title: Dose-dependent dual role of PIT-1 (POU1F1) in somatolactotroph cell proliferation and apoptosis.
abstract: To test the role of wtPIT-1 (PITWT) or PIT-1 (R271W) (PIT271) in somatolactotroph cells, we established, using inducible lentiviral vectors, sublines of GH4C1 somatotroph cells that allow the blockade of the expression of endogenous PIT-1 and/or the expression of PITWT or PIT271, a dominant negative mutant of PIT-1 responsible for Combined Pituitary Hormone Deficiency in patients. Blocking expression of endogenous PIT-1 induced a marked decrease of cell proliferation. Overexpressing PITWT twofold led also to a dose-dependent decrease of cell proliferation that was accompanied by cell death. Expression of PIT271 induced a strong dose-dependent decrease of cell proliferation accompanied by a very pronounced cell death. These actions of PIT271 are independent of its interaction/competition with endogenous PIT-1, as they were unchanged when expression of endogenous PIT-1 was blocked. All these actions are specific for somatolactotroph cells, and could not be observed in heterologous cells. Cell death induced by PITWT or by PIT271 was accompanied by DNA fragmentation, but was not inhibited by inhibitors of caspases, autophagy or necrosis, suggesting that this cell death is a caspase-independent apoptosis. Altogether, our results indicate that under normal conditions PIT-1 is important for the maintenance of cell proliferation, while when expressed at supra-normal levels it induces cell death. Through this dual action, PIT-1 may play a role in the expansion/regression cycles of pituitary lactotroph population during and after lactation. Our results also demonstrate that the so-called "dominant-negative" action of PIT271 is independent of its competition with PIT-1 or a blockade of the actions of the latter, and are actions specific to this mutant variant of PIT-1.
authors.affiliation: Aix-Marseille Université, CNRS, UMR7286, 13015 Marseille, France.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Jullien
authors.affiliation: Aix-Marseille Université, CNRS, UMR7286, 13015 Marseille, France; Laboratory of Molecular Biology, APHM Conception, 13385 Marseille, France.
authors.forename: Catherine
authors.initials: C
authors.lastname: Roche
authors.affiliation: Aix-Marseille Université, CNRS, UMR7286, 13015 Marseille, France; Department of Endocrinology, APHM Timone, 13385 Marseille, France.
authors.forename: Thierry
authors.initials: T
authors.lastname: Brue
authors.affiliation: Laboratory of Neuropathology, APHM Timone, 13385 Marseille, France.
authors.forename: Dominique
authors.initials: D
authors.lastname: Figarella-Branger
authors.affiliation: Department of Neurosurgery, APHM Timone, 13385 Marseille, France.
authors.forename: Thomas
authors.initials: T
authors.lastname: Graillon
authors.affiliation: Aix-Marseille Université, CNRS, UMR7286, 13015 Marseille, France; Laboratory of Molecular Biology, APHM Conception, 13385 Marseille, France.
authors.forename: Anne
authors.initials: A
authors.lastname: Barlier
authors.affiliation: Aix-Marseille Université, CNRS, UMR7286, 13015 Marseille, France.
authors.forename: Jean-Paul
authors.initials: JP
authors.lastname: Herman
mesh_terms: D000236:Adenoma / Q000235:genetics / Q000473:pathology / Q000503:physiopathology; D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D000818:Animals; D017209:Apoptosis / Q000502:physiology; D001483:Base Sequence; D002460:Cell Line; D049109:Cell Proliferation / Q000502:physiology; D002470:Cell Survival / Q000235:genetics / Q000502:physiology; D002522:Chlorocebus aethiops; D006801:Humans; D052682:Lactotrophs / Q000166:cytology / Q000502:physiology; D008969:Molecular Sequence Data; D050505:Mutant Proteins / Q000235:genetics / Q000502:physiology; D010911:Pituitary Neoplasms / Q000235:genetics / Q000473:pathology / Q000503:physiopathology; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics; D051381:Rats; D052683:Somatotrophs / Q000166:cytology / Q000502:physiology*; D050817:Transcription Factor Pit-1 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology*; D014407:Tumor Cells, Cultured
chemical_list: D050505:Mutant Proteins; C494187:POU1F1 protein, human; C494186:Pou1f1 protein, rat; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D050817:Transcription Factor Pit-1
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