The mechanism of nicotinamide phosphoribosyltransferase whereby positive allosteric modulation elevates cellular NAD

In aging and disease, cellular NAD+ is depleted by catabolism to nicotinamide (NAM) and NAD+ supplementation is being pursued to enhance human healthspan and lifespan. Activation of nicotinamide phosphoribosyltransferase (NAMPT), the rate-limiting step in NAD+ biosynthesis, has potential to increase...

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Published inbioRxiv
Main Authors Ratia, Kiira M, Shen, Zhengnan, Gordon-Blake, Jesse, Lee, Hyun, Laham, Megan S, Krider, Isabella S, Christie, Nicholas, Ackerman-Berrier, Martha S, Penton, Christopher, Knowles, Natalie G, Soumya Reddy Musku, Fu, Jiqiang, Ganga Reddy Musku, Xiong, Rui, Thatcher, Gregory R J
Format Paper
LanguageEnglish
Published Cold Spring Harbor Cold Spring Harbor Laboratory Press 22.10.2022
Subjects
Affinity
Aging
Allosteric properties
Biosynthesis
Enzymatic activity
Enzyme kinetics
Feedback inhibition
Kinetics
Life span
NAD
Nicotinamide phosphoribosyltransferase
Phosphoribosyltransferase
Supplements
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Summary:In aging and disease, cellular NAD+ is depleted by catabolism to nicotinamide (NAM) and NAD+ supplementation is being pursued to enhance human healthspan and lifespan. Activation of nicotinamide phosphoribosyltransferase (NAMPT), the rate-limiting step in NAD+ biosynthesis, has potential to increase salvage of NAM. Novel NAMPT positive allosteric modulators (N-PAMs) were discovered in addition to demonstration of NAMPT activation by biogenic phenols. The mechanism of activation was revealed through synthesis of novel chemical probes, new NAMPT co-crystal structures, and enzyme kinetics. Binding to a rear channel in NAMPT regulates NAM binding and turnover, with biochemical observations being replicated by NAD+ measurements in human cells. The mechanism of action of N-PAMs identifies, for the first time, the role of the rear channel in regulation of NAMPT turnover coupled to feedback inhibition by NAM. N-PAM inhibition of low affinity, non-productive NAM binding via the rear channel, causes a right-shift in KI(NAM) that accompanies an increase in enzyme activity. Conversion of an N-PAM to a high-affinity ligand blocks both high and low affinity NAM binding, ablating enzyme activity. In the presence of an N-PAM, NAMPT boosts NAD+ biosynthesis at higher NAM concentrations, in addition to relieving inhibition by NAD+. Since cellular stress often leads to enhanced catabolism of NAD+ to NAM, this mechanism is relevant to supporting cellular NAD+ levels in aging and disease. The tight regulation of cellular NAMPT is differentially regulated by N-PAMs and other activators, indicating that different classes of pharmacological activators may be engineered for cell and tissue selectivity. Competing Interest Statement G.T. is an inventor on patents owned by the University of Illinois. This statement is required by a COI management plan
DOI:10.1101/2022.10.21.513220