Biology subjects

Bertrand, T.

Publications and source records attributed to Bertrand, T..

2 recordsLinked to original sources

bioRxiv2024

An NAMPT Inhibitor Decreases NAMPT Capture by an Antibody Directed against the 5-Phosphoribosyl-1-Pyrophosphate-Binding Loop: A Rational for an NAMPT Occupancy Assay

Nicotinamide phosphoribosyltransferase (NAMPT) catalyzes the rate-limiting step of nicotinamide adenine dinucleotide (NAD) biosynthesis. NAMPT inhibitors (NAMPTi) have been shown to be NAMPT substrates. The resulting NAMPTi-phosphoribose (RP) adduct binds tightly to NAMPT and inhibits the enzyme. Using new NAMPTi, SAR154782, structural analyses performed in this study unveiled a close proximity of the SAR154782-RP complex to the 5-phosphoribosyl-1-pyrophosphate-binding (PRPP-binding) loop within the NAMPT catalytic site. The PRPP-binding loop of NAMPT is subject to conformational flexibility. Interestingly, the PRPP-binding loop domain is oriented to the outer side of the NAMPT dimer and can potentially serve as an antigen-binding site for antibodies. Here we report for the first time that the NAMPTi-RP adduct bound to NAMPT decreases NAMPT capture by an antibody directed against the c-terminal PRPP-binding loop in NAMPT. This finding was then used to explore cellular NAMPT occupancy. The NAMPTi-RP complex displays a sustained, cellular NAMPT occupancy that correlates with the inhibition of NAMPT activity. Moreover, a good correlation between NAMPT occupancy, NAD decrease, and NAMPTi efficacy was observed in-vivo in a NCI-H82 small cell lung cancer (SCLC) xenograft model. NAMPT-occupancy assay can be used in clinical settings to better define the optimal dose levels and dose regimen for effective NAMPT inhibition.

cancer biology↗

bioRxiv2022

Solving the stochastic dynamics of population growth

Population growth is a fundamental process in ecology, evolution, and epidemiology. The population size dynamics during growth are often described by deterministic equations derived from kinetic models. Here, we simulate several population growth models and compare the size averaged over many stochastic realizations with the deterministic predictions. We show that these deterministic equations are generically bad predictors of the average stochastic population dynamics. Specifically, deterministic predictions overestimate the simulated population sizes, especially those of populations starting with a small number of individuals. Describing population growth as a stochastic birth process, we prove that the discrepancy between deterministic predictions and simulated data is due to unclosed-moment dynamics. In other words, the deterministic approach does not take into account the variability of birth times, which is particularly important at small population sizes. We evaluate different moment-closure approximations and show that they do not satisfactorily reduce the error between analytical predictions and simulated data. We present two novel solutions to the stochastic growth dynamics, one of which applies to any population growth model. We show that our solution exactly quantifies the dynamics of a community composed of different strains and correctly predicts the fixation probability of a strain in a serial dilution experiment. Our work sets the foundations for a more faithful modeling of community dynamics. It provides tools for a more accurate analysis of experimental results, including the inference of important growth parameters.

ecology↗