Aksoy Pinar, Escande Carlos, White Thomas A, Thompson Michael, Soares Sandra, Benech Juan Claudio, Chini Eduardo N
Department of Anesthesiology, Mayo Clinic and Foundation, Rochester, MN, USA.
Biochem Biophys Res Commun. 2006 Oct 13;349(1):353-9. doi: 10.1016/j.bbrc.2006.08.066. Epub 2006 Aug 22.
The SIRT 1 enzyme is a NAD dependent deacetylase implicated in ageing, cell protection, and energy metabolism in mammalian cells. How the endogenous activity of SIRT 1 is modulated is not known. The enzyme CD38 is a multifunctional enzyme capable of synthesis of the second messenger, cADPR, NAADP, and ADPR. However, the major enzymatic activity of CD38 is the hydrolysis of NAD. Of particular interest is the fact that CD38 is present on the inner nuclear membrane. Here, we investigate the modulation of the SIRT 1 activity by CD38. We propose that by modulating availability of NAD to the SIRT1 enzyme, CD38 may regulate SIRT1 enzymatic activity. We observed that in CD38 knockout mice, tissue levels of NAD are significantly increased. We also observed that incubation of purified recombinant SIRT1 enzyme with CD38 or nuclear extracts of wild-type mice led to a significant inhibition of its activity. In contrast, incubation of SIRT1 with cellular extract from CD38 knockout mice was without effect. Furthermore, the endogenous activity of SIRT1 was several time higher in nuclear extracts from CD38 knockout mice when compared to wild-type nuclear extracts. Finally, the in vivo deacetylation of the SIRT1 substrate P53 is increased in CD38 knockout mice tissue. Our data support the novel concept that nuclear CD38 is a major regulator of cellular/nuclear NAD level, and SIRT1 activity. These findings have strong implications for understanding the basic mechanisms that modulate intracellular NAD levels, energy homeostasis, as well as ageing and cellular protection modulated by the SIRT enzymes.
SIRT 1酶是一种依赖烟酰胺腺嘌呤二核苷酸（NAD）的脱乙酰酶，与哺乳动物细胞的衰老、细胞保护和能量代谢有关。SIRT 1的内源性活性是如何被调节的尚不清楚。CD38酶是一种多功能酶，能够合成第二信使环磷腺苷二磷酸核糖（cADPR）、烟酰胺腺嘌呤二核苷酸磷酸（NAADP）和腺嘌呤二磷酸核糖（ADPR）。然而，CD38的主要酶活性是NAD的水解。特别值得关注的是，CD38存在于内核膜上。在此，我们研究了CD38对SIRT 1活性的调节作用。我们提出，通过调节SIRT1酶可利用的NAD水平，CD38可能调节SIRT1的酶活性。我们观察到，在CD38基因敲除小鼠中，NAD的组织水平显著升高。我们还观察到，将纯化的重组SIRT1酶与CD38或野生型小鼠的核提取物一起孵育会导致其活性受到显著抑制。相比之下，将SIRT1与CD38基因敲除小鼠的细胞提取物一起孵育则没有效果。此外，与野生型核提取物相比，CD38基因敲除小鼠核提取物中SIRT1的内源性活性高出数倍。最后，在CD38基因敲除小鼠组织中，SIRT1底物P53的体内脱乙酰作用增强。我们的数据支持了一个新的概念，即核CD38是细胞/核NAD水平和SIRT1活性的主要调节因子。这些发现对于理解调节细胞内NAD水平、能量稳态以及由SIRT酶调节的衰老和细胞保护的基本机制具有重要意义。
