title: P53 apoptosis mediator PERP:  localization, function and caspase activation in uveal melanoma.
abstract: p53 apoptosis effector related to PMP-22 (PERP) is a transcriptional target gene of p53 tumour suppressor that is specifically induced during apoptosis and not during cell cycle arrest. In primary uveal melanoma (UM), the most common intraocular malignancy in adults that has a reportedly unaffected signalling pathway upstream of and including p53, PERP expression is down-regulated in the metastatic monosomy 3-type tumours, compared with the less aggressive disomy 3-type tumours. Here, we demonstrate experimentally, by the use of full-length PERP-green fluorescent protein (GFP) fusions and real-time confocal microscopy, the intracellular targeting and plasma membrane localization of PERP in living UM cells and show that expression of PERP induces caspase-mediated apoptosis in UM cells. Induction of PERP expression in GFP-PERP-transfected UM cells leads to increased levels of cleaved caspase-8 forms, as well as to reduction of its full-length substrate Bid, but not to detectable processing of caspase-9. The levels of mature caspase-8, -9 and -3 proteins significantly correlate with PERP expression levels in primary UMs. Transcriptional profiling of PERP and caspase-8 in tumour specimens indicates that the positive association of PERP and caspase-8 proteins is a consequence of post-translational processing, most likely at the level of caspase-8 cleavage, and not of increased transcription of pro-caspase-8. We conclude that PERP expression leads to activation of an extrinsic receptor-mediated apoptotic pathway, with a possible subsequent engagement of the intrinsic apoptotic pathway. The findings underline the apoptotic pathway mediated by PERP as a critical mechanism employed by UM tumours to modulate susceptibility to apoptosis.
authors.affiliation: Unit of Ophthalmology, School of Clinical Sciences, University of Liverpool, Liverpool, United Kingdom.
authors.forename: Lyndsay
authors.initials: L
authors.lastname: Davies
authors.affiliation: Unit of Ophthalmology, School of Clinical Sciences, University of Liverpool, Liverpool, United Kingdom.
authors.forename: Donna
authors.initials: D
authors.lastname: Gray
authors.affiliation: Centre for Cell Imaging, School of Biological Sciences, University of Liverpool, Liverpool, United Kingdom.
authors.forename: Dave
authors.initials: D
authors.lastname: Spiller
authors.affiliation: Centre for Cell Imaging, School of Biological Sciences, University of Liverpool, Liverpool, United Kingdom.
authors.forename: Mike R H
authors.initials: MRH
authors.lastname: White
authors.affiliation: St. Paul's Eye Unit, Royal Liverpool University Hospital, Liverpool, United Kingdom.
authors.forename: Bertil
authors.initials: B
authors.lastname: Damato
authors.affiliation: Unit of Ophthalmology, School of Clinical Sciences, University of Liverpool, Liverpool, United Kingdom.
authors.forename: Ian
authors.initials: I
authors.lastname: Grierson
authors.affiliation: Unit of Ophthalmology, School of Clinical Sciences, University of Liverpool, Liverpool, United Kingdom.
authors.forename: Luminita
authors.initials: L
authors.lastname: Paraoan
mesh_terms: D017209:Apoptosis / Q000502:physiology*; D001483:Base Sequence; D015153:Blotting, Western; D020169:Caspases / Q000378:metabolism*; D017931:DNA Primers; D004789:Enzyme Activation; D016147:Genes, Tumor Suppressor / Q000502:physiology*; D006801:Humans; D008545:Melanoma / Q000201:enzymology / Q000378:metabolism*; D008565:Membrane Proteins / Q000502:physiology*; D016133:Polymerase Chain Reaction; D014604:Uveal Neoplasms / Q000201:enzymology / Q000378:metabolism*
chemical_list: D017931:DNA Primers; D008565:Membrane Proteins; C416404:PERP protein, human; D020169:Caspases