title: Nicotinamide N-methyltransferase expression in SH-SY5Y neuroblastoma and N27 mesencephalic neurones induces changes in cell morphology via ephrin-B2 and Akt signalling.
abstract: Nicotinamide N-methyltransferase (NNMT, E.C. 2.1.1.1) N-methylates nicotinamide to produce 1-methylnicotinamide (MeN). We have previously shown that NNMT expression protected against neurotoxin-mediated cell death by increasing Complex I (CxI) activity, resulting in increased ATP synthesis. This was mediated via protection of the NDUFS3 subunit of CxI from degradation by increased MeN production. In the present study, we have investigated the effects of NNMT expression on neurone morphology and differentiation. Expression of NNMT in SH-SY5Y human neuroblastoma and N27 rat mesencephalic dopaminergic neurones increased neurite branching, synaptophysin expression and dopamine accumulation and release. siRNA gene silencing of ephrin B2 (EFNB2), and inhibition of Akt phosphorylation using LY294002, demonstrated that their sequential activation was responsible for the increases observed. Incubation of SH-SY5Y with increasing concentrations of MeN also increased neurite branching, suggesting that the effects of NNMT may be mediated by MeN. NNMT had no significant effect on the expression of phenotypic and post-mitotic markers, suggesting that NNMT is not involved in determining phenotypic fate or differentiation status. These results demonstrate that NNMT expression regulates neurone morphology in vitro via the sequential activation of the EFNB2 and Akt cellular signalling pathways.
authors.affiliation: Institute of Pharmaceutical Science, King's College London, London, UK.
authors.forename: M G
authors.initials: MG
authors.lastname: Thomas
authors.forename: M
authors.initials: M
authors.lastname: Saldanha
authors.forename: R J
authors.initials: RJ
authors.lastname: Mistry
authors.forename: D T
authors.initials: DT
authors.lastname: Dexter
authors.forename: D B
authors.initials: DB
authors.lastname: Ramsden
authors.forename: R B
authors.initials: RB
authors.lastname: Parsons
mesh_terms: D000818:Animals; D045744:Cell Line, Tumor; D048430:Cell Shape; D059329:Cholinergic Neurons / Q000378:metabolism; D004298:Dopamine / Q000378:metabolism; D059290:Dopaminergic Neurons / Q000201:enzymology*; D036388:Ephrin-B2 / Q000378:metabolism*; D015870:Gene Expression; D006801:Humans; D008636:Mesencephalon / Q000473:pathology*; D009447:Neuroblastoma; D055495:Neurogenesis; D050903:Nicotinamide N-Methyltransferase / Q000378:metabolism*; D010641:Phenotype; D051057:Proto-Oncogene Proteins c-akt; D051381:Rats; D015398:Signal Transduction; D016708:Synaptophysin / Q000378:metabolism
chemical_list: D036388:Ephrin-B2; C569014:SYP protein, human; D016708:Synaptophysin; C494406:NNMT protein, human; D050903:Nicotinamide N-Methyltransferase; D051057:Proto-Oncogene Proteins c-akt; D004298:Dopamine