title: Identification, characterisation and regulation by CD40 activation of novel CD95 splice variants in CD95-apoptosis-resistant, human, B-cell non-Hodgkin's lymphoma.
abstract: CD95 gene and splicing aberrations have been detected in B-cell non-Hodgkin lymphoma (B-NHL) where they are thought to contribute to CD95 apoptosis resistance. To further investigate this, we have performed extensive CD95 transcript sequencing and functional analysis in B-NHL with demonstrated resistance to CD95-induced apoptosis (B-NHLr). Strikingly, instead of showing CD95 mutations per se, B cells from B-NHLr co-expressed wild-type and multiple, normal (CD95nv) and novel alternatively spliced variant CD95 transcripts (CD95av). CD95av were predicted, by sequencing, to encode soluble, potentially apoptosis inhibitory proteins. However, their overexpression, by transfection, in Jurkat cells did not interfere with endogenous CD95 death signalling. Furthermore, CD95av-expressing B-NHLr did not show mutations in CD95 splice-regulatory elements and CD95av expression was 'reversible' by CD40 activation. This, in conjunction with treatment by the protein synthesis inhibitor, cycloheximide, could sensitise a subset of B-NHLr to CD95 apoptosis. In normal and lymphoma B cells, this correlated to increased CD95 membrane expression, enhanced DISC activity and engagement of the mitochondrial death pathway via Bid cleavage, although the latter occurred less efficiently in B-NHLr. Thus, immune modulation of CD95 transcription and alternative splicing combined with enhanced engagement of mitochondrial death signalling offer potential for restoration of CD95 apoptosis sensitivity in B-NHLr.
authors.affiliation: Institut National de la Santé et de la Recherche Médicale (INSERM), U823, Institut Albert Bonniot, Grenoble, France. alicia.lajmanovich@ujf-grenoble.fr
authors.forename: Alicia
authors.initials: A
authors.lastname: Lajmanovich
authors.forename: Juliana Bruder
authors.initials: JB
authors.lastname: Ribeyron
authors.forename: Anne
authors.initials: A
authors.lastname: Florin
authors.forename: Alexandra
authors.initials: A
authors.lastname: Fournier
authors.forename: Marie-Anne
authors.initials: MA
authors.lastname: Pasquier
authors.forename: Samuel
authors.initials: S
authors.lastname: Duley
authors.forename: Martine
authors.initials: M
authors.lastname: Chauvet
authors.forename: Joel
authors.initials: J
authors.lastname: Plumas
authors.forename: Thierry
authors.initials: T
authors.lastname: Bonnefoix
authors.forename: Remy
authors.initials: R
authors.lastname: Gressin
authors.forename: Dominique
authors.initials: D
authors.lastname: Leroux
authors.forename: Mary B
authors.initials: MB
authors.lastname: Callanan
mesh_terms: D017209:Apoptosis; D051017:Apoptosis Regulatory Proteins; D001483:Base Sequence; D019013:CD40 Antigens / Q000378:metabolism*; D006801:Humans; D019169:Jurkat Cells; D016393:Lymphoma, B-Cell / Q000473:pathology*; D024101:Mitochondrial Proteins; D020033:Protein Isoforms; D012333:RNA, Messenger / Q000235:genetics; D015398:Signal Transduction; D014162:Transfection; D019014:fas Receptor / Q000235:genetics*
chemical_list: D051017:Apoptosis Regulatory Proteins; D019013:CD40 Antigens; D024101:Mitochondrial Proteins; D020033:Protein Isoforms; D012333:RNA, Messenger; D019014:fas Receptor