title: Aryl Hydrocarbon Receptor-Interacting Protein (AIP) N-Terminus Gene Mutations Identified in Pituitary Adenoma Patients Alter Protein Stability and Function.
abstract: Mutations spanning the entire aryl hydrocarbon receptor-interacting protein (AIP) gene have been found in isolated familial cases of pituitary adenomas (PA). Missense mutations located in the N-terminus of the gene have been identified in several patients. However, the functional significance of these mutations remains a matter of controversy. In most studies, the N-terminus of AIP has been shown to regulate protein stability and subcellular localization of the AIP-AHR-HSP90 complex but not to be involved in protein-protein interactions. Other studies found that the N-terminal domain interacts directly with other proteins. The aim of this study was to analyze whether specific N-terminus AIP mutations identified in PA patients would be functionally different from wild-type (WT) AIP. In vitro analyses were used to assess the role of known N-terminus variants, a locally identified mutant, R9Q, and three other commonly genotyped N-terminus mutations R16H, V49M and K103R are found in PA patients. Given the functional effect of WT AIP on cAMP signalling alterations caused by N-terminus mutants on this pathway were also analyzed in GH3 cells. Results indicate that N-terminus mutations lead to de-regulation of the effect of WT AIP on cAMP signalling and increased cAMP thresholds in GH3 cells resulting in increased growth hormone (GH) secretion. Cycloheximide chase analysis identified a variation in protein degradation patterns between WT and N-terminus variants. Therefore, both functional and structural studies reveal that N-terminus mutations in the AIP gene alter protein behaviour significantly and hence can truly be pathogenic in nature.
authors.affiliation: Department of Medicine, Faculty of Medicine and Surgery, University of Malta, Msida, MSD2080, Malta. robert.formosa@um.edu.mt.
authors.forename: Robert
authors.initials: R
authors.lastname: Formosa
authors.affiliation: Department of Medicine, Faculty of Medicine and Surgery, University of Malta, Msida, MSD2080, Malta. josanne.vassallo@um.edu.mt.|Neuroendocrine Clinic, Mater Dei Hospital, Msida, Malta. josanne.vassallo@um.edu.mt.
authors.forename: Josanne
authors.initials: J
authors.lastname: Vassallo
mesh_terms: D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000235:genetics*; D000242:Cyclic AMP / Q000235:genetics; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D009154:Mutation; D010911:Pituitary Neoplasms / Q000235:genetics* / Q000473:pathology; D055550:Protein Stability; D013329:Structure-Activity Relationship
chemical_list: D047908:Intracellular Signaling Peptides and Proteins; C103265:aryl hydrocarbon receptor-interacting protein; D000242:Cyclic AMP