title: Nicotinamide N-methyltransferase increases complex I activity in SH-SY5Y cells via sirtuin 3.
abstract: Nicotinamide N-methyltransferase (NNMT, E.C. 2.1.1.1) N-methylates nicotinamide to 1-methylnicotinamide. We have previously shown that NNMT is significantly overexpressed in the brains of patients who have died of Parkinson's disease, and others have shown that NNMT is significantly overexpressed in a variety of diseases ranging from cancer to hepatic cirrhosis. In vitro overexpression has revealed many cytoprotective effects of NNMT, in particular increased complex I activity and ATP synthesis. Although this appears to be mediated by an increase in 1-methylnicotinamide production, the molecular mechanisms involved remain unclear. In the present study, we have investigated the role that sirtuins 1, 2 and 3, class III DNA deacetylase enzymes known to regulate mitochondrial energy production and cell cycle, have in mediating the effects of NNMT upon complex I activity. Expression of NNMT in SH-SY5Y human neuroblastoma cells, which have no endogenous expression of NNMT, significantly increased the expression of all three sirtuins. siRNA-mediated silencing of sirtuin 3 expression decreased complex I activity in NNMT-expressing SH-SY5Y cells to that observed in wild-type SH-SY5Y, and significantly reduced cellular ATP content also. These results demonstrate that sirtuin 3 is a key mediator of NNMT-induced complex I activity and ATP synthesis. These results further reinforce a central role for NNMT in the regulation of energy homeostasis and provide further mechanistic insight into the consequences of enhanced NNMT expression.
authors.affiliation: King's College London, Institute of Pharmaceutical Science, 150 Stamford Street, London SE1 9NH, UK.
authors.forename: Karolina Y
authors.initials: KY
authors.lastname: Liu
authors.affiliation: King's College London, Institute of Pharmaceutical Science, 150 Stamford Street, London SE1 9NH, UK.
authors.forename: Rakhee J
authors.initials: RJ
authors.lastname: Mistry
authors.affiliation: King's College London, Institute of Pharmaceutical Science, 150 Stamford Street, London SE1 9NH, UK.
authors.forename: Carlos A
authors.initials: CA
authors.lastname: Aguirre
authors.affiliation: King's College London, Institute of Pharmaceutical Science, 150 Stamford Street, London SE1 9NH, UK.
authors.forename: Eirini S
authors.initials: ES
authors.lastname: Fasouli
authors.affiliation: King's College London, Institute of Pharmaceutical Science, 150 Stamford Street, London SE1 9NH, UK.
authors.forename: Martin G
authors.initials: MG
authors.lastname: Thomas
authors.affiliation: Universidade Federal do Rio Grande do Sul, Instituto de Ciências Básicas da Saúde, Departmento de Bioquímica, Rua Ramiro Barcelos, Porto Alegre 90035 003, Brazil.
authors.forename: Fábio
authors.initials: F
authors.lastname: Klamt
authors.affiliation: University of Birmingham, Institute of Metabolism and Systems Research, Edgbaston, Birmingham B15 2TH, UK.
authors.forename: David B
authors.initials: DB
authors.lastname: Ramsden
authors.affiliation: King's College London, Institute of Pharmaceutical Science, 150 Stamford Street, London SE1 9NH, UK. Electronic address: richard.parsons@kcl.ac.uk.
authors.forename: Richard B
authors.initials: RB
authors.lastname: Parsons
mesh_terms: D000255:Adenosine Triphosphate / Q000096:biosynthesis; D045744:Cell Line, Tumor; D042967:Electron Transport Complex I / Q000378:metabolism*; D020868:Gene Silencing; D006801:Humans; D050903:Nicotinamide N-Methyltransferase / Q000378:metabolism*; D056566:Sirtuin 3 / Q000235:genetics / Q000378:metabolism*
chemical_list: D000255:Adenosine Triphosphate; C494406:NNMT protein, human; D050903:Nicotinamide N-Methyltransferase; D056566:Sirtuin 3; D042967:Electron Transport Complex I
keywords: ATP; Bioenergetics; Cancer; Complex I; Nicotinamide N-methyltransferase; Parkinson's disease