Figure 1. NAD+ Compartmentalization for Regulation.
The levels of free NAD+ are tightly controlled both temporally and spatially to precisely modulate signaling in cells. (A) Temporal fluctuations in NAD+ concentrations regulate circadian periodicity rhythms. (B) Spatial partitioning of NAD+ biosynthetic pathways permits signal-dependent initiation of adipogenic differentiation. (C) NAD+ compartmentalization may protect and prioritize support for particularly crucial cellular processes (e.g., in the mitochondria) in response to stress when other subcellular stores are depleted. Abbreviation: Ac, acylation.