Role of sirtuins in retinal function under basal conditions

Sirtuins are NAD ⁺ -dependent enzymes that govern cellular homeostasis by regulating the acylation status of their diverse target proteins. We recently demonstrated that both rod and cone photoreceptors rely on NAMPT-mediated NAD ⁺ biosynthesis to meet their energetic requirements. Moreover, we found that this NAD ⁺ -dependent retinal homeostasis relies, in part, on maintenance of optimal activity of the mitochondrial sirtuins and of SIRT3 in particular. Nonetheless, it is unknown whether other sirtuin family members also play important roles in retinal homeostasis. Our results suggest that SIRT1, SIRT2, SIRT4, and SIRT6 are dispensable for retinal survival at baseline, as individual deletion of each of these sirtuins does not cause retinal degeneration by fundus biomicroscopy or retinal dysfunction by ERG. These findings have significant implications and inform future studies investigating the mechanisms underlying the central role of NAD ⁺ biosynthesis in retinal survival and function.