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.

Dexmedetomidine attenuation of renal ischaemia-reperfusion injury requires sirtuin 3 activation

“…SIRT3 expression was knocked down using SIRT3-targeting siRNA (sc-61555; Santa Cruz Biotechnology, Santa Cruz, CA, USA) as described. 26 A scrambled-sequence siRNA (sc-37007; Santa Cruz) served as negative control. HK2 cells were transfected with these siRNAs using Entranster TM -R transfection reagent (Engreen Biosystem, Beijing, China).…”

Nicotinamide N-methyltransferase as a potential marker for cancer

“…Although NNMT is mainly expressed in the liver in healthy tissues [17,18] low NNMT expression has been detected in the brain, lung, heart, kidney, skeletal muscle and placenta [7]. In contrast, high expression is reported in the cerebellum and caudate nucleus of patients who have succumbed to Parkinson's disease (PD), and also in many other diseases including osteoarthritis, cirrhosis, chronic obstructive pulmonary disease, cardiovascular disease and cancer [19]. Most importantly, reports indicate that NNMT expression is significantly increased in tumors [20].…”

“…While further experimentation demonstrated that NNMT expression in SH-SY5Y cells notably induced the expression of all three sirtuins (SirTs), siRNA-mediated silencing of SirT3 expression decreased CxI activity and significantly reduced cellular ATP content. [19] Colorectal cancer. Colorectal cancer (CRC) is one of the most common malignancies in the world and it continues to be a serious public health concern [31].…”

Inhibitors of nicotinamide N-methyltransferase designed to mimic the methylation reaction transition state

“…[1][2][3][4] In this regard, the overexpression of NNMT has recently been shown to cause AdoMet depletion in cancer cells. 5 Other studies have suggested a role for NNMT as a cytoprotective agent in Parkinson's disease [6][7][8] while other findings point to a potential link between MNA and lifespan regulation. 9 In addition, the upregulation of NNMT is observed in a range of metabolic disorders including diabetes and obesity.…”