patients fibroblasts and in GH3 cells.

Abstract

Germline mutations in the aryl hydrocarbon receptor-interacting protein (AIP) gene predispose humans to pituitary adenomas through unknown molecular mechanisms. The best-known interacting partner of AIP is the aryl hydrocarbon receptor (AhR), a transcription factor that mediates the effects of xenobiotics implicated in carcinogenesis. As 75% of AIP mutations disrupt the physical and/or functional interaction with AhR, we postulated that the tumorigenic potential of AIP mutations might result from altered AhR signaling. We evaluated the impact of AIP mutations on the AhR signaling pathway, first in fibroblasts from AIP-mutated patients with pituitary adenomas, by comparison with fibroblasts from healthy subjects, then in transfected pituitary GH3 cells. The AIP protein level in mutated fibroblasts was about half of that in cells from healthy subjects, but AhR expression was unaffected. Gene expression analyses showed significant modifications in the expression of the AhR target genes CYP1B1 and AHRR in AIP-mutated fibroblasts, both before and after stimulation with the endogenous AhR ligand kynurenine. Kynurenine increased Cyp1b1 expression to a greater extent in GH3 cells overexpressing wild type compared with cells expressing mutant AIP Knockdown of endogenous Aip in these cells attenuated Cyp1b1 induction by the AhR ligand. Both mutant AIP expression and knockdown of endogenous Aip affected the kynurenine-dependent GH secretion of GH3 cells. This study of human fibroblasts bearing endogenous heterozygous AIP mutations and transfected pituitary GH3 cells shows that AIP mutations affect the AIP protein level and alter AhR transcriptional activity in a gene- and tissue-dependent manner.

• Authors: Anne-Lise Lecoq, Say Viengchareun, Mirella Hage, Jérôme Bouligand, Jacques Young, Audrey Boutron, Philippe Zizzari, Marc Lombès, Philippe Chanson, Peter Kamenický
• Journal: Endocrine-related cancer (Endocr Relat Cancer) Vol. 23 Issue 5 Pg. 433-43 (05 2016) ISSN: 1479-6821 [Electronic] England
• PMID: 27080473 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
• Copyright: © 2016 Society for Endocrinology.

Chemical References

• AHRR protein, human
• Basic Helix-Loop-Helix Transcription Factors
• Intracellular Signaling Peptides and Proteins
• Receptors, Aryl Hydrocarbon
• Repressor Proteins
• aryl hydrocarbon receptor-interacting protein
• CYP1B1 protein, human
• Cytochrome P-450 CYP1B1

Topics

• Adolescent
• Adult
• Animals
• Basic Helix-Loop-Helix Transcription Factors (genetics)
• Cell Line
• Cytochrome P-450 CYP1B1 (genetics)
• Female
• Fibroblasts (metabolism)
• Humans
• Intracellular Signaling Peptides and Proteins (genetics, metabolism)
• Male
• Mutation
• Pituitary Neoplasms (genetics)
• Rats
• Receptors, Aryl Hydrocarbon (genetics)
• Repressor Proteins (genetics)
• Signal Transduction
• Young Adult